Anatomy and Physiology of the Digestive Tract Flashcards
What do chief cells do and where are they located?
The chief cells of the stomach secrete lipase.
What does the lipase in the stomach do?
Breaks down dietary triglycerides (triacylglycerols) into free fatty acids and diglycerides (diacylglycerols), and pepsinogen (the precursor of pepsin, which initiates the hydrolysis of food proteins).
What do parietal cells do and where are they located?
The parietal cells of the stomach secrete Intrinsic factor.
What does the Intrinsic factor in the stomach do?
A small protein required for absorption of vitamin B12, and HCl.
What do mucous cells do and where are they located?
Mucous cells of the stomach secrete mucus containing glycoproteins and bicarbonate.
What does the mucus containing glycoproteins and bicarbonate in the stomach do?
Protect the gastric mucosa from acid damage and
auto digestion.
What does Gastric acid do and where is it located?
In the stomach. Gastric acid performs a number of preliminary digestive roles that require an acidic environment, including destruction of microorganisms, activation of pepsinogen to pepsin, activation of intrinsic factor, denaturation (loss of three-dimensional conformation) of macromolecules, and facilitation of the breakdown of protein and polypeptides by pepsin.
In the stomach, what triggers gastrin secretion and what secretes it?
The presence of food protein. It is secreted by gastric endocrine cells.
What acts on gastric parietal and chief cells to stimulate intragastric secretion of HCL and pepsinogen.
Gastrin
What stimulates gastric peristalsis and maintains the proliferation of gastric parietal cells.
Gastrin
What sections of the small intestine are the major sites of nutrient absorption?
The jejunum and Ileum
What does Acidic chyme do?
Acidic chyme entering the proximal duodenum stimulates the enteric secretion of secretin into the systemic circulation.
What does secretin do?
Secretin stimulates pancreatic secretion of bicarbonate into the ductal system that terminates in the common bile duct.
What stimulates cholecystokinin (CCK) into the
systemic circulation?
Fat or protein entering the proximal duodenum.
What does cholecystokinin (CCK) stimulate?
Cholecystokinin stimulates pancreatic secretion of zymogens (inactive digestive enzyme precursors) into the ductal system and stimulates gall bladder
contraction, propelling bile into the common bile duct.
What converts trypsinogen to trypsin?
Enterokinase
What converts the other zymogens to
elastase, chymotrypsin, colipase, carboxypeptidase A and carboxypeptidase B?
Trypsin
Carboxypeptidases require what mineral to cleave single carboxyterminal amino acids from polypeptides.
zinc
What does the pancreas secrete to digest starches?
amylase
What does the pancreas secrete to hydrolyze dietary fats that have been emulsified by bile salts into fatty acids and glycerol?
Lipase
What is the primary role of the liver in food digestion and nutrient absorption?
The excretion of bile, a watery greenish fluid stored in the gallbladder.
What contains cholic acid, chenodeoxycholic acid, taurine, glycine, cholesterol, electrolytes and water (6 to 7 L/day on average in adults).
Bile
Monoglycerides, free fatty acids, cholesterol, phospholipid digestion products and other fat soluble
food components cannot readily penetrate the unstirred water layer that separates the 25 epithelial surface of the small intestine from the intestinal lumen. Their absorption depends on what?
Their absorption depends on their ability to aggregate spontaneously with bile salts and become incorporated within vaguely spherical clusters of bile salts called micelles.
What are micelles?
Collections of lipid soluble dietary subcomponents surrounded by a layer of water soluble bile salts.
Within the endoplasmic reticulum of enterocytes, lipids and lipid soluble compounds are repackaged into large protein-coated (and therefore water soluble) what?
chylomicrons
Antimicrobial defenses within the intestinal tract rely heavily on the secretion of secretory IgA (sIgA) by what?
Antimicrobial defenses within the intestinal tract rely heavily on the secretion of secretory IgA (sIgA) by gut-associated lymphoid tissue (GALT).
The GALT contains what?
About 50% to 60% of the total number of immune cells in the body, scattered throughout the intestinal tract.
As the “first line of defense” against
environmental assault, GALT provides what?
Both cell-mediated immunity and humoral immunity
via secretory IgA.
