The Digestive System Lecture Review

Flashcards covering the anatomy, histology, physiology, and hormonal regulation of the human digestive system based on Chapter 24 of Tortora and Derrickson's 16th edition.

Gastrointestinal (GI) Tract

A long tube open at both ends for the transit of food during processing; includes the esophagus, stomach, small intestine, large intestine, and rectum.

Accessory Structures

Components not part of the GI tract that contribute to food processing, including the teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Ingestion

The process of taking food into the mouth.

Motility

The mixing and propulsion of food and secretions through the GI tract.

Defecation

The elimination of feces from the GI tract through the anus.

Mucosa

The innermost layer of the GI tract, consisting of an epithelium, lamina propria, and muscularis mucosae.

Myenteric Neural Plexus

A part of the enteric nervous system located in the muscular layer that regulates gastrointestinal motility.

Peritoneum

The largest serous membrane in the body.

Salivary Amylase

An enzyme produced by salivary glands that splits starch into smaller fragments like maltose, maltotriose, and $\alpha-dextrins$.

Lingual Lipase

An enzyme secreted by lingual glands in the tongue that breaks down triglycerides into fatty acids and diglycerides.

Mastication

The mechanical process of chewing, where food is mixed with saliva to form a bolus.

Deglutition

The act of swallowing, consisting of voluntary, pharyngeal, and esophageal stages.

Peristalsis

The esophageal stage of deglutition involving waves of muscular contraction that push a bolus toward the stomach.

Gastroesophageal Reflux Disease (GERD)

A condition occurring when the lower esophageal sphincter fails to close adequately, causing stomach contents to reflux into the esophagus.

Chyme

The semi-fluid mixture of saliva, food, and gastric juice formed in the stomach.

Parietal Cells

Stomach cells that secrete intrinsic factor (for vitamin $B_{12}$ absorption) and hydrochloric acid ($HCl$).

Chief Cells

Stomach cells that secrete pepsinogen, the precursor to pepsin, and gastric lipase.

G Cells

Enteroendocrine cells in the stomach that secrete the hormone gastrin into the blood.

Pepsin

An enzyme, activated from pepsinogen by $HCl$, that breaks down proteins into peptides.

Sodium Bicarbonate

A substance produced by the pancreas that buffers acidic stomach acid in the duodenum.

Hepatocytes

The primary functional cells of the liver involved in metabolism, secretory, and endocrine functions.

Emulsification

The breakdown of large lipid globules into a suspension of small lipid globules, aided by bile salts.

Bilirubin

A waste product from hemoglobin breakdown that is excreted in bile and partially eliminated in feces.

Circular Folds

Folds of the mucosa and submucosa in the small intestine that increase surface area for digestion and absorption.

Villi

Fingerlike projections of the small intestine mucosa that serve as sites for the absorption of digested food.

Microvilli

Microscopic, membrane-covered projections of absorptive epithelial cells that form the brush border and contain enzymes.

Segmentation

Localized, alternating contractions of circular smooth muscle in the small intestine that mix chyme with digestive juices.

Migrating Motility Complex (MMC)

A type of peristalsis in the small intestine consisting of waves of contraction that move chyme toward the ileal orifice.

Haustra

The series of pouches that characterize the colon.

Mass Peristalsis

A strong peristaltic wave beginning in the transverse colon that quickly drives contents into the rectum.

Gastrin

A hormone stimulated by stomach distension or high pH that promotes gastric juice secretion and increases gastric motility.

Secretin

A hormone stimulated by acidic chyme in the duodenum that induces the secretion of pancreatic juice and bile rich in $HCO_3^-$.

Cholecystokinin (CCK)

A hormone stimulated by amino acids and fatty acids in the small intestine that causes ejection of bile and secretion of enzyme-rich pancreatic juice.

Gluconeogenesis

The synthesis of new glucose molecules in the liver to provide energy for neurons.