Lecture 21: The Stomach and Pancreas Flashcards
What is peristalsis?
The contraction of muscle to move food to the stomach
What the oesophageal hiatus?
The hole in the diaphragm that the oesophagus passes through to get to the stomach
What is the lower oesophageal sphincter (including its function)?
The sphincter passing through the stomach that prevents reflux of food back up the oesophagus
What are the four main parts of the stomach called?
Cardia
Fundus
Body
Pylorus (pyloric antrum)
Which part of the stomach does the oesophagus open up into?
the cardia
What is the significance of the fundus part of the stomach?
there are lots of gastric glands here and it is where all the gases collect
What is the significance of the pylorus part of the stomach?
it contains the pyloric sphincter for regulating the movement of luminal contents into the duodenum of the small intestine
What is an omentum?
a double layer of peritoneum that connects one organ to another
What does the lesser omentum connect?
the stomach to the liver
What does the greater omentum connect?
the stomach to the transverse colon
What does the lesser omentum contain?
blood vessels
What does the greater omentum contain and what are the roles of these things?
- fat tissue to provide padding for the abdomen
- has clusters of immune cells to destroy pathogens in the peritoneal cavity
The four layers of the gut tube are mucosa, submucosa, muscularis and adventitia. How has the structure of the muscularis changed in the stomach and why?
The muscularis has been modified for motility and mixing to mechanically breakdown food and drive it towards the small intestine.
In the stomach, there is three layers (inner oblique, middle circular, outer longitudinal layer) instead of just the circular and longitudinal layers.
How does the thickness of the of the pyloris differ from the thickness of the fundus and why?
It is thicker in the pyloris because the stomach needs to mechanically breakdown food distally, closer to the small intestine.
What are rugae and what is their advantage?
they are temporary folds that allow for the expansion of the stomach
this is important to expand to accomodate more food
What is the role of sphincters in storage?
they control whether the food leaves the stomach or not and therefore they can keep food in the stomach for digestion.
Which layer of the gut wall are the rugae in and why?
the submucosa because the connective tissue in the submucosa allows them to flatten out
The four layers of the gut tube are mucosa, submucosa, muscularis and adventitia. How has the structure of the mucosa changed in the stomach and why?
The simple squamous epithelium has changed to simple columnar epithelium which invaginate down into the lamina propria to form glands.
This increases the surface area for secretion
Are glands in the mucosa of the stomach permanent
Yes
What four things do we need to be secreted from the glands?
- Acid and enzymes for digestion
- mucus for protection
- hormones for regulation
What is present in glands that allows them to secrete mucus, and where are these located in the gland?
There are lots of goblet cells on the surface and in the neck of the gland
What is present in glands that allows them to secrete acid, and where are these located in the gland?
There are parietal cells deep in the gland which secrete HCl
What is present in glands that allows them to secrete hormones, and where are these located in the gland?
There are G cells which produce hormones deep in the gland
Give an example of a hormone secreted by a G cell and what its role is
Gastrin is secreted which is for motility and secretion
What is present in glands that allows them to secrete enzymes, and where are these located in the gland?
Chief cells located deep in the gland
Give an example of an enzyme secreted by chief cells and what the role is
pepsinogen is the precursor of pepsin which is used for protein digestion
Chief cells produce enzymes. What is it about their structure that allows them to carry out this function?
enzymes are proteins so they need a lot of rough endoplasmic reticulum to produce them
there is also apical zymogen granules to transport the enzymes to the apical surface
basal nucleus due to the zymogens being at the apical surface
Parietal cells produce acid. What is it about their structure that allows them to carry out this function?
They need ion pumps to pump H+ ions and this requires energy. Therefore there is a lot of mitochondria to produce lots of energy
There is also a central nucleus and lots of folds to increase the surface area to maximise secretion
How are the stomach functions regulated?
endocrine control
neural control
Describe the endocrine control which regulates stomach function
- endocrine cells in the mucosa secrete hormones to regulate function
- gastrin and ghrelin are secreted into the bloodstream
Describe the neural control which regulateds stomach function
enteric nervous system has local reflexes for primary control such as the myenteric plexus regulating motility events and the submucosal plexus regulating secretory events
What is the role of ghrelin?
it is the hunger hormone
What is chyme?
partially digested food
What is the role of the pyloric sphincter?
to contract to stop movement of chyme from stomach to the duodenum of the small intestine but it can relax when this movement is required
As the chyme enters the small intestine, further digestion is required. What is required in the duodenum to allow for this to happen
- enzymes
- protection from acidic chyme through mucous and bicarbonate
Where does the mucous come from in the duodenum?
It is provided by glands in the submucosa of the duodenum
Where do the enzymes and the bicarbonate come from in the duo
from the pancreas
How does the enzymes and the bicarbonate get from the pancreas to the duodenum?
through the pancreatic duct
The pancreas is retroperitoneal. What does this mean?
It is behind the peritoneum as it doesn’t need to move
What organ produces bile and which organs stores it?
The liver produces it and the gallbladder stores it.
How does the bile get from the liver/gallbladder to the pancreatic duct?
Via the bile duct
Where do the bile duct and the bile duct meet up?
in the hepatopancreatic ampulla
What is the duodenal papilla?
Contents from the bile duct and pancreatic duct meet at the hepatopancreatic ampulla and they empty into the duodenum via the duodenal papilla
How is the release of bile and contents from the pancreas into the duodenum controlled?
by the hepatopancreatic sphincter
the pancreas has both ________ and _________ functions
endocrine and exocrine
What are the exocrine secretions of the pancreas?
- the acinar cells secreting digestive enzymes
- the duct cells secrete bicarbonate
What is the structure of the pancreatic acinar cells?
- apical zymogen granules
- basal nucleus
- abundant rough ER
What is the purpose of the acinar cells?
secrete enzymes to break down proteins, carbohydrates and fats
One acinus is made up of lots of
acinar cells
The secretions of the acinar cells travel down _____ and combine with bicarbonate from _____ ______
ducts
duct cells
What is it in the pancreas that produces the enzymes?
the acinar cells
What is it in the pancreas that produces the bicarbonate?
the duct cells
What two structures allow storage in the stomach?
- sphincters
2. rugae
What three things do you need in the stomach for mechanical digestion?
- smooth muscle;
- the additional oblique layer in the stomach
- sphinctors
What two things are needed for chemical digestion?
- secretion of strong chemicals (acids and enzymes)
2. protective epithelium
