kidneys

• Kidneys


  Excrete waste and regulate blood water potential
• Blood filtration at the start of the nephrons


  1. Blood is filtered

  2. At the glomerulus
• Glomerulus


  • Where the afferent arteriole enters
  • Where the efferent arteriole leaves
• Substances in the Bowman's capsule are known as the filtrate
• Larger molecules like protein and blood cells can't pass through, so stay in the blood
• Reabsorption along the nephron tubules

  1. Reabsorption takes place

  2. Along the proximal convoluted tubule (PCT)

  3. Along the loop of Henle

  4. Along the distal convoluted tubule (DCT)

  5. Into the collecting duct
• Urine doesn't usually contain protein and blood cells - they're too big to be filtered out of the blood
• Glucose is actively reabsorbed back into the blood above the DCT
• If the water potential of the blood is too low

  The body is dehydrated, more water is reabsorbed from the nephron tubules
• If the water potential of the blood is too high


  The body is too hydrated, less water is reabsorbed from the nephron tubules
• Maintaining a sodium ion gradient in the loop of Henle


  1. Sodium ions are pumped out into the medulla in the ascending limb

  2. The ascending limb is impermeable to water, so water stays in the tubule

  3. This creates a low water potential in the medulla
• The low water potential in the medulla


  Causes water to move from the descending limb into the medulla by osmosis
• The water in the medulla is reabsorbed into the blood through the capillary network
• Antidiuretic hormone (ADH)


  Hormone released by the posterior pituitary gland that increases the permeability of the DCT and collecting duct to water
• When blood water potential decreases


  ADH release increases, making the DCT and collecting duct more permeable to water
• When blood water potential increases

  ADH release decreases, making the DCT and collecting duct less permeable to water
• A small amount of concentrated urine is produced when ADH levels are high
• A large amount of dilute urine is produced when ADH levels are low
• The renal artery branches into smaller vessels called interlobar arteries, which branch further to form the arcuate arteries.
• The renal artery branches into smaller vessels called interlobar arteries, which then branch further to form the arcuate arteries.
• The arcuate arteries give rise to the afferent arterioles that supply blood to the glomeruli.
• Each nephron has its own efferent arteriole that carries blood away from the glomerulus.
• Arcuate arteries give rise to afferent arterioles, which supply blood to nephrons.
• The arcuate arteries give rise to afferent arterioles that supply blood to nephrons.
• Efferent arterioles carry blood away from glomeruli towards venules.
• Afferent arterioles lead to glomerular capillaries within Bowman's capsule.
• The efferent arteriole carries blood away from the glomerulus towards the peritubular capillaries.
• Venous drainage occurs through the renal vein, which carries deoxygenated blood back to the inferior vena cava.
• Blood flows through the peritubular capillaries surrounding the nephron tubules.
• Efferent arterioles carry blood away from the glomerulus towards the cortex.
• Blood flows through the peritubular capillaries surrounding the tubule.
• Peritubular capillaries surround the tubules and absorb filtered substances back into the bloodstream.
• Efferent arterioles carry blood away from the glomerulus.
• Vasa recta are long loops of capillary beds located between the cortex and medulla.
• Peritubular capillaries surround the proximal convoluted tubules (PCT) and loop of Henle.
• Vasa recta are small blood vessels found within the medullary pyramids.
• Afferent arterioles are responsible for regulating blood flow to the glomerulus.
• Peritubular capillaries surround the tubules and absorb filtered substances back into the circulation.
• Afferent arterioles are small arteries that bring blood into the glomerular capillaries.
• Bowman's capsule surrounds the glomerulus and is continuous with the proximal convoluted tubule.