Lecture 28 Flashcards
What are 4 components of gastric acid secretions?
- acid
- pepsin
- intrinsic factor
- mucus
What is the function of acid?
It has a protective role against bacteria such as that on our food. It also denatures proteins as part of chemical degradation. This is also the optimum pH for many digestive enzymes. It also renders the fluid isosmotic (150 mM HCl - HCO3–neutralised part to protect the epithelial lining)
What is the purpose of pepsin?
This breaks down proteins
What is the purpose of intrinsic factor?
This is for the absorption of vitamin B12 for the formation of DNA and RBC
What is the purpose of mucous?
This protects against the acid and mechanical forces - it makes the epithelium elastic
What are the different parts of the stomach and what is secreted in each part?
- LES and cardia for the secretion of m______ and ______-
- the fundus and body of the stomach for the secretion of ______, ________ factor, m______, l_____, _____-, p______n
- antrum and pylorus for the secretion of m_______ and ______-
- LES and cardia for the secretion of mucus and HCO3-
- the fundus and body of the stomach for the secretion of H+, intrinsic factor, mucus, lipase, HCO3-, pepsinogen
- antrum and pylorus for the secretion of mucus and HCO3-
Where is gastrin secreted from? Why is this location important?
It is released in the late part of the stomach to control the release of acid from the fundus
Describe the structure of the stomach
There are invaginations in the lamina propria which are the gastric glands. The cells in here have different functions of gastric secretions
Describe the functions of the different cells in the gastric glands
There are the _________ cells which produce _________ to protect against the ________. There are ________ cells which are close to the surface to make the epithelium _______ and so help with ________ forces and to protect against the ______. There are ________ cells which are further down the gland which secrete _______ and _______ factor. There are ________ cells further down which secrete ________ and then there are __________ like (ECL) cells which secrete _________ for the control of _______ ________ secretion
There are the surface cells which produce HCO3- to protect against the acid. There are mucus cells which are close to the surface to make the epithelium elastic and so help with mechanical forces and to protect against the acid. There are parietal cells which are further down the gland which secrete acid intrinsic factor. There are chief cells further down which secrete pepsinogen and then there are enterochromaffin like (ECL) cells which secrete histamine for the control of gastric acid secretion
How many litres of gastric secretions do we produce each day? The composition of these secretions depend on what?
2-3 L
The composition depends on whether you are eating or fasting
When we are not eating, how much gastric secretions do we produce per hour? What is the composition of this?
15 - 30 mL/h
This is secreted constantly whether you are eating or not. It is secreted by surface cells. This is an isosmotic solution with similar [Na+] to plasma but higher [HCO3-]. There is also mucus secreted
Describe the volume and composition of gastric secretions when we are eating. How much is it and what is the composition?
150 mL/h
- isosmotic (150mM) solution of HCl produced by parietal cells
- a bit of HCO3- to protect the surface cells
- pepsinogen secreted by the chief cells
- intrinsic factor secreted by the parietal cells
- mucus
Describe the volume and composition of gastric secretions when we are eating. How much is it and what is the composition?
150 mL/h
- isosmotic (150mM) solution of HCl produced by parietal cells
- a bit of HCO3- to protect the surface cells
- pepsinogen secreted by the chief cells
- intrinsic factor secreted by the parietal cells
- mucus
What is the final osmolarity of the gastric secretion with the 150mM of HCl and the HCO3- that is secreted to help protect the surface cells?
around 200mOsmol/L
What does the final composition of gastric secretion depend on?
the rate of secretion