excretion

• excretion

  the removal/ processing of waste from the body
• secretion

  a process by which substances are produced and discharged from cell, gland, or organ
• metabolic waste

  co2, urea
• egestion

  removal of undigested waste by defaction
• deamination

  removal of ammonia from amino acids
• hydrogen carbonate formation

  • co2 diffuses with rbc
  • combines with h2o to form h2co3
  • h+ lowers the pH of the blood to act as a buffer, haemoglobin binds to h+ to form haemoglobinic acid
  • carbonaminohaemoglobin where co2 binds to haemoglobin.
  • hco3- dissociates out of the cell
  • chloride shift occurs to balance the movement of ions
• deamination

  amino acid+ oxygen->keto acid ammonia
• ornithine cycle

  ammonia+ carbon dioxide-> urea + water
• hepatic artery

  brings oxygenated blood from the aorta for aerobic respiration for metabolic processes
• hepatic vein

  takes deoxygenated blood from liver to the heart
• hepatic portal vein

  delivers oxygenated blood from the digestive tract (toxins and nutrients) that need to be broken down
• bile duct

  • formed in hepatocytes
  • neutralises stomach acid
  • emulsifies fats
  • flows in the opposite direction of the blood supply
• detoxification of alcohol

  • alcohol is broken down by hepatocytes by ethanol dehydrogenase, which removes a hydrogen atom (dehydrogenation)
  • NAD becomes reduced as it gains an H+
  • the final product is acetyl coenzyme A which is used in respiration
• ultrafiltration

  • afferent arteriole has a larger diameter than the efferent arteriole
  • there is a high hydrostatic pressure is generated
  • the endothelium wall of the capillary has small fenestrations
  • these allow amino acids, ions and glucose to fit through
• fenestrations

  narrow gaps that allows blood and substances to pass through
• podocytes

  • specialised epithelial cells
  • fingerlike projections to ensure the passage of substances
• basement membrane

  stops the removal of large substances from the blood
• selective reabsorption in the PCT

  • all glucose and amino acids are reabsorbed into the PCT by facilitated diffusion
  • sodium ions are actively transported (using ATP) out of cells into tissue fluid using a co transporter protien
  • This creates a concentration gradient so sodium ions enter the blood
  • glucose or amino acids enter cells with sodium ions by facilitated diffusion
  • water moves in via osmosis because glucose or amino acids increase cell concentration and lower water potential
  • glucose and amino acids diffuse into the blood capillary by facilitated diffusion.
• Reabsorption of water in the loop of henle and the collecting duct

  ascending limb

  • impermeable to water
  • NA+ and Cl- ions are actively transported out of the loop of Henle, decreasing the water potential of the surrounding tissue of the medulla. The movement of ions causes a decrease in water potential, going down to the medulla
  • At the bottom, there is a high concentration of ions, so they diffuse out, and the water potential of the surrounding decreases
  • collecting duct- water potential is lower than the fluid inside

  descending limb

  • the wall of the descending limb is permeable to water.
  • Water is removed from the descending limb; by osmosis into the surrounding tissue
  • collecting duct- water removed from urine
• loop of henle

  • creates a high concentration of NA+ and Cl- in the tissue fluid of medulla
  • allows water to be reabsorbed from the contents of the nephron as they pass through the collecting duct
  • more concentrated urine is produced, conserves water, prevents dehydration
• larger loop of henle

  • more absorption of water
  • more ions will be facilitated, diffused/ actively transported to the surrounding
  • decreases water potential, more water will be moved by osmosis
• aquaporins

  • protein pores that form channels for molecules to pass through
  • only allows water to pass through
  • increases membrane permeability so more water is reabsorbed
• ADH

  • not lipid soluble
  • secreted from the pituitary gland and transported to the kidneys
  • attaches to the cell surface membrane
• osmoreceptors

  • controls water content in the body
  • detects low water concentration in the blood
• The control of the water potential of the blood

  • osmoreceptors in the hypothalamus detect low concentrations of water in blood
  • ADH is released from the posterior pituitary gland and transported to the kidney in the blood
  • collecting ducts have receptors that are specific and complementary in shape to the ADH hormone
• How ADH aids in water reabsorption from the collecting duct

  • ADH is bound to a complementary and specific-shaped receptor of the cell surface membrane
  • This causes a 2nd messenger response- (cAMP) triggers a vesicle to form.
  • The vesicles containing aquaporins move via the cytoskeleton by contracting microtubules using ATP
  • These aquaporins increase membrane permeability so more water is reabsorbed
• Haemodialysis

  • Blood from the patient's vein is passed through small tubes made from a partially permeable membrane. The fluid on the outside has the water potentials and concentrations of ions and glucose, the patients glucose should have
  • urea and excess water - out
  • glucose, ions, amino acids - in
  • heprin- stops blood clotting
  • air bubbles removed before re entering the body to prevent strokes and cardiac arrest
• haemodialysis advanatges

  • can be done at home
  • less risky than surgery
  • less risk of infection
• hameodialysis disadvantages

  • imposes heavy restrictions on the lives of patients
  • regular trips to the hospital
  • needs careful control of diet
• peritoneal dialysis

  peritoneum is the layer of tissue that lines the abdominal cavity. A catheter is inserted into the peritoneal cavity. dialysis fluid is passed in and fluid is drained off
• periotneal dialysis advantages

  • can be carried out at home
  • less eating and drinking restrictions than haemodialysis
• peritoneal disadvantages

  • interrupts daily routines
  • risks of infections
  • can cause swelling of the abdomen
• kidney transplant

  • new kidney is not recognised as self, different antigens are present on the new kidney, causing rejection by the immune system so immunosuppressants are needed.
• kidney transplant advantages

  • better quality of life
  • less restricted diet
  • feel better physically
• kidney transplant disadvantages

  • need immunossupressants for life
  • major surgery under anaesthetic
  • risk of bleeding and damage to major organs
• testing for hCG

  1. The stick is dipped into urine to the line
  2. hCG has a complementary shape to the mobilised monoclonal antibodies; hCG binds to the monoclonal antibodies to form an hCG complex which moves up the stick with the urine as well as antibodies
  3. The excess antibodies carried up with the urine bind to the immobilised antibody in the upper band as a control. A dye is released, and a line forms
  4. The hCG complex binds to immobilised antibodies due to complementary shape in the lower band if the women is pregnant