Swallowing and Stomach Histology Flashcards
Define peristalsis.
Wave-like contractions promoting motility in GIT
What muscles are involved in peristalsis in the esophagus?
Inner circular muscle and outer longitudinal muscle
How is primary peristalsis in the esophagus initiated?
By swallow
How is secondary peristalsis in the esophagus initiated?
Distension of esophagus
Can peristalsis in the esophagus still occur after vagotomy?
Yes. Normal swallowing involves both ANS and ENS
How is peristalsis controlled?
Sequential activation of motor neurons
Role of enteric nervous system to co-ordinate contractions
What neurotransmitter drives contraction behind the bolus?
ACh
What neurotransmitter drives relaxation infront of the the bolus?
NO
What type of inhibition occurs in the esophagus during multiple rapid swallow?
Deglutitive inhibition
What is Esophageal Achalasia?
Motility disorder
Impaired or absent peristalsis
Distended esophagus and ‘bird beak’ appearance
What is Corkscrew Esophagus?
Impaired motility
Un-coordinated contractions
Diffuse spasms
What allows the stomach to churn food in another way?
Oblique muscle layer
What are the 4 regions of the stomach?
Cardia, fundus, body/corpus, pylorus
What hormones are produced in the stomach?
Gastrin and Ghrelin
What is the cardia’s function?
Relaxation
Mainly mucous
What is the fundus/body’s function?
Mixing
Mainly gastric acid
What is the pylorus’ function?
Muscular - aids physical digestion
Mainly mucous
Describe the surface mucous cell?
Produces thick mucous
HIgh in bicarbonate
Protects stomach from itself
Describe the mucous neck cell?
Present in neck or isthmus
Less columnar - rounded nuclei
Less alkaline secretion - containing mucin
Describe the parietal cell?
Present in neck and deeper parts of the gland
Strong eosinophilic staining (pink)
Intracellular canaliculus - many folds for proton pump expression
Secretes HCL and intrinsic factor
Describe the chief cell?
Lower region of gastric gland
Produces pepsinogen and gastric lipase
Describe the enteroendocrine cell?
Gastrin producing cells in pylous
5HT producing cell
Describe the stem cell?
Undiiferentiated cells
What is the role of gastric mucous?
Mechanical and viscosity protection
Protects from auto-digestion
What is mucous secretion stimulated by?
Prostaglandins
What inhibits prostaglandins?
NSAIDS
What does gastric acid do?
Denatures proteins - exposes peptide bonds
Converts pepsinogen into pepsin
Protective role - low pH not permissive for bacterial growth (bar H.pylori)
What produces H+ and HCO3- in the parietal cell?
Carbonic anhydrase
How does H+ move in the parietal cell?
Moves apically by active transport
What maintains the pH of the parietal cell?
HCO3- moving out of the cell across the basolateral membrane
Where is H+/K+ATPase mainly found in the parietal cell?
Apical surface
What reabsorbs K+
Na+/K+ATPase using active transport
What intrinsic factor is produced by parietal cells?
Glycoprotein produced in fundus and corpus
What is the glycoproteins optimum pH?
7 - required for uptake of vitamin B12
What does vitamin B12 bind to before the glycoprotein?
Haptocorrin
Where is B12 absorbed?
Endocytosed by cells in the terminal ileum
How is B12 released?
In complexes with transcobalamin II in the cells
What is a clinical condition of loss of parietal cells?
Pernicious Anaemia
What do G-cells produce?
Gastrin hormone into the blood
Promotes gastric acid secretion
What do D-cells produce?
Somatostatin
Inhibits G cells
What do EC cells produce?
Serotonin and substance P
Promotes gut motility
