Renal System Flashcards
How is the blood flow through the nephron unique?
It has a capillary bed situated between 2 arterioles
Describe the blood vessels through the nephron
Renal artery, interlobular arterioles, afferent arteriole, glomerular capillary, efferent arteriole, peritubular capillaries, venules, renal vein
Describe the structure of the glomerulus.
A mesh network of capillaries with fenestrations, allows for fast filtration
Describe the structure of the bowman’s capsule
parietal layer and visceral layer with space between for the collection of filtrate. Visceral layer has specialised epithelium, with podocytes with pedicles which wrap around the glomerular capillaries
what makes up the filtration barrier
endothelial cells of glomerular capillaries, basement membrane and pedicle of podocyte
what molecules are filtered out of the capillaries
water, amino acids, glucose, urea, creatinine, sodium, bicarbonate, calcium, potassium, hydrogen
What pressures influence the glomerular filtration rate
hydrostatic pressure (glomerular and bowman’s capsule), osmotic pressure (glomerular and bowman’s capsule), systemic
how can kidney failure be detected.
glomerular filtration rate will be reduced so less urea and creatinine will be filtered out. therefore, there will be a higher concentration of these in the blood
describe how the first 50% of fluid is reabsorbed in proximal convoluted tubule
by passive diffusion down concentration gradient, from lumen of tubule to peritubular capillaries. water through aquaporin channels, Na travels through channels that can co-transport glucose and amino acids across to lumen wall then diffuse to blood
describe how the 15% of fluid is reabsorbed in proximal convoluted tubule
Na exchanged for K across to interstitial space using ATP. this causes Cl water to travel across, balancing the ionic and osmotic gradients. Glucose and amino acids are 100% reabsorbed using secondary active transport
describe counter-current multiplication
occurs in the loop of henle, 2 tubules running in the opposite direction to one another - one thin descending, one thick ascending. as the fluid goes down the descending the concentration is multiplied, as it then goes up the ascending, the concentration is reduced
how is water reabsorbed in the loop of henle
thick ascending limb is impermeable to water but allows reabsorption of Na ions. this increases the concentration in the medullary interstitium, making it salty. The thin descending limb is permeable to water so water is reabsorbed here to the medulla to balance the osmotic gradient. as the fluid goes down the descending limb, more water is reabsorbed so the concentration of the fluid in the tubule increases
what effect does ADH have on kidney function
increases aquaporin channels in the collecting duct and distal part of the DCT. this increases water reabsorption. also causes urea reabsorption in the collecting duct. urea then increases the osmolarity in the medulla, causing further water reabsorption in the loop of henle
what effect does aldosterone have on kidney function
increases Na reabsorption in the DCT. Na is reabsorbed and H ions are secreted. water follows the Na so increased water reabsorption also, increase BP
what is the role of atrial naturetic hormone of kidney function
inhibits aldosterone and ADH, prevents water reabsorption in DCT to lower blood pressure
Name the cells of the juxtaglomerular apparatus and describe their function
macula densa cells - detect Na concentration
juxtaglomerular cells - control diameter of afferent arteriole
where is the juxtaglomerular apparatus situated?
connecting the distal tubule to the glomerulus
describe the events in the juxtaglomerular apparatus when blood pressure is high
high blood pressure, high hydrostatic pressure - high GFR, more Na filtered so not all can be reabsorbed in proximal, higher concentration in distal - detected by macula densa cells. these release adenosine, this acts on the juxtaglomerular cells - cause constriction of the afferent arteriole, reduce hydrostatic pressure - reduce GFR
describe the events in the juxtaglomerular apparatus when blood pressure is low
low blood pressure, low hydrostatic pressure, low GFR. Less Na filtered, most reabsorbed in proximal, lower concentration of Na in distal - detected by macula densa. These release prostaglandins, act on juxtaglomerular cells to cause dilation of the afferent arteriole to increase hydrostatic pressure and GFR. Juxtaglomerular cells also release renin
how does renin increase the blood pressure
renin converts angiotensinogen in the blood to angiotensin I, this is then converted to angiotensin II (by ACE). This is a potent vasoconstrictor - increases venous return and TPR - increases MAP
describe some symptoms of chronic kidney disease
hypertension - could be symptom or cause
oedema - less fluid filtered so builds up in IS
anaemia - lack of erythropoeitin, lack of RBC
sore/weak bones - reduced Ca and vitamin D reabsorption, blood or protein in urine
describe the link between cardiovascular disease and kidney disease
hypertension can be caused by CKD as the kidneys can no longer control it. this would increase the load on the heart and could cause heart failure. also diabetes can cause CKD and CVD as high blood glucose can damage vessels
how can flurosemide be used to treat CKD?
flurosemide blocks Na channels in loop of henle, if no Na reabsorption, no water reabsorption so more water secreted, lowering blood fluid thus blood pressure. controlling hypertension is crucial for control of CKD
