renal system

• The renal system has two main functions: Excretion or removal of nitrogenous waste from the body in the form of urea, and Osmoregulation or regulation of the water balance of the body

  
• Proteins and nucleic acids both contain nitrogen. We usually take in more nitrogen containing compounds in our food than we need. Any excess is converted by the liver to urea. The urea is transported in the blood to the kidneys where it is removed from the blood when urine if formed

  
• The kidney


  • It is surrounded by a renal capsule and the cortex, offering protection in holding it firm
• Urine formation


  Urine formed in the cortex passes through the minor then major calyx, the internal structures, into the renal pelvis, and continues out down the ureter to the bladder. Peristalsis moves urine from one structure to the next

  
• The average nephron number is approximately 900,000 to 1 million per kidney, but some individuals have as much as 2.5 million per kidney

  
• Nephron


  The main functional unit of the kidney, a long U-shaped tube surrounded by capillaries

  
• Many nephrons connect with collecting ducts that take the urine formed towards the ureter and then the bladder. The blood is filtered in the nephron and water as well as other useful substances are reabsorbed. This makes urine

  
• Nephron


  • The length of the nephron means that there is a large surface area for exchange. The wall of the nephron is a single layer of epithelial cells close to capillaries with a single layer of endothelial cells, creating a short diffusion pathway. The loop of Henle within the nephron helps to maintain a concentration gradient
• Ureter


  Tube that takes urine from the kidney to the bladder

  
• Urethra


  Tube that takes urine from the bladder to outside the body, through which we urinate
• The left and right ureter take urine from each kidney to the bladder where it is stored until the bladder is emptied via the urethra during urination

  
• Bladder


  • Exterior bladder muscles contract to assist gravity to empty the bladder. The detrusor muscle controls bladder emptying
• Sometimes exercises improve incontinence but not always so pads maybe necessary or a catheter
• Blood flow through the kidney


  Blood travels in through the kidney. Waste products are filtered out and nutrients absorbed. The balance of water in the body is regulated. The efferent arterioles and renal vein takes filtered blood away

  
• Diseases and conditions that may slow blood flow to the kidneys and lead to kidney injury

  • Blood or fluid loss eg. spleen internal bleed
  • Blood pressure medications
  • Heart attack
  • Heart disease, gradual deterioration
  • Infection
  • Liver failure
  • Non-steroidal anti-inflammatory drugs (NSAIDs) eg. aspirin, ibuprofen, naproxen

  
• Urinary catheter


  A flexible tube used to empty the bladder and collect urine in a drainage bag. A balloon is inflated to keep it in place
• Nephron


  • It has five sections: Bowman's capsule - ultrafiltration, Proximal convoluted tubule - reabsorption, Loop of Henle - maintains concentration gradient, Distal convoluted tubule - reabsorption, Collecting duct - reabsorption
• Ultrafiltration


  A branch of the renal artery leads to an afferent arteriole. This divides into many capillaries (forming the glomerulus) in the space surrounded by the Bowman's capsule. The high pressure forces out fluids from the capillaries and into the lumen of the nephron forming the filtrate

  
• Reabsorption


  Many substances dissolved in the blood are required by the body and must be reabsorbed, including glucose, amino acids, water and ions
• Osmoregulation


  The process of regulating the water balance of the body, including reabsorption of water in the collecting duct controlled by ADH
• Every hour your blood supply circulates through the kidneys about 12 times. Each day your kidneys process around 200 litres of blood, with around 1 to 2 litres of waste leaving the body as urine. We have about a million hairpin-like glomeruli at birth, but lose about 100,000 of these every decade of life

  
• Osmoregulation


  The mechanism of osmoregulation
• Homeostasis


  The mechanisms of homeostasis
• Do


  1. Watch videos

  2. Complete booklets
• Show


  • Completed booklets
• Improve


  Reflect and record on a knowledge, skill or behaviour to improve
• The definition of homeostasis is the ability or tendency to maintain internal stability in an organism to compensate for environmental changes
• Example of homeostasis


  • The human body keeping a temperature of 37˚C or managing drink, sweat and urine – a fluid balance
• Osmoregulation


  The renal system maintains a healthy balance of fluid in the body which ensures blood pressure and the salt balance is kept at a consistent level
• If osmoregulation goes wrong cells could enter a state of having too much water or too little water. This could cause cells to die and organs to fail
• Lots of the bodies process and functions can only happen when the body has 70% water eg. pleural membrane lubrication for breathing
• Sweating


  Fluid and salt loss
• Chemical elements


  Sodium (Na) and Chloride (Cl) = Salt
• Monitoring Mechanism


  1. The hypothalamus has osmoreceptors which detects the level of fluid and salt in the blood (osmotic pressure)

  2. The hypothalamus sends a message to the pituitary gland which in turn releases Antidiuretic Hormone (ADH)

  3. The ADH message travels in the blood to the kidneys where it instructs the nephrons to act

  
• ADH changes


  1. The reabsorbing; more or less water and salt, back into the proximal and distal tubules, as well as the loop of Henle

  2. The collecting duct reabsorbs more or less water from the filtrate
• Dehydrated


  More salt is reabsorbed into the medulla within the proximal and distal convoluted tubule and the Loop of Henle. This creates a high salt concentration
• Hydrated


  Less salt is reabsorbed into the medulla within the proximal and distal convoluted tubule and the Loop of Henle. This creates a lower salt concentration
• Dehydrated


  ADH is released by the pituitary gland increasing the permeability of the collecting duct by forming aquaporins (water channels)
• Hydrated

  Less ADH is released by the pituitary gland decreasing the permeability of the collecting duct due to less aquaporins forming
• Dehydrated

  More water is reabsorbed into the blood as the body needs it, so less remains in the filtrate. As a result a small amount of concentrated urine is produced