Module 3: Digestion and Absorption — Vocabulary Flashcards

Vocabulary flashcards covering key terms from the lecture notes on digestion and absorption.

Digestion

The multistep process that breaks down food into smaller absorbable components through mechanical and chemical means within the GI tract.

Absorption

The uptake of nutrients from the GI lumen into the circulatory and/or lymphatic systems for transport to body tissues.

Gastrointestinal (GI) tract

The organs and structures involved in digestion, from the mouth to the anus, including accessory organs.

Bolus

A ball of chewed food mixed with saliva formed in the mouth and swallowed.

Chyme

The semifluid mass of partly digested food expelled from the stomach into the small intestine.

Mechanical digestion

Physical breakdown of food by chewing, grinding, segmentation, and peristalsis.

Chemical digestion

Chemical breakdown of food by enzymes and digestive secretions into absorbable molecules.

Segmentation

Rhythmic contractions in the small intestine that mix chyme with digestive juices to enhance contact with the intestinal walls.

Pendular movement

Constrictive waves in the small intestine that aid nutrient absorption.

Peristalsis

The forward, rhythmic movement that propels food through the GI tract.

Small intestine

The long, narrow, coiled portion where most digestion and absorption occur; consists of the duodenum, jejunum, and ileum.

Duodenum

The first section of the small intestine where chyme mixes with bile and pancreatic enzymes, initiating major chemical digestion.

Jejunum

The middle portion of the small intestine where most nutrient absorption occurs.

Ileum

The final portion of the small intestine where absorption continues and bile acids and vitamin B12 are absorbed.

Circular folds

Deep folds in the small intestine lining that increase surface area for absorption.

Villi

Fingerlike projections on the intestinal mucosa that increase surface area and contain blood and lymph vessels.

Microvilli

Tiny projections on the surface of villi that further increase absorptive surface area.

Lacteal

A lymphatic capillary inside a villus that absorbs fats and fat-soluble nutrients.

Blood capillaries

Small blood vessels in the villi that absorb water-soluble nutrients into the circulatory system.

Hepatic portal vein

The blood vessel that carries nutrient-rich blood from the GI tract to the liver for processing.

Liver

The largest internal organ; produces bile, metabolizes nutrients, stores vitamins/minerals, and detoxifies substances.

Gallbladder

Stores and concentrates bile and releases it into the small intestine when fat is present.

Pancreas

Produces digestive enzymes and bicarbonate; also secretes hormones like insulin and glucagon.

Bile

A digestive fluid produced by the liver and stored in the gallbladder that emulsifies fats.

Bicarbonate

Alkaline fluid released by the pancreas to neutralize stomach acid in chyme.

Amylase

Enzyme that digests carbohydrates; found in saliva and pancreatic juice.

Lipase

Enzyme that digests fats; produced by the pancreas.

Proteases

Enzymes that digest proteins (e.g., trypsin, chymotrypsin, carboxypeptidase).

Pepsin

Protein-digesting enzyme activated by HCl in the stomach.

Hydrochloric acid (HCl)

Acid in the stomach that activates pepsin and helps digest proteins.

Intrinsic factor

A stomach-secreted protein essential for vitamin B12 absorption in the small intestine.

Gastrin

Hormone that stimulates HCl secretion and promotes gastric motility and emptying.

Ghrelin

Hormone that stimulates hunger; produced mainly by the stomach.

Secretin

Hormone that stimulates the pancreas to release bicarbonate to neutralize stomach acid.

Cholecystokinin (CCK)

Hormone that stimulates pancreatic enzyme secretion and slows gastric emptying.

Gastric lipase

Enzyme in the stomach that begins fat digestion.

Pyloric sphincter

Valve between the stomach and small intestine that controls chyme entry.

Ileocecal sphincter

Valve between the ileum and cecum that prevents backflow of chyme.

Lower esophageal sphincter (LES)

Muscular ring at the esophagus-stomach junction that prevents reflux.

Gastroesophageal reflux disease (GERD)

Chronic reflux of stomach acid into the esophagus, causing heartburn.

Enterohepatic circulation

Recycling of bile acids from the intestine back to the liver.

Endocytosis

Process by which cells engulf whole molecules for absorption (less common in the small intestine).