, Homeostasis & The Kidney
Homeostasis - the maintenance of constant or steady state
conditions within the body
Excretion - the removal of the toxic waste
products of metabolism
Osmoregulation - the control of the water potential of body
fluids
Ultrafiltration - the filtration of plasma and small
substances into the bowman's capsule
Reabsorption - when filtered useful products are selectively
reabsorbed into the bloodstream
Ultrafiltration Loop of Henle
The ascending limb secretes sodium and chloride
Blood entering the glomerulus has a high ions into the medulla by active transport, creating
hydrostatic pressure for a number of reasons: a very low water potential in the medulla. The
• The short distance from the heart filtrate consequently becomes more dilute.
• The fact that the afferent arteriole is wider than
the efferent arteriole As a result of the low water potential in the
medulla and the permeability of the descending
• The coiling of capillaries in the glomerulus which limb, water moves out of the descending limb by
restricts blood flow osmosis. Therefore, the filtrate becomes more
concentrated as it moves down the limb.
The high hydrostatic pressure forces the smaller
components of the blood into the bowman's
capsule whilst the bigger components remain in Osmoregulation
the glomerulus. The collecting duct is where water regulation takes
place. Reabsorption in the collecting ducts can be
The walls of the glomerulus contain small pores controlled by varying the permeability of the
and the bowman's capsule is lined with podocytes. collecting duct walls. ADH is crucial in this process.
The basement membrane is the effective filter.
The role of ADH:
Reabsorption • solute potential becomes more negative and is
Useful blood products which were lost to the detected by osmoreceptors in the hypothalamus
glomerular filtrate are reabsorbed back into the • the posterior lobe of the pituitary body releases
blood as the filtrate passes along the PCT. Glucose more ADH into blood
and amino acids are selectively reabsorbed by • this causes the walls of collecting ducts and DCT
facilitated diffusion and active transport. to become more permeable and aquaporins open
• more water is reabsorbed and so solute potential
of blood returns to normal and a smaller volume of
concentrated urine is produced
Homeostasis - the maintenance of constant or steady state
conditions within the body
Excretion - the removal of the toxic waste
products of metabolism
Osmoregulation - the control of the water potential of body
fluids
Ultrafiltration - the filtration of plasma and small
substances into the bowman's capsule
Reabsorption - when filtered useful products are selectively
reabsorbed into the bloodstream
Ultrafiltration Loop of Henle
The ascending limb secretes sodium and chloride
Blood entering the glomerulus has a high ions into the medulla by active transport, creating
hydrostatic pressure for a number of reasons: a very low water potential in the medulla. The
• The short distance from the heart filtrate consequently becomes more dilute.
• The fact that the afferent arteriole is wider than
the efferent arteriole As a result of the low water potential in the
medulla and the permeability of the descending
• The coiling of capillaries in the glomerulus which limb, water moves out of the descending limb by
restricts blood flow osmosis. Therefore, the filtrate becomes more
concentrated as it moves down the limb.
The high hydrostatic pressure forces the smaller
components of the blood into the bowman's
capsule whilst the bigger components remain in Osmoregulation
the glomerulus. The collecting duct is where water regulation takes
place. Reabsorption in the collecting ducts can be
The walls of the glomerulus contain small pores controlled by varying the permeability of the
and the bowman's capsule is lined with podocytes. collecting duct walls. ADH is crucial in this process.
The basement membrane is the effective filter.
The role of ADH:
Reabsorption • solute potential becomes more negative and is
Useful blood products which were lost to the detected by osmoreceptors in the hypothalamus
glomerular filtrate are reabsorbed back into the • the posterior lobe of the pituitary body releases
blood as the filtrate passes along the PCT. Glucose more ADH into blood
and amino acids are selectively reabsorbed by • this causes the walls of collecting ducts and DCT
facilitated diffusion and active transport. to become more permeable and aquaporins open
• more water is reabsorbed and so solute potential
of blood returns to normal and a smaller volume of
concentrated urine is produced
