1.Human anatomyMedium
In which part of the nephron does most reabsorption of water and sodium take place?
- ACollecting duct
- BLoop of Henle
- CDistal convoluted tubule
- DProximal convoluted tubule
Anatomy and Physiology: cram pack
Formula sheets, the key method steps for every topic and 4 practice problems, with full solutions at the back.
1Practice problems
2.Human anatomyHard
Why is the proximal pole of the scaphoid at risk of avascular necrosis after a waist fracture?
- AIts only artery runs through the lunate
- BIts blood supply enters mainly from the distal end
- CIt is drained by a single vein that clots easily
- DIt has no blood supply at all
3.Human physiologyMedium
Which receptors respond mainly to a fall in arterial oxygen levels?
- AStretch receptors in the lungs
- BBaroreceptors in the carotid sinus
- CCentral chemoreceptors in the medulla
- DPeripheral chemoreceptors in the carotid and aortic bodies
4.Human physiologyHard
In pernicious anaemia, autoimmune destruction of gastric parietal cells leads to anaemia because:
- AAcid is lost, so iron is never absorbed in any form
- BIntrinsic factor is lost, so vitamin B12 is not absorbed
- CPepsin is lost, so haemoglobin cannot be made
- DGastrin is lost, so the bone marrow is no longer stimulated
2Solutions
1.Human anatomy
Answer: D · Proximal convoluted tubule
Why this is the answer
The proximal convoluted tubule reabsorbs about two thirds of the filtered sodium and water, plus nearly all glucose and amino acids.
Answer
D · Proximal convoluted tubule
2.Human anatomy
Answer: B · Its blood supply enters mainly from the distal end
Why this is the answer
Branches of the radial artery enter the scaphoid mainly distally and flow backwards. A fracture through the waist can cut off the proximal pole, causing avascular necrosis.
Answer
B · Its blood supply enters mainly from the distal end
3.Human physiology
Answer: D · Peripheral chemoreceptors in the carotid and aortic bodies
Why this is the answer
The carotid and aortic bodies detect low PaO₂ (and also high CO₂ and H⁺). The central chemoreceptors respond to CO₂ but not directly to oxygen.
Answer
D · Peripheral chemoreceptors in the carotid and aortic bodies
4.Human physiology
Answer: B · Intrinsic factor is lost, so vitamin B12 is not absorbed
Why this is the answer
Parietal cells secrete intrinsic factor, needed for B12 absorption in the terminal ileum. B12 deficiency impairs DNA synthesis and causes megaloblastic anaemia.
Answer
B · Intrinsic factor is lost, so vitamin B12 is not absorbed
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