Kitten sitting on blue blanket.

The Reproductive System

Diseases and conditions involving the reproductive tract tend to be either infectious or anatomical in nature. Prompt medical attention is warranted in any disorder involving the reproductive tract.

Anatomy and Physiology

The Male Reproductive System

Starting with the male cat, the major parts of the reproductive system include the testicles (with associated epididymis and ductus deferens), the scrotum (containing the testicles), the penis (containing the urethra), and the prostate gland.

Tomcats also have two bulbourethral glands, which contribute fluid to the semen. The testes are the organs responsible for the production of spermatozoa. This production is directly influenced by the hormone testosterone, also produced by the testicles.

Aside from regulating sperm production, testosterone is also responsible for normal male sexual behavior, as well as the aggressive, territorial behavior exhibited by some males.

Normally, the testicles should descend into the scrotum shortly after birth, usually no later than 8 weeks of age. If this event fails to occur, the pet is said to be cryptorchid, and surgical removal of the testicles is required to prevent medical problems (such as testicular tumors) in the future and to prevent the passage of that undesirable trait to offspring.

From the testicle, sperm is shunted into the epididymis, a structure closely attached to each testicle, where it finishes its maturation process. On copulation, the mature sperm is transported from the epididymis through the ductus deferens and to the tubelike urethra coursing within the penis.

The feline penis is covered with tissue “spines” that serve to stimulate ovulation in the female when mating occurs. The prostate gland, considered an accessory sex gland, is located surrounding the urethra near the neck of the bladder.

It functions to produce prostatic fluid, which mixes with sperm to form semen, and helps increase the survivability of the sperm within the female reproductive tract. Constipation, discharges from the penis, and painful urination can be clinical signs of a prostatic disorder.

The Female Reproductive System

The major reproductive organs of the female cat include the ovaries, the oviducts, the uterus, the vagina, the vulva, and the mammary glands.

The ovaries are responsible for the production and release of eggs destined to be fertilized by the male sperm. In addition, several important reproductive hormones are produced by these structures.

Unfertilized eggs are released, or ovulated, by the ovaries, and pass into the small oviducts. It is within these oviducts that fertilization takes place. The fertilized egg, or embryo, continues its passage down the oviducts on its way to the uterus.

When an embryo reaches the uterus, it attaches itself to the uterine wall and begins its development. If fertilization has not taken place, this attachment won’t occur and the body eventually resorbs the egg.

The uterus is separated from the vagina by a ring of muscle known as the cervix. Most of the time, this cervix remains open. During pregnancy, however, the cervix will close, preventing outside access to the uterine environment.

At time of parturition, the cervix relaxes, allowing the birth to take place. The external opening of the vagina is termed the vulva. Cats typically have a total of 8 to 10 mammary glands (4 to 5 on each side), designed to supply newborn offspring with life sustaining milk .

The size of these glands will fluctuate, depending on the stage of the estrous cycle and the pregnancy status of the female. The “estrous cycle” is the term used to describe a series of events that occurs within the female reproductive tract between actual heat, or periods of estrus.

On the average, this cycle lasts from 12 to 20 months in cats (queens). Cats are considered “seasonally polyestrous,” meaning that the estrous cycle tends to occur during only certain months of the year (February to October), with anestrus settling in during the fall and early winter. However, cats kept indoors exposed to continuous artificial lighting may not experience anestrus at all.

The four phases of the estrous cycle include anestrus, proestrus, estrus, and metestrus. Anestrus is the period of time in which there is no reproductive activity going on in the ovaries. As mentioned above, the period of anestrus in cats occurs seasonally and is influenced the length of daylight.

From anestrus, the reproductive cycle enters the period of proestrus. Signs seen during proestrus are related to the ovaries’ increased production of the hormone estrogen. Proestrus can last 3 days in the cat. Normally, females will not stand to be mated until the waning days of this phase.

The last stage in the estrous cycle is metestrus, which can last 3 to 14 days in the cat. This stage begins when the female refuses to accept the male for further breeding. It is the period of uterine repair or, if fertilization is achieved, the period of pregnancy. False pregnancies appear during this phase as well.