Large intestine structure and function Flashcards

1
Q

Anatomy of the colon

A
Begins at ileocaecal sphincter 
Ascending 
Transverse 
Descending 
Sigmoid 
The circular muscle layer is complete 
The longitudinal muscle layer is not 
Teniae coli- into haustra 
Crypts are a lot longer than in SI and contain goblet cells needed for the lubrificationof faeces
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2
Q

What are teniae coli?

A

Three bands which are continuous in the colon

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3
Q

What are haustra?

A

Contraction of the teniae coli leads to the formation of haustra- puffa jacket appearance

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4
Q

Epithelium in the colon

A

Simple columnar

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5
Q

Epithelium in the rectum

A

simple columnar

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6
Q

Rectum anatomy

A
  • Straight muscular tube which connects the sigmoid colon to the anal canal
  • Muscularis externa is very thick
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7
Q

Anal canal epithelium

A

From simple columnar to stratified squamous

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8
Q

Anatomy of the anal canal

A
  • Very thick muscularis externa: internal anal sphincter

- Skeletal muscle: external anal sphincter

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9
Q

Role of the colon?

A

-Absorption of H20 AND Nacl into the blood- concentrates faeces.
H20 follows the uptake of Na
-Large gut flora= breakdown of nutrients into FA, gas (Flatus) and vitamin K (used for blood clotting)

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10
Q

What is the number of colonic flora in the gut compared with the number of cells in the body?

A

gut flora= 10^14

Cells in the body= 10^12

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11
Q

How does defection occur

A

Ileocaecal sphincter reflex pushes chyme into the LI
When build up occurs: mass movement contraction= massive peristaltic movement of chyme into the rectum
Mechanoreceptors in the rectum detect change- defection reflex
Rectum contracts
IAS relaxes
EAS contracts
when enough pressure builds up- EAS relaxes

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12
Q

Control of the IAS and EAS

A

IAS- autonomic control

EAS- voluntary control

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13
Q

Control of defaecation reflex?

A

Parasympathetic control through pelvic-splanchnic nerves.

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