Digestive System Lecture Notes Flashcards

A set of vocabulary flashcards covering the anatomy, physiology, and pathophysiology of the human digestive system based on lecture notes.

Digestion

The process of dissolving and breaking down macromolecules into small molecules.

Secretion

The release of substances such as bile, digestive enzymes, water, ions, and mucus into the GI tract.

Absorption

The movement of digestion products, water, vitamins, and minerals from the lumen across epithelial cells into the blood or lymph.

Motility

Contractions of smooth muscle in the GI tract wall to mix and move luminal contents.

Mucosa

The innermost layer of the GI tract wall containing the epithelium, lamina propria, and muscularis mucosa.

Submucosal nerve plexus

A network of neurons in the submucosa that influences secretory activity.

Myenteric nerve plexus

A network of neurons in the muscularis externa that influences smooth muscle activity.

SGLT

The transporter used for secondary active transport of glucose and galactose coupled to $\text{Na}^+$ into epithelial cells.

Pepsin

An enzyme in the stomach that breaks proteins into peptide fragments, secreted as the zymogen pepsinogen from chief cells.

Micelles

Structures formed by fatty acids, monoglycerides, and bile salts that keep fat digestion products in solution until they can be absorbed.

Chylomicrons

Vesicles containing resynthesized triglycerides (approximately $1\,\mu\text{m}$ in diameter) that are released into the interstitial fluid and enter lacteals.

Ferritin

The cellular storage protein that binds iron ions within intestinal epithelial cells.

Intrinsic factor

A protein produced by stomach parietal cells required for the absorption of Vitamin $\text{B}_{12}$ in the ileum via endocytosis.

Enteric Nervous System (ENS)

A local autonomic nervous system within the GI tract consisting of the myenteric and submucosal plexuses.

Gastrin

A hormone produced in the antrum of the stomach that stimulates stomach acid secretion and motility, as well as ileum motility and large intestine mass movement.

Cholecystokinin (CCK)

A small intestine hormone stimulated by amino and fatty acids that triggers gallbladder contraction, pancreatic enzyme secretion, and relaxation of the Sphincter of Oddi.

Secretin

A small intestine hormone stimulated by acidity that triggers $\text{HCO}_3^-$ secretion from the pancreas and liver bile ducts.

Glucose-dependent Insulinotropic Peptide (GIP)

A small intestine hormone stimulated by glucose and fat that stimulates pancreatic insulin secretion.

Cephalic phase

The phase of gastrointestinal control initiated by receptors in the head, including sight, smell, taste, and chewing.

Enterohepatic circulation

The process where approximately $95\%$ of bile salts are absorbed in the ileum and returned to the liver via the portal vein.

Parietal cells

Gastric gland cells responsible for secreting $\text{HCl}$ and intrinsic factor using $\text{H}^+/\text{K}^+\text{-ATPases}$.

Enterokinase

An enzyme located on intestinal epithelial cells that activates trypsinogen to trypsin.

Segmentation

Stationary contractions and relaxations of the small intestine initiated by interstitial cells of Cajal for mixing chyme.

Migrating Myoelectrical Complex (MMC)

Peristaltic activity initiated by motilin that moves undigested material and bacteria into the large intestine after segmentation stops.

Bilirubin

A bile pigment derived from the breakdown of heme; its accumulation in the blood results in jaundice.

Helicobacter pylori

The bacteria primarily responsible for the breakdown of the GI mucosa leading to ulcers.

Cystic Fibrosis (CF)

A condition caused by mutations in the CFTR gene leading to decreased pancreatic $\text{HCO}_3^-$ secretion and thickened secretions that clog ducts.

Steatorrhea

The presence of fat in feces, often occurring when gallstones prevent bile from entering the duodenum.

Pernicious anemia

A Vitamin $\text{B}_{12}$ deficiency caused by a failure to secrete intrinsic factor or removal of the stomach or ileum.