Lecture 21: Stomach and Pancreas Flashcards
What is the peritoneum?
The peritoneum is a serous membrane that lines the abdomen
- Parietal layer:
lines the body wall - Visceral layer:
covers the organs
Between these layers is a fluid filled space
What does retroperitoneal mean?
Retroperitoneal:
posterior to the peritoneum
What is the mesentery and what is its function?
Mesentery:
Double layer of visceral peritoneum that connects organ to body wall
What is an omenta and what is its function?
Omenta:
Double layer of visceral peritoneum that connects an organ to another organ
Where is the stomach located?
J-shaped organ
* Located at the base of the esophagus
* Esophagus passes through diaphragm (esophageal hiatus)
What structure prevents reflux?
Lower esophageal sphincter (LES) prevents reflux
What are the four main parts of the stomach and where are these located?
- Fundus - top part of stomach where gases can build up
- Cardia - area around where the esophagus enters the stomach
- Body - the main section of the stomach
- Pylorus (pyloric antrum) - The end section close to where the stomach enters the duodenum
How is the stomach held in place?
Held in place by the two omenta:
Lesser omentum:
Stomach to liver
Greater omentum:
Stomach to transverse colon
How is the muscularis modified for the stomach?
It is modified for motility, with three layers (new inner layer):
- Oblique (inner)
- Circular (middle)
- Longitudinal (outer)
What modifications are made to the submucosa of the stomach?
- Rugae are temporary folds that allow for the expansion of the stomach (~1.5L)
- Core of submucosa
- Important for storage
What modifications are made to the mucosa of the stomach?
- Simple columnar epithelium
- In-folding increases surface area for secretion – gastric
glands - Glands do not flatten
What does the stomach need to function? (think secreted things)
- Acid and enzymes for digestion
- Mucous for protection
- Hormones for regulation
What do the gastric pits (top part) above gastric glands secrete?
Secrete mucous (protection) (goblet cells)
What are the three types of cells in gastric glands?
Parietal cells
Chief cells
G cells (bottom of gastric gland)
What do chief cells produce and what are some properties of the cell?
Chief Cells: Produce enzymes
* Abundant rough endoplasmic reticulum within the cell
* Apical zymogen granules (contain pepsinogen)
* Basal nucleus
What do parietal cells produce and what are some properties of the cell?
Parietal Cells: Produce acid
* Pump ions (H+)
* Abundant mitochondria
* Central nucleus
* Folded structure to increase surface area
What do G cells secrete?
Hormones (gastrin)
How is the stomach controlled?
Endocrine Control
* Endocrine cells in mucosa
* Gastrin and Ghrelin secreted into the bloodstream
Gastrin = stimulates the stomach to release gastric acid which is crucial for digestion
Ghrelin signals to the brain the stomach is empty and it is time to eat
Neural control:
* Enteric nervous system (ENS) - local reflexes (primary control)
* CNS modulates ENS function – long neural reflexes
How does digested material (chyme) enter the small intestine?
Through the pyloric sphincter, allowing for controlled release into the duodenum
What is required as chyme enters the small intestine from the stomach?
Requires:
– Further digestion (enzymes)
– Protection from acidic chyme
* Mucous
* Neutralize acid
Mucous provided by glands in the submucosa of the
duodenum.
Enzymes and bicarbonate provided by pancreas
How are the enzymes and bicarbonate produced transported into the small intestine from the pancreas?
Release of these substances is controlled by the hepatopancreatic sphincter (at end of pancreatic duct). This lies close to the Duodenal papilla – which projects into the duodenal lumen (allowing the substances to enter the SI)
What is the shape and position of the pancreas?
- Retroperitoneal
- Head in C-shaped duodenum
- Tail to spleen
- Posterior to the stomach
- Duct into duodenal lumen
What are the endocrine and exocrine functions of the pancreas?
Endocrine:
* Pancreatic islet alpha cells secrete glucagon
* Pancreatic islet beta cells secrete insulin
Exocrine:
* Acinar cells secrete digestive enzymes
* Duct cells secrete bicarbonate
What is the structure and function of acinar cells?
Structure:
* Apical zymogen granules
* Basal nucleus
* Abundant rough ER
Function:
* Secrete enzymes
