Module 22: The Digestive System

A complete set of vocabulary flashcards covering the components, layers, motility, and regulation of the digestive system, including specific anatomy of the stomach and teeth.

Digestive system

A muscular tube (lumen) lined with ridges and folds to increase surface area for absorbing nutrients for cell maintenance and growth.

Enteric nervous system

A network of sensory neurons and interneurons of the digestive system that controls most digestive activities and is influenced by the autonomic nervous system (ANS).

Parasympathetic nervous system effect

The division of the autonomic nervous system that increases digestive activity.

Sympathetic nervous system effect

The division of the autonomic nervous system that decreases digestive activity.

Mucosa

The inner lining of the digestive tract consisting of a mucous membrane moistened by glandular secretions and a lamina propria of areolar tissue.

Submucosa

A layer of dense connective tissue containing blood vessels, lymphatic vessels, a nerve plexus, and exocrine glands that may secrete buffers and enzymes.

Muscular layer

Consists of smooth muscle in two layers (inner circular and outer longitudinal) involved in mechanical processing and movement; note that the stomach has three layers.

Serosa

A layer of visceral peritoneum along most regions of the digestive tract in the abdominal cavity.

Adventitia

A network of collagen fibers that replaces the serosa in the oral cavity, pharynx, esophagus, and rectum.

Villi

Small mucosal projections in the small intestine that increase surface area for absorption and contain columnar epithelial cells.

Pacesetter cells

Cells that rhythmically stimulate smooth muscle cells in the digestive tract to contract as a single unit.

Peristalsis

A wave of muscle contraction where circular muscles contract behind a bolus and longitudinal muscles ahead of it contract to propel food along the tract.

Segmentation

Cycles of contraction in the inner circular muscle that churn and fragment the bolus to mix it with secretions, occurring without forward movement.

Short reflexes

Also known as myenteric reflexes; these are triggered by chemoreceptors or stretch receptors in the digestive tract walls with neurons located in the myenteric plexus.

Long reflexes

High-level control involving interneurons and motor neurons of the CNS, generally controlling large-scale peristalsis.

Enteroendocrine cells

Endocrine cells in the epithelium of the digestive tract that produce hormones affecting digestive function.

Oral cavity histology

Lined by stratified squamous epithelium to protect against abrasion; keratinized in areas like the hard palate and superior tongue surface.

Nitroglycerin

An example of a lipid-soluble drug that can be rapidly absorbed by the thin mucosa inferior to the tongue.

Gingival sulcus

An epithelial attachment that blocks bacteria from accessing the deeper tissues around the root of the tooth.

Gomphosis

The specific articulation between root dentin and alveolar bone created by the periodontal ligament.

Buccal phase

The strictly voluntary first phase of deglutition where the tongue forces the bolus into the oropharynx.

Pharyngeal phase

The second phase of swallowing where muscles contract, the larynx is elevated, and the epiglottis folds to move the bolus into the esophagus.

Greater omentum

A mesentery attached to the stomach and transverse colon containing adipose tissue for padding and protection.

Lesser omentum

A mesentery that connects the stomach to the liver and provides an access route for blood vessels.

Pylorus

The sharp curve of the J-shaped stomach that frequently changes shape during mixing movements.

Rugae

Prominent, temporary mucosal folds in the stomach that allow for expansion by flattening out.

Pyloric sphincter

A smooth muscle band that regulates the release of chyme into the duodenum.

Intrinsic factor (IF)

A substance secreted by parietal cells that aids in vitamin $B_{12}$ absorption in the small intestine.

Parietal cells

Stomach cells that secrete intrinsic factor and $HCl$ to maintain a stomach pH of $1.5 - 2.0$.

Chief cells

Stomach cells that secrete pepsinogen, which is activated by $HCl$ to produce pepsin for protein digestion.

G cells

Enteroendocrine cells that secrete hormones, such as gastrin, to regulate stomach acid.

Chyme

The acidic mixture of food bolus, saliva, and gastric secretions formed in the stomach.