Large intestine: structure and function Flashcards Preview

2ND YEAR SYSTEMS: GI > Large intestine: structure and function > Flashcards

Flashcards in Large intestine: structure and function Deck (25)
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1
Q

where does the large intestine start?

A

ileocaecal valve

2
Q

what are the 4 parts of the large intestine?

A

ascending
transverse
descending
sigmoid

3
Q

what’s different about the muscularis externa of the large intestine compared with S.I?

A

The large intestine has a complete circular muscle layer but the longitudinal layer is in 3 separate strips throughout the length of the large intestine

4
Q

what gives the large intestine it’s puckered appearance?

A

contracted haustra

5
Q

Main function of goblet cells in the lining of crypts in large intestine

A

Goblet cells are interspersed between simple columnar epithelium producing mucus that provides lubrication for movement of faeces

6
Q

describe rectum structure:

mucosa, and muscula externa

A

The rectum is a straight, muscular tube

mucosa - simple columnar epithelium

muscularis externa - thicker to hold onto faeces

7
Q

what is the mucosa of L.I comprised of?

A

simple columnar epithelium

8
Q

what are teniae coli?

A

the ribbon-like parts of longitudinal smooth muscle - entire length of colon

9
Q

where is the anal canal found?

A

between distal rectum and anus

10
Q

is the muscularis thicker in the rectum or anal canal?

A

anal canal due to the internal anal sphincter

11
Q

which type of muscle is found in:-
External anal sphincter
Internal anal sphincter

A

external - skeletal muscle

internal - ring of smooth muscle

12
Q

what type of control is the anal canal under?

A

voluntary - you can hold a poo in if you can’t find a toilet

13
Q

what is the outermost layer of the large intestine?

A

Ascending and descending colon - adventitia

Transverse colon - serosa

14
Q

main functions of the colon

A

actively transports Na+ from lumen into blood which in turn pulls H20 across with it - dehydrates chyme and makes solid faecal pellets

bacterial fermentation of undigested carbohydrate

15
Q

what products are made from bacterial fermentation of undigested carbohydrate?

A

short chain fatty acids
vitamin K
gas - nitrogen, CO2, H2, CH4 etc

16
Q

What is Vitamin K important for?

A

blood clotting

17
Q

in a normal state, how is the anus kept closed?

A

internal anal sphincter (s.m under automatic control) and external anal sphincter (skeletal muscle under voluntary control)

18
Q

what is the wave of intense contraction called that follows eating a meal

A

mass movement contraction

19
Q

Describe the defaecation reflex?

A

reflex that gives us the urge to go for a poo

it is initiated by the contraction of the rectum. The internal anal sphincter relaxes whilst the external contracts. Increased peristaltic activity moves material along and increases pressure on ext anal sphincter. This then relaxes under voluntary control and expels faeces

when this reflex is triggered you can either choose to delay or defecate

20
Q

What control is there over the defaecation reflex?

A

parasympathetic control via pelvic splanchnic nerves (no sympathetic influence)

however, there is a voluntary delay of defaecation - descending pathways

21
Q

symptoms associated with constipation? (4) and main reason for these?

A

headaches
nausea
loss of appetite
abdominal distension

due to distension of rectum

22
Q

Causes of diarrhoea (5)

A
pathogenic bacteria
protozoans
viruses
toxins
food
23
Q

give 2 types of enterotoxigenic bacteria that commonly cause diarrhoea

A

vibrio cholerae

excherichia coli

24
Q

how do enterotoxigenic bacteria work?

A

These toxins turn on intestinal Cl- secretion from crypts - they elevate intracellular second messengers like cAMP, cGMP etc and ensure the CFTR channel is always open so therefore the crypts secrete H20 all the time as H20 moves with Cl- => profuse watery diarrhoea

25
Q

treatment of secretory diarrhoea

A

Give sodium/glucose solution
oral rehydration therapy - drives H20 absorption

must let diarrhoea run but keep hydrating them