Digestive System – Vocabulary Review

Comprehensive vocabulary flashcards covering key anatomical structures, physiological processes, regulatory mechanisms, accessory organs, and clinical terms related to the digestive system as presented in the lecture notes.

Digestive System

Body system that takes in food, breaks it into nutrient molecules, absorbs them into the bloodstream, and eliminates indigestible remains.

Alimentary Canal (GI Tract)

Continuous muscular tube from mouth to anus that digests food and absorbs nutrients; includes mouth, pharynx, esophagus, stomach, small and large intestines, anus.

Accessory Digestive Organs

Structures that aid digestion by mechanical means or secretions; teeth, tongue, salivary glands, liver, gallbladder, pancreas.

Ingestion

The act of taking food into the mouth and alimentary canal.

Propulsion

Movement of food along the GI tract, including swallowing and peristalsis.

Peristalsis

Rhythmic waves of contraction and relaxation of smooth muscle that propel food through the digestive tract.

Segmentation

Non-adjacent contractions in the small intestine that mix food and digestive juices and enhance absorption.

Mechanical Digestion

Physical processes that break food into smaller pieces: chewing, churning, segmentation.

Chemical Digestion

Enzymatic breakdown of food molecules into their building blocks.

Absorption

Passage of digested nutrients from the GI lumen into blood or lymph.

Defecation

Elimination of indigestible wastes as feces via the anus.

Peritoneum

Serous membrane of the abdominal cavity consisting of parietal and visceral layers.

Visceral Peritoneum

Layer of peritoneum covering the external surfaces of most abdominal organs.

Parietal Peritoneum

Layer of peritoneum that lines the abdominal body wall.

Peritoneal Cavity

Fluid-filled space between parietal and visceral peritoneum that lubricates mobile organs.

Mesentery

Double layer of peritoneum that suspends digestive organs, providing blood-vessel and nerve routes and fat storage.

Intraperitoneal Organs

Digestive organs located within the peritoneal cavity.

Retroperitoneal Organs

Digestive organs positioned posterior to the peritoneum (e.g., pancreas, duodenum parts, portions of large intestine).

Peritonitis

Inflammation of the peritoneum, often from infection or abdominal injury; can be life-threatening.

Mucosa

Innermost tunic of the GI tract; secretes mucus, enzymes, hormones; absorbs nutrients; protects against infection.

Submucosa

Connective-tissue layer of GI tract containing blood vessels, lymphatics, and the submucosal nerve plexus.

Muscularis Externa

GI tunic with inner circular and outer longitudinal smooth muscle layers responsible for peristalsis and segmentation.

Serosa

Visceral peritoneum forming the outermost covering of intraperitoneal GI organs; replaced by adventitia in the esophagus.

Splanchnic Circulation

Arterial branches (celiac, mesenteric) and hepatic portal circulation supplying and draining digestive organs.

Enteric Nervous System (ENS)

“Gut brain” of the GI tract; intrinsic neurons regulating motility, secretion, and blood flow.

Submucosal Nerve Plexus

ENS plexus that regulates glandular secretion and muscularis mucosa activity.

Myenteric Nerve Plexus

ENS plexus between circular and longitudinal muscle layers controlling GI motility.

Short Reflex

Digestive reflex mediated entirely by ENS plexuses responding to local GI stimuli.

Long Reflex

Digestive reflex involving CNS integration (vagus or sympathetic fibers) in response to internal or external stimuli.

Gastrin

Hormone from stomach enteroendocrine cells that stimulates gastric acid secretion and motility.

Secretin

Duodenal hormone that stimulates pancreatic bicarbonate secretion and increases bile production.

Cholecystokinin (CCK)

Duodenal hormone that triggers release of enzyme-rich pancreatic juice, bile ejection, and sphincter relaxation.

Mouth (Oral Cavity)

Entry to GI tract where food is ingested, chewed, mixed with saliva, and swallowing begins.

Tongue

Skeletal-muscle organ that grips, repositions, and mixes food; forms bolus; aids swallowing, speech, taste.

Salivary Glands

Parotid, submandibular, and sublingual glands that produce saliva for lubrication, taste, and starch digestion.

Saliva

Mostly water secretion containing electrolytes, amylase, lingual lipase, mucin, IgA, lysozyme, and defensins.

Teeth

Calcified structures in alveoli that perform mastication.

Enamel

Hardest substance in the body; calcium-phosphate crystal layer covering tooth crown.

Dentin

Bone-like material forming bulk of tooth beneath enamel.

Pulp Cavity

Central space in a tooth containing blood vessels, nerves, and connective tissue (pulp).

Gingivae (Gums)

Dense irregular connective tissue with epithelium that surrounds tooth necks.

Dental Caries

Cavities caused by bacterial demineralization of enamel and dentin.

Gingivitis

Reversible inflammation of gums due to plaque and calculus formation.

Periodontitis

Advanced gum disease destroying periodontal ligament and bone, potentially causing tooth loss.

Pharynx

Muscular tube (oro- and laryngopharynx) that conveys food from mouth to esophagus.

Esophagus

Muscular tube from pharynx to stomach; collapsed when empty; conducts food by peristalsis.

Esophageal Hiatus

Opening in the diaphragm through which the esophagus passes.

Superior Esophageal Sphincter

Skeletal-muscle closure at pharynx-esophagus junction that stays closed during inhalation.

Inferior Esophageal (Gastroesophageal) Sphincter

Smooth-muscle ring that prevents stomach reflux into esophagus with aid from diaphragm.

Heartburn

Pain from gastric acid regurgitating into the esophagus; first symptom of GERD.

Deglutition

Swallowing process involving voluntary buccal phase and involuntary pharyngeal-esophageal phase.

Stomach

J-shaped organ that stores food, initiates protein digestion, and converts bolus to chyme.

Rugae

Large folds of the stomach mucosa that allow expansion after a meal.

Pyloric Sphincter

Valve regulating chyme passage from stomach into duodenum.

Gastric Pits

Mucosal depressions in stomach housing gastric glands that secrete gastric juice.

Parietal Cells

Gastric gland cells that secrete hydrochloric acid and intrinsic factor.

Chief Cells

Gastric gland cells that release pepsinogen and gastric lipase.

Enteroendocrine Cells

Gastric (and intestinal) cells releasing hormones or paracrines such as gastrin, histamine, serotonin.

Intrinsic Factor

Parietal-cell glycoprotein required for intestinal absorption of vitamin B12.

Pepsinogen

Inactive precursor of pepsin; activated by HCl to begin protein digestion.

Chyme

Creamy mixture of partially digested food and gastric juice exiting the stomach.

Mucosal Barrier

Protective layer of bicarbonate-rich mucus, tight junctions, and rapid cell turnover that shields stomach lining.

Cephalic Phase

Reflex gastric secretion phase triggered by sight, smell, taste, or thought of food.

Gastric Phase

Phase of gastric secretion initiated by stomach distension and peptides; mediated mainly by gastrin.

Intestinal Phase

Regulation phase where chyme entering duodenum first stimulates then inhibits gastric activity.

Gastritis

Inflammation of the stomach mucosa, often from barrier breach.

Peptic Ulcer

Erosion of stomach or duodenal wall, commonly caused by Helicobacter pylori or NSAIDs.

Liver

Largest gland; produces bile, processes nutrients, stores vitamins, detoxifies blood.

Bile

Yellow-green alkaline fluid containing bile salts, bilirubin, cholesterol, and phospholipids that emulsifies fats.

Gallbladder

Muscular sac under liver that stores and concentrates bile, releasing it via the cystic duct.

Pancreas

Retroperitoneal gland producing enzyme-rich pancreatic juice (exocrine) and hormones insulin and glucagon (endocrine).

Pancreatic Juice

Watery, alkaline (pH 8) secretion containing enzymes (proteases, amylase, lipase, nucleases) and bicarbonate.

Trypsin

Active pancreatic protease generated from trypsinogen by enteropeptidase; activates other proteases.

Enteropeptidase (Enterokinase)

Brush-border enzyme that converts trypsinogen to trypsin in the duodenum.

Hepatopancreatic Sphincter

Muscular valve controlling bile and pancreatic juice entry into the duodenum.

Small Intestine

Primary site of digestion and absorption; divided into duodenum, jejunum, and ileum.

Duodenum

First 25 cm of small intestine receiving chyme, bile, and pancreatic juice.

Jejunum

Middle section of small intestine, major region for nutrient absorption.

Ileum

Distal small intestine ending at ileocecal valve; absorbs bile salts and vitamin B12.

Circular Folds (Plicae Circulares)

Permanent folds of mucosa and submucosa that slow chyme and increase surface area.

Villi

Fingerlike mucosal projections containing blood capillaries and a lacteal for absorption.

Microvilli (Brush Border)

Microscopic membrane extensions of enterocytes bearing brush-border enzymes for final digestion.

Enterocytes

Simple columnar absorptive cells of intestinal villi; also secrete intestinal juice in crypts.

Goblet Cells

Mucus-secreting epithelial cells abundant in intestinal crypts and large intestine.

Paneth Cells

Intestinal crypt cells that secrete antimicrobial defensins and lysozyme.

Peyer’s Patches

Large lymphoid follicles in ileum mucosa that guard against intestinal pathogens.

Ileocecal Valve

Sphincter controlling flow from ileum to cecum of large intestine.

Large Intestine

Terminal GI segment that absorbs water, electrolytes, vitamins, and forms feces.

Cecum

Blind pouch of large intestine receiving chyme from ileum; bears the appendix.

Colon

Major portion of large intestine: ascending, transverse, descending, sigmoid segments.

Rectum

Straight intestinal segment storing feces; contains rectal valves separating gas from feces.

Anal Canal

Last 3 cm of GI tract; opens to exterior; contains internal and external sphincters.

Teniae Coli

Three longitudinal ribbons of smooth muscle in colon muscularis that create haustra.

Haustra

Pouch-like sacs of the colon formed by tonic contractions of the teniae coli.

Epiploic Appendages

Small fat-filled pouches of visceral peritoneum projecting from colon surfaces.

Bacterial Flora

Community of gut microbes that ferment undigested carbs, synthesize vitamins B and K, and crowd out pathogens.

Haustral Contractions

Segmental slow movements of the colon that mix and propel fecal matter.

Gastrocolic Reflex

Long reflex triggered by stomach filling that initiates mass movements in the colon.

Defecation Reflex

Parasympathetic spinal reflex triggered by rectal distension; contracts colon, relaxes internal sphincter.

Diarrhea

Watery stools from insufficient water absorption; can cause dehydration and electrolyte loss.