Objective :

• To learn the procedure for collection of the urogenital system from a euthanised rat
• To learn the anatomical structure of the urogenital system of rat

Theory :

            The urinary system of rat consists of the a pair of kidneys and ureters, an urinary bladder and  an urethra. The principal function of the urinary system is the maintenance of water and electrolyte homeostasis.  The kidney of the mature rat is bean-shaped, and weighs approximately 0.51% to 1.08% (with a mean of 0.65%) of the body weight, varying with age and sex. The kidney receives 25% of the cardiac output, with the cortex, receiving 850% of renal blood flow. The lower urinary tract consists of the ureters, urinary bladder and urethra. It functions primarily to transport urine formed in the kidneys to the urinary bladder for storage until ultimate excretion. The reproductive system of a male rat consists of a pair of testes, epididymis, vas deferens, the urethra and the penis. Each testis is enclosed in a scrotal sac that lies outside the abdominal cavity. At puberty, the testes descend through the inguinal canal, remaining connected to the internal inguinal ring by the cremaster muscles. The testicular parenchyma is composed of seminiferous tubules separated by interstitial tissue and enclosed in a capsule that has three layers: the outer tunica vaginalis, the middle tunica albuginea, and the innermost layer, the tunica vasculosa. The seminiferous tubules are long, highly convoluted tubes that empty at both ends into the rete tetis. In the rat there are approximately 30 separate tubules, folded to form about 12 m of tubule per gram of testis. The process whereby primitive stem cell spermatogonia develop to form highly specialized spermatozoa is termed spermatogenesis. The testis is supplied by the internal spermatic artery, a highly coiled tortuous vessel. The venous return from the testis enters the pamphiniform plexus, a system of venous channels that closely surrounded the incoming spermatic artery, acting as a countercurrent heat-exchange system.

            The epididymis consists of the caput, corpus and cauda epididymis. Epididymis is involved in synthesize and secretion of many macromolecules, reabsorption of seminiferous tubular fluid and storage of the mature motile sperm prior to ejaculation. The vas deferens (ductus deferens) is a thick walled convoluted tube that is continuous with the tail of the epididymis and extends to the prostatic urethra. The vas deferens transfers the sperm, which have been stored in the epididymis, to the urethra, where additional secretions are added to produce the semen. The accessory sex organs in rodents are the seminal vesicles, prostate, coagulating gland, bulbourethral gland, and preputial gland. They are located along the route of the urethra as it relays sperm from the vas deferens out through the penis. The glands secrete a variety of complex fluids that transport and sustain the sperm during their lengthy journey out of the male and through the female genital tract. The female reproductive system consists of ovary, oviduct, uterus, cervix and vagina, whose gross appearance varies with the stage of the reproductive cycle. In healthy sexually mature animals, follicles in different stages of development are present. The uterus is enlarged and hyperemic during proestrus and early estrus, reduced in size at metestrus, and small and pale during diestrus. The vagina consists of an inner layer, the mucosa, a middle layer, the muscularis, and an outer layer, the adventitia.