Anatomy for Nutrition's Sake and Digestion

Vocabulary flashcards covering human cellular structure, gastrointestinal organs, digestive enzymes, motility, nutrient absorption pathways, metabolism, and common GI disorders.

Essential Nutrients

Nutrients required for normal body functioning that cannot be synthesized by the body and must be supplied by the foods we eat.

Gastrointestinal (GI) Tract

The continuous muscular tube of the digestive system through which food travels, consisting of the mouth, esophagus, stomach, small intestine, and large intestine.

Mesentery

The outer layer of the GI tract that protects blood vessels, nerves, and lymphatic vessels, and prevents the intestines from twisting.

Mucosa

The innermost mucous membrane layer of the GI tract wall that secretes gastric juices, digestive enzymes, and protective mucus.

Submucosa

The layer of connective tissue in the GI tract wall containing blood vessels, lymphatic vessels, nerves, and lymphoid tissue.

Muscularis Externa

The muscle layer of the GI tract containing two layers of smooth muscle (longitudinal and circular) responsible for GI motility.

Serosa

The outer connective tissue cover that protects the GI tract.

Salivary Amylase

An enzyme in saliva, also known as ptyalin, that begins the chemical breakdown of complex carbohydrates by hydrolyzing $\alpha (1\text{-}4)$ bonds in starch.

Lingual Lipase

An enzyme secreted in the salivary glands that begins the chemical breakdown of fats in the mouth.

Bolus

A soft mass of swallowed food created by chewing and mixing food with saliva in the mouth.

Epiglottis

A flap of tissue that prevents food and liquids from entering the trachea during swallowing.

Peristalsis

Rhythmic, wave-like squeezing contractions of smooth muscle that push food and chyme along the digestive tract.

Lower Esophageal Sphincter (LES)

A ring of smooth muscle that opens to allow food to enter the stomach and closes to keep stomach acid and contents inside the stomach.

Chyme

A liquid mixture of partially digested food and gastric secretions produced by the churning action of the stomach.

Intrinsic Factor

A protein secreted by the stomach gastric glands essential for the absorption of vitamin $B_{12}$ in the small intestine.

Hydrochloric Acid (HCl)

Stomach acid that uncoils proteins, kills bacteria, activates pepsinogen to pepsin, and maintains gastric acidic pH ($1\text{--}3$).

Pepsin

A stomach protein-digesting enzyme activated from pepsinogen by hydrochloric acid that breaks down proteins into shorter amino acid chains.

Pyloric Sphincter

A circular sphincter muscle regulating the controlled flow of chyme from the stomach into the duodenum.

Rugae

Folds in the stomach lining that flatten as the stomach fills, allowing the stomach walls to expand.

Duodenum

The first and most proximal section of the small intestine where digestion continues with bile and pancreatic secretions.

Jejunum

The middle section of the small intestine primarily responsible for nutrient absorption.

Ileum

The final and longest section of the small intestine that connects to the large intestine.

Ileocecal Valve

A valve that controls the passage of unabsorbed contents moving from the small intestine into the large intestine.

Villi

Finger-like projections carpeted across inner intestinal folds that greatly increase surface area for nutrient absorption.

Microvilli

Tiny hair-like projections covering individual intestinal cells, forming a brush border with specialized transport networks.

Lacteal

A lymphatic capillary inside each villus that absorbs fat digestion products and fat-soluble vitamins packaged as chylomicrons.

Gut Microbiota

Trillions of bacteria in the large intestine that enhance immune function, synthesize vitamins ($K$, $B_{12}$), eliminate pathogens, and produce energy.

Probiotics

Friendly live bacteria that provide health benefits to the host when consumed or populated in adequate amounts.

Prebiotics

Non-digestible food components that serve as fuel for probiotic bacteria in the digestive tract.

Bile

A digestive secretion made by the liver and stored in the gallbladder that neutralizes chyme and emulsifies fat globules into smaller droplets.

Sphincter of Oddi

The muscular valve controlling the release of stored bile into the small intestine in response to cholecystokinin.

Acinar Cells

Exocrine cells of the pancreas that synthesize and secrete digestive enzymes (amylase, lipase, trypsin).

Duct Cells (Pancreas)

Exocrine cells of the pancreas that secrete an aqueous sodium bicarbonate solution to neutralize acidic stomach chyme.

Islets of Langerhans

The endocrine region of the pancreas containing cells that secrete metabolic hormones (insulin and glucagon) directly into the blood.

Sucrase

An intestinal enzyme that splits the disaccharide sucrose into its constituent monosaccharides, glucose and fructose.

Lactase

An intestinal enzyme that splits the disaccharide lactose into its constituent monosaccharides, glucose and galactose.

Maltase

An intestinal enzyme that splits the disaccharide maltose into two molecules of glucose.

Lipase

An enzyme produced by the salivary glands and pancreas that breaks down fats into fatty acids and glycerol fragments.

Trypsin

A pancreatic protease enzyme that splits short amino acid chains into single amino acids, dipeptides, or tripeptides.

Catabolism

The metabolic breakdown of complex body compounds into simpler units, typically releasing energy (e.g., breakdown of glycogen to glucose).

Anabolism

The metabolic synthesis of complex body structures from simpler molecules, requiring energy input (e.g., synthesis of proteins from amino acids).

Chylomicrons

Lipoprotein packages synthesized in intestinal cells to transport digested fats and fat-soluble vitamins through the lymphatic system into the bloodstream.

Gastroesophageal Reflux Disease (GERD)

A chronic condition characterized by frequent acid reflux, where stomach contents flow back into the esophagus, causing burning inflammation.

Lactose Intolerance

A condition resulting from insufficient lactase enzyme levels, causing unabsorbed lactose to ferment in the large intestine and produce bloating, gas, and diarrhea.

Mitochondrion

A cell organelle responsible for generating most of the cellular energy ($ATP$) through metabolic pathways.

Golgi Apparatus

A series of membrane sacks inside cells that process, modify, and package proteins after their synthesis in the rough endoplasmic reticulum.

Lysosome

A cell organelle loaded with digestive enzymes that breaks down proteins, lipids, and nucleic acids while recycling cellular waste products.

Rough Endoplasmic Reticulum

A network of membrane sacks studded with ribosomes that actively assemble and process proteins.

Smooth Endoplasmic Reticulum

A region of endoplasmic reticulum lacking ribosomes that is involved in lipid synthesis rather than protein synthesis.

Constipation

A common digestive condition defined by having 3 or fewer bowel movements per week, often caused by inadequate dietary fiber, fluid intake, or physical activity.