Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Yr 2 - GI & Metabolism > The Large Intestine > Flashcards

The Large Intestine Flashcards

1
Q

Describe the parts of the colon

A
  1. Cecum
  2. Ascending colon
  3. Transverse colon
  4. Descending colon
  5. Sigmoid colon
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the cecum

A
  • Blind ending sac

- Appendix dangling off (no known function)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are haustra?

A

Folds/small pouches (segments) of colon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the muscular layer of the colon made up of?

A

2 layers of smooth muscle:

  1. Inner circular layer
  2. Outer longitudinal layer
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is main job of colon?

A

Absorb salt and water from luminal contents which become fecal residue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does the colon secrete?

A

Large amounts of mucus (to help move fecal residue along), some hormones but no digestive enzymes

Secretes K+ and bicarbonate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the epithelium of the colon formed of?

A

Simple columnar epithelial cells, many goblet cells, endocrine cells and basal stem cells, but no Paneth cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the muscular layer of the colon called?

A

Muscularis externa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is the longitudinal smooth muscle in the muscularis externa arranged?

A

In 3 longitudinal bands called taenia coli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What separates the SI from the LI?

A

Ileo-caecal valve (one-way valve to stop stuff returning to SI –> flutter valve)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What causes the ileocaecal valve to open and close?

A

Mechanoreceptors

Stimulated by ileal distension causing valve to open and a contraction

Caecal distension causes valve to close

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is haustration?

A

Slow contractions of circular muscle squeeze contents to and fro, as in segmentation (called peristalsis in SI)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is mass movement?

A

Occasionally (a few times a day), become organised into a peristaltic wave (all along colon)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What happens to haustra as the mass movement sweeps by?

A

They briefly disappear, then reform (movement of stuff just relies on wave)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What do mass movements lead to?

A

Defecation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What can defecation be aided by?

A

Flattening of diaphragm, pushes onto sigmoid colon (pushing)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the smooth muscle of the colon controlled by?

A
  • Most is intrinsic via the enteric nervous system

- Some parasympathetic control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is a gastrocolic reflex?

A

A physiological reflex that controls the motility of the colon following a meal. As a result, the colon has increased motility in response to the stretch of the stomach with the ingestion of food. Triggers mass movement.

(poo immediately after meal)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Effect of increased sympathetic effect on colon?

A

Increased bowel movements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What hormones are involved in regulating colon motility?

A

Enteroendocrine and neurocrine influences, from cells releasing 5-HT and Peptide YY

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the ileal brake? What triggers it?

A

Caused by stuff moving through colon too quickly

Presence of undigested lipid in distal ileum and proximal colon releases peptide YY, slowing gastric emptying and small bowel peristalsis

22
Q

What performs digestion in the colon?

A

Bacteria, not human enzymes

23
Q

How do bacteria digest fibre?

A

To produce short chain fatty acids such as butyric acid, hydrogen, and methane

24
Q

How do bacteria digest urea and amino acids?

A

to produce ammonia

25
Q

How do bacteria digest bilirubin?

A

to produce urobilinogen and stercobilins

26
Q

How do bacteria digest cysteine and methionine?

A

to produce hydrogen sulphide

27
Q

How do bacteria digest primary bile aids?

A

to produce secondary bile acids

28
Q

How do bacteria digest conjugated bile acids?

A

to produce unconjugated bile acids

29
Q

What is bilirubin?

A

Bilirubin is an orange-yellow pigment that occurs normally when part of your red blood cells break down.

30
Q

How do bacteria break things down?

A

By fermentation

31
Q

What does fermentation release?

A

about 1L of nitrogen, hydrogen, and CO2

32
Q

What do the absorptive cells in the colon (that absorb Na and water) rely on?

A

Cells adapted to rely on short chain fatty acids (produced by bacteria on food we eat)

33
Q

How does the Na+ transporter work in the colon?

A

Secondary active transport

On one side of cell –> pushes out 3 Na+ into body/body and brings in 2 K+

Creates a cell low in Na+

On other side –> (inside colon) Na+ and short chain fatty acids drawn in

34
Q

What are short chain fatty acids used for?

A

Used by colonocyte for intracellular metabolism

35
Q

What channel allows Na+ to enter cell?

A

ENaC channel allows transcellular Na+ transport

36
Q

What is Na+ absorption controlled by?

A

Aldosterone (RAAS)

37
Q

How do Cl- ions enter cell?

A

Paracellular Cl- flux, followed by water

38
Q

What is a secretagogue?

A

Substance that causes another substance to be secreted

39
Q

What are the 2 major secretagogues in the colon?

A

cAMP and Ca2+ (produced by colon cells) –> effect on Cl- ions

40
Q

What toxins increase cAMP? What is effect of this?

A

Cholera and E. coli toxins

Secretory diarrhoea

41
Q

What toxin increases Ca2+? What does this lead to?

A

C. Difficile toxin

Secretory diarrhoea

42
Q

Describe movement of K+ in colon

A

Potassium can undergo secretion (in exchange for H+ ions) and absorption in the colon (usually net secretion)

Passive secretion exceeds active.

43
Q

What is K+ balance determined by?

A

Plasma [K+], aldosterone, cAMP

44
Q

Why are there so many nerve endings in anus?

A

Sampling - rectum releases a little bit of what is inside it (gas, liquid or solid) into the top of the anal canal

Anal canal can tell what it is (difference between solid, liquid and gas)

45
Q

What is the internal anal sphincter formed by?

A

Circular muscle (smooth muscle)

46
Q

What is the external anal sphincter formed by?

A

Skeletal muscle (voluntary)

47
Q

What happens as faeces enters rectum?

A
  1. Pressure rises
  2. This triggers reflex relaxation of the internal anal sphincter, and the urge to defecate
  3. A small amount of material enters the anus, allowing anal sampling
  4. The external anal sphincter contracts (relaxation when going to toilet)
48
Q

What does sitting or squatting aid with?

A

Increases the rectosigmoid angle, facilitating the passage of faeces.

49
Q

What else aids with increasing the rectosigmoid angle?

A

Relaxation of the puborectalis muscle

50
Q

What can provide additional force when going to the toilet?

A

Rectal peristalsis, sometimes triggering a colonic mass movement, plus raised intraabdominal pressure (Valsalva manoeuvre)

51
Q

What do bacteria in the colon do?

A

Digest fibre and other unused nutrients, and produce useful substances

52
Q

What is diverticulitis?

A

A gastrointestinal disease characterised by inflammation of abnormal pouches—diverticula—which can develop in the wall of the large intestine

Yr 2 - GI & Metabolism (51 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions