kidneys Flashcards
what are the ways which water and salts are lost and gained
-lost
-sweat and urine
-gain
-diet
what is the main functional unit in the kidney
-nephron
what happens in the kidney
-homeostatic control of water potential in the blood - known as osmoregulation
-acts as a natural filter for the blood
which blood vessels carry blood to the kidneys
-renal arteries
what blood vessels carry blood away
renal vien
what does the hepatic portal vein do
carries blood to the kidneys from the intestines - rich in the products of digestion
how is the kidney structured
-outer layer is called the capsule - fiboruos and protects the kidney
-when cut in half there are 2 layers
-outer layer is known as the cortex - where the renal capsules and convoluted tubules and blood vessels
-inner region is called the medulla - made up of the loop of henle,collecting ducts and blood vessels
-passes through the ureter into the bladder and then out of the body via the ureatha
what are the parts of the nephron
-renal capsule
-proximal convoluted tubule
-loop of henle
-distal convoluted tubule
-collecting duct
what is the renal capsule/bowmans capsule
-cup shaped structure enclosing a network of blood capillaries - which is the glomerulus
-the inner layer is made of cells called podocytes - allow substances of a certain size to pass through branches of their structure- fluids forced out of the blood
what is the proxial convoluted tubule
- a series of loops surronded by blood capillaries leading from the glomerulus
-the walls are made up of epithelial cells which have microvilli to increase the surface area for reabsorption
what is the loop of henle
-a long hair-pin shaped loop surronede by blood capillaries
-starts in the cortex and runs into the medulla and back into the cortex
what is the distal convoluted tubule
-a series of loops running from the end of the loop of henle surrounded by blood capillaries
-the walls are also made from epithelial like the proximal but there are fewer capillaries
what is the collecting duct
-Several nephrons empty into each collecting duct
-lined with epithelial cells
-empties into the pelvis of the kidney
what supplies the nephron with blood and how does the blood leave the bowmans capsule
-the afferent arteriole arises form the renal artery
-it enters the renal capsule and forms the glomerulus
-leaves by the efferent arteriole
-the afferent has a larger/wider lumen than the efferent - causes blood pressure to build up in the glomerulus as less blood can leave than can enter 0 hydrostatic pressure
how does the high hydrostatic pressure cause the removal of small molecules and ions from the blood
-forces them out into the renal space
-low water potential in the glomerulus
-known as ultrafiltration - not selective - based on size
what are the 3 layers of the filtering system in ultrafiltration - this is in the bowmans capusle + glomerulus
-the capillary endothelium which contains large gaps - allowing blood plasma through but not blood cells
-the basement membrane supports the capillary endothelium and acts as a fine filter allowing plasma proteins to pass through
-the podocytes - form the lining of the renal capsule and have large gaps bwt them - allow the glomerular filtrate to flow through into the renal space
how is ultrafiltration non-selective
-all substances are filtered out of the blood if they are below the renal threshold
-substances like glucose,AA, mineral ions, water and urea -form the glomerular filtrate - reabsorbed in the proximal convoluted tubule
-red blood cells and large proteins remain in the blood
how are the epithelial cells adapted
-microvilli and infolding at the base of the cell increases the surface area for reabsorption
-mitochondria - provide ATP for active transport
how are molecules like glucose and AA reabsorbed back into the blood - in the proximal convoluted tubule
-by active tansport
-sodium cotransport
-Na+ acitvely transported out of the cells lining the PCT into the blood capillaries and the blood carries them away - Na+ ions conc in the cells is lowered
-Na+ diffuse down a conc gradient from the lumen of the PCT into the epithelial lining cells through co-transporter proteins by facilitated diffusion
-these co-transporter proteins are specific to different molecules and transports them along with the Na+
-icnreases the conc of these molecules in the epithelial cell and they diffuse into the blood
-this loers the WP of the blood in that area so water follows byu osmosis
how does the loop of henle work
-creates a high conc of salts deep in the medulla
-allows to produce urine - which has a lower WP than the blood plasma as is more conc
-the descending loop of henle is narrow with thin walls that are highly permeable to water but not very permeable to salts
-the ascending limb has thicker walls which are not permeable to water
-counter current mechanism is created ensuring that there is always a WP gradient drawing water out of the tubule
Describe the process/mechanism of the loop of henle
-Na+ actively transported out of ascending limb using ATP from mitochondria
-this lowers the water potential in the interstitial fluid and water cannot follow from the impermeable ascending limb
-the walls of descending limb are permeable so water leaves by osmosis, and can enter the blood capillaries
-the filtrate loses water as it passes down the descending limb and reaches the lowest water potential at the tip of the hair-pin
-at the base of the hairpin, Na+ diffuse out of the filtrate, then are actively pumed out futer up the ascending limb. the filtrate develops a progressively higher WP - more conc
-in the interstital space bwt the ascending limb and the collecting duct there is a water potential gradient
-the collecting duct is permeable so water passes out by osmosis and enters the blood vessels
-the interstital fluid always has a lower potential so a counter-current exists
what happens in the distal convoluted tubule
-fine adjustments to the blood
-hormones control the amount of further readsorption by affecting the permeability of the DCT
-helps to control the pH of the blood
how is the distal convoluted tubule adapted for reabsorption
-microvilli - increase SA
-mitochondria - ATP for active transport
-permeability of the walls can be altered by hormones
how are hormones involved in osmoregulation when responding to a fall in the water potential
-osmoreceptors in the hypothyalamus lose water by osmosis and shrink
-the pituitary glands secretes ADH into the blood
-ADH increases the permeability to water of the cell membrane of the cells in the distal convoluted tubule, by activating phosphorylase enzyme
-the activation causes vesicles containing protein channels to fuse with the cell membrane - so increase the number of water channel proteins
-ADH also increases the permeability of the collecting duct to urea which powers the water potential if the fluid around the duct so more water leaves by osmosis
-osmoreceptors also stimulate thirst
-osmoreceptors detect a rise in the water potential and fewer impulses are sent to the pituitary gland
-less ADH is released and the permeability of the collecting ducts reverts to its usual state
what is the role of ADH in osmoregulation an example of
-negative feedback
how is the proximal convoluted tubule adapted for absorption - rapid reabsorption of glucose
1.Microvilli provide a large surface area
OR
Folded (cell-surface) membrane provides a
large surface area;
2. Many channel/carrier proteins for facilitated
diffusion;
3. Many carrier proteins for active transport;
4. Many channel/carrier proteins for co-transport;
5. Many mitochondria produce ATP
OR
Many mitochondria for active transport;
6. Many ribosomes to produce carrier/channel
proteins;
Antidiuretic hormone (ADH) binds to V receptors found in cell-surface membranes in
two parts of a nephron.
Name the two parts of a nephron where V receptors are found.
-distal convoluted tubule
-collecting duct
A decrease in blood pressure stimulates the release of ADH.
Give the location of the receptors that detect a decrease in blood pressure and
explain how the release of ADH will affect blood pressure.
- Aorta
OR
Carotid artery/sinus; - (ADH) increases (re)absorption of water;
- Increases volume of (blood) and pressure
increases
OR
Increases volume of (blood) and pressure
returns to normal;
name the part of the body that releases ADH into the blood
posterior pituitary
what are some signs/symptoms that may result from a decrease in ADH
- Dehydration/thirst;
- Frequent urination
OR
Increase in volume of urine;
3.Less concentrated urine
OR
Dilute urine
OR
Urine paler/lighter in colour;
describe the effect of ADH on the collecting duct of the kidneys
-addition of channel proteins into the membranes
-increases permeability to water
-so more water (re)absorbed
-by osmosis
Using your knowledge of the kidney, explain why glucose is found in the urine of a
person with untreated diabetes
- High concentration of glucose in blood/filtrate;
- Not all the glucose is (re)absorbed at the
proximal convoluted tubule; - Carrier/co-transport proteins are working at
maximum rate
OR
Carrier/co-transport proteins/ are saturated;
Alport syndrome (AS) is an inherited disorder that affects kidney glomeruli of both men and women. Affected individuals have proteinuria (high quantities of protein in their urine).
Suggest how AS could cause proteinuria.
- Affects/damages basement membrane
OR
More protein channels/carriers in basement
membrane; - Proteins can pass into the (glomerular)
filtrate/tubule;
