Large Intestine Structure and Function Flashcards

1
Q

Where does the ileum finish and the caecum begin?

A

The ileocaecal valve

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2
Q

What is the caecum?

A

The first part of the colon/ large intestine

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3
Q

Why is the caecum described as a blind sac?

A

Caecum means blind in latin, named because it has no function in humans

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4
Q

What two structures enter the caecum?

A

The ileocaval valve and vermiform appendix

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5
Q

What regions of the colon are there?

A

Ascending, transverse, descending and sigmoid

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6
Q

What layers of the muscluaris externa are there in the large intestine?

A

Circular muscles and longitudinal muscles

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7
Q

Which layer of the muscularis externa is incomplete?

A

Longitudinal

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8
Q

What muscles lead to puckered appearance of the large intestine?

A

Contraction of the teniae coli (run entire length of colon)

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9
Q

Describe the histology of the large intestine mucosa?

A

Mucosa comprised of simple columnar epithelium

Large straight crypts lined with large numbers of goblet cells for lubrication and movement of faeces

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10
Q

Describe the rectum?

A

Straight muscular tube between end of sigmoid colon and anal pit

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11
Q

What is the difference between the rectal muscular externa and other regions of the canal?

A

Thick compared to other regions of the canal

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12
Q

What is the anal canal?

A

2-3cm between the distal rectum and anus

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13
Q

Describe the type of muscles in the anal sphincters

A

Internal - smooth muscle

External - skeletal muscle

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14
Q

What is the osmotic role of the colon?

A

Dehydrates chyme and creates faecal pellets

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15
Q

What benefit is three to a long residence time within the large intestine?

A

Leads to bacterial colonisation which allows fermentation of undigestible carbohydrates to yield short chain fatty acids and vitamin K

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16
Q

Describe the anal sphincters at rest

A

Closed

17
Q

What is a mass movement contraction?

A

Distention of rectal wall produced stimulates mechanoreceptors which lead to the defection relaxation

18
Q

What nerve is responsible for the defecation relaxation?

A

Pelvic splanchnic nerve (parasympathetic)

19
Q

What are enterotoxigenic bacteria?

A

Bacteria which produce enterotoxins - maximally turn on intestinal chloride secretion, causing profuse watery diarrhoea

20
Q

How do enterotoxigenic bacteria stimulate chloride channels?

A

Act by elevating intracellular secondary messengers like cAMP cGMP and calcium

21
Q

What is the treatment for secretory diarrhoea?

A

Give sodium/glucose solution to drive H2O absorption

22
Q

What treatment method saves 2 million children lives per year for diarrhoea?

A

Oral rehydration therapy