PMT Definitions

• Ascending limb?


  The limb of the loop of Henle that rises into the cortex.

  • It is wider in diameter than the descending limb and its walls are impermeable to water.
  • Sodium ions are moved out of the ascending limb by active transport.
• Collecting Duct?


  The final region of the nephron that collects urine from the distal convoluted tubules and empties it into the renal pelvis.

  • Its permeability to water is altered by ADH.
• Descending Limb?


  The limb of the loop of Henle that dips down into the medulla. It is smaller in diameter than the ascending limb. The walls of the descending limb are permeable to water, so the filtrate loses water as it moves down.
• Distal convoluted tubule?


  The twisted region of the nephron between the loop of Henle and the collecting duct.

  • It controls blood pH by reabsorbing ions and alters the concentration of water and salts reabsorbed.
  • Its permeability to water is altered by ADH.
• EFFerent arteriole?


  The blood vessel that carries blood away from the glomerulus and sub-divides to form a network of capillaries.

  • Its diameter is smaller than the afferent arteriole, creating a build up of hydrostatic pressure in the glomerulus.
• Glomerular Filtrate?


  The fluid produced by ultrafiltration of the blood into the renal capsule. - It contains water, glucose, mineral ions and urea.
• Glomerulus ?


  A bundle of capillaries located in the renal capsule which are adapted for the filtration of blood.

  • They later merge to form the efferent arteriole.
• Loop of Henle?


  A loop consisting of a descending limb (dips into the medulla) and ascending limb (rises into the cortex) surrounded by blood capillaries. - It creates a low water potential in the medulla, enabling the reabsorption of water
• AFFerent arteriole?


  The blood vessel that stems from the renal artery and supplies blood to the nephron.

  • It has a larger diameter than the efferent arteriole and divides into a complex system of capillaries, the glomerulus.
• Nephron?


  The functional unit of the mammalian kidney.
• nephron 


  nephron

  
• Osmoregulation?


  The regulation of the water potential of the blood by the kidney.
• Osmoreceptors?


  Sensory receptor cells located in the hypothalamus that detect a decrease in water potential.
• Posterior Pituitary Gland?


  The gland responsible for the secretion of ADH into the

  bloodstream
• Proximal convoluted tubule?


  The twisted portion of the nephron between the renal capsule and the loop of Henle.

  • Its walls consist of epithelial cells that are adapted for the reabsorption of glucose and water into the blood.
• Renal (Bowman's ) Capsule


  The cup-like structure at the start of a nephron that surrounds the glomerulus.

  • The inner layer of the capsule, through which filtration of the blood takes place, is composed of podocytes.
• Podocytes?


  The epithelial cells, called podocytes, have finger-like projections that the substances can flow between.