II stimulates secretion of aldosterone from the adrenal glands, which stimulates resorption of Na and Cl in the DCT, leading to an increase in blood volume and pressure.
Blood circulation in the kidney: Blood picks up stuff reabsorbed by the nephron. Renal artery enters the hilus of the kidney and branches into interlobar arteries in between pyramids. These branch in to arcuate arteries forming arches at the corticomedullary junction. These give off interlobular arteries, which branch into afferent arterioles and lead to efferent arterioles. Efferent arterioles branch differently depending on if they are cortical or juxtamedullary. Cortical nephrons have efferent arterioles that go to a peritubular capillary network around the PCT and DCT. Juxtamedullary nephrons have efferent arterioles that descend into the medulla as vasa recta, then loop back towards cortex. These descending and ascending vasa recta are closely associated, and function as a counter-current exchange for diffusible substances in the plasma of the medulla. The vasa recta lose water and gain salt as they descend, but then gain back the water and lose the salt as they ascend. So, the looped structure prevents them from disturbing the medulla’s gradient. Veins parallel arteries, and they leave as the renal vein.
Urinary passages: Calyces to renal pelvis to ureters to bladder. All are lined with transitional epithelium (stratified with large, ovoid surface cells). Stones can occur anywhere here. Ureters muscular tubes that use peristalsis. Beneath epithelium is lamina propria of CT, surrounded by inner longitudinal and outer circular muscle. Valves at site of entry to bladder prevent backflow. Surface cells of bladder maintain the impermeability to urine. Bladder epithelium varies in # of layers depending on fullness of bladder. Beneath the epithelium is a muscular tunica of several layers of obliquely oriented smooth muscle.
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