Large Intestine and Diarrhoea

Question 1

What parts of the large intestine are retroperitoneal?

Answer 1

Ascendign and Descending colon

Question 2

What differentiates large intestine from small intestine?

Answer 2

• Taenia Coli - three longitudinal bands of muscle
• Appendices epiploicae - fatty tags on surface
• Haustra - sacculations

Question 3

What cells make up the crypts of lieberkuhn in LI?

Answer 3

Goblet cells - mucous for lubrication

Absorptice cells - water absorption

stem cells - at bottom to migrate up and differentiate into these two cell types

Question 4

Describe the motility of the large intestine and initiation of each

Answer 4

Haustruations are the predominant contraction in caecum and proximal colon, contracting circular muscle in order to squeeze and roll faecal material about, aiding water and electrolyte absorption - Initiated by acetylcholine and substance P release

The remainder of colon shows propulsive movements by peristalsis. Controlled through vagal stimulation, gastrin and CCK

Question 5

What effect does symmpathetic innervation have on gut motility?

Answer 5

Decreases it

Question 6

What effect do opiates have on gut motility?

Answer 6

Decrease it

Question 7

Describe the process of defaecation

Answer 7

Internal anal sphincter relaxes due to paraasympathetic innervation

External anal sphincter relaxes due to pudendal nerve

Conscious control to inhibit reflex is overcome with addition of extra faecal matter

Question 8

What makes up faecal matter?

Answer 8

cellulose
epithelial cells
bacteria
salt
stercobilin

Odour - hydrogen and organic sulphides

Question 9

What is the function of the large intestine?

Answer 9

water absoprtion
electrolyte absorption
Storeage of faecal matter

Question 10

How is water absorbed in the large intestine

Answer 10

Na and Cl pumped into paracellular spaces and water follows by osmosis. Then all pass ito epithelial cells

Question 11

What ion travels against water flow but aids water absorption?

Answer 11

potassium

Question 12

How are electrolytes absorbed in the large intestine?

Answer 12

• Na - in lumen exchanged for H
• Cl/HCO3 - Chloride out of lumen, Carbonate in
• Potassium into lumen, sodium out

Question 13

What happens to urea in large intestine?

Answer 13

secreted into colon for bacterial metabolism to produce NH4 and HCO3 - converted to NH3, CO2 and H2O which can freely diffuse

NH3 trasnported to liver for amino acid synthesis

Question 14

What is the most abundant type of gut flroa?

Answer 14

Strict anaerobes

Question 15

List the functions of gut flora

Answer 15

• salvage energy and nutrients which escape absorption in SI
• compete with pathogenic bacteria for space and nutrients
• Convert CB
• Degrade cholesterol and some drugs
• Synthesis certain vitamins (K, B12, thiamine and riboflavbin)
• Fermentation of indigestible carbohydrate into short chain fatty acids

Question 16

What effect to broad spectrum antibiotics have on gut flora?

Answer 16

diminish them - increases risk of diarrhoea

Question 17

What is osmotic diarrhoea

Answer 17

AKA Malabsorpive diarrhoea - Decreased intesinal absorption

Question 18

What causes osmotic diarrhoea?

Answer 18

- laxatives
pancreatic insufficiency
- acarbose
- orlistat (lipase inhibitor)
- enzyme deficiencies
- inflammatory disease
- short bowel syndrome

Question 19

What is secretory diarrhoea?

Answer 19

Excess secretion of electrolytes into the intestine causes decreased intestinal absorption

Question 20

What causes secretory diarrhoea?

Answer 20

• Zollinger-Ellison syndrome
• acute infections
• malabsoprtion of fat
• laxative abuse
• failure o bile salt absorption
• carcinoid syndrome

Question 21

What is inflammatory diarrhoea?

Answer 21

increased secretion with propulsibe bowel activity

Question 22

What causes inflammatory diarrhoea?

Answer 22

inflammatory bowel disease
infectious disease
irritable colon

Question 23

What is the most common pathogen which causes diarrhoea?

Answer 23

Campylo bacter

Question 24

What does vomitting alongside diarrhoea suggest in terms of enteric infection?

Answer 24

Due to a pre-formed toxin - S.aureus or B.cereus

Question 25

What toxins are produced after consumption?

Answer 25

E.Coli and C.Difficile

Question 26

Name a reason someone would be at increased risk of campylo bacter infection

Answer 26

decreased acid production - omeprazole etc. as campylo bacter are sensitive to stomach acidity

Question 27

Which pathogen causes the production of shiga toxin?

Answer 27

E.Coli - shiga toxin causes enterocyte death

Question 28

How can C.Difficile be treated?

Answer 28

Metrondiazole

Vancomycin

Question 29

How does ORT treat diarrhoea?

Answer 29

Infusion of electrolytes such as sodium and chloride increases their absorption within the intestine, and therefore encourage water movement out of intestine

Potassium IV also encourages Sodium transport as potassium moves into lumen. Water follows sodium. Must monitor with ECG

Question 30

How do quinolones treat diarrhoea?

Answer 30

Deactivate the enzyme involved in microsomal replication - e.g. ciproflaxin

Question 31

How do zinc supplements affect diarrhoea?

Answer 31

Decrease severity and duration

Question 32

Name and describe the mechanism of action for one diarrhoea causing bacteria

Answer 32

Clostridium Difficile - causes a decrease in colonisation resistance and therefore leads to colonic colonisation. This leads to toxin production, inducing an inflammatory response and colitis. Results in cell damage and therefore diarrhoea

Question 33

Name and describe the mechanism of action for one diarrhoea causing protozoa

Answer 33

Giardia (Giardiasis) - these cause decreased expression of brush border enzymes and progammed cell death of small intestinal cells. This results in decrease of food absorption and therefore decrease in water absorption, resulting in diarrhoea

Question 34

Name and describe the mechanism of action for one diarrhoea causing virus

Answer 34

Rotavirus - malabsoprtion through destruction of enterocytes.

Toxin produced (NSP4) unduces Ca-dependent chloride secretion, disrupts SGLT1 transport-mediated reabsoprtion of water and can activate calcium secretory mechanisms - results in increased watery stool bulk - diarrhoea