Excretion

Excretion

The need for Excretion
1. Removal of metabolic waste from the body
  1. Carbon Dioxide
    1. Respiratory acidosis
    2. Breathing out
  2. Nitrogenous Waste
    1. Deamination
      1. Ornithine Cycle
        Urea
The Liver
1. Rich blood supply to carry out metabolic functions
  1. Deoxygenated blood
    1. From the digestive system
      1. Contains varying amounts of compounds (some potentially toxic compounds)
    2. Via hepatic portal vein
  2. Oxygenated blood
    1. From the heart
    2. From aorta via hepatic artery
    3. Supplies oxygen for aerobic respiration
2. Blood leaves via hepatic vein
3. Bile duct carries bile from the liver to the gall bladder where it is stored
4. Divided into lobes
  1. Divided into lobules
5. Hepatocytes
  1. Cuboidal with microvilli
  2. Metabolic functions
    1. Protein Synthesis
    2. Transformation + storage of carbohydrates
    3. Synthesis of bile
    4. Detoxification
6. Kupffer cells
  1. Specialies macrophages
  2. Move about sinusoid and breakdown/recycle RBCs
    1. One of the products is bilirubin
7. Functions
  1. Detoxification
    1. Liver is filled with enzymes with detoxification functions
      1. E.g catalase that can convert hydrogen peroxide into water and oxygen
    2. Alcohol
  2. Storage
  3. Productions of Bile
  4. Break down of RBCs
  5. Deamination + formation of urea
The Kidney
1. The nephron
  1. About 1 million in each kidney
  2. Starts in the cortex
    1. In the cortex capillaries form a knot (Glomerulus)
      1. Surrounded by the Bowman's Capsule
        Ultrafiltration pushes the blood into the Bowman's Capsule
        Leads to the Nephron
        Narrow gaps between endothelium of capilaries
        Basement membrane consists of fine mesh of collagen fibres
        Podocytes have finger-like projections to ensure gaps between cells.
      2. Blood flows from afferent to efferent arteriole
        Large to small diameter, increases pressure
  3. Four Parts
    1. Proximal Convoluted Tubule
    2. Loop of Henle
      1. Descending limb into medulla
      2. Ascending limb into the cortex
      3. Hairpin Countercurrent Multiplier
    3. Distal Convoluted Tubule
    4. Collecting Duct
      1. After short section of DCT where salt concentrations are altered slightly
      2. Carries high water potential fluid back through medulla to the pelvis
        As the water potential of the medulla decreases water begins to diffuse out by osmosis
2. Selective reabsorption
  1. Mostly occurs in the PCT
  2. CSM in contact with tubule fluid has microvilli
  3. Contains co-transporter proteins (Glucose/AA + sodium ions)
  4. Other membrane also folded + contains sodium-potassium pumps
  5. Many mitochondria for active processes
Osmoregulation
1. Control of water and salt levels in the body
2. The permeability of the wall of the collecting duct can be altered
  1. The walls respond to antidiuretic hormone (ADH) in the blood
    1. End result places more aquaporins into the csm by forming vesicles that attatch/detach from the memberane
    2. Concentration of ADH in the blood can be adjusted
      1. Water potential monitored by osmoresceptors in the hypothalamus
        When water potential drops, they lose water and shrink, stimulating neurosecretory cells
        Neurosecretory cells are specialised neurones that produce and release ADH where it is stored in the pituitary gland until needed
Kidney Failure
1. Once they fail completely the body is unable to remove excess water and certain waste products
2. Treatment
  1. Dialysis
    1. Passes the blood across a dialysis membrane to remove excess fluid, salts + wastes
  2. Kidney Transplant
3. Testing Urine

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	Created by Harry Archer almost 9 years ago