Human Digestion and Absorption - Vocabulary

Vocabulary flashcards covering human digestion, tissue organization, GI tract anatomy, digestive enzymes, hormones, absorption mechanisms, and related gastrointestinal disorders.

Filiform Papillae

Structures located on the human tongue that help sense food and texture.

Cell

The smallest functional unit of the human body, possessing the ability to grow, absorb nutrients, use energy, conduct metabolic and physiological functions, and excrete waste.

Adenosine Triphosphate (ATP)

The usable cellular energy form created when the body transforms energy from carbohydrates, proteins, and lipids.

Epithelial Tissue

Human tissue made of cells that cover both internal and external body surfaces.

Connective Tissue

Human tissue that supports and protects body structures, with examples including tendons, cartilage, and bone.

Muscle Tissue

Human tissue designed to contract and relax to allow bodily movement.

Nervous Tissue

Human tissue found in the brain and spinal cord that transmits nerve impulses throughout the body.

Organ System

A combination of several organs working together to perform a specific physiological function.

Microbiota

The population of microorganisms inhabiting the gastrointestinal tract that assist in digestion, support immunity, and synthesize essential vitamins.

GI Tract (Alimentary Canal)

A long, hollow, muscular tube measuring approximately $15\,\text{ft}$ from the mouth to the anus through which nutrients pass to be absorbed.

Mucosa

The innermost layer of the GI tract wall composed of epithelial cells and glands, surrounding the hollow central space called the lumen.

Submucosa

The second layer of the GI tract wall containing blood vessels that carry absorbed nutrients to the rest of the body.

Muscle Layer (GI Tract)

A double-layered muscular coat in the GI tract wall responsible for propelling food forward.

Serosa

The outermost protective tissue layer of the gastrointestinal tract.

Sphincters

Ring-like muscles that open and close to control the flow of contents through various sections of the GI tract.

Lower Esophageal Sphincter

The sphincter located between the esophagus and stomach that prevents the reflux of acidic stomach contents into the esophagus.

Pyloric Sphincter

The sphincter located between the stomach and small intestine that controls the passage of chyme into the small intestine.

Sphincter of Oddi

The sphincter controlling the release of bile from the common bile duct and pancreatic juice into the small intestine.

Ileocecal Valve

The valve connecting the small intestine to the large intestine that prevents large intestine contents from reentering the small intestine.

Anal Sphincters

Sphincters under voluntary and involuntary control that prevent defecation until a person desires to do so.

Peristalsis

Coordinated waves of muscle contraction and relaxation that squeeze, shorten, and propel food forward along the GI tract.

Segmentation

A back-and-forth muscular contraction occurring primarily in the small intestine that breaks apart and mixes chyme with digestive secretions.

Mass Movements

Peristaltic waves occurring over widespread regions of the large intestine to push fecal matter toward the rectum.

Digestive Enzymes

Proteins produced by salivary glands, stomach, pancreas, and small intestine that catalyze hydrolysis reactions to split large food molecules into absorbable units.

Lysozyme

An enzyme present in saliva that destroys bacteria to protect the body from oral pathogens.

Salivary Amylase

An enzyme in saliva that begins starch breakdown by digesting approximately $5\%$ of ingested starch into simple sugars.

Lingual Lipase

A digestive enzyme produced in the mouth that initiates fat breakdown.

Umami

The fifth basic taste sensation triggered by savory taste receptors sensitive to amino acid compounds, such as those found in fresh chicken.

Epiglottis

A flap of tissue that closes over the larynx during swallowing to prevent food from entering the trachea.

Gastric Juice

An acidic fluid produced by the stomach (approximately $8\,\text{cups/day}$) containing hydrochloric acid, intrinsic factor, pepsinogen, gastric lipase, and gastrin.

Gastrin

A hormone produced in the stomach that stimulates parietal and chief cells to release hydrochloric acid (HCl) and pepsinogen.

Hydrochloric Acid (HCl)

Stomach acid produced by parietal cells that inactivates ingested proteins, destroys microbes, dissolves minerals, and converts pepsinogen to active pepsin.

Pepsin

An active protein-digesting enzyme in the stomach converted from pepsinogen by hydrochloric acid.

Intrinsic Factor

A protein produced by stomach parietal cells that is essential for Vitamin B12 absorption in the terminal ileum.

Ghrelin

A hormone secreted by the stomach that increases appetite, rising before meals and dropping after eating.

Chyme

A watery, acidic mixture created in the stomach when swallowed food bolus is combined with gastric secretions.

Enterocytes

Intestinal absorptive epithelial cells lining the villi of the small intestine that secrete enzymes and absorb nutrients.

Glycocalyx

A enzyme-containing carbohydrate layer covering the microvilli brush border on intestinal enterocytes.

Bile

A cholesterol-containing digestive fluid produced by the liver and stored in the gallbladder that emulsifies fat into micelles.

Enterohepatic Circulation

The recycling process wherein bile salts are reabsorbed in the ileum and transported back to the liver via the portal vein.

Cholecystokinin (CCK)

A hormone secreted by the small intestine in response to fat in chyme that triggers pancreatic enzyme secretion and gallbladder contraction.

Secretin

A hormone released by the small intestine in response to acidic chyme that stimulates the pancreas to secrete sodium bicarbonate.

Passive Diffusion

Nutrient transport moving down a concentration gradient without energy or carrier proteins, used for fats, water, and select minerals.

Facilitated Diffusion

Nutrient transport down a concentration gradient using a carrier protein without expending energy, used for fructose absorption.

Active Absorption (Active Transport)

Nutrient transport requiring energy (ATP) and a carrier protein to move nutrients against a concentration gradient, used for amino acids and glucose.

Endocytosis

An absorptive mechanism where the cell membrane engulfs fluid or particles to form an intracellular vesicle.

Hepatic Portal Vein System

The blood vessel network that transports water-soluble nutrients absorbed from the small intestine directly to the liver.

Lacteals

Lymphatic vessels inside intestinal villi that absorb long-chain fatty acids and fat-soluble vitamins for delivery to the thoracic duct.

Probiotics

Live microorganisms (bacteria or yeast) found in fermented foods or supplements that colonize the large intestine and offer health benefits.

Prebiotics

Nondigestible carbohydrate fibers (such as inulin and resistant starch) that serve as food to foster the growth of beneficial gut bacteria.

Gastroesophageal Reflux Disease (GERD)

A chronic condition defined by stomach acid refluxing into the esophagus two or more times per week.

Peptic Ulcer

An erosion of the top epithelial tissue layer in the stomach or duodenum, commonly caused by H. pylori infection or heavy NSAID use.

Gallstones

Crystalline structures composed of cholesterol and bile pigments that form in the gallbladder due to impaired motility or altered bile composition.

Irritable Bowel Syndrome (IBS)

A functional gastrointestinal disorder marked by irregular bowel habits, abdominal pain, and distention without structural inflammation.

Inflammatory Bowel Disease (IBD)

A group of serious chronic inflammatory conditions, including Ulcerative Colitis and Crohn's disease, involving recurring mucosal inflammation and ulceration.

Crohn's Disease

A type of Inflammatory Bowel Disease characterized by patchy, full-thickness inflammation and ulcers anywhere along the entire GI tract.

Ulcerative Colitis

A type of Inflammatory Bowel Disease causing continuous inflammation and ulceration restricted to the innermost layer of the large intestine.