Physiology 1021 Study Guide - Quiz Guide: Digestion, Esophagus

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Published on 16 Oct 2011
School
Western University
Department
Physiology
Course
Physiology 1021
Digestion Lecture 1
Appreciation of other units to understand GT
Neurophysiology
-stomach has its own nervous system
-this affects activity
-stomach secrets peptides into bloodstream into body
Cardiac output
1/3 of cardiac output goes to stomach
Diagram of Digestive tract
Basic function of the gut is to take in nutrients, break them down and absorb them
Does them through the 3 major functions of the gut
1. Secretion ( 2 major types, exocrine - refers to hormones /out of body / endocrine-secreted into
the blood stream)
2. Motility
3. Absorption
Going to talk about endocrine / exocrine
Secretion
Salivary Glands ( Primary digestion glands) - b/c they secrete an enzyme amylase - breaks down COH -
starts in the mouth , only COH starts in the mouth
Submandibular - in the jaw
Parotid - in the mouth
Sublingual - under the tongue
HC03(bicarbonate)- neutralizes oral acids ( like a citrus fruit) , also neutralizes from oral bacteria , b/c
lining of mouth is very susceptible to a low PH , and tooth enamel is also very susceptible to low PH
Enzyme work best at a neutral PH , amylase likes a PH around 6-7
Salivary Secretion
Converging Duct System
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Primary ducts converging to a main duct into the mouth
Starts off as a large functional unit and drains into a very small duct
All these ducts converge eventually into one main duct
Talking about formation of Saliva by looking at one of those converging ducts
Diagram
Salivon is the functional unit of secretion of the salivary glands
Striated duct and Acinus duct main ducts we are focusing on
There is a dense network of capillaries surrounding the Acinus
Saliva is formed by plasma filtration , need pressure for plasma filtration ( more pressure in the
blood vessels)
concentration of salt in the Acinus lumen is isotonic to salt
Striated duct - active transport system of. ..Absorbs sodium , for exchange of potassium
It's a fixed rate active transport system , regardless of the level of stimulation
Juice starts in the acinus , moves to the mouth , it started as isotonic ..as it moves down to the
mouth it becomes less concentrated
And it becomes isotonic to plasma
How do we get more juice formed in our salivary system
Process is plasma filtration ..what do we do to get more
Answer is we get more blood flow , or change the perm and increase the pores and reduced
barrier for the ions to flow
Also want to vasodilation the vessels
As you pump more fluid through the Salivon , the efficiency decreases
Summary
At rest , the juice in the Acinus is isosmotic to plasma
At rest, the juice in the mouth is isosmotic to plasma
If it moves really fast, it becomes less efficient and becomes hypotonic to plasma
Regulation
ANS -perm /symp - both increase secretion
1. Para nerves release AcH and it causes vasodilation , causes an increase in the aqueous(water)
content ..b/c of the increase in plasma filtration and blood flow
2. Sympathetic - causes vasoconstriction, opposite of perm , you get secretion of glyco and mucuo
proteins ( they are very sticky) - makes the mouth feel gummy and sticky
Difference is a lot of water in PARA release and little in SYMP
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HC03 originates into the striated duct - there's an active transport system for HC03
SYMP/PARA both release the same amount of HC03-
HC03 concentration is higher in mouth when released SYMP
Solute/ Solvent - PARA/SYMP have same effect on SOLUTE - def of conc is SOLUTE/SOLVENT
Solvent is increased more by SYMP release, because of larger volume of water in PARA release
PARA / SYMP have same effect on solvent
Digestion Lecture 2
Topic - Stomach
Divided into 2 segments for the purpose of gastric secretion
Oxyntic Gland in the lower Esophogaus , compromises 2/3rds of the exocrine secretory
Secretes pepsinogen, and HCI (hydrochloric acid)
Pyloric Gland at the top of the Duodenum
Secretes gastrin
Oxyntic- exclusively exocrine, and main secretion is HCI
Oxyntic / parietal (same cell) secretes HCI
Pyloric area of the stomach (bottom half 1/3) -minor exocrine secretion
Pyloric area primary purpose is endocrine , releases a hormone into the blood(opposed to lumen)
called gastrin (released by g cell)
Cephalic , gastric and intestinal are the 3 areas of secretion of acid
1. Cephalic is stimulus in the brain , before the food even enters the stomach (thinking or smelling of
food)
2. Gastric secretion is in the stomach
3. Intestinal secretion is when food is out of the stomach
*Cephalic and gastric can occur same time*
1. Cephalic Phase
Hypothalamus Role
Major secretory nerve to the stomach is the Vegas ( Discovered by a Russian physiologist , Pad-
lov)
Vegas innervates both Oxyntic and pyloric glands
Vegas releases AcH on both glands, and causes Oxyntic to release HCI, and gastrin in Pyloric
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Document Summary

Basic function of the gut is to take in nutrients, break them down and absorb them. Does them through the 3 major functions of the gut: secretion ( 2 major types, exocrine - refers to hormones /out of body / endocrine-secreted into the blood stream, motility, absorption. Going to talk about endocrine / exocrine. Salivary glands ( primary digestion glands) - b/c they secrete an enzyme amylase - breaks down coh - starts in the mouth , only coh starts in the mouth. Hc03(bicarbonate)- neutralizes oral acids ( like a citrus fruit) , also neutralizes from oral bacteria , b/c lining of mouth is very susceptible to a low ph , and tooth enamel is also very susceptible to low ph. Enzyme work best at a neutral ph , amylase likes a ph around 6-7. Primary ducts converging to a main duct into the mouth. All these ducts converge eventually into one main duct.