Excretion

• exretion is the removal of the watse substances of metabolic reaction,toxic materials and substances in excess of requirement
• co2 is a waste product produced during respiration and is excreted through the lung
• urea is a waste product produced in the liver from the breakdown of excess amino acids
• kidney is a 2 bean shaped organ that filter the blood removing urea and excess salts and water as urine
• ureter is a tube connecting the kidney to the bladder
• bladder organ that stores urine produced by the kidney
• urethra a tube that conects the bladder to the exterior where urine is released
• co2 dissolved in water easily which forms an acidic soln which may lower the ph of cells reducing activity of the enzyme essential for controlling the rate of metabolic reaction
• urea is toxic for the body in higher concentration thus must be excreted
• learn the following

  
• function of kidney:

  1)regulates water content of the blood

  2)excretes toxic waste product of metabolism

  3)maintain ions level in blood
• each kidney contain million tiny structure called nephrones


  it starts in the cortex,loop down into the medulla and back to the cortex
• arteriols from renal artery lead to each nephrones where they form a knot of capillalaries called the gromerulus


  the glomerulus gets narrower increasing the pressure on the blood moving through them which was already at a high pressure, this causes the smaller molecules carried in the blood to be forced out of capillaries to the bowmans capsule which is known as filtrate. known as ultrafiltration.
• learn the diagram

  
• glucose is the first substance to be re absorbed at the proximal(first) covoluted tubule only as the gates to facilitate is only found there


  the nephrone has many mitochondria to provide energy to the active transport
• salt is reabsorbed back into the blood by diffusion and active transport through the loop of henle
• water is reabsorbed by osmosis depending on how much water is needed by the body at that time


  hypoyhalamus detects the concentration of water in the blood stream and then sends signal to pituitary gland to release a hormone ADH to tell the kidney to reabsorbed more water.
• the remaining fluid containing excess water mineral salts and urea, continues to move along the tubules and forms urine
• digested food moleecules absorbed into the blood in the small intestine are carried are to the liver for assimilation


  assimilation: when food molecules are converted to other molecules that the body need
• eg of Assimilation: amino acids which are used to build proteins


  protein such as fibrinogen found in plasma and is impotrtant for blood clotting
• excess amino acids are broken down in a process called deamination


  amino acids contain: 1) carbon which is turn into glycogen

  2)nitrogen which is turned into ammonia whichis highly toxic, so it is convert into urea which is less toxic.
• toxic consequences of high urea levels: 1) cell death

  2) reduced reponse to insulin, leading to diabetes

  3) deposits into blood vessels