L8 Anatomy, histology + control of GI tract Flashcards
what makes up the GI tract?
Continous muscular tube - oesophagus, stomach, intestines, anal canal.
Anything else is an accessory organ - teeth, tongue, oral cavity, glands.
Describe the muscularis externa (under serosa) of the stomach.
3 layers:
- longitudinal (superficial)
- circular (middle)
- oblique layer (deep)
Layers of the GI tract from superficial to deep.
Superficial
- Serosa
- Muscularis externa (two layers: wide inner band of circular SM and outer band of longitudinal SM).
- submucosa (dense collagen fibres)
- mucosa
where will you find the submucosa plexus and myenteric plexus?
submucosa and muscularis layer of GI tract
what is distension?
stretch of the GI wall
which nerves provide intrinsic/extrinsic stimuli for GIT?
Extrinsic:
Autonomic nerves (CNS, Long reflexes)
- parasymp (vagus)
- symp
Intrinsic: Enteric nerves (found within plexuses - short reflexes)
Function of submucosa/myenteric plexuses.
Submucosa plexus
- motor nerves to glands
- secretion of fluid and mucus
myenteric
- motor nerves to muscles
- contraction of muscles to push object
is the GIT an endocrine or exocrine organ?
The GIT is the largest endocrine organ, hormones directly into blood stream
which cells in the GIT produce hormones?
enterochromaffin cells (scattered through mucosal layer)
Gastrin?
- 17 AA
- stimulates acid and pepsin and pancreatic secretions
- duodenum/gastric antrum
Cholecystokinin (CCK)?
- 33AA
- cells of duodenum, jejunum
- stimulates gall bladder contractions
- increases digestive enzyme conc (pancreas)
- dec motility
Secretin?
- Duodenum, Jejunum
- 27AA
- stimulates bicarbonate secretion
- inhibits gastric secretion
Motilin?
- Small intestine
- 22AA
- Increases motility
- stimulates release of pancreatic polypeptide
- stimulates gall bladder contractions
which hormone stimulates bicarbonate secretion?
secretin
