Topic 7.3 - Control of Blood Water Potential Flashcards
What are the parts of the kidney?
Fibrous capsule
Cortex
Medulla
Renal pelvis
Ureter
Renal artery
Renal vein
What is the fibrous capsule?
An outer membrane that protects the kidney
What is the cortex?
A lighter coloured outer region made up of renal (Bowman’s) capsules,convoluted tubules and blood vessels
What is the medulla?
A darker coloured inner region made up of loops of Henle, collecting ducts and blood vessels
What is the renal pelvis?
A funnels shaped cavity that collects urine into the ureter
What is the ureter?
A tube that carries urine to the bladder
What is the renal artery?
Supplies the kidney with blood from the heart via the aorta
What is the renal vein?
Returns blood to the heart via the vena cava
What are nephrons?
Tiny tubular structures that are the basic structural and functional units of the kidney
What are the parts of the nephron?
Renal (Bowman’s) capsule Proximal convoluted tubule Loop of Henle Distal convoluted tube Collecting duct
What is the Bowman’s capsule?
The closed end at the start of the nephron. Cup shaped and surrounds a mass of blood capillaries known as the glomerulus. The inner layer of the capsule is made up of specialised podocytes
What is the proximal convoluted tubule?
A series of loops surrounded by blood capillaries. Its walls are made of epithelial cells which have microvilli
What is the loop of Henle?
A long, hairpin loop that extends from the cortex into the medulla of the kidney and back again. It is surrounded by blood capillaries
What is the distal convoluted tube?
A series of loops surrounded by blood capillaries. It’s walls are made of epithelial cells, but it is surrounded by fewer capillaries than the proximal tube
What is the collecting duct?
A tube into which a number of distal convoluted tubules from a number of nephrons empty. It is lined by epithelial cells and becomes increasingly wide as it empties into the pelvis of the kidney
What is the afferent arteriole?
A tiny vessel that ultimately arises from the renal artery and supples the nephron with blood. Enters the renal capsule of the nephron where it forms the glomerulus.
What is the glomerulus?
A many branched knot of capillaries from which fluid is forced out of the blood. The glomerular capillaries recombine to form the efferent arteriole
What is the efferent arteriole?
A tiny vessel that leaves the renal capsule. It has a smaller diameter than the afferent arteriole and so causes an increase in blood pressure within the glomerulus
What are the stages of osmoregulation in the nephron?
The formation of a glomerular filtrate by ultrafiltration
Reabsorption of glucose and after b the proximal convoluted tubule
Maintenance of a gradient of sodium ions in the medulla by the loop of Henle
Reabsorption of water by the distal convoluted tubule and collecting ducts
Where does blood enter the kidney from?
The renal artery
What is the glomerular filtrate formed of?
Water, glucose and mineral ions squeezed out of the capillary
What is movement of filtrate out of the glomerulus resisted by?
Capillary epithelial cells
Connective tissue and epithelial cells of the blood capillary
Epithelial cells of the renal capsule
The hydrostatic pressure of the fluid in the renal capsule space
The low water potential of the blood in the glomerulus
What are the modifications made to reduce the barrier to flow of the filtrate?
The inner layer of the renal capsule is made up of highly specialised podocytes high allow the filtrate to pass beneath them
The endothelium of the glomerular capillaries has spaces up to 10nm wide between its cells
How much of the filtrate is reabsorbed back into he blood, and where?
Nearly 85%, by the proximal convoluted tubule
How are the epithelial cells in the proximal convoluted tubule adapted for reabsorption?
Microvilli provide a large surface area to reabsorb substance from the filtrate
Infolding at their bases to give a larger surface area to transfer reabsorbed substances into blood capillaries
A high density of mitochondria to provide ATP for active transport
What is the process of reabsorption of glucose through the proximal convoluted tubule?
Sodium ions are actively transported out of the cells lining the tubule into blood capillaries which carry them away. Sodium ion concentration of these cells lowered
Na+ now diffuse down a concentration gradient from the lumen of the PCT into epithelial lining cell through carrier proteins
Carrier proteins are specific types, each of which carries another molecule along its the sodium, cotransport
The molecules cotranported into cells them diffuse into the blood
What is the loop of Henle responsible for?
Water being reabsorbed front he collecting duct, concentrating the urine so that it has a lower water potential than the blood
What are the features of the descending limb?
It is narrow, with thin walls that are highly permeable to water
What are the features of the ascending limb?
It is wider, with thick walls that are impermeable to water
What does the water potential of the blood depend on?
The concentration of solutes like glucose, proteins, sodium chloride and other mineral salts
What may cause the water potential of the blood to lower?
To little water being consumed
Too much sweating
Large amounts of ions, eg sodium chloride, being taken in
What detects a fall in water potential?
Osmoreceptors in hypothalamus of the brain
When is ADH produced?
When water is lost and osmoreceptor cells shrink, causing the hypothalamus to produce ADH
What effect does ADH have on the kidneys?
It increases the permeability to water of the cell surface membrane of the cells making up the distal convoluted tubule and the collecting duct
What can cause the water potential of the blood to be increased?
Large volumes of water being consumed
Salts used in metabolism or excreted not being replaced in the diet
How does the body respond to an increase in water potential of the blood?
The osmoreceptors in the hypothalamus detect the rise in water potential and increase the frequency of nerve impulses to the pituitary gland to edge crease ADH release
Less ADH via the blood leads to a decrease in the permeability of the collecting ducts to water and urea
Less water is reabsorbed into the blood from the collecting duct
More dilute urine is produced and the water potential of the blood falls
When the water potential of the blood has returned to normal, the osmoreceptors in the hypothalamus cause the pituitary to raise its ADH back to normal levels
