9.3 2 Osmoregulation in mammals-the kidney Flashcards
water moves in and out of cells
by osmosis
Osmoregulation definition
the maintenance of a constant osmotic potential in the tissues of living organism by controlling water and salt concentrations
By controlling the water potential of the blood
body can control the water potential of the tissue fluid and protect the cells from osmotic damage
deamination definition
the removal of the amino group from excess amino acids in the ornithine cycle in the liver .
body
cannot store protein or amino acids and without the action of the liver any excess protein you eat would be excreted and wasted
hepatocytes (liver cells)
deaminate excess amino acids
remove amino group (NH2)
convert to ammonia which is very toxic
then very quickly to less toxic urea
ammonia produced in deamination process
converted into urea by a series of enzyme controlled reactions known as ornithine cycle
remainder of amino acid can then be used for celluar respiration or converted into lipid for storage
amino acid +oxygen
keto acid +ammonia (ammonia then goes to ornithine cycle)
Urine produced
is more concentrated (hypertonic to) the body fluids –makes it possible to conserve water
where are kidneys
attached to the back of abdominal cavity
surrounded by a thick layer of fat which helps prevent them from mechanical damage
kidneys purpose
control water potential of the blood removing substances that would affect the water balance as well as getting rid of urea- urea ,excess salts and water is removed
the urine
is stored in the bladder and released from the body in regular intervals
cortex
rich capillary network contains malpighian bodies of all the nephrons
pelvis
central chamber where urine arrives from collecting ducts
two roles of kidney in body
remove urea and osmoregulation
cortical nephrons
found in renal cortex have loop of Henle that only just reaches into medulla (majority)
Juxtamedullary nephrons
have long loops of Henle that penetrate right through the medulla -particularly efficient at producing conctrated urine
Three processes of osmoregulation
ultrafiltration ,selective reabsorption and tubular secretion
why does ultrafiltration occur
high blood pressure in the glomerular capillaries and the structure of Bowmans capsule and glomerulus
Malpighian body
combination of Bowman’s capsule and the glomerulus
how is there a high blood pressure
because diameter of blood vessel coming into glomerulus (afferent arteriole) is greater then blood vessel leaving (efferent arteriole)
the high blood pressure
squeezes blood out through pores in the capillary wall-size of pores mean almost all the contents of the plasma can pass out of the capillary -only blood cells and the largest plasma proteins cannot get through the pores
cells of Bowman’s capsule
act as an additional filter -wall of capsule made up of special cells called podocytes. They have extensions called pedicles that wrap around the capillaries forming slits that ensure any cells platelets or large plasma proteins that have left the capillary do not get into the tubule itself
Filtrate that enters bowmans capsule
contains glucose ,salt ,urea and many other substances in the same concentration as they are in the blood plasma
ultrafiltration
is passive and indiscriminate -removes urea from blood but also a lot of water as well as glucose,salt and other
proximal convoluted tubule
cells lining tubule have microvilli that greatly increase surface area through which substances can be absorbed -have large numbers of mitochondria indicating this is an active process
what is moved back into the blood by active transport
glucose,amino acids ,vitamens and most hormones
sodium ions
are actively transported and chloride and water ions follow passively along the gradient
once substances removed from tubule cells
into intracellular spaces they diffuse into the capillary network that surrounds the tubules
time filtrate reaches loop of Henle
isotonic to fluid that surrounds the tubule
loop of Henle
found in medulla of kidneys in close contact with network of capillaries known as the vasa recta
creation of high concentration of sodium and chloride ions in the tissue fluid of the medulla
is due to the flow of fluid in opposite directions in the adjacent limbs of the loop of Henle combined with different permeabilities to water in different sections and a region of active transport
Countercurrent multiplier
A system that produces a concentration gradient in living organisms using energy from cellular respiration
Descending limb
Freely permeable to water but not permeable to sodium and chloride ions
No active transport
The fluid entering here is isotonic with the blood
As travels down limb into medulla external concentration of sodium and chloride ions in tissue fluid of medulla and the blood of the vasa recta is higher and higher
Water moves out into the blood of vasa recta down water potential gradient
By time at bottom the loop is very concentrated are hypertonic to arterial blood
The first section ascending limb
First section of the limb is very permable to sodium and chloride ions but not to water
No active transport takes place in this section
Sodium ions and chloride ions move out the very concentrated fluid in the loop of Henle into tissue fluid of medulla
The second section of the ascending limb
Impermeable to water
Thicker
Sodium ions and chloride ions are actively pumped out of the tubule into the tissue fluid of the medulla and the blood of vasa recta a
Gives tissue of medulla the very high sodium and chloride ion concentration which causes water to pass out the descending limb
Fluid left in ascending limb becomes less concentrated
Distal convoluted tubule
Permable to water
Distal convoluted tubule and collecting duct
Balancing of the water of the body takes place
If not enough salt in body sodium may be pumped out of tubule with chloride ions following
The collecting duct
Water moves out of the collecting duct down a water potential gradient as passes through medulla
Urine becomes steadily more concentrated
Allows creation of hypertonic urine
Kangaroo rat
Spend time in in burrows where temperature is cooler
Generate majority of water by oxidative methods
Large portion of juxtamedullary nephrons
Long loops of henle - particularly descending loop
Higher numbers of infoldings in the cell membranes of the epithelial cells lining the tubules
Higher number of mitochondria
Under a microscope the proximal convoluted tubule will appear
Fuzzy
The distal convoluted tubule
Will appear clear
Glomeruous
Will appear under a microscope concentrated red blood cells
Barrier between blood in capillary and lumen of bowmans capsule
Three layers
- Endothelium of capillary - narrow gaps between cells blood plasma can pass through
- Basement membrane - fine mesh of collagen fibres and glycoproteins prevent big molecules passing through
- Epithelial cells of bowmans capsule - specialised shape and finger like projections ensure any gaps between cells allowing fluid to pass into the lumen of bc
