The Digestive System: Anatomy and Physiology Flashcards

Comprehensive vocabulary flashcards covering the anatomy, function, and secretions of the human digestive system as described in the provided lecture notes.

Digestive system

An organ system that processes food, extracts nutrients, and eliminates residue.

Ingestion

The selective intake of food.

Digestion

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

Absorption

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

Compaction

The process of absorbing water and consolidating indigestible residue into feces.

Defecation

The elimination of feces from the body.

Mechanical digestion

The physical breakdown of food into smaller particles through actions such as cutting, grinding, and churning.

Chemical digestion

A series of hydrolysis reactions that break dietary macromolecules into their monomers, carried out by enzymes.

Digestive tract

A muscular tube approximately $30\text{ ft}$ long extending from the mouth to the anus, also known as the alimentary canal.

Accessory organs

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

Gastrointestinal (GI) tract

The subdivision of the digestive system specifically comprising the stomach and intestines.

Mucosa

The innermost layer of the digestive tract wall.

Hard (bony) palate

The anterior portion of the palate supported by the maxillae and palatine bones, featuring transverse ridges called palatine rugae.

Soft palate

The posterior portion of the palate composed of skeletal muscle and glandular tissue with no bone.

Uvula

A conical medial projection at the rear of the mouth that helps retain food until one is ready to swallow.

Dentition

A collective term for the teeth, which number $32$ in a typical adult.

Plaque

A sticky residue on teeth made of bacteria and sugars that can lead to dental cavities.

Mastication

The process of chewing, which serves as the first step in mechanical digestion.

Bolus

A soft mass of moistened food bound together by saliva to aid in swallowing.

Salivary amylase

An enzyme in saliva that begins the digestion of starch in the mouth.

Lingual lipase

An enzyme produced by the lingual glands that begins fat digestion, primarily acting after the food is swallowed.

Lysozyme

An enzyme found in saliva that kills bacteria.

Parotid glands

Extrinsic salivary glands located beneath the skin anterior to the earlobe.

Pharyngeal constrictors

Circular skeletal muscles in the pharynx that force food downward during swallowing.

Lower esophageal sphincter (LES)

A muscular ring at the inferior end of the esophagus that prevents stomach contents from regurgitating.

Deglutition

The medical term for swallowing, involving over $22$ muscles.

Chyme

An acidic, soupy mixture of semiditgested food that passes from the stomach to the small intestine.

Pyloric sphincter

A ring of smooth muscle that regulates the passage of chyme into the duodenum.

Greater omentum

A fatty membrane hanging from the greater curvature of the stomach that covers the small intestine.

Gastric pits

Depressions in the gastric mucosa where tubular glands open.

Parietal cells

Cells in the gastric glands that secrete hydrochloric acid ($HCl$), intrinsic factor, and ghrelin.

Chief cells

The most numerous cells in gastric glands, which secrete gastric lipase and pepsinogen.

Intrinsic factor

A glycoprotein secreted by parietal cells essential for the absorption of vitamin $B_{12}$.

Emetic center

A region in the medulla oblongata that integrates the muscle actions required for vomiting.

Liver

The body’s largest gland, weighing about $1.4\text{ kg}$, whose only digestive contribution is the secretion of bile.

Hepatic sinusoids

Blood-filled channels in the liver lined with fenestrated endothelium.

Hepatocytes

Liver cells responsible for absorbing nutrients for metabolism, breaking down glycogen, and degrading toxins.

Bilirubin

The primary bile pigment derived from the decomposition of hemoglobin.

Gallbladder

A pear-shaped sac on the underside of the liver that stores and concentrates bile.

Pancreatic juice

An exocrine secretion containing enzymes such as pancreatic amylase, lipase, and ribonuclease.

Mesentery

A connective tissue sheet that suspends the stomach and intestines from the abdominal wall.

Retroperitoneal

The status of an organ that lies against the posterior body wall and is covered by peritoneum only on its anterior side.

Lacteal

A lymphatic capillary found in the core of an intestinal villus that absorbs most lipids.

Brush border enzymes

Enzymes contained in the plasma membrane of microvilli that carry out the final stages of enzymatic digestion.

Segmentation

A type of intestinal motility characterized by stationary ringlike constrictions.

Micelles

Minute droplets in bile that facilitate the absorption of free fatty acids and monoglycerides.

Chylomicrons

Lipids coated with phospholipids and protein that are taken up into lacteals.

Gut microbiome

More than $1000$ species of microbes populating the large intestine that digest cellulose and synthesize vitamins $B$ and $K$.

Intrinsic defecation reflex

A relatively weak response mediated by the myenteric plexus that causes the muscularis to contract and the internal sphincter to relax.