EL HUSSEINYS ESSENTIALS OF NEPHROLOGY BY MOHAMED EL HUSSEINYS PDF
EL HUSSEINYS ESSENTIALS OF NEPHROLOGY BY MOHAMED EL HUSSEINYS PDF kidney development involves the sequential formation of 3 sets of nephric systems termed the pronephros, mesonephros, and metanephros.
The urinary structures formed during these stages are derived from the nephrogenic cord, which develops from the urogenital ridge formed by intermediate mesoderm.
First, the pronephros, a very primitive structure arising from the cephalic portion of the nephrogenic cord, forms and later completely regresses.
Next, the mesonephros forms from the midportion of the nephrogenic cord.
The structures of the mesonephros persist in the male as the Wolffian ducts, which ultimately form important elements of the reproductive duct system, including the ductus deferens and epididymis.
EL HUSSEINYS ESSENTIALS OF NEPHROLOGY BY MOHAMED EL HUSSEINYS PDF In females, the mesonephros regresses and becomes vestigial Gartner’s ducts.
Development of the metanephros, or true kidney, begins with formation of the
metanephric diverticulum (ureteric bud), which sprouts off the caudal portion of the mesonephric duct by the fifth to sixth week of gestation.
The ureteric bud then penetrates into the sacral intermediate mesoderm to induce the formatioN of the metanephric mesoderm (metanephric blastema).
The reciprocal exchange of inductive signals between the ureteric bud and metanephric blastema drives their differentiation into the structures that form the mature kidney.
The ureteric bud ultimately gives rise to the collecting system of the kidney, including the collecting tubules and ducts, major and minor calyces, renal pelvis, and the ureters.
The metanephric blastema gives rise to the glomeruli, Bowman’s space, proximal
tubules, the loop of Henle, and distal convoluted tubules.
The kidneys migrate in a cephalad direction during fetal development, forming new vascular connections with the aorta as they travel. Some of these vestigial blood vessels may persist in the adult as accessory renal arteries.
The ureteric bud is initially present as a solid cord, but it is fully canalized by the tenth week of gestation. Occasionally, the metanephros will begin producing urine before canalization of the ureteric bud is complete, and this leads to the development of a transient hydronephrosis.
The ureteropelvic junction, the junction between the kidney and the ureter, is the last segment of the fetal ureter to canalize. It is also the most common site of obstruction.
The timeline and sources of kidney development are summarized in the table below..