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Lecture 19

BIO210Y5 Lecture Notes - Lecture 19: Helicobacter Pylori, Parietal Cell, Greater Omentum

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Sanja Hinic- Frlog

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Lecture 19A Notes – Digestive System Function
Digestive System Organization
The greater omentum is like the skirt that goes around the entire digestive system
oStructurally hold and protect the digestive system
oHelps fix damage that can occur (infection and physical protection)
The mesentery proper connects every piece of the digestive system to help it fold into a compact unit
oHolds parts of the digestive system together
The only way to stretch out the intestine is to rip this mesentery proper apart
oImportant for immune system and circulatory system integration
Ilium connects to the large intestine (iliosecal valve)
Oral Cavity
In the oral cavity you have secretions that help process fats or sugars
Salivary amylase or lingual lipase start the breakdown of the macromolecules
The low pH of your stomach lining helps further breakdown
Chemical Digestion in Stomach
The wall of the stomach (or the rugae) contain different cells
There are different cells in the lining of the stomach parietal cells are important in maintaining pH
G cells are important in maintain gastri
In addition to enzymes that are important for continued digestion, parietal cells can lower the pH of the
stomach or buffer
oFor example, when you have a large meat meal (lots of protein) your pH will increase so that it’s easier
to digest this big meal
In the parietal cell, HCl is not produced inside the cell (would compromise cell structure)
You have a buildup of carbonic acid which is converted to bicarbonate and H+ ions
The outside of the lumen of the gland is where you have a bicarbonate chloride exchanger
The source of chloride is independent of source of hydrogen
Hydrogen is pumped into the lumen of the gland and the chloride moves from the interstitial side to the lumen
of the gland
oThis is where the hydrochloric acid will be produced
The lumen of the gland is really the outside space
Stomach ulcers are holes created in the stomach lining from a buildup of bacteria Helicobacter pylori (so the
cells inflame so there is damage to the lining of the stomach)
oThis can also happen from taking too much advil
oThe acid builds up and burns holes through the walls
Parietal Cells
You need H+ to go into the stomach to lower the pH, that’s why bicarbonate goes outside because it is not
needed for the pH
You need as much space as possible for nutrients to cross the thin boundary layers from the digestive system
to the blood for example
To increase surface area you creates folds in the small intestine
The smallest folds are villi the membrane is very thin so that different nutrients can pass through
TWO-FOLD IMPORTANCE of the two-folds decreased membrane thickness and increasing the surface area
Each section of the small intestine is structurally different depending on its function
The duodenum has glands because you want to neutralize the acid that is coming from the stomach
In the jejunum you have numerous circular folds and long villi because this is where majority of absorption
occurs (increased surface area)
Ilium has few circular folds with stumpy villi and lymphoid nodules immune system is fighting off things and
protecting the digestive system
Carbohydrate Digestion and Absorption
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