Oesophagus and stomach Flashcards
Oesophagus: list the main functions, anatomical levels, anatomical relations, organisation and function of muscle types, and epithelia of the oesophagus Gatsrooesophageal spincter: summarise the structure and function of the gastrooesophageal sphincter Stomach: list the main functions, distinguish between the functional regions and recall the movements of the stomach Gastric gland: recall the structure and function of a typical gastric gland and its constituent cells (including mucous cells,
What is the basic structure of the gut wall? (x6)
- MUCOSA EPITHELIUM – single-cell lining.
- Lamina propria – loose layer of connective tissue.
- Muscularis mucosae – thin layer of muscle.
- SUBMUCOSA – connective tissue, blood vessels and nerve plexus.
- MUSCULARIS – Smooth muscle. Containing nerve plexus.
- SEROSA/ADVENTITIA – connective tissue and epithelium.
- Some secretory tissue exists outside of these walls.
Position of the oesophagus? And proximity to other major structures?
Originates C5. Extends through the diaphragm and into the abdomen.
Comes into contact with the trachea, aorta and nerves – clinically significant if there’s an issue with the oesophagus.
How is the epithelial lining of the oesophagus adapted for its function? (x3 points)
Epithelial lining of oesophagus needs to be robust and no absorption needed.
Therefore, it is stratified squamous and non-keratinising.
Also has mucus secreting glands (and saliva) for lubrication.
What happens to the oesophagus at rest? Describe the process that reverses this change.
When not eating, oesophagus shuts at both ends: AT REST, upper and lower oesophageal sphincter close. At swallowing, the swallowing centre in the brain recognises this process, and has a larger effect on the upper sphincter as it does with the lower sphincter – both sphincters = tonically active.
How does the upper and lower oesophageal sphincter differ in make-up?
Upper = more skeletal muscle.
Lower = predominantly smooth muscle, with some skeletal.
How does peristalsis occur? What is bolus is too big?
In peristalsis, nerve stimulus contracts muscle immediately above the bolus (food), and relaxes the muscle immediately below. Works independent of gravity.
If bolus is too big, the contraction is insufficient to move it any further. SO, a second peristaltic wave is triggered by the brain.
What two types of muscle do you have in the muscularis in the oesophagus?
You have circular and longitudinal muscular walls in the oesophagus.
What is the gastro-oesophageal junction?
Gastro-oesophageal junction – when oesophagus meets the stomach.
What happens to the epithelium at the gastro-oesophageal junction?
From stratified squamous epithelium to simple columnar epithelium.
Why is the lower oesophageal sphincter less well-defined as the upper sphincter? (x2)
(1) diaphragm. Diaphragm naturally puts pressure on the oesophagus, acting as the sphincter.
(2) When stomach is empty, it folds, so the oesophagus becomes much thinner anyway – essentially acts like a sphincter.
Lining of stomach is quite ridged – what’s the name of these ridges? (x2)
Gastric folds or RUGAE.
Why are gastric folds important?
When empty, the folds allow the stomach to reduce in size.
When full, the folds allow stomach expansion i.e. the folds stretch and walls seem smooth instead.
What are the two functions of the stomach?
Break down macromolecules.
Immunological function because of acidity.
What are the five regions of the stomach?
- CARDIAC: immediately entering the stomach.
- PYLORUS: immediately leaving the stomach.
- BODY: main region of the stomach.
- FUNDUS: region above the body.
- PYLORIC ANTRUM: towards the bottom of the stomach.
What is the function of each of the five regions of the stomach?
- CARDIAC: produce a lot of mucous.
- PYLORUS: produce a lot of mucous.
- BODY: digestion site, so produce a lot of mucus, HCl and pepsinogen.
- FUNDUS: digestion site, so produce a lot of mucus, HCl and pepsinogen.
- ANTRUM: produces gastrin – hormone produced to facilitate function.
How does the antrum, body and fundus, and cardia and pyloric epithelium differ?
All have simple columnar invaginations – which create glands.
- CARDIAC AND PYLORIC: mostly mucous/HCO3- producing cells (in blue).
- BODY AND FUNDUS: surface = mucous/HCO3- producing cells (blue). Less superficially, there are mucous producing cells that do not produce bicarbonate (black), and deep inside the invaginations are pepsinogen and HCl producing cells (purple).
- ANTRUM: superficially, there are mucous/HCO3- producing cells (blue). Dotted with gastrin producing cells (in yellow).
What is a gastric chief cell? Cellular components? (x3)
GASTRIC CHIEF CELL: protein-secreting epithelial cells – in this case, the protein is PEPSINOGEN. Have lots of RER and Golgi. Masses of blue apical secretion granules.
What is a parietal cell? Cellular components? (x3) Cell in the resting and active state?
PARIETAL CELL: acid secreting cell.
AT REST: not producing acid. Contains lots of mitochondria, internal canaliculi (indicated by ‘C’ in the photo) which are reservoirs, and cytoplasmic tubulovesicles containing H+/K+ ATPase (indicated by ‘T’).
WHEN ACTIVE: secreting acid. Tubulovesicles fuse with membrane and microvilli project into the canaliculi – providing large membranous surface area for canaliculi to secrete their acid.
