Kidney and excretion
Kidney
Vital organ that ensure that the animal can regulate water and ion content of their blood
plasma.
Maintains osmotic pressure of blood relative to surroundings.
Structurally and physiologically diverse across the animal kidney. However, all kidneys contain
common features, which include tubular element that is filled with fluid and will be eliminated
outside of the animal, such as water, excess ions, toxic
Produce aqueous fluid, which is urine
Function: ensure that the composition and volume of the blood plasma and ECF is maintained.
ECF is similar to blood plasma as there is no barrier in the movement of ions and water.
Urine formation
Urine contains water, organic ions and inorganic ions.
Urine is produced by the kidneys in a two-step formation.
First step produces primary urine, which is very similar to the blood plasma in terms of the ion
content and osmotic potential of the fluid. The main difference is that proteins in the blood
plasma do not pass into the urine and as a result an aqueous solution is obtained that is called
filtrate.
Ultrafiltration and active secretion are the process that produces primary urine.
As the aqueous solution passes further through the kidney tubule, definitive urine is produced,
which is modified urine and differs in composition compared to blood plasma
General structure of nephron
Pedicels are so close to each other that there are
narrow filtration slits between them, which allows
small molecules to pass though
Nephron=single layer of epithelia cells
The kidneys are made up of many nephron cells and has a single layer of epithelial cells running
across the tubule
Bowman’s capsule= no opening
Other end= opening end that eliminates to the bladder or to the outside environment
bowman’s capsule, full of fluid
Inside the Bowman’s capsule is the renal corpuscle
In the renal corpuscle, blood travels through the
capillaries and forced into the capsular space
through the hydrostatic pressure of the blood in
the core muscle.
Blood is traveling at a relatively high pressure to
force fluid from the blood into the capsular fluid.
As the blood travels through it is filtered at two
levels, at the capillary endothelial cells and then
through the second layer, which is the podocyte
cells (specialised epithelial cells).
, Podocyte cells have extensions that produces slits. So, there are slits between cells, which filter
fluid out of the renal core muscle and into the capsule, which will allow water, ions, small
molecular weight, such as glucose, AA to pass through the filtration process.
Sue to no permeability, there is an isosmotic to the blood plasma. The only difference is that the
blood plasma will retain large proteins.
The fluid movement is regulated by hydrostatic pressure (blood pressure) in vasculature
(vascular system), which produces hydrostatic pressure that forces fluid from the blood into the
capsule.
There is some hydrostatic pressure in the capsule, as the
capsule fills there will be some resistance to the filling,
the pressure will be forcing the fluid back into the blood
The pressure of fluid from the capsule to the blood is
much lower than the pressure of fluid from the blood to
the capsule.
Colloid osmotic pressure is due to the increase
concentration of protein, which will cause water to
osmotically flow back into the blood capillary.
They hydrostatic pressure entering is greater than the
osmotic pressure and hydrostatic pressure from the
blood supply.
Hydrostatic pressure entering is enough to overcome the
hydrostatic pressure from the capsule to the capillary and the osmotic pressure due to the
concentration gradient between the two fluids.
Ultimately, we have excess pressure, which is the filtration pressure that varies.
Ultrafiltration-formation of primary urine
2 systems; ultrafiltration, which produces primary urine and active transport.
Ultrafiltration is the system that is employed by mammals and vertebrates.
There is a rate of primary urine formation, which is dependent upon the glomerular filtration.
The glomerular filtration rate is 120ml/min in adult human (4-4.5 litres)
Every 30 minutes blood is being filtered. If all of that produced urine. There would be a large
amount of urine. Therefore, most of the water is reabsorbed, maintaining osmotic pressure of
the blood plasma.
The glomerular filtration rate is
much greater than the rate of
definitive urine excretion
Although a large amount of water
enters the nephron most of it is
reabsorbed into the capillaries
Depending on the situation, we can
alter the rate of glomerular
filtration
Changing GFR (rate at which blood
is being filtered) and the rate of
urine being produced, essentially
changes blood pressure in
glomerular
Kidney
Vital organ that ensure that the animal can regulate water and ion content of their blood
plasma.
Maintains osmotic pressure of blood relative to surroundings.
Structurally and physiologically diverse across the animal kidney. However, all kidneys contain
common features, which include tubular element that is filled with fluid and will be eliminated
outside of the animal, such as water, excess ions, toxic
Produce aqueous fluid, which is urine
Function: ensure that the composition and volume of the blood plasma and ECF is maintained.
ECF is similar to blood plasma as there is no barrier in the movement of ions and water.
Urine formation
Urine contains water, organic ions and inorganic ions.
Urine is produced by the kidneys in a two-step formation.
First step produces primary urine, which is very similar to the blood plasma in terms of the ion
content and osmotic potential of the fluid. The main difference is that proteins in the blood
plasma do not pass into the urine and as a result an aqueous solution is obtained that is called
filtrate.
Ultrafiltration and active secretion are the process that produces primary urine.
As the aqueous solution passes further through the kidney tubule, definitive urine is produced,
which is modified urine and differs in composition compared to blood plasma
General structure of nephron
Pedicels are so close to each other that there are
narrow filtration slits between them, which allows
small molecules to pass though
Nephron=single layer of epithelia cells
The kidneys are made up of many nephron cells and has a single layer of epithelial cells running
across the tubule
Bowman’s capsule= no opening
Other end= opening end that eliminates to the bladder or to the outside environment
bowman’s capsule, full of fluid
Inside the Bowman’s capsule is the renal corpuscle
In the renal corpuscle, blood travels through the
capillaries and forced into the capsular space
through the hydrostatic pressure of the blood in
the core muscle.
Blood is traveling at a relatively high pressure to
force fluid from the blood into the capsular fluid.
As the blood travels through it is filtered at two
levels, at the capillary endothelial cells and then
through the second layer, which is the podocyte
cells (specialised epithelial cells).
, Podocyte cells have extensions that produces slits. So, there are slits between cells, which filter
fluid out of the renal core muscle and into the capsule, which will allow water, ions, small
molecular weight, such as glucose, AA to pass through the filtration process.
Sue to no permeability, there is an isosmotic to the blood plasma. The only difference is that the
blood plasma will retain large proteins.
The fluid movement is regulated by hydrostatic pressure (blood pressure) in vasculature
(vascular system), which produces hydrostatic pressure that forces fluid from the blood into the
capsule.
There is some hydrostatic pressure in the capsule, as the
capsule fills there will be some resistance to the filling,
the pressure will be forcing the fluid back into the blood
The pressure of fluid from the capsule to the blood is
much lower than the pressure of fluid from the blood to
the capsule.
Colloid osmotic pressure is due to the increase
concentration of protein, which will cause water to
osmotically flow back into the blood capillary.
They hydrostatic pressure entering is greater than the
osmotic pressure and hydrostatic pressure from the
blood supply.
Hydrostatic pressure entering is enough to overcome the
hydrostatic pressure from the capsule to the capillary and the osmotic pressure due to the
concentration gradient between the two fluids.
Ultimately, we have excess pressure, which is the filtration pressure that varies.
Ultrafiltration-formation of primary urine
2 systems; ultrafiltration, which produces primary urine and active transport.
Ultrafiltration is the system that is employed by mammals and vertebrates.
There is a rate of primary urine formation, which is dependent upon the glomerular filtration.
The glomerular filtration rate is 120ml/min in adult human (4-4.5 litres)
Every 30 minutes blood is being filtered. If all of that produced urine. There would be a large
amount of urine. Therefore, most of the water is reabsorbed, maintaining osmotic pressure of
the blood plasma.
The glomerular filtration rate is
much greater than the rate of
definitive urine excretion
Although a large amount of water
enters the nephron most of it is
reabsorbed into the capillaries
Depending on the situation, we can
alter the rate of glomerular
filtration
Changing GFR (rate at which blood
is being filtered) and the rate of
urine being produced, essentially
changes blood pressure in
glomerular
