NOTE: You will dissect only one rat, therefore you will only see one sex during the actual dissection. You are, however, responsible for knowing the reproductive organs both male and female. Be sure to prepare your specimen so that it will be clear enough for another student to study. Also make certain you examine a specimen of the sex that you did not dissect.
Male (Figure 3)
Locate the scrotum, a large sac of skin, muscle and connective tissue containing the testes on the exterior of the body just ventral to the anus. During non-breeding periods the testes may be retracted into the abdominal cavity and the scrotum will not be enlarged. However, sperm cannot develop completely within the high temperatures of the abdominal cavity; the slightly lower temperature of the scrotum is necessary for the final stages of sperm formation.
Carefully cut open the scrotum and locate the paried testes which are oval in shape. Around the outside of each testes is a C-shaped structure knows as the epididymis, which is a very long, highly coiled tubule. Three regions of the epididymis can be recognized; the caput epididymis covering the anterior end of the testes, the corpus epididymis lying along the lateral surface of the testes and the cauda epididymis on the posterior end of the testes. Sperm produced in the seminiferous tubules of the testes pass into the caput epididymis via the vas efferentia (very small tubules which are not visible). The sperm moves through the corpus and cauda epididymes into the vas deferens, which is a moderately large tube leading from the epididymis to the urethra. (The vas deferens is usually closely allied with the testicular artery and vein.) The prostate glands is found on either side of the urethra region of the urinary bladder. Locate the large lobed vesicular glands, and the coagulating glands which are closely applied to the inner curve of the vesicular glands. The above glands and some other glands in this region comprise the accessory sex glands. The secretions of these glands form the seminal fluid, which carries the sperm during ejaculation, activates and provides certain nutrients for them, and contains substances which neutralize the somewhat acid environment in the vagina. Trace the urethra to the posterior and locate the penis.
Examine the slide of a section of the testes (slide #41). Note the circular outlines of the sections of seminiferous tubules and the mature sperm in the centres of some of the tubules (Figure 3).
Figure 3
A- male urogenital system
B- Section of mammalian testes. The seminiferous tubules are the site of sperm production. Differentiation of spermatagonia into spermatocytes then to spermatids leads to the development of mature spermatazoa which are released from the testes.