Anatomy and Physiology Module 7: The Digestive System and Body Metabolism

Comprehensive vocabulary flashcards covering the anatomical structures, physiological processes, hormonal control, and metabolic pathways of the digestive system.

Alimentary Canal (Gastrointestinal Tract)

A continuous, coiled, hollow muscular tube that winds through the ventral body cavity from the mouth to the anus, measuring approximately $9\,\text{m}$ (about $30\,\text{feet}$) long in a cadaver but considerably shorter in a living person due to muscle tone.

Pharynx Divisions

The three anatomical regions of the pharynx: the nasopharynx (part of the respiratory passageway), the oropharynx (posterior to the oral cavity), and the laryngopharynx (continuous inferiorly with the esophagus).

Esophagus (Gullet)

A muscular passageway approximately $25\,\text{cm}$ ($10\,\text{inches}$) in length that extends from the pharynx through the diaphragm to the stomach, conducting food via peristalsis.

Tunics of the Alimentary Canal Wall

The four fundamental tissue layers comprising the alimentary canal from the esophagus to the large intestine: the mucosa (innermost layer consisting of surface epithelium, lamina propria, and a scanty smooth muscle layer), submucosa, muscularis externa (inner circular and outer longitudinal smooth muscle layers), and serosa (visceral peritoneum).

Lesser Omentum

A double layer of peritoneum that extends from the liver to the lesser curvature of the stomach.

Greater Omentum

An extension of the peritoneum that drapes downward and covers the abdominal organs like a lacy apron before attaching to the posterior body wall.

Stomach

A C-shaped organ located on the left side of the abdominal cavity that serves as a temporary storage tank for food, churns and mechanically breaks food down into chyme, and initiates the chemical digestion of proteins.

Small Intestine

The body's major digestive and absorptive organ, extending from the pyloric sphincter to the large intestine with an average length of $2\text{ to }4\,\text{m}$ ($7\text{ to }13\,\text{feet}$) in a living person.

Villi

Fingerlike projections of the small intestinal mucosa that impart a velvety nap-like texture, each containing a rich blood capillary bed and a specialized lymphatic capillary termed a lacteal for nutrient absorption.

Microvilli (Brush Border)

Tiny projections of the plasma membrane of mucosal absorptive cells in the small intestine that give the luminal surface a fuzzy appearance and greatly expand absorptive surface area.

Circular Folds (Plicae Circulares)

Deep, permanent folds of the mucosa and submucosa layers in the small intestine that do not disappear when the lumen fills with food.

Large Intestine

The terminal portion of the digestive tract, measuring about $1.5\,\text{m}$ ($5\,\text{feet}$) long from the ileocecal valve to the anus, responsible for absorbing water to dry out indigestible food residues and eliminating them as feces.

Deciduous Teeth

The initial set of 20 temporary teeth (also called baby or milk teeth) that begin erupting at roughly $6\,\text{months}$ (starting with the lower central incisors) and are completely emerged by age 2.

Anatomical Regions of a Tooth

The three main regions of a tooth: the crown (enamel-covered exposed section above the gumline), the neck (junction connecting crown and root), and the root (portion embedded in alveolar bone containing the root canal and periodontal membrane).

Salivary Glands

Three pairs of exocrine glands—the parotid glands (anterior to the ears), submandibular glands, and sublingual glands—that empty saliva (a mixture of mucus and serous fluids) into the mouth.

Pancreas

A soft, pink, triangular gland extending across the abdomen from the spleen to the duodenum that secretes an alkaline, enzyme-rich juice into the duodenum capable of digesting all food classes, as well as producing the endocrine hormones insulin and glucagon.

Bile

A yellow-to-green watery fluid manufactured by the liver containing bile salts, bile pigments (mainly bilirubin), cholesterol, and phospholipids; it contains no enzymes but physically emulsifies fat globules into smaller particles.

Peristalsis

Involuntary waves of contraction and relaxation in adjacent or neighboring segments of the alimentary canal wall that propel contents distally along the tract.

Segmentation

Rhythmic, alternating contractions of single intestinal segments separated by inactive regions that propel foodstuffs forward and backward to thoroughly mix them with digestive juices.

Retropulsion

The mechanical stomach action wherein peristaltic waves close the pyloric valve, squirting $3\,\text{ml}$ or less of chyme into the duodenum while propelling the remaining approximately $27\,\text{ml}$ backward into the gastric body for further mixing.

Cholecystokinin (CCK)

An enterogastrone hormone released by the duodenum in response to fatty chyme and partially digested proteins that induces secretion of enzyme-rich pancreatic juice, triggers gallbladder contraction to release stored bile, and relaxes the hepatopancreatic sphincter.

Secretin

An intestinal hormone released by the duodenum in response to acidic chyme that stimulates pancreatic secretion of bicarbonate-rich juice, increases hepatic bile output, and inhibits gastric motility and secretions.

Catabolism

The metabolic breakdown of complex substances into simpler molecules, typically accompanied by the liberation of chemical energy.

Anabolism

The energy-consuming metabolic synthesis of larger, more complex cellular structures or molecules from simpler precursors.

Cellular Respiration

The series of catabolic pathways—glycolysis, citric acid cycle, and oxidative phosphorylation—that oxidizes glucose ($C_6H_{12}O_6 + 6 O_2 \rightarrow 6 CO_2 + 6 H_2O + \text{ATP}$) to generate cellular energy in the form of ATP.

Glycogenesis

The process by which the liver converts excess glucose molecules into glycogen for storage in response to elevated blood glucose levels.

Glycogenolysis

The hydrolysis of stored liver glycogen into free glucose molecules to be released into the blood when circulating glucose levels decline.

Gluconeogenesis

The hepatic synthesis of new glucose molecules from non-carbohydrate precursors, specifically amino acids and fats, during periods of falling blood glucose.

Basal Metabolic Rate (BMR)

The baseline amount of energy expended by the body to sustain essential life processes at rest, modulated by surface area, sex, age, thyroxine production, and emotional state.

Kilocalorie (kcal)

The standard metric unit for quantifying the energy value of food; carbohydrates and proteins yield $4\,\text{kcal/g}$, whereas fats yield $9\,\text{kcal/g}$.