The Digestive System Practice Flashcards

Flashcards covering the overview, anatomy, physiology, and regulation of the human digestive system including organs, histology, functions, and specific digestion of the digestion and absorption of major nutrients.

Alimentary Canal

A continuous passage through which food moves, also known as the gastrointestinal (GI) or digestive tract, including the oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine.

Accessory Organs

Organs that assist in digestion but are not part of the continuous alimentary canal, including teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Ingestion

The process where food and water are brought into the mouth.

Propulsion

The movement of food and liquids from one organ to the next through rhythmic contractions of smooth muscle called peristalsis.

Peristalsis

Rhythmic contractions of the alimentary canal's smooth muscle that move food and liquids forward.

Mechanical Digestion

The physical breakdown of food into smaller pieces, such as through chewing and mixing by muscle movements in the GI tract.

Chemical Digestion

The process where enzymes catalyze reactions that break chemical bonds within food particles.

Absorption

The movement of nutrients, water, electrolytes, and vitamins through the wall of the alimentary canal into blood or lymphatic vessels.

Parietal Peritoneum

The outer layer of the largest serous membrane in the body that lines the inner surface of the body wall.

Visceral Peritoneum

An inner layer of peritoneum, also called serosa, that forms the outer tissue layer of the abdominal organs.

Peritoneal Cavity

The space between the parietal and visceral peritoneum layers containing serous fluid to lubricate moving organs.

Mesenteries

Folds of the visceral peritoneum that bind organs together, provide shape, and house lymphatic vessels, blood vessels, and nerves.

Peritonitis

Inflammation of the peritoneum resulting from substances like blood or organ contents leaking into the peritoneal cavity, often treated with antibiotics and surgery.

Splanchnic Circulation

A collection of vessels including the celiac trunk, mesenteric arteries, and hepatic portal vein that supply and drain the abdominal digestive organs.

Enteric Nervous System (ENS)

A self-contained branch of the autonomic nervous system that supplies the alimentary canal to control secretions and movement.

Mucosa

The innermost layer of the alimentary canal consisting of epithelium, lamina propria, and muscularis mucosae.

Submucosa

A layer of dense irregular connective tissue containing blood vessels, lymphatic vessels, and the submucosal plexus of the ENS.

Muscularis Externa

A layer of the alimentary canal usually consisting of inner circular and outer longitudinal smooth muscle regulated by the myenteric plexus.

Long Reflexes

Nervous system regulations of the digestive process that must travel to the Central Nervous System (CNS) to function.

Short Reflexes

Nervous system regulations where the pathways are limited to local neurons of the Enteric Nervous System (ENS).

Bolus

A moist, chewed mass of ingested food turned by the teeth, tongue, and saliva.

Mastication

The process of chewing and grinding ingested food into smaller pieces using the teeth and muscles like the masseter and temporalis.

Enamel

The hardest substance in the body, made of calcium hydroxyapatite crystals, which covers the crown of a tooth.

Dentin

The elastic tissue under the enamel that is about $70\%$ hydroxyapatite crystals and is made throughout life by odontoblasts.

Pulp Cavity

The inner portion of a tooth composed of loose connective tissue, blood vessels, and nerves, extending into the root via the root canal.

Salivary Amylase

An enzyme in saliva that catalyzes the beginning of carbohydrate digestion.

Lysozyme

An antimicrobial enzyme in saliva that catalyzes the perforation of bacterial plasma membranes.

Deglutition

A specialized type of propulsion, also known as swallowing, that pushes a bolus from the oral cavity to the stomach.

Rugae

Folds in the interior of the stomach that allow it to expand considerably when eating.

Chyme

A liquid created by the rhythmic churning and chemical digestion of food in the stomach.

Parietal Cells

Gastric gland cells that secrete hydrochloric acid ($HCl$) and intrinsic factor.

Chief Cells

Gastric gland cells that secrete pepsinogen, the precursor for the protein-digesting enzyme pepsin.

G Cells

Diffuse neuroendocrine system (DNES) cells that secrete the hormone gastrin to stimulate acid secretion.

Cephalic Phase

The phase of acid secretion, responsible for $30\text{--}40\%$ of stomach acid, triggered by the sight, smell, taste, or thought of food.

Gastric Phase

The phase of acid secretion, responsible for $50\text{--}60\%$ of stomach acid, that begins when food enters and distends the stomach.

Intestinal Phase

The phase of acid secretion, responsible for $10\%$ of stomach acid, triggered when partially digested proteins enter the duodenum.

Gastroesophageal Reflux Disease (GERD)

A chronic condition where acidic chyme regurgitates into the esophagus, potentially causing pain and vocal cord damage.

Enterocytes

The epithelial cells of the small intestine that produce digestive enzymes, hormones, and mucus, and absorb nutrients.

Duodenum

The first segment of the small intestine, approximately $25\,cm$ long, where secretions from the gallbladder and pancreas enter.

Villi

Mucosal folds in the small intestine containing enterocytes, goblet cells, and lacteals to increase surface area for absorption.

Microvilli

Folds of the enterocyte’s plasma membrane that form the brush border and contain digestive enzymes.

Migrating Motor Complex

Slow, rhythmic contractions during fasting that clear leftover food and secretions from the small intestine.

Cholecystokinin (CCK)

A hormone produced by the duodenum that causes the gallbladder to contract and the pancreas to secrete digestive enzymes.

Secretin

A hormone triggered by low $pH$ in the duodenum that inhibits gastric acid secretion and stimulates bicarbonate release.

Haustra

Pockets in the large intestine formed by the bunching of the taeniae coli ribbons of muscle.

Normal Flora

A symbiotic group of about $500$ bacterial species in the large intestine that produce vitamins and deter harmful bacteria.

Pancreatic Juice

A collective secretion of acinar and duct cells consisting of water, digestive enzymes, and bicarbonate ions.

Hepatocytes

Liver cells arranged in hexagon-shaped lobules that produce bile and process nutrients.

Emulsification

The process where bile salts coat lipids and physically break them into smaller pieces to increase surface area for enzymes.

Bilirubin

A waste product from the breakdown of hemoglobin by the spleen that is secreted into bile by hepatocytes.

Hydrolysis Reactions

Chemical reactions that use a water molecule to break a chemical bond, utilized by most digestive enzymes.

Chylomicrons

Packages of triglycerides, cholesterol, and apoproteins that are released by enterocytes into lacteals during lipid absorption.

Intrinsic Factor

A substance produced by parietal cells of the stomach required for the intestinal absorption of vitamin $B_{12}$.