Changes

===The Bladder===

===The Bladder===

The widening of the cranial part of the urogenital passage forms the bladder. It is connected caudally to a closed urethra and cranially to a wide allantoic duct (the urachus).  This connects the bladder to the allantoic sac outside the embryo which collects urine during foetal life.  At birth the urachus degenerates and closes however there is usually a scar on the wall of the bladder.  The ends of the meso and metanephric ducts are attached to the urogenital passage.  The metanephric ducts form the ureters and enter the bladder.  The mesonephric ducts enter more caudally in the urogenital sinus.  The mesoderm from the mesonephric ducts forms epithelium of the trigone of the bladder.  The remaining epithelium comes from the endothelium of the hindgut and the external layers are derived from local mesoderm.

The widening of the cranial part of the urogenital passage forms the bladder. It is connected caudally to a closed urethra and cranially to a wide allantoic duct (the urachus).  This connects the bladder to the allantoic sac outside the embryo which collects urine during foetal life.  At birth the urachus degenerates and closes however there is usually a scar on the wall of the bladder.  The ends of the meso and metanephric ducts are attached to the urogenital passage.  The metanephric ducts form the ureters and enter the bladder.  The mesonephric ducts enter more caudally in the urogenital sinus.  The mesoderm from the mesonephric ducts forms epithelium of the '''trigone of the bladder'''.  The remaining epithelium comes from the endothelium of the hindgut and the external layers are derived from local mesoderm.

===The Urethra===

===The Urethra===