Kidney Ch 26
The nephron – functional units of kidney – 2 parts • Renal corpuscle – filters blood plasma – Glomerulus – capillary network – Glomerular (Bowman’s) capsule – double-walled cup surrounding glomerulus • Renal tubule – filtered fluid passes into – Proximal convoluted tubule – Descending and ascending loop of Henle (nephron loop) – Distal convoluted tubule
Nephrons – Renal corpuscle and both convoluted tubules in cortex of kidney – loop of Henle extends into medulla – Distal convoluted tubule of several nephrons empty into single collecting duct – Cortical nephrons – 80-85% of nephrons • Renal corpuscle in outer portion of cortex and short loops of Henle extend only into outer region of medulla – Juxtamedullary nephrons – other 15-20% • Renal corpuscle deep in cortex and long loops of Henle extend deep into medulla • Ascending limb has thick and thin regions • Enable kidney to secrete very dilute or very concentrated urine
Histology of nephron and collecting duct Glomerular capsule • Visceral layer has podocytes that wrap projections around single layer of endothelial cells of glomerular capillaries and form inner wall of capsule • Parietal layer forms outer wall of capsule • Fluid filtered from glomerular capillaries enters capsular (Bowman’s) space
Overview of renal physiology 1. Glomerular filtration – Water and most solutes in blood plasma move across the wall of the glomerular capillaries into glomerular capsule and then renal tubule 2. Tubular reabsorption – As filtered fluid moves along tubule and through collecting duct, about 99% of water and many useful solutes reabsorbed = returned to blood 3. Tubular secretion – As filtered fluid moves along tubule and through collecting duct, other material secreted into fluid such as wastes, drugs, and excess ions – removes substances from blood • Solutes in the fluid that drains into the renal pelvis remain in the fluid and are excreted • Excretion of any solute = glomerular filtration + secretion - reabsorption
Structures and functions of a nephron Renal corpuscle Renal tubule and collecting duct Peritubular capillaries Urine (contains excreted substances) Blood (contains reabsorbed substances) Fluid in renal tubule Afferent arteriole Filtration from blood plasma into nephron Efferent arteriole Glomerular capsule 1 Tubular reabsorption from fluid into blood 2 Tubular secretion from blood into fluid 3
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- Fall '11
- Nephron, Glomerulus, glomerular capillaries