excretion Flashcards
(24 cards)
Excretory organs
- Lungs
- Skin
- Kidneys
products of excretory organs
- Lungs- CO2 and water vapour + heat
- Skin- sweat [water, salts + urea]
- kidneys - urine [water salts + urea]
Where does urea come from
the breakdown of excess amino acids in the liver
Where are the kidneys located
below the diaphragm at the small of the back
abdominal cavity
How do the kidneys control the water content of the body
By varying the water content of the urine
ADH
How do the kidneys control the salt content of body fluids
by varying the ammount of salt released in the urine
How are the kidneys an osmoregulatory organ
By controlling the water and salt balance the kidneys ensure that blood plasma is the same concentration as the body cells. This means osmosis will not occur.
How do kidneys maintain the pH of bodily fluids at 7.4
By producing urine that is more or less acidic. It does this by secreting H+ ions from the blood into the cortex of the kidney.
Filtration
- occurs from the glomerulus into the bowmans capsule
- called ultrafiltration
- its a passive non selective process
- All small molecules pass through while large proteins and blood cells dont pass.
*
Why does pressure force these small molecules
- the efferent arteriole is narrower than the afferent arteriole
- blood in the glomerulus is coming from the renal artery which is already under high pressure
Where does filtration occur in the kidney?
The nephron
Suggest a treatment that may be used for a person whose kidneys are not carrying out their
normal functions.
Transplant or dialysis
Give two features of the nephron that aid filtration
- Glomerular capillaries are very porous
- Thin walls- glomerulus and bowmans capsule consist of 1 layer of cells
What does the glomerular filtrate consist of
- Glucose
- amino acids
- vitamins
- salts
- water
- urea
- uric acid
Reabsorption
High threshold substances are taken from the glomerular filtrate and returned to the blood
What substances are reabsorbed into the blood
- All amino acids, glucose and vitamins [active transport]
- most water 7/8 [osmosis]
- most salts [active trasnport]
- urea [diffusion, passively]
Adaptions of the proximal convuluted tubule
- microvilli increase surface area
- one cell thick
- many mitochondria for active transport
Should glucose be present in urine
No- diabetes
Secretion
Substances put into the nephron
what substances are secreted and why
Give the location where they are secreted also.
Hydrogen and potassium ions are secreted into the distal convuluted tubule to maintain a blood ph of 7.4
What causes low ADH levels
- High water intake
- Low salt intake
- High protein diet- excess aminoa cids converted to urea- higher leve of urea in urine.
What happens if we drink alot of water
- blood concentration falls and becomes dilute
- This is detected by osmoreceptors in the hypothalamus which sends a message to the pituitary gland to stop releasing ADH
- No ADH is released
- The DCT and collecting duct remain impermeable to water allowing large volumes to pass into bladder.
- Water levels in blood and body drop to normal levels.
What causes high ADH levels
- excessive sweating
- low water intake
- high salt intake
- excercise
What happens when the body doesnt have enough water
- Blood becomes concentrated detected by osmoreceptors in the hypothalamus.
- the hypothalamus sends a message to the pituitary gland to release the hormone ADH
- This increases the permeability of the walls of the collecting duct.
- more water is reabsorbed and a small volume of concentrated urine is produced.
- There is a behavioural response to drink more water. (thirst sensation)
