Excretory

• Excretory system

  Processes waste and excretes waste products
• Organs involved in processing and removing wastes

  • Lungs
  • Liver
  • Sweat glands
  • Alimentary canal
  • Kidneys
• Sweat glands

  • Secrete water -> dissolved in water is sodium chloride, latic acid, urea
  • Located in lower layers of the skin, a duct carries sweat to hair follicle or skin surface where it opens at a pore. Cells surrounding the gland can contract and squeeze sweat to skins surface
• Deamination


  1. Uses enzymes to remove the amino group (NH2) from the amino acids

  2. Converts the amino group to ammonia (NH3)

  3. Converts ammonia to urea, which is eliminated from the body in urine

  4. Converts the remaining part of the amino acid, which is mainly carbon and hydrogen, into a carbohydrate that can be readily broken down by the cells to release energy + carbon dioxide + water
• Production of urine

  1. Glomerular filtration

  2. Selective reabsorption

  3. Tubular secretion
• Urine composition


  • Normal urine is a solution of water with dissolved wastes, such as urea and creatine, and ions such as sodium, chloride and potassium, as well as low levels of other solutes
  • A healthy adult produces about 1.5 L of urine a day, but this varies
• Liver 


  The liver processes chemicals into a safer form (amonia -> urea through deamination).
• Liver also:


  • Detoxifies alcohol and drugs
  • Deactivates hormones -> coverts into a form that can be excreted by the liver
  • Breaks down haemoglobin from dead red blood cells -> produces bile pigments -> goes into faeces
• Skin


  Provides a protective covering over the surface of the body and regulates body temperature.
• Lungs 


  Involved in the excretion of the carbon dioxide that is produced by cells during cellular respiration
• Kidney


  Located in the abdomen, each is approximately 11cm long. Each kidney is enclosed by the renal capsule, under this is the outer renal cortex then the inner renal medulla. The medulla consists of lots of renal pyramids (tooth) and are separated by renal columns where blood vessels lie. Then the renal pelvis funnels urine into the ureter and the renal helium is where vessels enter and leave.
• Nephrons


  Responsible for removing wastes from the blood and regulating blood composition. Blood enters the nephron through the afferent arteriole, it is then filtered in the glomerulus, a network of capillaries and then exits via the efferent arteriole.
• Glomerular filtration

  Happens in the renal corpsucle (bowmans capsule) blood enters through the afferent arteriole which has a wide diameter and exits through the efferent arteriole which has a small diameter, this increases the resistance in flow of blood which creates very high pressure in the glomerulus. This forces blood components through differentially permeable membrane into the capsule. The glomerular capillaries are one cell thick and the capsule wall is one cell thick, which makes diffusion easy.
• What is in filtrate

  The fluid that is absorbed into the glomerulus is called filtrate, it contains water, salts, amino acids, fatty acids, glucose, urea creatine and ions.
• Reabsorption

  Some components of the filtrate that are of use to the body and are selectively reabsorbed back into the blood. It is carried out by cells in renal tubule, materials reabsorbed are water, glucose, amino acids and ions such as sodium, potassium, calcium. A large surface area is required for reabsorption, this is achieved by 2 sets of convolutions + the loop of Henle + number of nephrons in each kidney. Depending on bodies water requirements more or less water will reabsorbed or excreted. This is an active process which is under hormone control.

   
• Tubular secretion

  Adds materials to the filtrate from the blood because too much has been reabsorbed. Includes materials such as potassium and hydrogen ions, creatine, and drugs (penacillin). It can be active or passive and maintains blood pH (7.4-7.5) and urine pH (6)
• Kidney Stones

  Are formed from solid crystals that build up inside the kidneys, usually when urine becomes too concentrated. Small crystals may pass unnoticed or crystals can combine to form stones. Large stones can get stuck in the ureter, bladder or urethra, causing intense pain, and may need to be broken up with sound waves or physically removed during surgery.
• Kidney Failure

  Affects glomeruli which affects kidneys ability to filter blood. Proteins and red blood cells may leave blood at glomerulus and can be passed as urine ->blood in urine. Too much losss of protein in urine cause fluid to build up in hands + feet -> swelling. When the kidneys lose ability to excrete waste + control fluid levels = kidney failure.
• Lifestyle measure to maintain kidney health

  • Regulate diet + maintain heathly weight
  • Don't smoke= smokers 3 times more likely to have impaired kidney function
  • Drink water
  • Consumer alcohol in moderation
  • Don't do drugs
• Dialysis

  Method to remove wastes from kidneys when failure occurs. Two types:

  • Peritoneal dialysis
  • Haemodialysis
• Peritoneal dialysis

  The peritoneum is a membrane that lines the abdominal cavity and covers organs (stomach, liver), has a rich blood supply. Peritoneal dialysis uses this membrane to remove wastes. A catheter is placed in the wall of the abdominal cavity, and fluid is passed through. It contains glucose and other substances similar to those in blood, but there are no wastes in the fluid. Because of the concentration difference wastes will diffuse out of the blood into the fluid and useful substances will stay in the blood. After time fluid is drained out, this is usually done once a day.
• Haemodialysis

  Involves passing blood through an artificial kidney or dialysis machine. Blood passes through thousands of tiny tubes made of differentially permeable membrane and immersed in fluid. The concentrations of substances in fluid are similar to those in blood without waste. Because of concentration difference wastes will diffuse from blood into the fluid. Usually takes 4-5 hours x3 a week
• Liver disease

  Occurs when liver is not able to process toxins for elimination. Caused by infection, genetic disorders, autoimmune problems, cancer, and lifestyle factors (excessive alcohol + fatty diet)
• Symptoms of liver disease

  • Jaundice
  • Abdominal pain
  • Swelling in legs and feet
  • Nausea + vomiting
  • Dark urine + faeces
• Kidney

  label:

  A) Capillaries

  B) renal pyramid

  C) renal pelvis

  D) Cortex

  E) Renal cortex

  F) Ureter

  G) Medulla

  H) Renal artery

  I) renal vein

  J) renal column

  
• Nephron structure

  label:

  A) Afferent arteriole

  B) efferent arteriole

  C) distal convoluting tubule

  D) collecting duct

  E) loop of henle

  F) proximal convoluting tubule

  G) glomerular (bowmans) capsule

  H) Glomerulus