Physiology 3 Flashcards
What are the different parts of the large intestine?
Caecum and appendix
Colon
Rectum
Anal canal and anus
What are the different parts of the colon?
Ascending
Transverse
Descending
Sigmoid
What are the sack-like bulges in the large intestine, caused by contraction of the circular muscle?
Haustra
What is the appendix?
Blind ended tube with extensive lymphoid tissue connected to the distal caecum via the appendiceal orifice (obstruction –> appendicitis)
Which substances are absorbed in the large intestine?
Na+, Cl- and water
Short chain fatty acids (from any carbs not absorbed in small intestine)
Which substances are secreted in the large intestine?
K+, HCO3 and mucus
Which features of the colon increase the surface area?
Colonic folds
Crypts
Microvilli
Which cells are responsible for ion and water absorption in the colon?
Colonocytes –> surface epithelial cells
Which cells mediate ion secretion?
Crypt cells
Which cells are responsible for secretion of much into the colon?
Goblet cells
Which ion may be lost significantly in the faeces in secretory diarrhoea?
K+
What is the effect of aldosterone on the colon?
Na+ absorption
K+ secretion
Which pattern of motility is responsible for non-propulsive segmentation in the colon?
Haustration
What are the main functions of the liver?
- Carbohydrate, fat and protein metabolism
- Deactivation/activation of some hormones
- Storage
- Synthesis of proteins
- Protection
- Detoxification
Which substances are stored in the liver?
Fat soluble vitamins (A, D, E and K) Water soluble vitamin B12 Iron Copper Glycogen
What happens to bile between meals?
Stored and concentrated in gall bladder
What happens to bile during a meal?
Gall bladder contraction and sphincter of Oddi opens (due to CCK)
Bile spurts into duodenum via cystic and common bile ducts
How do the bile juices get to the ducts?
Secreted from hepatocytes –> canaliculi –> biliary ductules and ducts
What does the primary binary juice contain?
Primary bile acids Water and electrolytes Lipids and phospholipids Cholesterol IgA Bilirubin Metabolic wastes and conjugated drug metabolites
What happens if there is too much cholesterol in the bile juices?
May precipitate into micro crystals that aggregate into gall stones –> cholelithiasis
What is bilirubin?
Breakdown product of the porphyrin component of haemoglobin
What is the best treatment for symptomatic gall stones?
Laproscopic cholecystectomy
Which treatment may be suitable for patient with small/medium sized radiolucent stones and unimpaired gall bladder function?
Ursodeoxycholic acid –> dissolves them
SE: diarrhoea
What happens to most of the bile salts entering the duodenum?
Reabsorbed in the terminal ileum
–> enterohepatic recycling
How does hepatic encephalopathy occur?
Severe hepatic failure –>
Failure of detoxification of ammonia to urea (via urea cycle) –>
Blood ammonia levels rise and exert toxic effect on CNS
What are the clinical features of hepatic encephalopathy?
Incoordination
Drowsiness
Coma
Death due to cerebral oedema
What are the treatment options for hepatic encephalopathy and hw do they work?
Lactulose
–> ammonia converted to ammonium which is not absorbed
Antibiotics –> suppress gut flora so inhibit ammonia production
What is the process of water absorption from the lumen of intestines into the blood stream?
Passive process driven by transport of solutes (mainly Na+)
What is the normal role of CFTR?
Normally little secretion of Cl- occurs because apical CFTR is either closed of not present
Give some examples of factors that indirectly activate CFTR leading to secretion?
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
What is the overall effect of increased secretion via CFTR?
Secretory diarrhoea
What are some of the net effects of diarrhoea?
Dehydration –> Na+ and water loss
Metabolic acidosis –> HCO3 loss
Hypokalaemia –> K+ loss
What are the main mechanisms of development of diarrhoea?
Impaired absorption of NaCl e.g. congenital, inflammation, infection, excess bile
Non-absorbable solutes in lumen e.g. lactase deficiency
Hypermotility
Excessive secretion
Which membrane transporter is exploited in Oral Rehydration Solution and how does it work?
SGLT1
Absorption of Na+ and glucose –> accompanying absorption of water
