NEPHRON ::
Structural and functional unit of the kidney is the nephron There are about one million nephrons in one kidney normally all are not functioning Each nephron consists of Bowman s capsule glomerulus proximal convoluted tubule loop of henle distal convoluted tubule and collecting tubule
Bowman s Capsule :: it is a proximal blind dilated end which covers up like a cap on the glomerular tufts So that the glomerular blood is filtered into the nephron
Glomerulus :: It is a tuft of capillaries with an afferent capillary coming in from the circulation and an efferent capillary going out into the circulation Glomeruli act as positive ultra filters Deproteinised plasma is filtered through the glomerulus into the nephron
Renal Tubule :: Tubular part of the nephron is about 0.3 cm in length There are about 2 millions of them in both kidneys if they are put end to end its length would be about 60 kilometers
Renal tubule has the following parts-1 Narrow neck 2.First or proximal convoluted tubule 3.Henle s loop or Loop of Henle 4.Second or distal convoluted tubule 5. Straight or collecting tubule and 6.Duct of Bellini
1.Neck : it is constricted and lined by cubical cells
2.Proximal Convoluted Tubule :: it is lined by cubical cells These cells are markedly active and secrete some enzymes like carbonic anhydrase etc which help in maintenance of acid base balance in the blood
3.Henle s Loop : it is a U- shaped tube and has a descending limb and an ascending limb Histologically it resembles a capillary but the loop is little wider than the capillary it is the constricted part of the nephron Loop of henle is physiologically important because it reabsorbs a number of important substances that are filtered by the glomerulus back into the blood
4.Distal Convoluted Tubules :: They are lined by cuboidal cells The absorption of Na+ is under the control of aldosterone which takes place in this part of the nephron
5.Collecting Tubules :: They are lined by cuboidal cells Collecting tubules of many nephrons combine into one straight tubule
6.Duct of Bellini :: This arises from the final combination of many straight tubules and finally drains into the apex of the pyramid of the kidney
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