kidneys Flashcards
(33 cards)
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 proximal 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
