Physiology 3

Question 1

What are the different parts of the large intestine?

Answer 1

Caecum and appendix
Colon
Rectum
Anal canal and anus

Question 2

What are the different parts of the colon?

Answer 2

Ascending
Transverse
Descending
Sigmoid

Question 3

What are the sack-like bulges in the large intestine, caused by contraction of the circular muscle?

Answer 3

Haustra

Question 4

What is the appendix?

Answer 4

Blind ended tube with extensive lymphoid tissue connected to the distal caecum via the appendiceal orifice (obstruction –> appendicitis)

Question 5

Which substances are absorbed in the large intestine?

Answer 5

Na+, Cl- and water

Short chain fatty acids (from any carbs not absorbed in small intestine)

Question 6

Which substances are secreted in the large intestine?

Answer 6

K+, HCO3 and mucus

Question 7

Which features of the colon increase the surface area?

Answer 7

Colonic folds
Crypts
Microvilli

Question 8

Which cells are responsible for ion and water absorption in the colon?

Answer 8

Colonocytes –> surface epithelial cells

Question 9

Which cells mediate ion secretion?

Answer 9

Crypt cells

Question 10

Which cells are responsible for secretion of much into the colon?

Answer 10

Goblet cells

Question 11

Which ion may be lost significantly in the faeces in secretory diarrhoea?

Answer 11

K+

Question 12

What is the effect of aldosterone on the colon?

Answer 12

Na+ absorption

K+ secretion

Question 13

Which pattern of motility is responsible for non-propulsive segmentation in the colon?

Answer 13

Haustration

Question 14

What are the main functions of the liver?

Answer 14

• Carbohydrate, fat and protein metabolism
• Deactivation/activation of some hormones
• Storage
• Synthesis of proteins
• Protection
• Detoxification

Question 15

Which substances are stored in the liver?

Answer 15

Fat soluble vitamins (A, D, E and K)
Water soluble vitamin B12
Iron
Copper
Glycogen

Question 16

What happens to bile between meals?

Answer 16

Stored and concentrated in gall bladder

Question 17

What happens to bile during a meal?

Answer 17

Gall bladder contraction and sphincter of Oddi opens (due to CCK)
Bile spurts into duodenum via cystic and common bile ducts

Question 18

How do the bile juices get to the ducts?

Answer 18

Secreted from hepatocytes –> canaliculi –> biliary ductules and ducts

Question 19

What does the primary binary juice contain?

Answer 19

Primary bile acids
Water and electrolytes
Lipids and phospholipids
Cholesterol
IgA
Bilirubin
Metabolic wastes and conjugated drug metabolites

Question 20

What happens if there is too much cholesterol in the bile juices?

Answer 20

May precipitate into micro crystals that aggregate into gall stones –> cholelithiasis

Question 21

What is bilirubin?

Answer 21

Breakdown product of the porphyrin component of haemoglobin

Question 22

What is the best treatment for symptomatic gall stones?

Answer 22

Laproscopic cholecystectomy

Question 23

Which treatment may be suitable for patient with small/medium sized radiolucent stones and unimpaired gall bladder function?

Answer 23

Ursodeoxycholic acid –> dissolves them

SE: diarrhoea

Question 24

What happens to most of the bile salts entering the duodenum?

Answer 24

Reabsorbed in the terminal ileum

–> enterohepatic recycling

Question 25

How does hepatic encephalopathy occur?

Answer 25

Severe hepatic failure --> Failure of detoxification of ammonia to urea (via urea cycle) --> Blood ammonia levels rise and exert toxic effect on CNS

Question 26

What are the clinical features of hepatic encephalopathy?

Answer 26

Incoordination Drowsiness Coma Death due to cerebral oedema

Question 27

What are the treatment options for hepatic encephalopathy and hw do they work?

Answer 27

Lactulose --> ammonia converted to ammonium which is not absorbed Antibiotics --> suppress gut flora so inhibit ammonia production

Question 28

What is the process of water absorption from the lumen of intestines into the blood stream?

Answer 28

Passive process driven by transport of solutes (mainly Na+)

Question 29

What is the normal role of CFTR?

Answer 29

Normally little secretion of Cl- occurs because apical CFTR is either closed of not present

Question 30

Give some examples of factors that indirectly activate CFTR leading to secretion?

Answer 30

Enterotoxins from e.g. cholera, E.coli, C.diff Hormones/neurotransmitters e.g. VIP, ACh, bradykinin, 5-HT Immune cell products e.g. PGs, histamine Some laxatives e.g. bile salts

Question 31

What is the overall effect of increased secretion via CFTR?

Answer 31

Secretory diarrhoea

Question 32

What are some of the net effects of diarrhoea?

Answer 32

Dehydration --> Na+ and water loss Metabolic acidosis --> HCO3 loss Hypokalaemia --> K+ loss

Question 33

What are the main mechanisms of development of diarrhoea?

Answer 33

Impaired absorption of NaCl e.g. congenital, inflammation, infection, excess bile Non-absorbable solutes in lumen e.g. lactase deficiency Hypermotility Excessive secretion

Question 34

Which membrane transporter is exploited in Oral Rehydration Solution and how does it work?

Answer 34

SGLT1 | Absorption of Na+ and glucose --> accompanying absorption of water