Crash Course : Digestive system Part 3

Small Intestine

Primary site of chemical digestion and nutrient absorption; consists of duodenum, jejunum, ileum.

Duodenum

First segment of small intestine; receives chyme, bile, and pancreatic juice; site of most chemical digestion.

Jejunum

Middle segment of small intestine; main site of nutrient absorption.

Ileum

Final segment of small intestine; absorbs B12 and bile salts; ends at ileocecal valve.

Villi & Microvilli

Finger-like projections and microscopic folds in small intestine that massively increase surface area for absorption.

Liver

Accessory organ that produces bile for fat emulsification.

Bile

Secretion from liver (stored in gallbladder); contains bile salts that emulsify dietary fats.

Gallbladder

Pear-shaped sac that stores, concentrates, and releases bile into duodenum.

Pancreas

Accessory organ that secretes digestive enzymes and bicarbonate into duodenum.

Pancreatic Enzymes

Include amylase (carbs), trypsin (proteins), lipase (fats); secreted by pancreas to complete digestion

Bicarbonate

Alkaline secretion from pancreas that neutralizes acidic chyme in duodenum.

Large Intestine (Colon)

Organ that absorbs water and electrolytes; houses bacterial flora; forms and stores feces.

Intestinal Flora

Bacteria in colon that ferment indigestible fiber, producing gases and some vitamins.

Rectum

Final section of large intestine that temporarily stores feces.

Defecation Reflex

Spinal reflex triggered by rectal stretch; leads to expulsion of feces.

Lactose Intolerance

Inability to digest lactose due to lack of lactase enzyme; causes gas, bloating, diarrhea.

Ileocecal Valve

Sphincter between ileum and cecum; regulates flow into large intestine.

Chyme

Semi-fluid mass of partly digested food that enters duodenum from stomach.

CCK (Cholecystokinin)

Hormone that stimulates gallbladder contraction and pancreatic enzyme secretion.