Physiology of Gastrointestinal System Flashcards

Vocabulary flashcards for reviewing the physiology of the gastrointestinal system.

Motility

Refers to the digestive tract’s muscular contractions.

Propulsive Movements

Push the contents forward through the digestive tract (Peristaltic movements).

Mixing Movements

Mix food with the digestive juices and facilitate absorption by exposing all parts of the intestinal contents to the absorbing surfaces of the digestive tract (Segmentation).

Secretion (Digestive System)

Produces both exocrine and endocrine secretions consisting of water, electrolytes, and specific organic constituents important in the digestive process, such as enzymes, bile salts, or mucus.

Digestion

The chemical breakdown of the structurally complex foodstuffs of the diet into smaller, absorbable units.

Monosaccharides

Simple sugars like glucose, fructose, and galactose.

Triglycerides

Most dietary fats consist of glycerol with three fatty acid molecules attached.

Enzymatic Hydrolysis

Breakdown by water accomplished by enzymes in the digestive secretions to break down the bonds that hold the small molecular subunits.

Absorption

The process through which small absorbable units that result from digestion, along with water, vitamins, and electrolytes, are transferred from the digestive tract lumen into the blood or lymph.

Mucosa

The innermost layer of the digestive tube.

Submucosa

The layer of the digestive tube between the mucosa and the muscularis externa.

Muscularis Externa

The layer of the digestive tube between the submucosa and the serosa.

Serosa

The outermost layer of the digestive tube.

Interstitial Cells of Cajal

Pacemaker cells located throughout the layers of the muscularis externa that generate slow wave potentials.

Enteric Nervous System

The submucosal plexus and the myenteric plexus.

Extrinsic Nerves

Nerve fibers from both branches of the autonomic nervous system.

GI Hormones

Hormones produced by specialized endocrine cells tucked within the mucosa, exert excitatory or inhibitory influences on digestive smooth muscle and exocrine gland cells.

Chemoreceptors (Digestive Tract)

Sensory receptors sensitive to chemical components within the lumen of the digestive tract.

Mechanoreceptors (Digestive Tract)

Pressure receptors sensitive to stretch or tension within the wall of the digestive tract.

Osmoreceptors (Digestive Tract)

Sensory receptors sensitive to the osmolarity of the luminal contents.

Mastication

Chewing, the motility of the mouth that involves the slicing, tearing, grinding, and mixing of ingested food by teeth.

Saliva

Produced largely by three major pairs of salivary glands that lie outside the oral cavity; about 99.5% H2O and 0.5% electrolytes and protein.

Salivary Amylase

Enzyme that begins digestion of carbohydrates in the mouth by breaking polysaccharides down into maltose.

Simple Salivary Reflex

Occurs when chemoreceptors and pressure receptors within the oral cavity respond to the presence of food.

Conditioned Salivary Reflex

Salivation that occurs without oral stimulation.

Bolus

A ball of chewed or liquid food.

Swallowing Center

Located in the medulla of the brain stem.

Gastric Reflux

Acid and enzymes in gastric juice.

Chyme

A thick liquid mixture produced when ingested food is pulverized and mixed with gastric secretions.

Receptive Relaxation

Reflex relaxation of the stomach, during a meal, stomach relaxes slightly with each mouthful.

Enterogastric Reflex

Neural response mediated through both the intrinsic nerve plexuses (short reflex) and the autonomic nerves (long reflex) which inhibits antral contractions to reduce gastric emptying.

Enterogastrones

Several hormones released from the small intestine mucosa that inhibits antral contractions to reduce gastric emptying.

Secretin

An enterogastrone produced by endocrine cells known as S cells in the duodenal and jejunal mucosa.

Cholecystokinin (CCK)

An enterogastrone produced by endocrine cells known as I cells in the duodenal and jejunal mucosa.

Gastric Mucosa

The lining of the stomach.

Oxyntic Mucosa

The area that lines the body and fundus of the stomach.

Pyloric Gland Area (PGA)

The area that lines the antrum of the stomach.

Mucous Cells

Line the gastric pits and the entrance of the glands; secrete a thin, watery mucus.

Chief Cells

Found in the deeper parts of the gastric glands, secrete the enzyme precursor pepsinogen.

Parietal Cells

Found in the deeper parts of the gastric glands, secrete HCl and intrinsic factor.

Pepsinogen

An inactive enzymatic molecule produced by the chief cells that converts to pepsin when secreted into the gastric lumen by way of HCl cleavage.

Pepsin

Initiates protein digestion by splitting certain amino acid linkages in proteins to yield peptide fragments.

Intrinsic Factor

Secretory product of the parietal cells that is important in the absorption of vitamin B12.

G Cells

Endocrine cells found in the gastric pits only in the PGA, secrete the hormone gastrin into the blood.

Enterochromaffin-like (ECL) Cells

Dispersed among the parietal and chief cells in the gastric glands of the oxyntic mucosa, secrete the paracrine histamine.

D Cells

Scattered in glands near the pylorus but are more numerous in the duodenum, secrete the paracrine somatostatin.