ppt

URINARY TRACT – II

Maria M. Picken MD, PhD [email protected]

Nephron = functional & structural unit - glomerulus - proximal tubule - loop of Henle, - distal tubule

collecting duct system - kidneys produce 125 ml of filtrate/minute - 124 ml is reabsorbed - approximately 1.5 L of urine/day

nephros – greek = kidney

Two general classes of nephrons: cortical (superficial, 6/7) and juxtamedullary nephrons (1/7): important in producing hypertonicity in medullary interstitium – see physiology lecture. Both types are classified according to the length of their associated loop of Henle and location of their glomerulus. While all nephrons have their glomeruli in the cortex, cortical nephrons have their loop of Henle in the renal medulla near its junction with the renal cortex, while the loop of Henle of juxtamedullary nephrons is located deep in the renal medulla; they are called juxtamedullary because their glomerulus is located near the medulla (but still in the cortex).

The glomerulus of each

*

^^

Proximal convoluted tubule (PCT) - high cuboidal to low columnar epithelium: -prominent brush border (*) to increase reabsorption, (carbonic anhydrase on apical surface, 80-90% of bicarbonate reabsorbed)

- many mitochondria - basal infoldings (^^) abutting on fenestrated capillaries with diaphragms

NEPHRON – SUMMARY – see physiology and pharmacology lectures Proximal convoluted tubule: - reabsorption of 2/3 of water - 100% of proteins