The Kidneys Flashcards
What is osmoregulation?
The maintenance of the osmotic potential in the tissues of living organisms
What is the liver and kidneys involvement in homeostatic control?
-The liver breaks down excess amino acids and removes toxins from the blood
-The kidneys remove these from the blood
What is deamination?
Breakdown of amino acids
What do the kidneys do?
-Control the water potential of blood
-Filter blood by removing unwanted or excess products as urine
What products do the kidneys remove and reabsorb?
Remove:
-Urea
-Excess ions and water
Reabsorb:
-Glucose
-Dissolved ions
-Some water
What is the general structure of the kidneys?
-Fibrous capsule = membrane which protects the kidney
-Cortex = light coloured outer region
-Medulla = darker coloured inner region
-Ureter = carries urine to the bladder
-Renal artery = supplies kidney with oxygenated blood
-Renal vein = returns blood to the heart from kidney
What are the two main types of nephrons?
-Cortical nephron
-Juxtamedullary nephron
What is the cortical nephron?
-85% of human nephrons
-Mainly found in renal cortex
-Have a loop of Henle that only just reaches into the medualla
What is the juxtamedullary nephron?
-Have a long loop of Henle that penetrates right through the medulla
-Efficient at producing concentrated urine
What is ultrafiltration?
-Blood is filtered to form filtrate
-Everything small enough leaves e.g. water, urea, glucose, salt, hormones
-Blood cells and proteins are too large to leave
What happens at the proximal convoluted tubule (PCT)?
-Selective reabsoption e.g. glucose is absorbed back into the blood
How are cells in the proximal convoluted tubule (PCT) adapted?
-Microvilli to increase surface area
-Lots of mitochondria to provide ATP for active transport
What does the loop of Henle do?
Acts as a counter current multiplier to increase the reabsorption of water
What happens at the descending limb?
-Permeable to water
-Water moves out by osmosis
What happens at the ascending limb?
-Impermeable to water
-Water can’t leave
-Sodium and chloride ions are moved out by active transport
-This increases the concentration of medulla
What happens at the distal convoluted tubule (DCT)?
-Permeable to water
-Permeability varies with ADH
-Balances water in the body
What happens at the collecting duct?
-Permeable to water
-Permeability varies with ADH
-Water moves out the collecting duct down the water potential gradient
What is anti diuretic hormone (ADH)?
-Used in dehydration
-It is a chemical messenger released from gland and transported in bloodstream
-If ADH is released, urine is highly concentrated and volume is lower
How does ADH work?
-Osmoreceptors in the hypothalamus monitors water content of blood and how much ADH should be released from the pituitary gland
-ADH joins to receptors on collecting duct, making it more permeable to water
-Water leaves and moves to blood
What is diabetes insipidus?
-Individuals produces large volumes of very dilute urine
-Happens when people don’t produce any/little ADH or kidneys don’t respond to it
-Makes the collecting duct and DCT permanently impermeable to water
-Treated with drugs to replace ADH
What happens when there is fluid intake?
-Osmoreceptors in the hypothalamus detect an increase in blood water levels
-Pituitary gland releases less ADH into the bloodstream
-ADH decreases permeability of collecting duct so less water is reabsorbed
-Produces large volumes of dilute urine
What happens when there is no fluid intake/sweating?
-Osmoreceptors in the hypothalamus detect a decrease in blood water levels
-Pituitary gland releases more ADH into bloodstream
-There is more ADH so permeability of collecting duct increases and more water is reabsorbed
-Produces a small volume of concentrated urine
What is an endotherm?
-Rely on their own metabolism to provide warmth
-Can survive in most environments
-Often have much higher metabolisms than ectotherms so need to eat more to supply metabolic needs
e.g. mammals and birds
What is an ectotherm?
-Rely heavily on their environment to control their body temperature
-Often require less food as they have lower metabolisms
