Collecting duct Ascending limb Collecting duct Renal tubule Nephron Renal corpuscle Efferent arteriole Glomerulus Proximal convoluted tubule (PCT) Nephron loop Distal convoluted tubule (DCT) Collecting tubule Intercalated cells Principal cells Thick segment Thin segment Descending limb Medulla Cortex Capsular space Afferent arteriole Vascular pole Glomerular capsule Tubular pole Visceral layer Parietal layer Thin segment Thick segment (b)
Tubular secretion Tubular reabsorption Glomerular filtration The movement of substances from the blood within the glomerulus into the capsular space The movement of substances from the tubular fluid back into the blood The movement of substances from the blood into the tubular fluid Collecting tubule Collecting duct Vasa recta Capsular space Glomerular capsule Glomerulus Afferent arteriole Efferent arteriole Nephron loop DCT Descending limb Ascending limb PCT Peritubular capillaries
Visceral layer of glomerular capsule Podocyte cell body Filtration slits Pedicels Capillary lumen Glomerular capillary Filtration membrane Endothelium of fenestrated capillary Basement membrane of capillary Filtration slits of visceral layer Filtration Membrane Mesangial cells (not shown) Specialized contractile cells positioned in and between glomerular capillary loops
Afferent arteriole Blood colloid osmotic pressure (OP g ) osmotic pressure exerted by dissolved solutes it contains e.g., plasma proteins opposes glomerular hydrostatic pressure draws fluids back into glomerulus Capsular hydrostatic pressure pressure in glomerular capsule due to filtrate already present impedes movement of additional fluid Glomerular hydrostatic (blood) pressure Blood pressure in glomerulus called glomerular hydrostatic (blood) pressure (HP g )force that “pushes” water and some solutes out of glomerulus pushed into capsular space of renal corpuscle higher value than blood pressure of other systemic capillaries required for filtration to occur larger diameter of afferent arteriole smaller diameter of efferent arteriole
Substances Filtered by Filtration Membrane Filtration membrane Endothelium (blocks formed elements) Basement membrane (blocks large proteins) Filtration slits of visceral layer (block small proteins) Filtrate includes water, glucose, amino acids, ions, urea, many hormones, vitamins B and C, ketones, and very small amounts of protein Capsular space Capillary Filtered Small protein Leukocyte Large protein Platelet Erythrocyte Not filtered
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