The Kidney

• The renal system removes toxins from the blood and produces urine
• The job is to filter the blood. The kidney removes urea and sends it all to the bladder, it then removes all of the glucose but then puts it all back in the blood. It removes water and sends some of it to the bladder, the rest is put back into the blood. It removes salt and sends some of it to the bladder, the rest is put back into the blood
• Glomerulus - ball of capillaries that filters blood
• Nephron - functional unit of the kidney
• Loop of Henle - descending limb absorbs no water or solute, ascending limb absorbs sodium chloride
• Proximal convoluted tubule - absorbs most substances including glucose, amino acids and sodium chloride
• Distal convoluted tubule - absorbs more sodium chloride than potassium chloride
• Ultrafiltration

  • Occurs in the glomerulus due to high blood pressure there
  • The difference in available volume raises the pressure and blood builds up in the glomerulus
  • Water, glucose and ions are forced into the bowman's capsule which forms the glomerular filtrate
  • Proteins and cells are too large so they stay in the blood
• The afferent arteriole is wider than the efferent arteriole
• Reabsorption in the PCT

  The filtrate passes out of the bowman's capsule into something called the proximal convoluted tube. The PCT absorbs all the glucose back from the filtrate along with some water and ions
• PCT reabsorbs about 85% of the filtrate. Glucose and ions are absorbed, water is reabsorbed by osmosis along the entire length of the convoluted tube
• DCT

  Alters the pH of the filtrate by absorbing some water or ions. It uses active transport to do this so there are numerous microvilli and mitochondria in the cells. It selects which ions to reabsorb
• Osmoreceptors are located in the hypothalamus and shrink in size when water levels in blood fall
• The capillaries reabsorb materials
• The renal vein takes blood from the kidney to the heart
• The renal artery supplies the kidneys with oxygenated blood from the heart
• The ureter takes urine to the bladder
• The medulla are layers of tissue containing nephrons
• The fibrous capsule is there for protection
• The renal pelvis is where nephrons drain into
• Nephrons filter blood selectively and reabsorb products
• The cortex are layers of tissue containing nephron
• Loop of Henle absorbs sodium chloride, water
• Glomerulus filters blood