MMED2931 Lecture Notes - Lecture 12: Submucosa, Myenteric Plexus, Lamina Propria
Gut lectures:
1. Gut structure – gross/fine 2. Secretion & digestion
3. Nerves & smooth muscle 4. Motility of the gut
Gut lecture 1: structures of the gut
Mechanisms for gut function:
- Motility: propels/mixes gut contents, exposes them to surface for absorption, expels
hazardous materials
- Secretion: exocrine: digestive juices, mucous, lubricating fluids, etc. Endocrine
(hormones): gut is like a huge endocrine organ
- Absorption: digested material absorbed into blood stream, pass thru liver, to be
available to body
- Digestion: the result of motility, secretion and absorption. Efficiency affected by
motility and secretion and by regulation (nerves/hormones)
- Blood flow: adjusted to needs of digestion and systemic circulation
- Immune defence: prevent translocation of pathogens into body
Gross anatomy of the GI tract: continuous tube from mouth → anus
- Mouth → pharynx → oesophagus → stomach → small intestine → colon → anus
- Also, accessory organs: salivary glands, pancreas, liver, biliary system
- Oesophagus: tube that connects pharynx-stomach, no digestion at all
- Upper stomach: a reservoir, stores food and secretes acid, etc.
- Lower stomach grinds food into paste, pumps food → duodenum
- Small intestine: where almost all of digestion takes place. 3 components: duodenum,
jejunum, ileum.
o Gall bladder → bile duct (pancreas shares a common duct) → small intestine
- Colon: ascending colon, transverse colon, descending colon
7 sphincters: rings of thickened circular muscle (usually smooth muscle), control flow of gut
content
- Closed at rest, inhibitory neural input required to actively relax and open
- Upper oesophageal sphincter Lower oesophageal sphincter
- Phyloric sphincter Sphincter of Oddi Ileo-caecal junction
- Internal anal sphincter External anal sphincter
- Sphincter of Oddi: regulates bile and pancreatic juice flow, also prevents small
intestine contents entering the duct
- Striated: upper oesophageal sphincter & external anal sphincter
Human colonic (aka large intestine) structure:
- Teniae coli: 3 separate longitudinal ribbons of smooth muscle on outside of colon
o Small intestine mostly fluid easy to move doest eed this
o Fluid mostly absorbed by the time contents reach colon solid
Blood supply to the gut: arterial, microcirculation, venous
- Arterial supply: from dorsal aorta
o Coeliac artery: oesophagus, stomach, liver, spleen, pancreas, duodenum
o Superior mesenteric artery: small intestine, first half of large intestine
o Inferior mesenteric artery: lower large intestine
- Microcirculation in the gut: anastomoses (arteries join with each other, form loops)
- Venous collection occurs in parallel to arterial supply but drains into hepatic portal
vein → liver (except for oesophagus and rectum veins)
find more resources at oneclass.com
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Document Summary
Gut lectures: gut structure gross/fine, nerves & smooth muscle, secretion & digestion, motility of the gut. Motility: propels/mixes gut contents, exposes them to surface for absorption, expels hazardous materials. Secretion: exocrine: digestive juices, mucous, lubricating fluids, etc. Endocrine (hormones): gut is like a huge endocrine organ. Absorption: digested material absorbed into blood stream, pass thru liver, to be available to body. Digestion: the result of motility, secretion and absorption. Efficiency affected by motility and secretion and by regulation (nerves/hormones) Blood flow: adjusted to needs of digestion and systemic circulation. Immune defence: prevent translocation of pathogens into body. Gross anatomy of the gi tract: continuous tube from mouth anus. Mouth pharynx oesophagus stomach small intestine colon anus. Also, accessory organs: salivary glands, pancreas, liver, biliary system. Oesophagus: tube that connects pharynx-stomach, no digestion at all. Upper stomach: a reservoir, stores food and secretes acid, etc. Small intestine: where almost all of digestion takes place.