Question

Which organs are associated with a major excretory system in mammals? Describe briefly the structure of a nephron.

Answer 1

Kidneys are associated with the major excretory system in mammals.

The nephron is the functional unit of the kidney, with each nephron being comprised of the following components:

• Bowman’s capsule – the first part of the nephron where blood is initially filtered (to form filtrate).
  
• Proximal convoluted tubule – folded structure connected to the Bowman’s capsule where selective reabsorption occurs.
  
• The loop of Henle – a selectively permeable loop that descends into the medulla and establishes a salt gradient.
  
• Distal convoluted tubule – a folded structure connected to the loop of Henle where further selective reabsorption occurs
• The blood to be filtered enters the Bowman’s capsule via an afferent arteriole and leaves the capsule via an efferent arteriole. Within the Bowman’s capsule, the blood is filtered at a capillary tuft called the glomerulus.
• The efferent arteriole forms a blood network called the vasa recta that reabsorbs components of the filtrate from the nephron.
  
• Each nephron connects to a collecting duct (via the distal convoluted tubule), which feed into the renal pelvis.