Excretion in humans- Biology chapter 13

• Carbon dioxide is excreted by the lungs. If carbon dioxide level becomes abnormally high, a condition called hypercarbia occurs.
• Kidneys excrete urea and excess water and ions
• *the urethra is also part of the male reproductive system.

  A) Ureter

  B) Urinary bladder

  C) Urethra

  
• Kidney

  A) Medulla

  B) Cortex

  
• • Glomerulus function:
  • Ultrafiltration of blood because the arteriole carrying blood into the glomerulus is wider than the arteriole carrying blood away, creating a high blood pressure in the glomerulus. As blood flows through a nephron, part of the blood plasma is forced out of the glomerular blood capillaries. Only small, soluble molecules pass into the renal capsule forming the filtrate. (water, ions, glucose, urea)
  • Filters water, ions, urea, glucose out of the blood.
  • It doesn't filter out proteins, red blood cells and platelets (PRP), their too big
• How is the glomerulus suited to filtration?

  • There are numerous glomeruli in the kidney and the blood capillaries are highly coiled. These provide a large surface area for filtration
  • The walls of the blood capillaries are one cell thick and contain tiny pores
  • The blood capillaries are covered by a thin basement membrane. The membrane is partially permeable and only allows very small, soluble molecules or ions to pass through. It is impermeable to blood cells, platelets and large molecules like proteins (Proteins, Red blood cells, Platelets)
• Collecting duct:

  • The collecting duct of the nephron forms urine containing urea, excess ions and excess water

  
• Nephron functions:

  • Reabsorption of all of the glucose, some of the ions and most of the water back into the blood

  
• Nephron functions

  A) Ultrafiltration

  B) Reabsorption

  C) Formation of urine

  
• Our bodies need mineral ions, or else we would suffer from deficiency diseases.

  • Excess ions in the blood can be harmful. They may make the blood plasma more concentrated.
  • Water may pass out of the tissue cells into the blood by osmosis. The cells may become dehydrated
• Water is essential to life, and a metabolic waste product as it is produced during aerobic respiraiton.

  • Excess water in the body is harmful. It will make the blood plasma less concentrated.
  • Water will enter the tissue cells by osmosis. The cells may swell and burst.
• Excretion is the removal of metabolic waste products, toxic substances and substances that are in excess of the body's requirements. These waste products and substances are called excretory products
• Excretion is important as too much urea is toxic to the body
• The liver assimilates amino acids by converting them into proteins. These proteins are found in blood plasma, including prothrombin and fibrinogen, which are essential for clotting of blood.
• Deanimation: The removal of the nitrogen-containing part from the amino acid in the liver, to form urea.

  (The remaining portion of the amino acid is converted to glucose that can be used by the body.)
• Function of liver in excretion:

  • Deanimation of excess amino acids
  • Makes ammonia (deanimation of amino acids results in ammonia)
  • Convert ammonia to urea/ produce urea