Digestive System Anatomy and Physiology: Part 1

Comprehensive vocabulary flashcards covering the organs, anatomical layers, nervous controls, secretions, and accessory structures of the human digestive system.

Digestion

The mechanical and chemical breakdown of foods into forms that cell membranes can absorb.

Alimentary Canal

The continuous muscular tube open at both ends that extends from the mouth to the anus, measuring approximately $8\,\text{meters}$ ($25\,\text{feet}$) in length and consisting of four tissue layers: mucosa, submucosa, muscularis, and serosa.

Accessory Organs

Organs that assist in digestion by releasing secretions into the alimentary canal without having food pass directly through them, including the salivary glands, liver, gallbladder, and pancreas.

Segmentation

A mixing movement in the small intestine where circular muscle contractions rhythmically pinch and squeeze contents back and forth to blend them together.

Peristalsis

A propelling, wave-like muscular contraction that moves food contents progressively forward through the digestive tract.

Submucosal Plexus

An autonomic nerve plexus within the alimentary canal wall that controls secretions.

Myenteric Plexus

An autonomic nerve plexus within the muscular layer of the alimentary canal that regulates motility.

Mastication

The mechanical process of chewing food in the mouth.

Oral Vestibule

The space inside the mouth situated between the lips/cheeks and the teeth/gums.

Lingual Frenulum

The midline membranous fold of tissue that connects and anchors the tongue to the floor of the mouth.

Deciduous Teeth

The initial set of $20$ primary or baby teeth that erupt during childhood and are subsequently shed.

Permanent Teeth

The secondary set of $32$ adult teeth that replace the deciduous teeth, categorized into incisors, canines, premolars, and molars.

Dentin

The calcified tissue beneath tooth enamel that makes up the bulk of the tooth surrounding the pulp cavity.

Parotid Glands

The largest of the three paired salivary glands, located anterior and inferior to the ears within the cheeks.

Salivary Amylase

A digestive enzyme secreted by serous cells of the salivary glands that initiates the chemical breakdown of carbohydrates like starch and glycogen.

Bolus

A mass of chewed food mixed with saliva that is rolled into a swallowable shape by the tongue.

Epiglottis

A flaplike cartilaginous structure that presses downward during the second stage of swallowing to cover the larynx and trachea, preventing food from entering the respiratory tract.

Lower Esophageal Sphincter

A circular band of smooth muscle at the inferior end of the esophagus that opens to allow food into the stomach and closes to prevent regurgitation; also termed the cardiac sphincter.

Rugae

Thick mucosal folds in the stomach wall that unfold to allow expansion as the stomach fills with food and liquids.

Pyloric Sphincter

A muscular valve located at the end of the pyloric canal that regulates the release of chyme from the stomach into the duodenum.

Chief Cells

Gastric gland cells that secrete the inactive enzyme precursor pepsinogen, which begins protein digestion once activated.

Parietal Cells

Gastric gland cells that secrete hydrochloric acid ($\text{HCl}$) to convert pepsinogen into active pepsin, as well as intrinsic factor.

Intrinsic Factor

A glycoprotein secreted by gastric parietal cells that is required for the absorption of vitamin $B_{12}$ in the small intestine.

Chyme

The acidic, semifluid paste produced in the stomach by the mechanical churning and mixing of food with gastric juice.

Enterogastric Reflex

A neural reflex triggered by the stretching of the duodenal wall that inhibits gastric peristalsis and slows stomach emptying.

Pancreatic Acinar Cells

Exocrine secretory cells in the pancreas that produce and release digestive enzymes comprising pancreatic juice.

Secretin

A duodenal hormone released in response to acidic chyme that stimulates the pancreas to secrete a fluid rich in alkaline bicarbonate ions.

Cholecystokinin

A hormone released by the small intestine that prompts the pancreas to release enzyme-rich pancreatic juice and stimulates gallbladder contraction.

Hepatocytes

The functional liver cells responsible for metabolic functions, synthesis of plasma proteins, detoxification, and bile production.

Hepatic Sinusoids

Vascular channels within liver lobules through which nutrient-rich blood from the hepatic portal vein and oxygenated blood from the hepatic artery percolate past hepatocytes.

Bile

A yellowish-green fluid secreted by hepatocytes containing water, bile salts, bile pigments (bilirubin), cholesterol, and electrolytes.

Emulsification

The process by which bile salts break large fat globules into tiny droplets, vastly increasing the surface area for digestive lipases.

Common Bile Duct

The tube formed by the union of the hepatic duct from the liver and the cystic duct from the gallbladder that empties bile into the duodenum.