Gastrointestinal Physiology: Secretion Flashcards
What do the salivary glands secrete? What is the composition of its secretions? (3)
Mucus, dilute solution of NaHCO3 and NaCl, digestive enzymes (salivary amylase and lingual lipase)
What regulates the secretion of the salivary glands?
Nervous stimuli, autonomic nervous system
This stimulates the secretion of copious amounts of fluid in the salivary glands.
Parasympathetic nervous system
This stimulates the secretion of small volumes of viscous fluid in the salivary glands.
Sympathetic nervous system
- this augments the parasympathetic response
What is the composition of gastric secretions? (4)
Mucus, intrinsic factor, digestive enzymes and acid + bicarbonate
What secretes mucus and bicarbonate in the stomach?
Epithelial cells
What secretes intrinsic factor in the stomach?
Parietal cells
What secretes digestive enzymes like pepsinogen in the stomach?
Chief cells
This contains bicarbonate which buffers acid at the epithelial surface. It also protects from abrasion at the stomach.
Mucus
This stabilises vitamin B12 and facilitates its absorption in the small intestine. It is secreted by the stomach.
Intrinsic factor/acid
This is an inactive for of pepsin, and is responsible for the digestion of proteins in the stomach.
Additional question:
What activates this protein in the stomach?
Pepsinogen
Pepsinogen activated by acid
This creates the optimum pH for pepsin action, dilutes food and denatures protein in the stomach.
Gastric acid
What are the 3 phases of gastric secretion? What stimulates each of the secretions?
The different regions of the body control secretion.
Cephalic phase (head) - CNS and ENS (local reflex and then the long reflex) - extrinsic
Gastric phase (stomach) - nervous (parasympathetic nervous system) and hormones
Intestinal phase (intestine) - nervous (enterogastric reflex) and hormonal (CCK and secretin)
What stimulates the cephalic phase? (2)
CNS and extrinsic parasympathetic nervous response via ENS
This is responsible for stimulating the secretion of parietal cells, chief cells and goblet cells during the cephalic phase. It also stimulates the secretion of the hormone gastrin.
Extrinsic parasympathetic response.