Lecture 8 Secretion in GI Tract Flashcards
The cells closer to the surface epithelium of the GI tract that are either mucous or goblet cells are called?
Single cell
The next deepest layer of pink cells that have infoldings that show cavernations are called?
Oxyntic (or parietal) cells
Deeper to Oxyntic cells are these cells that pump pepsin
Peptic (or chief) cells
Describe the composition of saliva. What ions are absorbed, and which are secreted? What is the tonicity of saliva?
Saliva: Ptyalin (amylase), Mucus (mucin), ECF (ions)
Absorbs Na & Cl
Secretes K & HCO3
Saliva is hypotonic BUT very close to plasma composition
(lipase present in peds, no use in adults)
Inactive precursor digestive enzymes that live in enteric secretion cells are called?
Zymogens
What 3 local influences cause local secretion?
Tactile, distention, irritation
What is reflex secretion?
Secretion via nervous input through the meissner plexus and parasympathetic loop
What does a hormone like cholecystokinin do in the GI tract?
Inhibitis gastric motility, and stimulates gall contraction and bile release
What does secretin do?
Tell pancreas to release bicarb (to neutralize stomach HCL)
Typically sympathetic tone IS inhibitory, BUT can w/o any parasympathetic tone at all, can sympathetic stimulation increase rate of secretion?
Yes (only a little bit)
What is the role of mucous in the GI tract?
amphoteric: doesnt hold a shape
To adhere the secretions to the food, protect mucosa from autodigestion, slide the food along, and buffer (only slightly)
What is the average volume in secretion of
- Saliva
- Gastric secretion
- Pancreas secretion
- Saliva = 1 liter/day
- Gastric = 1.5 liter/day
- Pancreas = 1 liter/day
Why would submandibular and sublingual glands respond to aldosterone?
As salt is normally reabsorbed in normal flow, when the body has less salt, the presence of aldosterone increases reabsortion, causing water to follow, and dry mouth.
What the the rate of saliva flow have to do with its ionic composition compared to that of plasma?
The higher the rate of flow, the less time the tubular cells have to reabsorb, and will therefore be closer in composition to plasma. Slower flow eqals, lower composition (more reabsorbed)
What is the pathway of excitation of appetite?
Taste or tactile touch of the bolus in the mouth, travels via tractus solarius (facial nerve and glossopharyngeal nerve) to the superior and inferior salivatory nucleus in the anterior hypothalamus, and excites the amygdala (the limbic center of emotion/memory)
