Lecture Monday September 10: UG Embryology I

Urorectal septum (a plate of mesoderm) separates the cloaca into urinary bladder and rectum.



Allantosis connected to the apex of the bladder becomes the urachus (median umbilical ligament). Clinical conditions include; urachal fistula, cyst or sinus when portions of the allantois remain open.

Kidney Development
1. Mesonephros forms mesonephric (Wolffian) duct and a set of tubules


2. Metanephros forms as an outgrowth of the distal portion of the mesonephric duct (ureteric bud) and includes the surrounding mesoderm that forms the metanephric blastema.


Ureteric bud = ureter, pelvis, calyces and collecting ducts
Metanephric blastema = kidney tubules or nephrons

Common Clinical Conditions
1. Metanephric kidneys "ascends" from the pelvis. Clinical condition may occur when the inferior poles of the two kidneys fuse to create a horseshoe kidney.
2. Bifid ureter if the ureteric bud splits as it enters the blastema.
3. Multiple renal arteries

Gonadal/Genital Ridges
Develops next to the Mesonephros. Populated by germ cells that migrate in from the yolk sac.

A second longitudinal duct forms called Paramesonephric (Mullerian) Duct.



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