202 digestion terms

Ingestion

The intake of food, typically through the mouth, marking the first step in digestion.

Digestion

The mechanical and chemical breakdown of food into forms usable by the body.

Mechanical digestion

The physical breakdown of food into smaller particles (e.g., chewing).

Chemical digestion

Hydrolysis reactions that break dietary macromolecules into monomers.

Absorption

The uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood or lymph.

Compaction

Absorbing water and consolidating indigestible residue into feces.

Defecation

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

Alimentary canal

A muscular tube from mouth to anus including the oral cavity, pharynx, esophagus, stomach, small and large intestines.

Accessory organs

Organs that aid digestion but are not part of the digestive tract (e.g., teeth, tongue, salivary glands, liver, gallbladder, pancreas).

Peristalsis

Wave-like muscular contractions that move food through the digestive tract.

Enzyme

A biological catalyst that speeds up chemical digestion of macromolecules.

Saliva

A fluid secreted into the mouth containing enzymes (like amylase) and mucus to aid in digestion and lubrication.

Amylase

An enzyme in saliva that begins the chemical digestion of starch into maltose.

Gastric juice

Secretions from the stomach lining that include hydrochloric acid and pepsinogen.

Pepsin

An active enzyme in the stomach that digests proteins into shorter peptides.

Pepsin

An enzyme activated from pepsinogen that breaks down proteins in the stomach.

Chyme

A semi-fluid mixture of partially digested food and digestive secretions in the stomach.

Bile

A substance produced by the liver that emulsifies fats and aids in their digestion and absorption.

Bile

Contains bile salts, pigments, and cholesterol to emulsify fats for digestion.

Liver

An accessory organ that produces bile, processes nutrients, and detoxifies chemicals.

Gallbladder

Stores and concentrates bile before releasing it into the small intestine.

Pancreas

Secretes digestive enzymes and bicarbonate into the small intestine to neutralize stomach acid and aid digestion.

Villi

Fingerlike projections of the small intestinal mucosa that increase surface area for absorption.

Microvilli

Microscopic projections on the villi that further increase absorptive surface area.

Small intestine

Site of most chemical digestion and nutrient absorption.

Large intestine

Absorbs water and forms feces; includes the colon, rectum, and anal canal.

Mastication

The process of chewing food to begin mechanical digestion.

Swallowing (deglutition)

The reflexive act of moving food from the mouth to the esophagus.

Hydrochloric acid (HCl)

A component of gastric juice that activates pepsin and helps digest proteins.

Intrinsic factor

A glycoprotein secreted by the stomach needed for vitamin B12 absorption in the small intestine.

Intrinsic factor

Essential for vitamin B12 absorption in the ileum.

Lacteal

A lymphatic vessel in the villus of the small intestine that absorbs dietary lipids.

Segmentation

Mixing contractions in the small intestine that churn chyme and promote contact with digestive enzymes and absorptive cells.

Segmentation

Contractions in the small intestine that mix chyme with digestive enzymes.

Segmentation

Aids in nutrient absorption by increasing chyme contact with intestinal wall.

Enteric nervous system

A nervous network within the digestive tract wall that regulates digestive tract motility, secretion, and blood flow.

Enteric nervous system

A localized nervous network controlling digestion, secretion, and motility.

Ghrelin

Hunger hormone secreted by parietal cells; stimulates appetite and gastric motility.

Intrinsic factor

Glycoprotein secreted by parietal cells; essential for vitamin B12 absorption in the ileum.

Zymogen

Inactive enzyme precursor that must be activated to become functional; e.g., pepsinogen to pepsin.

Brush border enzymes

Enzymes embedded in microvilli of intestinal cells; responsible for final digestion steps of nutrients.

Contact digestion

Digestion that occurs when chyme contacts microvilli and brush border enzymes break down nutrients.

Segmentation

Contractions in small intestine that churn chyme and mix it with enzymes, aiding digestion.

Haustral contractions

Slow segmenting movements in the colon; mix contents and promote water absorption.

Mass movements

Strong peristaltic contractions in large intestine that move feces toward the rectum.

Defecation reflex

Involuntary reflex triggered by rectal stretching, leading to internal sphincter relaxation.

Defecation reflex

Initiated by stretch receptors in the rectal wall triggering muscle contractions.

Chylomicrons

Lipid-protein complexes formed in enterocytes; absorbed into lacteals and transported in lymph.

Micelles

Lipid transport structures formed by bile acids that carry lipids to the intestinal brush border.

Bilirubin

Pigment formed from hemoglobin breakdown; gives feces their brown color after conversion to urobilinogen.

CCK (cholecystokinin)

Hormone that stimulates gallbladder contraction and pancreatic enzyme secretion.

Secretin

Hormone that stimulates bicarbonate secretion from the pancreas and liver to neutralize stomach acid.

Urobilinogen

Product of bilirubin metabolism by gut bacteria; contributes to fecal and urinary coloration.

Lacteals

Lymphatic capillaries in intestinal villi that absorb dietary fats in the form of chylomicrons.

Pernicious anemia

Anemia caused by vitamin B12 deficiency due to lack of intrinsic factor.

Aminopeptidase

Brush border enzyme that removes amino acids from the amino end of peptides.

Dipeptidase

Brush border enzyme that splits dipeptides into free amino acids.

Nucleosidases

Brush border enzymes that break down nucleotides into nitrogenous bases and sugars.

Phosphatases

Brush border enzymes that remove phosphate groups from nucleotides during digestion.

Transferrin

Blood protein that binds and transports iron to tissues like bone marrow and liver.

Lecithin

Phospholipid that helps emulsify fats in the intestine with bile acids.

Gomphosis

A fibrous joint where a tooth is anchored into its socket by the periodontal ligament.

Periodontal ligament

Modified periosteum that anchors a tooth to the alveolar bone via collagen fibers.

Gingiva

Also known as the gum; covers the alveolar bone and surrounds the teeth.

Alveolus

The socket in the alveolar bone where a tooth is held.

Enamel

Hard, noncellular surface layer of a tooth that covers the crown.

Cementum

A bone-like material covering the root of the tooth, capable of regeneration.

Dentin

The yellowish tissue making up most of the tooth beneath the enamel and cementum.

Root canal

The tunnel within a tooth's root containing nerves and blood vessels.

Apical foramen

Opening at the end of a root canal that allows nerves and blood vessels to enter.

Occlusion

The contact between teeth when the mouth is closed.

Tight junctions

Connections between epithelial cells preventing leakage of gastric juice.

Mucous coat

Thick, alkaline mucus that protects the stomach lining from acid and enzymes.

Epithelial cell replacement

Rapid regeneration of stomach epithelium every 3 to 6 days.

Enterogastric reflex

Inhibitory reflex that slows gastric activity as chyme enters the small intestine.

Hepatic triad

A structure in the liver composed of a bile ductule, hepatic portal vein branch, and hepatic artery branch.

Bile canaliculi

Small ducts between hepatocytes that collect bile and transport it to bile ductules.

Lymphatic uptake

Absorption of chylomicrons by lacteals in the intestinal villi for transport via lymph.

Brush border

Microvilli-covered surface of intestinal epithelial cells where enzymes carry out final digestion.

Gastrectomy

Surgical removal of the stomach, requiring B12 supplementation due to loss of intrinsic factor.