endothelial cells are the structures of the nephron where filtration occurs.
list the structures of the nephron where filtration occurs?
endothelial cells
the renal corpuscle acts to filter blood. fluid from blood in the glomerulus is collected in the bowman's capsule to form "glomerular filtrate", which is then further processed along the nephron to form urine. it does this via a filtration barrier. the renal corpuscle filtration barrier is composed of: the fenestrated endothelium of glomerular capillaries, the fused basal lamina of endothelial cells and podocytes, and the filtration slits of the podocytes. this barrier permits passage of water, ions, and small molecules from the bloodstream into bowman's space (the space between the visceral and parietal layers). large and/or negatively charged proteins are prevented from passing into bowman's space, thus retaining these proteins in the circulation. the basal lamina is composed of 3 layers: lamina rara externa, lamina densa, and lamina rara interna. the lamina rara externa is adjacent to the podocyte processes. the lamina densa is the central layer consisting of type iv collagen and laminin. this layer acts as a selective macromolecular filter, preventing the passage of large protein molecules into bowman's space. the lamina rara interna is adjacent to endothelial cells. this layer contains heparan sulfate, a negatively charged glycosaminoglycan that contributes to the electrostatic barrier of the glomerular filter.
renal corpuscle
the four mechanisms used to create and process the filtrate (the result of which is to convert blood to urine) are filtration, reabsorption, secretion and excretion. filtration occurs in the glomerulus and is largely passive: it is dependent on the intracapillary blood pressure. about one-fifth of the plasma is filtered as the blood passes through the glomerular capillaries; four-fifths continues into the peritubular capillaries. normally the only components of the blood that are not filtered into bowman's capsule are blood proteins, red blood cells, white blood cells and platelets. over 150 liters of fluid enter the glomeruli of an adult every day: 99% of the water in that filtrate is reabsorbed. reabsorption occurs in the renal tubules and is either passive, due to diffusion, or active, due to pumping against a concentration gradient. secretion also occurs in the tubules and is active. substances reabsorbed include: water, sodium chloride, glucose, amino acids, lactate, magnesium, calcium phosphate, uric acid, and bicarbonate. substances secreted include urea, creatinine, potassium, hydrogen, and uric acid. some of the hormones which signal the tubules to alter the reabsorption or secretion rate, and thereby maintain homeostasis, include (along with the substance affected) antidiuretic hormone (water), aldosterone (sodium, potassium), parathyroid hormone (calcium, phosphate), atrial natriuretic peptide (sodium) and brain natriuretic peptide (sodium). a countercurrent system in the renal medulla provides the mechanism for generating a hypertonic interstitium, which allows the recovery of solute-free water from within the nephron and returning it to the venous vasculature when appropriate.
nephron