Accessory Excretory Structures Balance



Attached to each kidney is a 25 to 30cm tube called the ureter. This tube transports the urine from the renal pelvis to the urinary bladder.

Histologically, in cross section the lumen of the ureter is star shaped and has three layers of tissue.


Innermost layer, the tunica mucosa faces the lumen - transitional epithelium


Middle layer, the tunica muscularis, consisting of two layers of smooth muscle - an inner longitudinal and an outer circular layer.


Outermost layer, the fibrous tunica adventitia, consisting of connective tissue.


The ureters enter the bladder in an oblique manner. This course acts as a check valve - as the bladder fills up, the pressure closes the openings and preventing back flow into the kidneys.