Lecture 21- The stomach and pancreas Flashcards
What is the process that propels food down the esophagus to the stomach?
Peristalsis= is the contraction of smooth muscle behind the bolus
What is the shape of the stomach and where is it located?
- J-shaped organ
- Located at the base of the esophagus
What does the esophagus pass through in order to reach the stomach?
- Passes through diaphragm
- Therefore there is a break in the diaphragm called the esophageal hiatus
What structure at the esophageal hiatus prevents reflux?
- Lower esophageal sphincter (LES)
- Is a band of smooth muscle
- Relaxes to allow bolus/ food to pass into the stomach and contracts to prevent acid going back when the stomach contracts
Where is the stomach located in relation to other organs in the abdominal-pelvic cavity?
- Liver takes most of the upper right quadrant and is associated with the gall bladder (mostly behind)
- Middle part is the stomach in front of the pancreas
- Spleen is then in the left corner
What are the 4 ‘sections’ of the stomach?
- Cardia: what the esophagus opens into
- Fundus: Find lots of gastric glands
- Body: Central area of the stomach/ makes up most of it
- Pylorus (pyloric antrum): Cave like area. Is the gate keeper as it contains the pylorus sphincter
What is the role of the pylorus sphincter?
- Regulates the process of gastric (stomach) emptying into the duodenum (small intestine)
- Relax to let pass through, contract to restrict access
What are the functions of the lesser and greater curvature of the stomach?
Act as attachment points for omentum (double layer of visceral peritoneum which connects organ to organ).
What does the lesser omentum connect? What does it contain?
- Lesser curvature (stomach) to liver.
- Include blood vessels
What does the greater omentum connect? What does it contain?
- Greater curvature (stomach) to transverse colon
- Include blood vessels, fat/adipose providing cushioning and immune cells (provides first line of defense for infection)
- Hangs down like an apron
What does the greater omentum have a yellowish appearance?
Due to adipose tissue it contains
What is the muscalris of the Stomach specialized for?
Motility, need strong contractions (peristalsis) as well as the ability to mix
How many layers of muscle are there in the stomach wall and what are these called?
3 Layers:
- Oblique (inner)
- Circular (middle)
- Longitudinal (outer)
Where in the stomach is the muscle thickest?
In the distal area (pyloric) of the stomach as more contraction needed
What are Rugae?
-Feature of the internal wall of the stomach
-Are temporary folds that allow for the expansion of the
stomach
-Important to allow for storage
What is an additional feature of the stomach that is important for its storage function?
Both sphincters (Lower esophageal sphincter+ Pyloric sphincter) need to be closed
What is the structure of a Rugae like?
- Folded core of submucosa with overlying mucosa
- Glands are also formed which are permeant (i.e don’t disappear even when Rugae are flattened out)
Describe the epithelium of the stomach? Why do we need this structure?
-Simple columnar epithelium
-In-folding increases surface area for secretion
-Glands are permanent!
Need…
-Acid and enzymes for digestion
-Mucous for protection (stop digestion of self)
-Hormones for regulation
What part of the gastric glands are most superior? What do they secrete?
-Mucous epithelia cells secrete mucus for protection
What cells exist further down the gastric gland? What do they secrete?
- Parietal cells secrete acid (HCl) and intrinsic factor (Important for vitamin B 12 absorption)
- G cells secrete hormones (gastrin) which regulate motility and secretion
- Chief cells secrete pepsinogen (an inactive precursor of pepsin which digests protein)
How are chief cells specialized for their function?
Produce enzymes so have…
- Abundant rough endoplasmic reticulum
- Apical zymogen granules (contain enzymes)
- Basal nucleus as top part full of granules about to be exocytosed
How are Parietal cells specialized for their function?
Produce acid so…
- Pump ions (H+) which needs energy
- Abundant mitochondria
- Central nucleus
- Folded structure to increase surface area
How is stomach function regulated with regards to endocrine control?
- Endocrine cells in mucosa
- Gastrin and Ghrelin secreted into the bloodstream
How is stomach function regulated neutrally?
-Enteric nervous system (ENS): local reflexes
(primary control)
-CNS modulates ENS function – long neural reflexes as going from the brain
What acts to control the release of chyme from the stomach to the small intestine?
Pyloric Sphincter (PS)
What is chyme?
- Partially digested material from the stomach
- All mechanical digestion is complete but some chemical digestion in the small intestine is still needed
- Is acidic
How many layers of smooth muscle does the duodenum/small intestine have?
2:
- Circular inner
- Longitudinal outer
What features are required in the small intestine wall due to chyme passing through?
- Further digestion (enzymes)
- Protection from acidic chyme via mucous and bicarbonate to neutralize acid
Where does the mucous in the small intestine come from?
Mucous provided by glands in the submucosa of the duodenum.
Where does the enzymes and bicarbonate in the small intestine come from?
Provided by the pancreas
What is the shape and location of the pancreas?
- Head in C-shaped duodenum
- Tail to spleen
- Posterior to the stomach
- Retroperitoneal
Is the duodenum retroperitoneal? If so why?
Yes, as is just acting as a receiving chamber doesn’t need to move
Where does the pancreas enter into?
- Pancreatic duct leads into the duodenal lumen
- Some people also have accessory pancreatic duct which leads to the same place
What does the pancreatic duct meet and where?
Bile duct meets pancreatic duct at the
entrance to the hepatopancreatic ampulla
Where does the Duodenal papilla project into?
Duodenal lumen
What does the liver produce and where is this stored?
Bile, stored in the gall bladder
What is the release of bile controlled by?
Hepatopancreatic sphincter
What are the exocrine functions of the pancreas?
- Acinar cells secrete digestive enzymes
- Duct cells secrete bicarbonate
Due to acinar cells secreting enzymes what structure do they have?
- Apical zymogen granules
- Basal nucleus
- Abundant rough ER
What other cells have the same structure as acinar cells and why?
- Chief cells of Stomach
- Salivary acinar cells
Because are all specialized for the secretion of enzymes
What structures in the stomach allow for storage?
- Sphincters
- Rugae: distention (folded submucosa)
Why is the pancreas secreting into the lumen of the GI tract considered excrine?
Lumen continuous with the outside world
For mechanical digestion in the stomach you need?
- Smooth muscle, additional oblique layer in stomach
- Sphincters
What is needed for chemical digestion in the stomach?
- Secretion of strong chemicals (acid, enzymes)
- Protective epithelium
