Basic Male Dog Reproduction

By Deb Haines

Let’s begin by going over the reproductive anatomy of the male dog and pointing out some unique features

One unique feature of male dogs as compared to many other mammals is the presence of only one accessory sex gland. On this diagram, locate the prostate. The prostate gland is the only accessory sex gland of male dogs. The prostate produces a watery secretion that is ejaculated prior to the sperm-containing fraction of the ejaculate.

The dog’s penis itself has two unique features. One is the os penis, or penis bone. This functions to provide rigidity for intromission, or entering the female’s vagina. Once inserted, another important feature comes into play…the bulbus glandis. This area of the penis will swell when the penis is inside the vagina, which forms a sort of locking mechanism to allow for prolonged contact during and after ejaculation. This increases the chance of successful fertilization.

The bulbus glandis (also called a bulb or knot) is an erectile tissue structure on the penis of canid mammals. During mating, immediately before ejaculation the tissues swell up to lock (tie) the male’s penis inside the female. The main function of the bulbus glandis is to produce the fluids in the urethra that serve to neutralize the acidity of the environment that may develop from the residual fluids of urine inside the urethra. This gland also works to lubricate the urethra. The fluid is usually clear and very sleek allowing for easy slippage. Swelling of these glands are normal during arousal.

The swelling of the bulbus glandis, once inside the female reproductive tract, causes what is known as the copulatory tie. This is sometimes also called the coital tie, or just tie.

After intromission, the male will usually step down from the mounting position so that the two animals are in the position you see here.

During the tie, the two animals are physically unable to separate. The copulatory tie usually lasts anywhere from five minutes to an hour, and after this time the animals will separate naturally. It is important that humans to allow this natural separation to occur. Major damage can be done to the reproductive tracts when humans try to physically separate the animals prematurely.

It’s not unusual for dogs to mate and tie several times.

So, what’s all this mean?

Sexual reproduction is accomplished through various periods in which both dogs, male and female, are prepared to mate. Much unlike the female dog who has distinctive heat cycles that distinguish her eagerness to mate, the male dog can be sexually aroused at any time during his lifetime and will usually oblige unless other physical factors keep him from doing so.

The dog reproductive system is made up of the reproductive anatomy. In the male, the main organs that are involved in sexual intercourse are the:

  • penis,
  • prostate gland,
  • testicles,
  • vas deferens or ductus, and
  • sperm production.

When the male is aroused, these organs prepare for coitus by the arousal of the penis as the testicles are raised into position. During ejaculation, the sperm is transported via the vas deferens to the prostate gland where it is joined with essential, nourishing fluids then enter the urethra and finally to the penis. From the penis, the semen is directed into the uterus of the female for semination.The penis is designed with two basic frameworks that work in unison for canine reproduction. The bulb-like structure at the base of the penis, called the glans penis, fills with blood and is used to hold the penis erect inside the vagina. The penis is simultaneously shielded and protected within the prepuce, while the inner bone helps to maintain the shape and position.


The dog urinary bladder is a small sac located in the pelvic region above the pubic bone. The shape of the bladder resembles the shape of a pear when empty. It is here where urine is transported by the ureters from the kidneys. The bladder is what contains the urine in any given species. The urine is then transported into the urethra to the outside of the body in normal circumstances.


The male prostate gland functions mainly as a passageway for prostate fluid to flow. The fluid that flows via the prostate is for the nourishment and sheer protection of the semen. This fluid is literally squeezed through the urethra mixed in as it is expelled during the ejaculation phase of the sexual reproduction cycle. This course of action of expelling prostate gland fluid with semen is enabled by the male prostate gland muscle.

Without the prostate, semen cannot be properly and forcefully produced and excreted


Inside the penis, small sponge-like tissue compartments allow blood to fill when the male is sexually aroused.

The penis is the physical organ used in coitus and is the organ responsible for achieving the copulatory tie with the female. Inside the penis, small sponge-like tissue compartments allow blood to fill when the male is sexually aroused. This process causes the penis to stay erect during mating until the orgasm is reached, in which it becomes soft again. Unneutered male dogs who suffer from BPH are prone to bloody discharges of the penis.


The urethra is the tube directly located inside the penis for easy passage of fluids. The fluids in a male’s anatomy need somewhere to easily pass through to be expelled, however, there needs to be an accommodating source that controls the flow of conflicting fluids, such as urine and semen. When the penis is erect, the urethra blocks the flow of urine to allow the easy passage of semen until ejaculation is complete. When the male is not aroused, urine is passed through.


The testes, or gonads, are the small organs located inside the scrotum of the male sexual anatomy. Each testicle, or testes, is secured in place by the spermatic cord and come in two, however, some males have been known to contain just one which is usually rare. The two main functions of the testicles in the canine reproductive system are to produce the male sex hormone, testosterone, and the dog’s sperm.

Seminiferous tubules are coiled tubes inside the testes that assist in sperm cell production. Injuries to the testicles can cause testicular swelling, a common condition in male dogs, or cryptorchidism which is when the testes are not descended. Furthermore, the measurement and examination of the testicles can help one to determine any reproductive diseases and evaluate fertility.

Vas and Ductus deferens

The main function of the vas deferens, or also referred to as the ductus deferens, is to transport sperm from where it is stored into the urethra when the sperm is readily mature and ripe for semination.

The vas deferens is a long and thick tube, muscular in structure, that travels into the pelvic cavity from the epididymis. The ductus deferens comes in two, identical structures that function together in the same fashion.

Semen & Sperm

The semen is the viable liquid that is expelled from the urethra and penis during ejaculation. The semen is a protective fluid and is what carries the sperm, the reproductive cells.

The semen fluid contains spermatozoa, fructose, enzymes, and proteolytic and functions mainly as the carrying vehicle for the sperm cells. Common abnormalities and conditions in the male canine reproductive system related to semen are infertility issues where a male, for any reason, cannot impregnate a female. There is a vast array of various causes that can lead to infertility.


The male reproductive system is comprised of hormones which act as the catalysts for cell activity. Reproductive cells and organs within the dog’s body are regulated by hormonal chemicals. There are three primary hormones that are involved in the male reproductive system:

  1. testosterone,
  2. luteinizing hormone (LH), and
  3. follicle-stimulating hormone (FSH).

Both LH and FSH are produced by the pituitary glands in the brain. The LH hormone stimulates testosterone production while the FSH hormone stimulates sperm production. Testosterone is responsible for producing the masculine qualities in the male including sexual drive, muscle and bone mass, and fat distribution. Some conditions can cause elevated sex hormones in males caused by factors such as uncastrated males or tumors, for example. Hormonal problems, whether it be a lack or overproduction, can lead to an array of symptoms such as hair loss, weight fluctuations, or increased thirst and urination. Always keep the hormones in check and regularly tested.

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