Reproductive System of Rat
Anatomy of Earthworm,Cockroach & Frog of Class 11
A large sac of skin, muscle and connective tissue called scrotum contains 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.
Around the outside of each testes is a C-shaped structure known 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.
Sperms 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 prostate gland 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.
Fig. Urinogenital System in Male Rat
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 slight acidic environment of the vagina.
Ovaries appear as a mass of follicles just posterior to the kidneys. The adult non-pregnant rat is usually in breeding condition with mature or well developed ova in the ovaries.
The oviducts are small highly coiled tubes leading from the ovaries to the uterus. The cornua of the uterus unite to form the vagina.
The vagina leads to the exterior separately from the urethra. The vagina opens to the exterior via the external vaginal orifice which opens just posterior to the urethral opening.
The clitoris, which is the female homologue of the male penis, is associated with the urethra and therefore is not connected with the vagina in the rat.
When a follicle is ripe and its ovum is mature, it bursts, releasing the ovum which is then picked up by the oviduct. The oviduct is ciliated internally. The cilia beat to create currents to draw the ovum inside and propel it towards the uterus.
The rats are prolific breeders and have a short gestation period of 3-4 weeks and produce 5-6 litters a year. Each litter has 5-8 young ones.
Fig. Urinogenital System in Female Rat
These are viviparous i.e. give rise to young ones, which are blind and naked at the time of birth. They become sexually mature in 8 - 11 weeks.