Crash course : Digestive system Part 2

Salivary Amylase

Enzyme in saliva that begins chemical digestion of starches (carbohydrates).

Bolus

Soft, moist mass of chewed food mixed with saliva, ready to be swallowed

Chyme

Thick, soupy liquid of partially digested food and gastric juices produced in the stomach

Hydrochloric Acid (HCl)

Strong acid secreted by parietal cells in stomach; denatures proteins, activates pepsin, kills microbes.

Pepsinogen

Inactive precursor of pepsin, secreted by chief cells in stomach.

Pepsin

Active protein-digesting enzyme formed from pepsinogen in the presence of HCl.

Gastric Juice

Acidic digestive fluid secreted by gastric glands, containing HCl, pepsinogen, and mucus.

Cephalic Phase

First phase of gastric regulation triggered by sensory stimuli (sight/smell of food); mediated by vagus nerve.

Gastric Phase

Second phase of gastric regulation triggered by food in stomach; mediated by gastrin hormone and local reflexes

Intestinal Phase

Third phase of gastric regulation triggered by chyme in duodenum; slows gastric activity via secretin and CCK.

Gastrin

Hormone secreted by stomach G-cells; stimulates HCl and pepsinogen secretion during gastric phase.

Secretin

Hormone secreted by duodenum in response to acid; stimulates pancreatic bicarbonate release, inhibits gastric motility.

Cholecystokinin (CCK)

Hormone secreted by duodenum in response to fats/proteins; stimulates digestion, inhibits gastric emptying.

Vagus Nerve (CN X)

Primary parasympathetic nerve that stimulates digestive activity, especially during cephalic phase.

Parietal Cells

Stomach cells that secrete hydrochloric acid (HCl) and intrinsic factor.

Chief Cells

Stomach cells that secrete pepsinogen (inactive pepsin).

G-Cells

Stomach cells that secrete the hormone gastrin.

Enterogastric Reflex

Neural reflex triggered by duodenal stimuli; inhibits gastric motility and secretion to slow gastric emptying.