Kidneys Flashcards
How is water lost
Excretion and sweat
What organ regulates the water potential
Kidneys
What do the kidneys do if the water potential is too low
More water reabsorbed by osmosis into the blood from the tubules in the nephron
Urine more concentrated (less water lost from excretion)
What happens when the blood water potential is too high
Less water reabsorbed into the blood by osmosis from tubules in Nephron
Urine more dilute
More lost in excretion
Where is the loop of henle
Medulla
How is water potential maintained by the loop of henle: top of ascending limb (1)
- Top of ascending limb = Na pumped into the medulla using at
- Ascending limb is impermeable to water = water stays inside the tubule
- Low water potential in medulla due to high conc of ions
How is water potential maintained by the loop of henle: descending limb (2)
- Lower water potential in medulla than in the descending limb
- The descending limb is permeable to water so water moves out of the descending limb into the medulla by osmosis
- The filtrate inside of the descending limb gets more conc as ions can’t leave
- Water in the medulla is reabsorbed by blood capillaries
How is water potential maintained by the loop of henle: bottom of ascending limb (3)
- Na+ diffuse out of ascending limb into medulla
- Water potential decreases in medulla
- Water can’t leave ascending limb because it’s impermeable
How is water potential maintained by the loop of henle: distal convoluted tubule (4)
- Water moves out DCT by osmosis and reabsorbed by blood
How is water potential maintained by the loop of henle: collecting duct (5)
- The medulla now has a high Na conc and low water potential
- Water moves out of collecting duct into medulla by osmosis
- Water reabsorbed by capillary network into blood
What controls the volume of water reabsorbed
The permeability of the distal convoluted tubule and collecting duct controlled by hormones
What cell monitors water potential of blood
Osmoreceptors
Where are osmoreceptors
Hypothalamus
What is the hormonal response when water potential of blood decreases (dehydrated)
- Water moves out of osmoreceptors by osmosis
- Cells decrease in volume
- Sends signal to other cells in hypothalamus
- Sends signal to posterior pituitary gland
- Releases more anti diuretic hormone into blood
- DCT and CD more permeable to water
- More water reabsorbed into blood stream
- Small amount of highly concentrated urine produced
What is the effect of antidiuretic hormone
Walls of distal convoluted tubule and collecting duct get more permeable to water
More water is reabsorbed into medulla and then into the blood stream by osmosis
Less water lost from body
What is the hormonal response when water potential of blood increases (hydrated)
- osmoreceptors detect high water potential
- Sends signal to other cells in hypothalamus
- Sends signal to posterior pituitary gland
- Releases less anti diuretic hormone into blood
- DCT and CD less permeable to water
- Less water reabsorbed into blood stream
- Large amount of dilute urine produced
What is the function of kidneys
Excrete waste products (urea)
Regulate blood water potential
What is ultrafiltration
Substances are filtered out from capillaries into tubules
What is selective réabsorption
Useful substances (glucose and water) and reabsorbed back into the blood
What is a nephron
Long tubules and network of capillaries in the kidney
Explain the ultrafiltration pathway
- Blood enters artérioles in the cortex from the renal artery
- The artériole splits into the glomerulus (inside of a bow mans capsule)
- Blood enters the glomerulus by the afférent arteriole
- Blood leaves by the efferent arteriole = small diameter = higher p
- High p forces small molecules out of the glomerulus into the bowmans capsule
- The small molecules pass through 3 layers: capillary wall, basement membrane and epithelium of the bowmans
- Liquid in bowmans = glomerular filtrate
- Large proteins can’t leave so stay inside the glomerulus
- Glomerular filtrate goes through nephron until the collecting duct and passes out of kidney by the ureter
What puts the glomerulus at high pressure
The small diameter of the efferent arteriole
What is the structure surrounding the glomerulus
The bowmans capsule
Where does ultrafiltration happen
Glomerulus
What are the 3 layers filtrate passes through from the glomerulus to the bowmans capsule
Capillary wall
Basement membrane
Bowmans capsule epithelium
What is the name of the liquid that enters the bowmans capsule from the
glomerulus
Glomerular filtrate
What doesn’t pass into the bowmans capsule
Large proteins and blood cells
Where does selective réabsorption happen
Proximal convoluted tubule
Loop of henle
Distal convoluted tubule
What is an adaption of the proximal convoluted tubule
The epithelium has microvilli to increase surface area
What substances are in urine
Water
Urea
Hormones
Excess vitamins
What substances are not in urine
Proteins
Blood cells
Glucose
How does glucose get reabsorbed
Active transport and facilitated diffusion on the proximal convoluted tubule
How is water réabsorbed (simple)
Osmosis
Because the water potential of the blood is lower than the filtrate
On the PCT loop of henle and DCT
