Lecture 8 - The stomach Flashcards
Stomach functions: what is it, where does it connect to in the GI tract, and what does it do?
Expanded portion of the gut
Extends from the oesophagus to the duodenum
Functions
– Stores food & controls the rate of
delivery of chyme into the duodenum
– Mechanical & chemical digestion
digestion → chyme
– Secretes intrinsic factor
– Destroys pathogenic bacteria
– Helps regulate digestion and appetite
Stomach location in anatomy: its location, its anterior relations, and posterior relations
Located mainly in the epigastrium and left
hypochondrium – varies in size & shape
and may extend into other regions
Anterior relations:
– Posterior to the anterior abdominal wall
– Left lobe of the liver
– Inferior to the diaphragm
Posterior relations:
– Diaphragm
– Lesser sac
– Spleen
– Splenic artery
– Pancreas
– Left kidney
– Left suprarenal gland
– Transverse colon and transverse mesocolon
The stomach: the four compartments of it and its curvatures/notches
Cardia - connects to the oesophagus
Body - The main, largest part of the stomach
Fundus - Above the body
Pyloris - bottom part of the stomach, connects to the duodenum: comprised of the antrum and the canal & sphincter
Lesser curvature - smaller curve at the top of the stomach
Greater curvature - bigger curve at the bottom of the stomach
Cardiac notch - located just behind the cardia
The stomach: its size
Varies in size - shape & location according to contents, muscle tone & position of individual
Rugae – longitudinal folds in mucosa & submucosa which allow the stomach to expand in response to food
Folds flatten when the stomach is distended
Omenta: what are they, what are the two types, and what do they do?
A fold of the peritoneum connecting the stomach with other abdominal organs
- Lesser omentum - extends from the lesser curvature to the liver
- Greater omentum - extends from the greater curvature to the transverse colon
Microscopic anatomy of the stomach
Slide 11 watch podcast 6/11
Why isn’t the mucosa destroyed by the stomach’s acidic environment?
1 - The surface cells & the cells of the pits produce a protective mucous layer
2 - Surface epithelial cells possess tight intercellular junctions
3 - Rich submucosal vasculature – provides bicarbonate ions, nutrients and oxygen and removes toxic products
Modifications of the mucosa: what are gastric glands arranged into, what zones are they, and what are the structures of the zones?
Gastric glands are arranged in three histological
zones:
Cardiac zone:
* Branched tubular glands with coiled secretory portions
* Secrete mucous and lysozyme
Pyloric zone
* Branched tubular glands with coiled secretory portions
* Secrete mucous, lysozyme & gastrin
Principle (stomach body) zone:
* Branched tubular gastric glands
* Contain a variety of cells that collectively secrete gastric
The principle zone: the gastric gland structure, the cells present, and their cell locations
The pit at the top, leads into the isthmus, leading into the neck, and finally ending in the base
Surface mucous cells – located on the luminal surface, before the pit of the gastric gland
Parietal cells - located throughout the gland but mainly in the isthmus
Stem and mucous neck cells – located mainly in the neck
Neuroendocrine and Chief cells – located in the base
The gastric gland - surface mucous, mucous, parietal, chief, and neuroendocrine cells: what is their location, and what do they do?
- Surface mucous cells & mucous neck cells - secrete mucous which forms a viscous barrier to protect against the acidity of the gastric juices
- Parietal cells in the isthmus - secrete HCl & intrinsic factors, HCl kills microbes in food and activates pepsinogen and intrinsic factor which facilitates the absorption of vitamin B12 in the
terminal ileum - Chief cells in the base - secrete pepsinogen, activated to pepsin which breaks down proteins
- Neuroendocrine cells in the base - secrete hormones e.g. gastrin, serotonin, somatostatin, Ghrelin, etc:
Gastrin stimulates HCl production
Serotonin increases peristalsis
Somatostatin inhibits local neuroendocrine cells
Ghrelin induces hunger
Stomach submucosa: what is it and what does it contain?
Dense, irregular connective tissue
Contains:
* Blood vessels
* Lymphatic vessels
* Meissener’s plexus
Modifications of the muscularis externa: its three layers and the pyloric sphincter
Inner oblique
Middle circular
Outer longitudinal
The extra layer is an adaptation for churning and mixing the chyme with the mucosal secretions (? leccy)
Pyloric sphincter – thickening of the muscle layer prevents emptying when
Serosa: why is the outer layer of the stomach serosa and what is the serosa?
The stomach is an intraperitoneal organ therefore the outer layer is a serosa
Consists of a thin layer of connective tissue covered by a simple squamous mesothelium
(visceral peritoneum)
Neurovascular stomach supply
Stomach is in the foregut:
* Blood supply from the coeliac trunk
* Innervation from T5-T9, greater splanchnic nerve, coeliac ganglion
* Lymphatic drainage into the coeliac nodes
Arterial stomach supply: what is the main artery, what are the subdivisions of the artery, why are there subdivisions, and
Coeliac trunk
Left gastric, splenic, and common hepatic
The stomach needs a rich blood reservoir to ensure an adequate supply for churning and secretion of gastric juices
