01 / Location & anatomical relationships
Between the stomach and large intestine, coiled in the abdomen.
02 / Structure & organization
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.
03 / Function
Its folded inner surface gives nutrients lots of space to enter the body.
04 / Mechanism
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.
Working together: digestive system
Teeth break food into pieces, the stomach mixes it, and the small intestine absorbs nutrients. Your blood then carries these nutrients around your body.
Meet this body system →FOR DEEPER STUDY
Connect structure with function
Many water-soluble nutrients enter portal blood; much absorbed dietary lipid travels first through intestinal lymph. Segmental mixing and peristaltic movement support contact with the lining.
Check your understanding
Locate the small intestine in relation to its neighbors. Explain how the structural features described above support its function, then distinguish it from a nearby structure with a different role.
Keep learning
Further reading: NIDDK: Your Digestive System & How It Works.
Continue with OpenStax Anatomy and Physiology for system-level study. This atlas is educational and has not undergone independent medical peer review.