Functional Anatomy of the Male Dog

The male reproductive system consists of the testes and epididymis, the vas deferens, the prostate gland, and the penis. The activities of both male and female reproductive systems are coordinated by hormones secreted from a variety of endocrine organs.


The testicles (testes) are the analogues of the female ovaries. They are smooth solid and ellipsoid in shape. In dogs and cats, the testicles reside in sacs called scrotum which has a groove distinguishing one from another. The skin is rather thin and hairless and has many sweat and sebaceous glands. The testicles are suspended within the scrotum at the end of the spermatic cord, a connective tissue tube that includes a large number of blood vessels. The testes descend from the abdomen into the scrotal sac before birth. When a testicle fails to descend at a proper time, the condition is called cryptorchidism This problem is usually hereditary and is corrected surgically.

The testes are divided into lobules, each of which contains the long, tightly coiled seminiferous tubules. Cells lining the seminiferous tubules are responsible for the production of spermatozoa. The Leydig cells, located between the tubules, produce testosterone. The seminiferous tubules eventually empty into ductules, which merge to form epididymis (a duct that runs on the side of a testicle), where sperm maturation takes place. Each epididymis empties into vas deferens, which eventually empties into the urethra, a hollow tube running through the penis from its origin at the neck of the bladder. It serves to transport urine, and, during mating, to transport the sperm-containing semen during ejaculation.

Prostate Gland

The prostate gland is a reproductive gland that plays an important physiological role and increases in size with age. It secretes fluid to help the sperm survive longer outside of the body. It surrounds the urethra, where it joins the urinary bladder. As in humans, enlargement of the prostate can be benign or malignant, although prostate cancer in animals is much rarer than in humans.


Penis and Prepuce

The penis is the male organ of copulation through which urine and semen pass by way of the penile urethra. The prepuce is an invaginated fold of the skin (an outpouching of the abdominal cavity) that surrounds the free extremety of the penis. The glans (free portion of the penis) has a small bone called os penis. This bone gives the penis support during the early stages of mating.



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