Body parts names.
From head to toe.

Your cheeks form the sides of your face and mouth. Cheek muscles help keep food between your teeth while you chew.

Where to find it

On either side of your mouth, below your eyes.

Structure

The cheek wall includes skin, subcutaneous tissue, buccinator muscle and oral mucosa. Buccal fat occupies a deeper space. The parotid duct crosses the masseter, turns inward and passes through buccinator to reach the mouth.

How it works

Cheeks have skin outside and a moist lining inside. Muscles in their walls press against food so it stays near the teeth during chewing. They also help control air when you blow or speak.

Your chin is the lower front part of your face. It is formed by the front of your lower jawbone.

Where to find it

At the front of the lower jaw, below your bottom lip.

Structure

The mental prominence forms the anterior midline contour of the mandible. Skin, connective tissue and the mentalis muscle cover the bone. The mental nerve emerges through a foramen on either side to supply sensation to the chin and lower lip.

How it works

Bone gives the chin its shape, and skin and soft tissue cover it. When your jaw opens, your chin moves with it. Small muscles in this area also change the position of your lower lip.

Your ears help you hear and keep your balance. Sound travels through the outer and middle ear to the inner ear.

Where to find it

On each side of your head, with deeper parts inside the skull.

Structure

The external ear leads to the tympanic membrane. The middle ear contains the malleus, incus and stapes, and communicates with the nasopharynx through the auditory tube. The inner ear contains the cochlea and vestibular apparatus.

How it works

The outer ear collects sound. Sound vibrates the eardrum and tiny middle-ear bones, then reaches fluid in the inner ear. Special cells change the movement into nerve signals. Separate inner-ear structures help sense head movement.

Your eyes detect light so you can see shapes and colors. They send messages to your brain, which makes sense of what you see.

Where to find it

In two bony sockets at the front of the skull.

Structure

The globe has an outer fibrous layer, a vascular middle layer and the retina internally. The cornea and lens refract light, while aqueous and vitreous compartments help maintain its optical arrangement. Extraocular muscles position the globe within the orbit.

How it works

Light passes through the cornea and pupil, then the lens helps focus it on the retina. Light-sensitive cells create signals that travel along the optic nerve. The brain interprets those signals as a picture of the world.

Eyebrows are lines of hair above your eyes. They help guide sweat away from your eyes and help show feelings.

Where to find it

Along the ridge above each eye.

Structure

Eyebrow hairs emerge at angles that contribute to the contour above the orbit. Frontalis elevates the brow, while corrugator supercilii and nearby muscles draw it medially or downward. The underlying supraorbital margin belongs to the frontal bone.

How it works

The direction of eyebrow hairs helps guide moisture sideways. Muscles underneath can raise, lower or draw the brows together. These movements often accompany questions, concentration and other expressions.

Eyelashes grow along the edges of your eyelids. They help keep small particles out of your eyes.

Where to find it

Along the edges of the upper and lower eyelids.

Structure

Eyelashes are specialized terminal hairs arising near the anterior lid margin. Follicles are associated with small glands and sensory endings. Their arrangement creates a physical fringe without forming a complete seal against dust.

How it works

Lashes form a small fringe in front of the eye. Touching them can trigger a blink reflex, which closes the eyelids quickly. This helps the eye react before a particle reaches its surface.

Eyelids are folds of skin that close over your eyes. Blinking spreads tears across your eyes to keep them moist.

Where to find it

In front of each eye, with an upper and a lower lid.

Structure

Each eyelid contains skin, muscle, a supportive tarsal plate and an inner conjunctival lining. Meibomian glands in the tarsal plates supply lipids to the tear film. Orbicularis oculi closes the lids; levator palpebrae superioris elevates the upper lid.

How it works

Muscles lift a lid to open the eye and draw the lids together to close it. Each blink spreads a thin tear film over the cornea. This smooth, moist surface helps the eye focus light clearly.

Your face includes your eyes, nose, mouth and cheeks. Muscles under your skin help you smile and make expressions.

Where to find it

At the front of your head, from your forehead to your chin.

Structure

Most muscles of facial expression insert into skin rather than moving a joint between two bones. They receive motor supply from the facial nerve. Facial sensation is supplied mainly by branches of the trigeminal nerve, a separate cranial nerve.

How it works

Small muscles pull on the skin around your eyes and mouth to create expressions. Your face also contains openings that let light, air and food reach the right places. Many facial movements happen together when you speak.

Your forehead is the area above your eyebrows. The frontal bone lies underneath it.

Where to find it

Between your eyebrows and your hairline.

Structure

The forehead overlies the frontal bone and the frontal belly of the occipitofrontalis muscle. This muscle connects to a broad tendon sheet across the scalp. Its contraction raises the eyebrows and creates horizontal skin folds.

How it works

Skin, connective tissue and a thin layer of muscle cover the forehead bone. When forehead muscles contract, your eyebrows rise and the skin folds. This is one way your face can show surprise.

Gums are the tissue around your teeth. They cover the bone that supports your teeth.

Where to find it

Around the necks of teeth and over the jawbones.

Structure

Gingiva is part of the oral mucosa, with attached and free marginal regions. Junctional epithelium forms an attachment near the tooth surface. The gingiva covers the alveolar process but does not provide the tooth's main mechanical anchorage.

How it works

Gum tissue forms a close seal around each tooth. Together with deeper supporting tissues, it helps protect the places where teeth are anchored. The visible gum is only part of the tooth's support system.

Hair grows from tiny pockets in your skin called follicles. Hair on your head helps protect your scalp.

Where to find it

On your scalp and on much of your skin.

Structure

Each follicle contains a root surrounded by epithelial tissue. Dividing matrix cells near the bulb produce the keratinized shaft. A dermal papilla supports the growing region, while sebaceous glands usually open into the follicle.

How it works

Living cells at the bottom of each follicle build a hair. As new cells form, older cells move upward and become the hair shaft. The hair you see outside the skin is made of hardened, nonliving cells.

The top part of your body contains your brain and many sense organs. Your skull protects the brain inside your head.

Where to find it

Above your neck, at the top of your body.

Structure

The head contains the cranial cavity and facial skeleton, as well as the oral, nasal and orbital spaces. Its tissues include bone, skeletal muscle, skin, vessels and specialized sensory organs. The skull base contains openings through which the spinal cord, cranial nerves and major vessels pass.

How it works

Your head brings several sensing tools close to your brain. Eyes collect light, ears respond to sound, and your nose detects smells. Bones form a protective case, while neck muscles let you turn toward something interesting.

Your jaws hold your teeth and give shape to your mouth. Your lower jaw moves when you chew or talk.

Where to find it

In the lower and middle face, around your teeth.

Structure

The maxilla forms the upper jaw and contributes to the orbit and hard palate. The mandible has a body and two rami; each condylar process articulates with the temporal bone. An articular disc divides the temporomandibular joint.

How it works

The upper jaw is fixed to the skull. The lower jaw moves at joints near your ears, guided by chewing muscles. It can move up and down and a little from side to side to break food down.

Lips surround the opening of your mouth. They help you form words and keep food in your mouth.

Where to find it

Around the upper and lower edges of your mouth.

Structure

The lips contain orbicularis oris and other interlacing facial muscle fibers. The external skin transitions through the vermilion to moist oral mucosa. A dense sensory supply supports precise contact detection and coordinated movements.

How it works

Lips contain muscle covered by sensitive tissue. They close to hold a sip of water and change shape to produce speech sounds. Sounds such as p and b begin with the lips together.

Your mouth takes in food and helps you speak. Digestion begins here as you chew and mix food with saliva.

Where to find it

Below your nose, opening into the throat.

Structure

The oral vestibule lies between the lips or cheeks and the teeth. The oral cavity proper lies within the dental arches and continues toward the oropharynx. Its roof contains the hard and soft palates; its floor supports the tongue.

How it works

Teeth cut and crush food while the tongue moves it around. Saliva moistens the pieces so they can join into a soft mouthful. When you swallow, coordinated muscles move that mouthful toward the esophagus.

Your nose lets air enter and helps you smell. Tiny hairs and mucus help trap particles in the air.

Where to find it

In the middle of your face, above your mouth.

Structure

The nasal septum divides the nasal cavity, and curved conchae increase its internal surface area. Much of the lining is respiratory mucosa, while the olfactory region occupies a smaller superior area. The cavity continues posteriorly into the nasopharynx.

How it works

Air passes through a moist space inside the nose before moving toward the throat. This helps warm and moisten it. Smell-sensitive cells high inside the nose respond to molecules in the air and send messages to the brain.

Nostrils are the two openings in your nose. Air moves through them when you breathe through your nose.

Where to find it

At the bottom of your nose, one opening on each side.

Structure

Each external naris opens into the nasal vestibule, where skin transitions toward the deeper nasal lining. Cartilage supports the opening. The vestibule often contains coarse hairs that intercept larger particles before air reaches the nasal cavity.

How it works

Each nostril leads into the nasal cavity. Air can flow in during a breath and out during an exhalation. The tissue between the two sides of the nose is called the nasal septum.

Your scalp is the skin covering the top of your head. It contains hair follicles and many blood vessels.

Where to find it

Over the top, sides and back of your skull.

Structure

Five layers are commonly described: skin, dense connective tissue, epicranial aponeurosis, loose connective tissue and pericranium. Vessels travel through the dense connective tissue, while the loose layer permits the superficial scalp to move over the skull.

How it works

The scalp has layers containing skin, blood vessels, nerves and connective tissue. It supplies growing hair roots with nutrients. Sensory nerves let you notice light touches, such as a hat resting on your head.

Your tongue is a muscular organ inside your mouth. It moves food, helps you speak and carries many taste buds.

Where to find it

On the floor of your mouth, extending back toward your throat.

Structure

Intrinsic muscles alter tongue shape; extrinsic muscles change its position. Papillae cover much of the dorsal surface, but not all papillae contain taste buds. Motor supply is mainly through the hypoglossal nerve, with an exception for palatoglossus.

How it works

Groups of muscles change the tongue's shape and position. It pushes food toward the teeth, gathers it for swallowing and adjusts air to form words. Taste buds respond to dissolved substances and send signals through nerves.

Teeth bite and grind food into smaller pieces. The hard outer layer of a tooth is called enamel.

Where to find it

Set into sockets in your upper and lower jaws.

Structure

Enamel covers the crown, dentin forms most of the tooth, and cementum covers the root. Pulp occupies the central chamber and root canals. The periodontal ligament attaches the root to alveolar bone and transmits forces during biting.

How it works

A tooth has a visible crown and a root anchored below the gum. Enamel covers the crown; beneath it is dentin. The soft pulp contains nerves and blood vessels. Front teeth cut food and broader back teeth grind it.

Your abdomen is the area between your chest and pelvis. It contains your stomach, intestines and several other organs.

Where to find it

Below the diaphragm and above the pelvis.

Structure

The abdominal wall surrounds a cavity containing digestive organs and associated vessels. Some organs are covered by peritoneum and suspended by mesenteries; others lie behind the peritoneal lining. The diaphragm separates the abdomen from the thorax.

How it works

Abdominal muscles form a flexible wall around many organs. They help steady your trunk when you move, while the digestive organs inside process food. Organs can shift a little as the diaphragm moves with breathing.

Your back is the rear of your torso. Its bones and muscles support you and help you move.

Where to find it

Along the rear of your torso, from your neck to your pelvis.

Structure

The vertebral column and deep back muscles support posture and controlled movement. More superficial muscles connect the trunk with the shoulder girdle and upper limbs. Fascia separates layers and distributes tension across the back.

How it works

Layers of muscles help hold your body upright and guide bending and turning. The spine runs through the middle, and the shoulder blades lie over the upper ribs. Strong connective tissues help share the work of supporting you.

Your belly button is a scar on your abdomen. Before birth, the umbilical cord connected your body to the placenta.

Where to find it

On the front of your abdomen.

Structure

The umbilicus marks the former attachment of the umbilical cord. After birth, cord vessels close and their remnants become associated with internal ligaments. The visible scar lies in the anterior abdominal wall rather than opening into the digestive tract.

How it works

Before birth, the umbilical cord attached here and carried blood between the developing baby and the placenta. After birth, the remaining cord dries and separates, leaving a scar. The shape of that scar varies.

Your buttocks are the rounded areas at the back of your pelvis. Large muscles here help you stand up and climb stairs.

Where to find it

At the back of your pelvis, above your thighs.

Structure

Gluteus maximus forms much of the posterior bulk, with gluteus medius and minimus deeper and more lateral. Subcutaneous fat also contributes to contour. These muscles act on the femur and help stabilize the pelvis during gait.

How it works

The gluteal muscles help move and stabilize the hips. They work when you rise from a chair, climb a step or stand on one leg. Fat and skin cover these muscles and help cushion sitting.

Your chest is the upper front of your torso. Your ribs help protect the heart and lungs inside it.

Where to find it

Between your neck and the bottom of your rib cage.

Structure

The thorax is bounded by the ribs, sternum, thoracic vertebrae and diaphragm. The lungs occupy pleural compartments, while the mediastinum between them contains the heart, major vessels, trachea and esophagus.

How it works

The ribs and breastbone form a protective, movable frame. Muscles between the ribs help change the size of the chest during breathing. The heart sits between the lungs, with the diaphragm forming the floor below them.

Your hip is where your thigh meets your pelvis. Its ball-and-socket joint lets your leg move in several directions.

Where to find it

On each side where your thigh meets your pelvis.

Structure

The femoral head fits into the acetabulum of the pelvis. Articular cartilage, a fibrocartilaginous labrum and a strong capsule support a stable weight-bearing joint. Surrounding muscle groups produce flexion, extension, abduction and rotation.

How it works

The round head of the femur fits into a cup-shaped socket in the pelvis. Cartilage helps the surfaces glide, while ligaments and muscles keep the joint stable. This arrangement permits bending and rotation.

Nails are firm coverings on the ends of fingers and toes. They are made mostly of a protein called keratin.

Where to find it

On the upper surface of each fingertip and toe tip.

Structure

The nail plate is produced mainly by the nail matrix and advances over the nail bed. The proximal fold protects the growing region. The plate consists of tightly packed keratinized cells, while the tissues supporting it remain living.

How it works

New nail cells form near the root and push the nail plate forward. The firm plate supports the soft tip underneath. Fingernails also help with precise tasks, such as picking up a thin piece of paper.

Your neck connects your head to your torso. It contains bones, muscles and passages for air and food.

Where to find it

Between your head and your shoulders.

Structure

The cervical vertebrae support the neck posteriorly. Anteriorly lie the airway, pharynx, esophagus and thyroid region, with major neurovascular bundles to either side. Fascial layers organize muscles and create routes between head and chest.

How it works

A stack of small vertebrae supports the head. Muscles turn and tilt it, while blood vessels carry blood to and from the head. The windpipe and esophagus pass through this crowded region on their way to the chest.

Skin covers your body and forms a protective barrier. It helps you feel touch and control body temperature.

Where to find it

Around the entire outside of your body.

Structure

The epidermis is an epithelial barrier above the connective-tissue dermis. The dermis contains vessels, nerves and many skin appendages. Subcutaneous tissue beneath the skin provides variable fat storage, cushioning and attachment to deeper structures.

How it works

The outer layer forms a barrier. A deeper layer contains blood vessels, glands and sensory endings. These structures help you notice touch and temperature while protecting the tissues below. Old surface cells are continually replaced.

Sweat glands make sweat inside your skin. As sweat evaporates, it helps cool your body.

Where to find it

Within the skin, connected to an opening or hair follicle.

Structure

Eccrine glands have coiled secretory portions in the dermis and ducts that usually open onto the surface. They release watery sweat. Apocrine glands occur in selected regions and generally empty into hair follicles.

How it works

Many sweat glands send watery sweat through a tiny duct to the surface. Heat is carried away as that water evaporates. Nerves help regulate this response when the body needs to release extra warmth.

Your throat is a passage behind your mouth and nose. It helps move air toward your windpipe and food toward your esophagus.

Where to find it

Behind your nose and mouth, leading down into your neck.

Structure

The pharynx is divided into nasopharynx, oropharynx and laryngopharynx. It is a muscular passage shared by respiratory and digestive pathways. During swallowing, coordinated elevation and closure mechanisms direct the bolus toward the esophagus.

How it works

The throat is a shared route for air and swallowed food. A coordinated swallow temporarily protects the airway while food is directed into the esophagus. Muscles squeeze in sequence to keep the mouthful moving.

Your waist is the area between your ribs and hips. Muscles around it help you bend and turn.

Where to find it

Around the middle of your torso, between the lower ribs and hips.

Structure

The waist is a surface region involving the lateral abdominal walls between the rib cage and pelvis. External and internal oblique muscles and transversus abdominis contribute to its deeper structure. Their fibers run in different directions.

How it works

Your waist contains muscles that wrap around the abdomen. They work with back muscles to steady your trunk and control twisting. This support matters even during small movements such as reaching across a table.

Your arm extends from your shoulder toward your hand. Its muscles and bones work together to lift and carry things.

Where to find it

From the shoulder toward the hand on either side of the body.

Structure

In everyday speech, arm may mean the entire upper limb; anatomically, the brachium is the shoulder-to-elbow region. The upper limb includes arm, forearm and hand, each with separate bones and muscle compartments.

How it works

Different joints place your hand where it needs to go. The shoulder aims the arm, the elbow changes its reach, and forearm movement turns the palm. Nerves coordinate muscles so these actions happen smoothly.

Your elbow is the joint between your upper arm and forearm. It bends and straightens so you can move your hand closer to your body.

Where to find it

Where the upper arm meets the two forearm bones.

Structure

The elbow region includes humeroulnar, humeroradial and proximal radioulnar articulations. A shared capsule encloses the main articulations, while collateral and annular ligaments provide support. Flexion and extension occur alongside forearm rotation.

How it works

The humerus and ulna mainly make a hinge for bending. A nearby connection with the radius helps the forearm rotate. Cartilage covers the moving surfaces, and ligaments help keep the bones aligned.

Fingers help you touch, grip and handle objects. Their joints let them bend around things you hold.

Where to find it

Extending from the palm, alongside the thumb.

Structure

Most fingers have proximal, middle and distal phalanges, linked by interphalangeal joints and a metacarpophalangeal joint. Flexor tendons run in sheaths, while an extensor mechanism coordinates straightening across the digit.

How it works

Most fingers contain three small bones linked by joints. Tendons bend or straighten them, and ligaments guide the motion. Sensitive fingertips report pressure and texture so the brain can refine small movements.

Your forearm is between your elbow and wrist. It contains two bones, the radius and ulna.

Where to find it

Between your elbow and wrist.

Structure

The radius and ulna are joined by an interosseous membrane. Anterior compartments contain many flexors and pronators; posterior compartments contain many extensors and supinators. Long tendons continue across the wrist into the hand.

How it works

The radius and ulna sit side by side. When the palm turns, the radius rotates around the ulna. Muscles in the forearm send long tendons into the hand to help move the wrist and fingers.

Your hands help you hold, feel and make things. Many bones, joints and muscles let them make precise movements.

Where to find it

At the end of your forearm, beyond the wrist.

Structure

The hand contains carpal bones, metacarpals and phalanges. Intrinsic muscles lie within it, while extrinsic tendons arrive from the forearm. Sensory input and fine motor control support precision grip as well as powerful grasping.

How it works

The palm provides a base for the fingers and thumb. Muscles and tendons arrange these parts around objects, while touch signals help adjust the grip. A light paper cup and a heavy book call for different forces.

A knuckle is a joint in a finger. Knuckles let your fingers bend and straighten.

Where to find it

At the joints along your fingers, especially where they meet the palm.

Structure

Knuckle commonly refers to the visible prominence of a metacarpophalangeal or interphalangeal joint. Joint capsules, ligaments, cartilage and tendons support each articulation. The prominence becomes more obvious when the joint flexes.

How it works

The rounded end of one bone moves against the next bone. Cartilage and joint fluid help the surfaces slide, while tendons pull from either side. The bump you see changes shape as the joint bends.

Your palm is the inner surface of your hand. Sensitive skin helps you notice the shape and texture of objects.

Where to find it

On the inner side of your hand, opposite the knuckles.

Structure

Palmar skin is thick and firmly attached to underlying connective tissue. The palmar aponeurosis protects deeper tendons, vessels and nerves. Thenar and hypothenar muscle groups form the prominences near the thumb and little finger.

How it works

A tough layer of connective tissue lies beneath the skin. The skin has ridges that improve contact and many sensory endings. The palm changes shape as its bones and muscles help cup or flatten the hand.

Your shoulder joins your arm to your torso. Its bones and muscles let your arm reach in many directions.

Where to find it

At the upper corner of your torso, where each arm begins.

Structure

The shoulder complex includes the glenohumeral, acromioclavicular and sternoclavicular joints and movement of the scapula over the thorax. The rotator cuff centers the humeral head as larger muscles move the arm.

How it works

Several joints work together at the shoulder. The upper-arm bone meets a shallow socket in the shoulder blade, and nearby muscles guide it. The shoulder blade also slides over the ribs as you reach upward.

Your thumb can move across your palm toward your fingers. This movement helps you grip objects such as a pencil.

Where to find it

On the side of your hand, near the wrist.

Structure

The thumb has two phalanges and a highly mobile first carpometacarpal joint between the trapezium and first metacarpal. Thenar muscles contribute to opposition, which combines several movements to bring the thumb pad toward the fingers.

How it works

A special joint at its base allows the thumb to move across the palm. It can meet the fingertips for a precise pinch or wrap around an object for a strong grip. Small hand muscles control these movements.

Your upper arm is between your shoulder and elbow. The bone inside it is called the humerus.

Where to find it

Between your shoulder and elbow.

Structure

The humerus separates anterior and posterior muscle compartments. Biceps brachii, brachialis and coracobrachialis lie anteriorly; triceps dominates posteriorly. Major vessels and nerves travel through the region toward the elbow and forearm.

How it works

Muscles attach around the humerus and cross the shoulder or elbow. The biceps helps bend the elbow, while the triceps straightens it. When one action is needed, the muscles coordinate rather than all pulling equally.

Your wrist connects your forearm to your hand. Several small bones let your hand bend and move.

Where to find it

At the junction of your forearm and hand.

Structure

The radiocarpal and midcarpal joints coordinate wrist motion. Eight carpal bones form two rows, with ligaments maintaining their arrangement. Flexor tendons and the median nerve pass through the carpal tunnel beneath the flexor retinaculum.

How it works

Small wrist bones form a flexible bridge between the forearm and palm. Their joints share movement rather than acting as one large hinge. Tendons pass across the wrist to reach the fingers.

Your ankle joins your leg and foot. It helps your foot move up and down.

Where to find it

Between the lower leg and the top of the foot.

Structure

The distal tibia and fibula form a mortise around the talus. This arrangement supports dorsiflexion and plantarflexion. Inversion and eversion occur mainly through joints below and in front of the talus.

How it works

The tibia and fibula form a bracket around a foot bone called the talus. This joint lets the foot move up and down. Nearby joints add side-to-side adjustment for uneven ground.

Your calf is the muscular back of your lower leg. Its muscles help raise your heel when you walk or stand on tiptoe.

Where to find it

At the back of the lower leg.

Structure

Gastrocnemius and soleus form the main superficial calf mass and contribute to the calcaneal tendon. Gastrocnemius crosses both knee and ankle; soleus crosses the ankle only. Deeper muscles also act on the foot and toes.

How it works

Calf muscles pull through the Achilles tendon, which attaches to the heel. This raises the heel and helps push your body forward. The muscles also contribute to steadiness when standing.

Your feet support you and help you balance. Their bones and arches spread the forces of standing and walking.

Where to find it

Below the ankle, from heel to toes.

Structure

The foot contains tarsals, metatarsals and phalanges arranged into longitudinal and transverse arches. Ligaments, the plantar aponeurosis and muscle activity help maintain these arches as body weight moves across the foot.

How it works

Many bones are arranged into arches, connected by ligaments and muscles. The arches can change slightly as weight moves across the foot. This helps the foot both absorb force and become a firm lever for pushing off.

Your heel is the back part of your foot. A pad of tissue cushions the large heel bone underneath.

Where to find it

At the back of the foot, beneath the ankle.

Structure

The calcaneus forms the heel's bony base. A specialized fibrofatty pad beneath it distributes impact, while the calcaneal tendon attaches posteriorly. The subtalar articulation above contributes to hindfoot movement.

How it works

The calcaneus is the large bone that forms the heel. A pad of soft tissue underneath helps spread pressure against the ground. The Achilles tendon attaches at the back and transfers the pull of the calf muscles.

Your knee joins your thigh to your lower leg. It bends and straightens and helps support your weight.

Where to find it

Between your thigh and lower leg.

Structure

The knee includes tibiofemoral and patellofemoral articulations. Menisci improve contact between femur and tibia; cruciate and collateral ligaments limit excessive displacement. A small amount of rotation accompanies flexion and extension.

How it works

The femur moves against the tibia, with cartilage and two cushioning menisci between them. Ligaments guide the movement. The kneecap slides at the front as the thigh muscles pull to straighten the knee.

Your legs support your body and move you from place to place. Bones and muscles work together when you walk or jump.

Where to find it

Below the pelvis, ending at the foot.

Structure

In anatomical terminology, the leg is the knee-to-ankle region, while the whole lower limb also includes thigh and foot. Its anterior, lateral and posterior muscle compartments act on the ankle and toes.

How it works

The hip, knee and ankle work in a sequence during each step. One leg supports weight while the other swings forward, then they exchange jobs. Muscles also make tiny adjustments to keep your balance.

Your shin is the front of your lower leg. The tibia lies just under the skin in this area.

Where to find it

At the front of the lower leg, between knee and ankle.

Structure

The anterior tibial border is easily palpable because it lies close to the skin. Muscles in the anterior compartment lie mostly lateral to it and dorsiflex the ankle or extend the toes.

How it works

The tibia carries much of the load from the thigh toward the ankle. Its front edge has little soft tissue covering it. Nearby muscles help lift the foot so the toes clear the ground during a step.

Your sole is the bottom of your foot. Its skin feels the ground and helps protect the tissues underneath.

Where to find it

Along the underside of the foot.

Structure

Plantar skin is thick and adapted to repeated loading. Fibrous septa anchor cushioning fat, and the plantar aponeurosis runs beneath deeper structures. Intrinsic foot muscles occupy several layers above this sheet.

How it works

Thick skin and cushioning tissue handle contact with the ground. Sensory endings report pressure, helping your nervous system track where your weight is. Strong tissue beneath the sole helps support the arches.

Your thigh is between your hip and knee. It contains the femur and large muscles that move your leg.

Where to find it

Between the hip and knee.

Structure

The femur supports anterior, medial and posterior muscle compartments. Quadriceps extends the knee, adductors draw the thigh toward the midline, and hamstrings contribute to hip extension and knee flexion.

How it works

The femur forms its strong central support. Quadriceps muscles at the front help straighten the knee, while hamstrings at the back help bend it. Other thigh muscles move the leg toward or away from the body.

Toes are the small digits at the front of your foot. They help with balance and pushing off the ground as you walk.

Where to find it

At the front end of each foot.

Structure

Toes two through five usually have three phalanges; the great toe has two. Flexor and extensor tendons coordinate with intrinsic muscles. The great toe is particularly important during the final phase of stance.

How it works

Small bones and joints let toes bend as your weight moves forward. Muscles and tendons guide that movement. The big toe is particularly useful during push-off at the end of a walking step.

Your brain helps you think, learn, remember and move. It works with nerves and the spinal cord to receive information and send instructions.

Where to find it

Inside the skull, above the spinal cord.

Structure

The brain includes cerebrum, diencephalon, brainstem and cerebellum. Gray matter contains many neuronal cell bodies and synapses; white matter contains major axonal pathways. Meninges and cerebrospinal fluid provide protection and support.

How it works

Billions of nerve cells communicate in connected networks. Different regions contribute to memory, language, movement and sensing, and many tasks involve several regions at once. The brain also helps regulate automatic body functions and keeps working while you sleep.

Your brainstem connects your brain to your spinal cord. It helps control automatic jobs such as breathing.

Where to find it

At the base of the brain, continuing into the spinal cord.

Structure

The midbrain, pons and medulla form the brainstem. Ascending and descending pathways pass through it, alongside cranial nerve nuclei and networks involved in arousal and automatic regulation.

How it works

Nerve pathways pass through it between the brain and body. Groups of cells also help regulate breathing, alertness and swallowing. These jobs continue without you having to plan each individual movement.

The cerebellum is at the lower back of your brain. It helps coordinate movement and balance.

Where to find it

Below the back of the cerebrum, behind the brainstem.

Structure

The cerebellar cortex surrounds white matter and deep nuclei. Connections through three pairs of cerebellar peduncles link it with the brainstem. It compares incoming sensory information with motor-related signals.

How it works

The cerebellum compares information about planned movement with signals from the body. It helps adjust timing and accuracy so movements are coordinated. Practice helps this wider brain network make learned actions smoother.

The cerebrum is the largest part of your brain. It helps with thinking, memory, senses and voluntary movements.

Where to find it

The large upper part of the brain.

Structure

Two cerebral hemispheres contain a folded cortex, underlying white matter and deep nuclei. Major lobes are named frontal, parietal, temporal and occipital; the insula lies deeper within the lateral sulcus.

How it works

Its folded outer layer is called the cerebral cortex. Different areas process sensory information and help plan actions, while deeper structures contribute to memory and movement. The left and right hemispheres communicate through bundles of nerve fibers.

The cochlea is a curled structure in your inner ear. It changes sound vibrations into signals that travel to your brain.

Where to find it

Deep inside the skull, in the inner ear.

Structure

The cochlea contains fluid-filled compartments and the sensory organ of Corti on the basilar membrane. Hair-cell deflection changes electrical signaling, which influences auditory nerve activity. Different positions respond preferentially to different frequencies.

How it works

Vibrations move fluid inside the spiral-shaped cochlea. Movement bends tiny structures on sensory hair cells, triggering signals in the hearing nerve. Different parts of the cochlea respond best to different sound frequencies.

The cornea is the clear front surface of your eye. It helps focus light and protects the front of the eye.

Where to find it

Covering the front of the eye over the iris and pupil.

Structure

The cornea is transparent and normally avascular. Its organized layers and controlled hydration allow light transmission, while sensory nerves provide high sensitivity. The tear film contributes to a smooth anterior optical surface.

How it works

Its clear, curved surface bends incoming light before it reaches the lens. A tear film keeps the surface smooth. The cornea is highly sensitive, so reflexes help protect it from contact and drying.

Your eardrum is a thin membrane inside your ear. Sound makes it vibrate, passing movement to tiny middle-ear bones.

Where to find it

At the inner end of the outer ear canal.

Structure

The tympanic membrane separates the external acoustic canal from the middle ear. Its main tense portion has epithelial, fibrous and mucosal layers. The handle of the malleus attaches to its inner surface.

How it works

Sound waves make the thin membrane move back and forth. It passes those vibrations to the first of three tiny middle-ear bones. These bones carry the movement toward the inner ear.

The iris is the colored part of your eye. It changes the size of the pupil to control how much light enters.

Where to find it

Behind the clear cornea and in front of the lens.

Structure

The iris contains pigmented tissue and smooth muscles controlling the pupil. Circular sphincter fibers constrict the opening, while radial dilator fibers enlarge it. Autonomic pathways regulate these muscles in response to light and other influences.

How it works

Tiny muscles change the diameter of the pupil in the middle. A smaller pupil admits less light in bright conditions; a wider one admits more when light is dim. Pigment contributes to the iris's color.

The lens is a clear structure inside your eye. It changes shape to help focus on near and far objects.

Where to find it

Inside the eye, just behind the iris.

Structure

The lens is enclosed by a capsule and suspended through zonular fibers connected to the ciliary body. Changes in ciliary muscle activity alter zonular tension and lens curvature during accommodation.

How it works

Tiny supporting fibers connect the lens to a ring of muscle. Changes in tension alter its curvature, helping focus light from objects at different distances. It works with the cornea to place a sharp image on the retina.

Nerves carry signals between your central nervous system and the rest of your body. Some signals bring information from your senses; others tell muscles to move.

Where to find it

Branching through your head, torso and limbs.

Structure

Peripheral nerves contain bundles of axons surrounded by connective-tissue layers called endoneurium, perineurium and epineurium. Some axons are myelinated by Schwann cells, supporting faster conduction. A nerve may carry sensory, motor and autonomic fibers.

How it works

A nerve is a bundle of long cell fibers wrapped in supporting tissue. Sensory fibers carry information inward, while motor fibers carry instructions outward. Signals travel electrically along fibers and often cross between cells using chemical messengers.

The pupil is the opening in the center of your iris. It looks dark because light enters the eye through it.

Where to find it

In the center of the iris, at the front of the eye.

Structure

The pupil is a variable aperture within the iris. Light passes through it toward the lens and retina. Changes in its diameter result from iris-muscle activity rather than contraction of the opening itself.

How it works

Light passes through this opening toward the lens and retina. The iris muscles make it wider or narrower. Both pupils normally respond when lighting changes, as the eyes and nervous system work together.

The retina is a light-sensitive layer at the back of your eye. Its special cells help turn light into nerve signals.

Where to find it

Lining the inside back wall of each eye.

Structure

Photoreceptors communicate through retinal circuits with ganglion cells, whose axons form the optic nerve. Cones support detailed daylight vision, while rods contribute strongly in dim light. The fovea is specialized for high visual acuity.

How it works

Rods respond well in dim light, while cones support color vision and fine detail. These cells pass information into retinal nerve circuits. The signals then leave the eye through the optic nerve for further processing.

Your spinal cord is a bundle of nervous tissue inside your spine. Messages travel through it between your brain and body.

Where to find it

Inside the protective canal formed by the vertebrae.

Structure

Central gray matter forms horns surrounded by white-matter tracts. Sensory fibers enter through dorsal roots, and motor fibers leave through ventral roots. In adults, the cord usually ends near the upper lumbar vertebral region.

How it works

Bundles of nerve fibers carry signals upward and downward. Some connections within the cord also produce quick reflex responses. For example, a withdrawal reflex can begin before the brain fully interprets a painful touch.

Alveoli are tiny air sacs in your lungs. Their thin walls allow oxygen and carbon dioxide to move between air and blood.

Where to find it

At the ends of the smallest airways within the lungs.

Structure

Thin type I pneumocytes form much of the gas-exchange surface. Type II pneumocytes produce surfactant and contribute to epithelial renewal. Closely apposed capillary endothelium and supporting layers create a short diffusion path.

How it works

A dense network of capillaries surrounds these tiny sacs. Their moist, thin walls allow gases to cross a very short distance. A substance called surfactant helps keep the sacs from collapsing as air moves out.

Arteries are blood vessels that carry blood away from your heart. Their strong walls handle the pressure created by the heartbeat.

Where to find it

In branching networks leading away from the heart.

Structure

Most arterial walls have intima, media and adventitia. Elastic arteries buffer pulsatile output, while muscular arteries distribute blood and arterioles regulate resistance. Smooth-muscle tone changes vessel caliber and tissue perfusion.

How it works

Stretchy, muscular walls handle pulses of pressure and help control blood distribution. Larger arteries divide into smaller ones before reaching capillaries. Most carry oxygen-rich blood, but arteries going to the lungs carry oxygen-poor blood.

Blood carries oxygen, nutrients and other materials around your body. It also carries cells that fight infection and help stop bleeding.

Where to find it

Inside the heart and blood vessels throughout your body.

Structure

Plasma carries dissolved substances, while red cells, white cells and platelets provide specialized functions. Hemoglobin in red cells binds oxygen. Platelets and coagulation proteins cooperate to form a hemostatic response when vessels are damaged.

How it works

Plasma is the liquid carrying dissolved substances and cells. Red blood cells transport oxygen using hemoglobin, white blood cells help defend the body, and platelets help form clots. Blood also distributes heat as it circulates.

The bronchi are the two main air passages that branch from your windpipe. They divide into smaller passages inside your lungs.

Where to find it

Branching from the trachea into the right and left lungs.

Structure

Main bronchi enter the lungs and branch into lobar and segmental bronchi. Cartilage and smooth muscle support the larger conducting airways. Smaller bronchioles lack cartilage and lead toward respiratory portions of the lung.

How it works

Each main bronchus enters a lung and divides repeatedly. Smaller bronchi lead to bronchioles and eventually to air sacs. Supporting tissue and airway muscles help maintain and adjust the passages.

Capillaries are tiny blood vessels with very thin walls. Oxygen, nutrients and wastes pass between blood and body tissues here.

Where to find it

In tiny networks within most body tissues.

Structure

A capillary wall consists mainly of endothelium and its basal lamina. Continuous, fenestrated and sinusoidal capillaries have different permeability characteristics. Their large collective surface area and short diffusion distances facilitate exchange.

How it works

Their very thin walls put blood close to cells. Materials move across these walls according to local conditions: oxygen and nutrients can enter tissues, while carbon dioxide and other wastes enter blood. Capillaries connect the arterial and venous sides of circulation.

The diaphragm is a broad muscle below your lungs. When it contracts, it helps draw air into your lungs.

Where to find it

Separating the chest from the abdomen, below the lungs.

Structure

The diaphragm has a central tendon and muscular attachments to the sternum, ribs and lumbar region. The phrenic nerves supply its motor function. Openings transmit the inferior vena cava, esophagus and aorta at different levels.

How it works

This dome-shaped muscle flattens when it contracts. The chest cavity becomes larger, pressure falls and air moves into the lungs. When it relaxes, the chest becomes smaller and air can move out.

Your heart is a muscular organ that pumps blood. The right side sends blood to your lungs; the left side sends it around your body.

Where to find it

In the chest between the lungs, with its tip pointing toward your left.

Structure

Four chambers are separated by septa and connected through valves. The right ventricle supplies pulmonary circulation; the left ventricle supplies systemic circulation. The myocardium receives its own blood supply through the coronary vessels.

How it works

Four chambers fill and squeeze in a coordinated pattern. The upper chambers receive blood and the lower chambers pump it out. Valves keep it moving forward, and an electrical signal sets the rhythm. The heart muscle has its own blood supply through coronary arteries.

The larynx is your voice box, above your windpipe. Its vocal folds vibrate to make sounds when you speak.

Where to find it

In the neck, above the trachea.

Structure

The laryngeal framework includes thyroid, cricoid and arytenoid cartilages. Intrinsic muscles adjust vocal-fold position and tension. The glottis includes the vocal folds and the space between them.

How it works

Air from the lungs passes between the vocal folds. When the folds are brought close together, airflow makes them vibrate. Muscles adjust their tension and position, changing the voice's pitch and helping protect the airway.

Your lungs help your body take in oxygen and release carbon dioxide. Air travels into tiny air sacs, where these gases move between air and blood.

Where to find it

On either side of the heart, inside the rib cage.

Structure

The right lung usually has three lobes and the left two. Pleural membranes surround each lung, while branching airways conduct air toward respiratory surfaces. Pulmonary vessels carry blood for gas exchange; bronchial vessels nourish supporting tissues.

How it works

Airways branch into smaller tubes ending in air sacs. Oxygen passes across the air-sac walls into surrounding capillaries, while carbon dioxide moves the other way. The diaphragm and chest muscles move air; the lungs themselves are not breathing muscles.

The trachea, or windpipe, carries air toward your lungs. Rings of cartilage help keep it open.

Where to find it

Down the front of the neck into the upper chest.

Structure

C-shaped hyaline cartilage supports the anterior and lateral walls. The posterior wall contains trachealis muscle adjacent to the esophagus. Ciliated epithelium and mucus contribute to clearance of inhaled material.

How it works

C-shaped cartilage supports the airway so it stays open. Its lining traps particles in mucus, and tiny moving cilia help carry the mucus upward. At the bottom, the windpipe splits into the main bronchi.

Veins are blood vessels that carry blood toward your heart. Many veins have valves that help blood flow in one direction.

Where to find it

In networks returning blood from tissues toward the heart.

Structure

Veins generally have thinner walls and larger lumens than comparable arteries. Their capacitance allows them to hold a substantial fraction of circulating blood. Limb valves and surrounding muscle activity help return blood against gravity.

How it works

Small veins collect blood from capillaries and join into larger vessels. In many parts of the body, valves and the squeezing of nearby muscles help blood return. The pulmonary veins bring oxygen-rich blood from the lungs.

The anus is the opening where stool leaves your body. Rings of muscle help control when stool passes out.

Where to find it

At the end of the digestive tract, below the pelvis.

Structure

The anal canal ends at the external opening. Internal smooth-muscle and external skeletal-muscle sphincters provide different forms of control. The lining changes along the canal, as do aspects of sensory supply and drainage.

How it works

Inner and outer rings of muscle help keep the opening closed between bowel movements. Nerve signals coordinate relaxation when stool passes. Some of this control is automatic and some is learned voluntary control.

Your appendix is a small pouch attached to the beginning of your large intestine. It contains immune tissue and may help support useful gut bacteria.

Where to find it

Attached near the beginning of the large intestine, usually in the lower right abdomen.

Structure

The vermiform appendix arises from the cecum and has a narrow lumen surrounded by gut-wall layers and prominent lymphoid tissue. Its exact position varies, often extending behind or below the cecum.

How it works

This narrow, closed-ended pouch contains lymphoid tissue, which participates in immune activity. Researchers also study its possible role as a sheltered place for helpful gut microbes. It is not a main food-digestion chamber.

Your esophagus is the tube from your throat to your stomach. Its muscles squeeze food along, even when you are not standing up.

Where to find it

From the throat down through the chest to the stomach.

Structure

The esophageal wall contains mucosa, submucosa and muscle layers that coordinate peristalsis. Its upper region contains skeletal muscle, transitioning toward smooth muscle below. It passes through the diaphragm to reach the stomach.

How it works

Waves of muscle contraction, called peristalsis, push a swallowed mouthful downward. Muscular rings at the ends help control entry and exit. Gravity can assist, but coordinated squeezing is the key movement.

Your gallbladder is a small pouch beneath your liver. It stores bile and releases it into the small intestine.

Where to find it

Beneath the liver in the upper right abdomen.

Structure

The gallbladder has a folded mucosa and a muscular wall. It concentrates stored bile by absorbing water and electrolytes. Its cystic duct connects with the biliary tree, allowing filling and emptying.

How it works

This small pouch stores and concentrates bile made by the liver. When food enters the small intestine, signals can make the gallbladder squeeze. Bile then travels through ducts to help break fats into small droplets.

Your intestines are long tubes that continue digestion after the stomach. The small intestine absorbs most nutrients, while the large intestine absorbs water and forms stool.

Where to find it

Coiled within the abdomen, continuing from the stomach toward the rectum.

Structure

The intestinal wall generally includes mucosa, submucosa, muscular layers and an outer covering. Enteric neural circuits coordinate secretion and movement. Small and large intestines differ in diameter, mucosal architecture and predominant roles.

How it works

The small intestine finishes much chemical digestion and absorbs nutrients. The large intestine handles much of the remaining material, taking up water and forming stool. Muscular walls keep contents moving along both sections.

Your large intestine absorbs water from material left after digestion. It helps turn the remaining material into stool.

Where to find it

Around much of the small intestine, continuing toward the rectum.

Structure

The large intestine includes cecum, colon, rectum and anal canal. Its mucosa contains abundant goblet cells and lacks the villi characteristic of the small intestine. Colonic movement supports water recovery and fecal transport.

How it works

Its lining absorbs water and salts from remaining material. Gut microbes also act on some undigested substances. The contents become more solid as muscle movements guide them toward storage and removal.

Your liver processes nutrients and makes bile to help digest fats. It also stores some nutrients and changes many substances in your blood.

Where to find it

In the upper right abdomen, mostly beneath the ribs.

Structure

Liver tissue is organized around hepatocytes, sinusoids and bile drainage pathways. Blood arrives through both the portal vein and hepatic artery. Hepatocytes process absorbed nutrients, synthesize plasma proteins and modify many endogenous and external substances.

How it works

The liver receives blood carrying absorbed nutrients from the gut. It changes, stores or releases many of these materials and produces important blood proteins. It also makes bile and processes many substances so the body can use or remove them.

Your pancreas makes digestive enzymes and hormones. Its enzymes help break down food, and insulin helps control blood sugar.

Where to find it

Across the upper abdomen, behind the stomach.

Structure

Exocrine acini produce digestive enzymes, and ducts provide bicarbonate-rich fluid to the duodenum. Endocrine islets release hormones into blood, including insulin from beta cells and glucagon from alpha cells.

How it works

One part sends digestive enzymes through a duct into the small intestine. Other cells release hormones into the blood, including insulin and glucagon. Those hormones help regulate how glucose is used and stored.

Your rectum is the last section of your large intestine. It holds stool before it leaves your body.

Where to find it

At the end of the large intestine, inside the pelvis.

Structure

The rectum follows the sigmoid colon and lies within the pelvis before the anal canal. Its wall can accommodate temporary filling. Distension activates sensory pathways involved in the defecation reflex.

How it works

Its wall stretches when stool arrives. Nerves signal that it is filling, and muscles coordinate with the anal sphincters when stool is passed. It is mainly a temporary holding area rather than a place of digestion.

Salivary glands make saliva in and around your mouth. Saliva moistens food and starts breaking down starch.

Where to find it

Around the cheeks and jaw and beneath the tongue, with smaller glands in the mouth lining.

Structure

The parotid, submandibular and sublingual glands form the major paired glands, supplemented by many minor glands. Acini produce secretion, and ducts modify and deliver it. Saliva includes water, electrolytes, mucus and protective components.

How it works

Glands release saliva through ducts into the mouth. It softens food, contains an enzyme that begins starch digestion and helps keep oral surfaces moist. The amount can increase when you smell or think about food.

Your small intestine breaks food down further and absorbs most nutrients. Its folded inner surface gives nutrients lots of space to enter the body.

Where to find it

Between the stomach and large intestine, coiled in the abdomen.

Structure

The duodenum, jejunum and ileum form the small intestine. Circular folds, villi and microscopic brush-border projections expand the absorptive surface. Capillaries and lymphatic lacteals transport absorbed substances through different routes.

How it works

Digestive juices mix with food here. Folds and tiny projections called villi create a broad absorbing surface. Nutrients cross the lining into blood or lymph so they can reach body cells.

Your stomach stores food briefly and mixes it with digestive juices. Its muscles churn food before it moves into the small intestine.

Where to find it

In the upper abdomen, mostly on your left, below the diaphragm.

Structure

The stomach includes cardia, fundus, body and pyloric region. Its mucosal glands contain several cell types, including acid-secreting parietal cells and enzyme-precursor-secreting chief cells. Multiple muscle layers support mixing.

How it works

Muscle layers squeeze and mix a meal with acid and enzymes, beginning much of protein digestion. A protective lining helps shield the stomach wall. Food leaves gradually through the pylorus as a soft mixture called chyme, entering the small intestine.

Your bladder is a stretchy organ that stores urine. When it fills, nerves send messages that you need to urinate.

Where to find it

Low in the pelvis, behind the pubic bones.

Structure

Urothelium lines the bladder and accommodates changing volume. The detrusor smooth muscle forms its muscular wall. The trigone is bounded by the two ureteric openings and the internal urethral opening.

How it works

Its wall stretches as urine arrives and contracts to help empty it. Nerves monitor filling, while muscles around the outlet help hold urine in. Brain signals coordinate when it is time to release it.

Your kidneys filter blood and make urine. They remove wastes and help balance water and salts in your body.

Where to find it

Toward the back of the upper abdomen, on either side of the spine.

Structure

The cortex and medulla contain nephrons and collecting pathways. Filtration begins at glomeruli, followed by selective tubular reabsorption and secretion. Urine drains through calyces into the renal pelvis and ureter.

How it works

Microscopic units called nephrons first filter small substances and water from blood. Their tubules then return much of what the body needs to the blood. The remaining fluid becomes urine. This careful sorting helps regulate water, salts and acid balance.

Ureters are the tubes that carry urine from the kidneys to the bladder. Muscles in their walls help move urine along.

Where to find it

Running from each kidney down to the bladder.

Structure

Each ureter is a muscular tube lined by urothelium. Peristaltic waves propel urine from the renal pelvis toward the bladder. The oblique passage through the bladder wall helps limit backward flow during filling.

How it works

Each tube has a muscular wall that squeezes in waves. These movements propel urine toward the bladder. The way the tubes enter the bladder helps limit urine flowing backward.

The urethra is the tube through which urine leaves your body. It leads from the bladder to an opening outside the body.

Where to find it

From the bladder outlet to an opening outside the body.

Structure

The urethra carries urine from the bladder to the external opening. Its length, surrounding tissues and subdivisions differ between typical male and female anatomy. In male anatomy, it also provides a passage for semen at a different time.

How it works

The urethra provides urine with its final exit route. Sphincter muscles help control that exit. Its length and route vary with anatomy; in a penis it also carries semen at different times after puberty.

Bone marrow is soft tissue found inside many bones. Red marrow makes blood cells.

Where to find it

In spaces inside many bones.

Structure

Red marrow contains hematopoietic cells within a supporting vascular environment. Yellow marrow contains a larger fat component. Distribution changes with age, with adult active marrow concentrated particularly in parts of the axial skeleton and proximal long bones.

How it works

Blood-forming stem cells in red marrow give rise to red cells, many white cells and platelets. Yellow marrow contains more stored fat. The proportions and locations change as a child grows.

Cartilage is firm, flexible connective tissue. It cushions many joints and gives shape to parts such as your nose.

Where to find it

At many joint surfaces and in structures such as the nose and outer ear.

Structure

Chondrocytes maintain an extracellular matrix rich in water and structural molecules. Hyaline, elastic and fibrocartilage have different fiber compositions. Cartilage generally lacks its own blood vessels, relying on diffusion for nutrition.

How it works

Cartilage cells maintain a firm, water-rich supporting material. Its smooth joint surfaces spread pressure and reduce friction. Elsewhere it forms a flexible framework that bends more easily than bone.

Your clavicle is your collarbone. It connects the breastbone to the shoulder blade.

Where to find it

Across the top front of the chest, between sternum and shoulder.

Structure

The clavicle links the sternum with the acromion of the scapula. Its curved shaft acts as a strut that holds the shoulder away from the chest. Several ligaments stabilize its medial and lateral joints.

How it works

The collarbone acts as a brace that holds the shoulder away from the chest. It transfers forces from the arm toward the trunk while allowing the shoulder complex to move. Muscles and ligaments attach along it.

Your femur is the bone in your thigh. It is the longest bone in the human body.

Where to find it

Inside the thigh, between hip and knee.

Structure

The femur has a proximal head and neck, trochanters for muscle attachment, a shaft and distal condyles. Its head articulates with the acetabulum, while the distal end participates in the knee.

How it works

The rounded upper end fits into the hip socket, while the lower end meets the tibia at the knee. A strong outer layer surrounds inner bone tissue and marrow. Muscle attachments make it a lever for walking.

The fibula is the thinner bone on the outer side of your lower leg. It helps stabilize your ankle and provides places for muscles to attach.

Where to find it

Along the outer side of the lower leg.

Structure

The fibula articulates with the tibia at both ends and forms the lateral malleolus distally. Its shaft provides muscle attachments. It does not articulate with the femur as part of the main knee joint.

How it works

This slender bone provides attachment points for muscles and ligaments. Its lower end forms the outer ankle bump and helps keep the ankle joint aligned. It carries much less body weight than the tibia.

Your humerus is the bone in your upper arm. It joins your shoulder at one end and your elbow at the other.

Where to find it

Inside the upper arm.

Structure

The humeral head articulates with the scapula. Tubercles provide attachment for rotator-cuff muscles, while the distal trochlea and capitulum articulate with ulna and radius. The shaft has close relationships with major nerves.

How it works

Its rounded head fits into the shoulder joint, and its lower end helps form the elbow. Muscles attach at different points so they can lift, rotate or bend the arm. The shaft supports the space between the joints.

A joint is a place where bones meet. Some joints move freely, while others move little or not at all.

Where to find it

Where two or more bones meet.

Structure

Joints can be classified structurally as fibrous, cartilaginous or synovial. Synovial joints contain articular cartilage, a cavity, synovial lining and a capsule. Joint shape and soft-tissue constraints determine permitted motion.

How it works

Freely moving joints often have cartilage-covered surfaces inside a capsule containing lubricating fluid. Ligaments help guide the movement. Other joints, such as skull sutures, are built mainly for strong connections.

A ligament is a strong band of tissue that commonly joins bone to bone. It helps keep a joint stable.

Where to find it

Around joints and in some other supporting locations.

Structure

Ligaments commonly connect bones and constrain joint motion. Their collagen bundles are arranged according to local mechanical demands; some also contain substantial elastic fibers. Sensory endings contribute information about joint position and strain.

How it works

Strong fibers limit excessive movement and help bones stay aligned. They provide stability without preventing all motion. Sensory endings in ligaments also contribute information about the joint's position.

Muscles are tissues that contract to produce force. They move your body, pump blood and push food through your digestive tract.

Where to find it

Throughout your body: around the skeleton, in organs and in the heart.

Structure

Skeletal muscle contains striated fibers under somatic motor control. Cardiac muscle is striated with specialized cell connections, while smooth muscle lacks visible striations. All use interactions between contractile proteins to generate force.

How it works

Muscle cells shorten when their internal proteins slide past one another. Skeletal muscles pull on bones, smooth muscles move materials inside organs, and cardiac muscle pumps blood. These muscle types differ in how they are controlled.

The patella is your kneecap, at the front of your knee. It protects the joint and helps your thigh muscles straighten your leg.

Where to find it

At the front of the knee, within the quadriceps tendon.

Structure

The patella is a sesamoid bone embedded in the quadriceps tendon. Its posterior articular surface glides against the femur. The patellar ligament continues from it toward the tibial tuberosity.

How it works

The kneecap moves along a groove in the femur as the knee bends and straightens. It changes the angle of the tendon so the thigh muscles can pull effectively. Its position also shields the front of the joint.

Your pelvis is a ring of bones at the base of your spine. It supports organs and connects your spine to your legs.

Where to find it

At the base of the trunk, between the spine and thigh bones.

Structure

Each hip bone develops from ilium, ischium and pubis. Together with the sacrum, the paired bones form a ring transmitting load between spine and lower limbs. The acetabula receive the femoral heads.

How it works

The hip bones connect with the sacrum to form a strong ring. This arrangement transfers body weight toward the legs. It also provides attachment points for muscles and surrounds organs in the lower trunk.

The radius is one of the two bones in your forearm. It lies on the thumb side when your palms face forward.

Where to find it

On the thumb side of the forearm when the palm faces forward.

Structure

The radius has a disc-shaped proximal head and a broader distal end contributing substantially to the wrist. It articulates with the ulna proximally and distally. The interosseous membrane links the shafts.

How it works

The radius joins the humerus near the elbow and helps form the wrist at its lower end. It can rotate around the ulna to turn the palm. That motion is useful for turning a page or holding a bowl.

Your ribs are curved bones in your chest. Together with the breastbone and spine, they help protect your heart and lungs.

Where to find it

Curving around the chest from the spine.

Structure

Most people have twelve pairs of ribs. The first seven pairs attach to the sternum through their own costal cartilages; the next three attach indirectly, while the final two lack anterior sternal attachment.

How it works

Most ribs connect to the breastbone through cartilage, either directly or indirectly. Muscles between them help lift and lower the rib cage. This gives the lungs protection while allowing breathing movements.

Your scapula is your shoulder blade, a flat bone in your upper back. It helps form the shoulder joint and anchors many muscles.

Where to find it

Over the back of the upper ribs.

Structure

The scapular spine separates supraspinous and infraspinous fossae posteriorly. The glenoid cavity articulates with the humeral head, while acromion and coracoid processes provide attachment and leverage points.

How it works

A shallow socket at its outer corner receives the head of the humerus. Muscles move the shoulder blade around the rib cage and stabilize it during reaching. This makes the arm's range of motion larger.

Your skull is a group of bones that gives your head its shape. It surrounds and protects your brain.

Where to find it

Around the brain and forming much of the face.

Structure

The neurocranium surrounds the brain, while the facial skeleton supports the face and its cavities. Most skull bones meet at sutures. Openings in the cranial base transmit nerves and vessels between compartments.

How it works

Flat and irregular bones meet at strong joints called sutures. Their arrangement forms a hard protective case while leaving openings for nerves and blood vessels. Facial bones support the eyes, nose and jaws.

Your spine is a column of bones called vertebrae. It supports your body, lets your back bend and protects your spinal cord.

Where to find it

From the base of the skull down to the pelvis.

Structure

The vertebral column includes cervical, thoracic, lumbar, sacral and coccygeal regions. Intervertebral discs and paired facet joints permit controlled motion between many adjacent vertebrae. Ligaments support alignment and limit excessive movement.

How it works

Individual vertebrae stack together, with discs between many of them. Joints and ligaments guide controlled bending and twisting. Openings through the vertebrae form a canal around the spinal cord.

The sternum is your breastbone in the middle of your chest. Many ribs connect to it through cartilage.

Where to find it

At the center front of the rib cage.

Structure

The sternum consists of manubrium, body and xiphoid process. Costal cartilages attach along its sides, and the clavicles articulate superiorly. The sternal angle marks the manubriosternal junction.

How it works

This flat bone joins the collarbones above and receives cartilage connections from many ribs. Together they form the front of the chest's protective framework. Its broad surface also provides muscle attachments.

A tendon is strong connective tissue that usually connects muscle to bone. It transfers the pull of a muscle to move a body part.

Where to find it

Between many muscles and the bones they move.

Structure

Tendons contain dense, predominantly parallel collagen bundles organized to transmit tension. Cells maintain the matrix, and connective-tissue coverings permit gliding or integration with neighboring structures. Some tendons pass through synovial sheaths.

How it works

Bundles of strong collagen fibers carry tension from a contracting muscle to an attachment point. Some tendons are long enough to transmit force over a joint or into a finger. They move with the muscle's pull.

The tibia is the larger bone in your lower leg. It carries much of your weight between your knee and ankle.

Where to find it

On the inner side of the lower leg, below the knee.

Structure

The tibial plateau supports the femoral condyles through the menisci. The tibial tuberosity receives the patellar ligament, and the distal medial malleolus forms part of the ankle mortise.

How it works

The wide top receives weight from the femur, and the lower end meets the ankle. Its strong shaft transfers force between these joints. It works with the fibula and surrounding muscles to support the leg.

The ulna is one of the two bones in your forearm. Its upper end forms the bony point of your elbow.

Where to find it

On the little-finger side of the forearm when the palm faces forward.

Structure

The olecranon and coronoid process frame the proximal trochlear notch that articulates with the humerus. The distal ulna is smaller and separated from the carpal bones by an articular disc.

How it works

Its upper end hooks around part of the humerus, forming much of the elbow hinge. It gives the forearm a stable framework while the radius rotates. Muscles and connective tissues link the two bones.

Your adrenal glands sit above your kidneys. They make hormones that help with stress responses and salt balance.

Where to find it

One above each kidney.

Structure

The cortex has zones that produce mineralocorticoids, glucocorticoids and androgens. The medulla contains chromaffin cells that release catecholamines. These regions have distinct tissue organization and regulatory inputs.

How it works

An outer cortex and inner medulla make different hormones. These help regulate salt balance, energy use and responses to stress. Adrenaline can help prepare the body for rapid action, alongside signals from the nervous system.

The hypothalamus is a small region near the base of your brain. It helps control body temperature, hunger, thirst and hormone signals.

Where to find it

At the base of the brain, above the pituitary.

Structure

Hypothalamic nuclei surround part of the third ventricle and connect with autonomic, endocrine and behavioral pathways. The region communicates with the pituitary through vascular and neural routes. Different nuclei contribute to different homeostatic functions.

How it works

It receives information about the body's internal condition and helps organize responses. These include thirst, hunger, temperature regulation and hormone control. It connects nervous-system signals with endocrine messages.

Lymph nodes are small structures found along lymph vessels. They filter lymph fluid and contain immune cells.

Where to find it

Along lymph vessels, including in the neck, armpits and groin.

Structure

Lymph enters through afferent vessels, passes through sinuses and leaves through efferent vessels near the hilum. Cortical follicles, paracortical regions and medullary areas organize different immune-cell populations.

How it works

Lymph fluid passes through internal spaces containing immune cells. These cells can recognize foreign material and help start a defense response. Many nodes work together as part of the body's immune network.

Lymph vessels carry lymph fluid through the body. They return extra tissue fluid to the bloodstream and support immune defenses.

Where to find it

Branching through many tissues, alongside parts of the circulatory network.

Structure

Blind-ended lymphatic capillaries collect interstitial fluid. Larger collecting vessels contain valves and transport lymph through nodes toward major ducts that drain into veins. Intestinal lacteals also carry absorbed dietary lipids.

How it works

They collect fluid that has left small blood vessels and remains between cells. One-way valves, muscle movements and breathing help it move along. The fluid eventually returns to the bloodstream near the neck.

Parathyroid glands are small glands usually behind the thyroid. Their hormone helps control the amount of calcium in your blood.

Where to find it

Usually on the back of the thyroid gland.

Structure

Usually four small glands lie near the posterior thyroid, although number and position vary. Chief cells secrete parathyroid hormone in response to calcium-related signals. Its actions involve kidney, bone and vitamin D pathways.

How it works

These small glands release parathyroid hormone when blood calcium needs adjustment. The hormone influences bones, kidneys and indirectly the gut to help restore balance. Calcium is important for muscle and nerve activity as well as bones.

The pineal gland is a small gland in your brain. It makes melatonin, which helps signal nighttime to your body.

Where to find it

Near the center of the brain.

Structure

The pineal gland lies in the epithalamic region near the roof of the third ventricle. Pinealocytes secrete melatonin, with timing influenced by light-related signals transmitted through a multisynaptic neural pathway.

How it works

The pineal gland releases melatonin in a daily pattern influenced by light-dark signals reaching the brain. This helps tell body systems when it is nighttime. It is one part of a larger body-clock network.

The pituitary gland is a tiny gland at the base of your brain. Its hormones help control growth and several other glands.

Where to find it

Beneath the brain, connected to the hypothalamus.

Structure

The anterior pituitary is glandular tissue that secretes several hormones under hypothalamic regulation. The posterior pituitary stores and releases oxytocin and vasopressin synthesized in hypothalamic neurons. The gland sits in the sella turcica.

How it works

This small gland releases hormones that affect growth, reproduction and other endocrine glands. The hypothalamus helps direct its activity. Feedback from the body adjusts hormone release so messages match changing needs.

Your spleen is an organ in the upper left part of your abdomen. It filters blood and helps your immune system respond to germs.

Where to find it

High in the left abdomen, near the stomach.

Structure

Splenic red pulp filters blood and helps remove aging red cells. White pulp contains organized immune tissue associated with vessels. A connective-tissue capsule and internal framework support these regions.

How it works

Blood passes through tissue that removes worn-out blood cells and helps monitor for germs. Immune cells inside can respond to signs of infection. Other organs can take over many of its jobs if it is removed.

The thymus is an organ behind your breastbone. It helps certain immune cells, called T cells, mature during childhood.

Where to find it

Behind the breastbone, especially prominent in childhood.

Structure

The thymus contains lobules with cortical and medullary regions. Developing T cells undergo selection that supports useful immune recognition while limiting harmful self-reactivity. Its proportion of active tissue changes substantially with age.

How it works

Developing T cells enter the thymus and go through selection steps. This helps build cells that can recognize useful defense targets while limiting harmful reactions to the body itself. The organ becomes smaller after childhood.

Your thyroid is a small gland at the front of your neck. Its hormones help set how quickly your body uses energy.

Where to find it

At the front of the lower neck, wrapped around the windpipe.

Structure

Thyroid follicles contain colloid and epithelial cells that synthesize thyroid hormones using iodine. Parafollicular cells form a different endocrine population. The gland is usually arranged as two lobes joined by an isthmus.

How it works

The thyroid releases hormones that influence how cells use energy. Signals from the pituitary help regulate its activity. Thyroid hormones are also important for growth and development, so their effects reach well beyond the neck.

Your tonsils are patches of immune tissue near the back of your throat. They help your body notice germs entering through your mouth and nose.

Where to find it

Near the back of the throat and in nearby tissue.

Structure

Palatine, pharyngeal and lingual tonsillar tissues help form a ring around the pharyngeal entrance. Lymphoid tissue lies close to surface epithelium, permitting interaction with material entering the mouth and nose.

How it works

Their location lets immune tissue sample material entering through the nose and mouth. Immune cells can respond to signs of infection. Tonsils are one part of a larger defense system, not the body's only protection.

Breasts include fat, connective tissue and mammary glands. Mammary glands can make milk after pregnancy.

Where to find it

On the front of the chest, over the chest muscles.

Structure

Mammary tissue includes lobes, smaller lobules and a duct system opening at the nipple. Fat and fibrous connective tissue contribute to shape and support. Glandular development and activity respond to hormonal conditions.

How it works

Fat and connective tissue give support around gland tissue and ducts. Hormones influence development during puberty and pregnancy. When milk is produced, ducts carry it toward openings at the nipple.

The cervix is the lower, narrow part of the uterus. It opens into the vagina.

Where to find it

At the lower end of the uterus, where it meets the vagina.

Structure

The cervix contains a canal connecting the uterine cavity with the vagina. Glandular epithelium lines much of the canal, while squamous epithelium covers the vaginally exposed surface. Cervical mucus changes with hormonal conditions.

How it works

A narrow canal passes through the cervix. Its glands make mucus whose properties change with hormone signals. During childbirth, the opening can widen as part of the process that allows birth through the vagina.

The clitoris is a sensitive part of the vulva with many nerve endings. Most of this organ lies inside the body.

Where to find it

At the front of the vulva, with much of its structure extending internally.

Structure

The clitoral glans is the visible portion of a larger erectile organ. Its body and paired crura extend internally and attach along the pubic region. Rich sensory innervation supports its role in sexual sensation.

How it works

A small external portion is partly covered by a fold of skin. The larger internal structure includes sensitive tissue and many nerve endings. It is an anatomical body part, separate from the opening used for urination.

Fallopian tubes connect the area near the ovaries to the uterus. An egg cell can travel through a tube toward the uterus.

Where to find it

Extending from the upper uterus toward the ovaries.

Structure

Each uterine tube has an infundibulum with fimbriae, an ampulla, an isthmus and a uterine portion. Ciliated lining and smooth-muscle activity support transport. The ovarian end opens into the peritoneal cavity near the ovary.

How it works

Fingerlike ends help guide a released egg toward a tube. Tiny cilia and muscular movement move it along. If fertilization occurs, it usually begins in a tube before the developing cells travel to the uterus.

Ovaries are reproductive organs in the pelvis that contain egg cells. They also make hormones involved in puberty and reproduction.

Where to find it

Usually one on either side of the uterus in the pelvis.

Structure

The ovarian cortex contains follicles at different stages of development, while the medulla contains supportive tissue and vessels. Follicular cells participate in hormone production, and the corpus luteum forms after ovulation.

How it works

Ovaries contain follicles with developing egg cells. After puberty, hormonal signals can guide a follicle's growth and the release of an egg during a cycle. Ovarian hormones also influence changes elsewhere in the body.

The penis is an external body part that contains part of the urethra. Urine passes through the urethra to leave the body.

Where to find it

On the outside of the body, in front of the scrotum in people who have this anatomy.

Structure

The penis contains paired corpora cavernosa and a corpus spongiosum surrounding the urethra. The spongiosum expands distally into the glans. Changes in blood inflow and outflow influence erectile tissue volume.

How it works

The urethra runs through the penis to carry urine out. It also contains nerves, blood vessels and tissue that can fill with blood. After puberty, semen can leave through the urethra at a different time from urine.

The placenta is a temporary organ that develops during pregnancy. It allows oxygen and nutrients to pass from the pregnant person's blood to the developing baby without their blood normally mixing.

Where to find it

Attached to the inside of the uterus during pregnancy.

Structure

Fetal chorionic villi interact with maternal blood in an exchange space, while fetal blood remains within its vessels. The organ also produces hormones that support pregnancy. The umbilical cord links fetal circulation with placental vessels.

How it works

Tiny branching structures bring the developing baby's blood close to the pregnant person's blood supply. Oxygen, nutrients and wastes cross between them through thin tissues. The umbilical cord links the baby with this temporary organ.

The prostate is a gland below the bladder in people who have it. It makes fluid that becomes part of semen after puberty.

Where to find it

Below the bladder, surrounding the first part of the urethra in people who have it.

Structure

The prostate surrounds the proximal male urethra below the bladder. Glandular tissue and fibromuscular stroma form distinct anatomical zones. Secretions enter the urethra through prostatic ducts and contribute to seminal fluid.

How it works

This gland makes some of the fluid that combines with sperm and other fluids to form semen. Its muscles help move that fluid during ejaculation after puberty. Its location links it closely to the urinary passage.

The scrotum is the pouch of skin that holds the testes. It helps keep them at a suitable temperature.

Where to find it

Below the penis, outside the pelvis.

Structure

The scrotal wall contains skin and dartos smooth muscle, with deeper coverings related to the testes and spermatic cords. Cremaster muscle activity changes testicular position. A septum separates the two sides.

How it works

Its skin and underlying muscles can tighten or relax, changing how close the testes sit to the body. This helps regulate temperature. It also provides an outer covering around the testes.

Testes are reproductive organs usually held in the scrotum. From puberty onward, they make sperm and produce hormones including testosterone.

Where to find it

Usually inside the scrotum, outside the main body cavity.

Structure

Seminiferous tubules contain developing germ cells supported by Sertoli cells. Leydig cells in the interstitial tissue produce testosterone. Sperm pass onward through connecting ducts toward the epididymis for further maturation.

How it works

After puberty, tiny coiled tubes produce sperm cells. Other cells produce testosterone, which influences development and several body functions. The surrounding scrotum helps regulate the temperature for these organs.

The uterus is a muscular reproductive organ in the pelvis. During pregnancy, a baby can develop inside it.

Where to find it

In the pelvis, between the bladder and rectum in people who have it.

Structure

The uterine wall includes endometrium, thick myometrium and an outer covering. Its body and fundus lie above the cervix. Endometrial tissue changes during the menstrual cycle under hormonal influence.

How it works

The uterus has a thick muscular wall and a lining that changes during menstrual cycles. If pregnancy develops, the lining supports implantation and the muscular organ grows. Without pregnancy, part of the lining can leave during menstruation.

The vagina is a muscular passage from the cervix to the outside of the body. It is an internal reproductive part, separate from the urethra.

Where to find it

Inside the pelvis, between the cervix and an external opening in the vulva.

Structure

The vaginal wall contains a folded mucosa, smooth muscle and an outer connective-tissue layer. The cervix projects into its upper end, creating surrounding recesses called fornices. Anteriorly, it is related to the bladder and urethra.

How it works

Its flexible muscular walls have a moist lining. Menstrual fluid can pass through it, and it can form the birth passage during vaginal delivery. The urinary tract is separate, even though its opening is nearby.

The vulva is the name for the external female genital parts. It includes the labia and clitoris and surrounds the vaginal and urethral openings.

Where to find it

On the outside of the body, around the vaginal and urethral openings.

Structure

The vulva includes the mons pubis, labia majora and minora, clitoris and vestibule. The vestibule contains the urethral and vaginal openings. Glands and erectile tissues contribute to lubrication and sexual function.

How it works

The labia are folds that help protect delicate openings and tissue. The clitoris is another part of this region. Size, color and shape vary naturally, just as they do in other body regions.