Your Male Dog’s Reproductive System
Posted by admin on June 22, 2010
The male reproductive system in a dog is made up of the scrotum, testicles, epididymides, deferent ducts, spermatic cords, prostate, penis and urethra. Understanding the structure and function of these organs can help you identify when any problems crop up which may need veterinary attention.
Elements of the reproductive tract
Hanging between the dog’s hind legs is a sac known as the scrotum which holds and protects the testicles. The scrotal pouch is divided into two separate areas by a thin wall running down the middle. Inside each area are one testicle, one epididymis, and the head of one spermatic cord. The scrotal sac, which does not contain any insulating fat, keeps the testicles several degrees cooler than the abdomen, which is important for sperm motility.
The testicles are oval shaped, with the left testicle usually hanging slightly behind the right. Inside the testicles are seminiferous tubules, responsible for the production of sperm. Sertoli cells fill the area around the tubules, supporting the tubules and providing nutrition to the sperm cells. The Leydig cells of the testicles are responsible for the production of the male hormone testosterone.
The epididymis (plural: epididymides) begins at the front of the testicle and runs along the edge to the back. It is responsible for storing and carrying sperm to the ductus deferens prior to ejaculation. The sperm stays in the epididymides for a relatively long period of time, allowing the cells to mature.
Spermatic cords are composed of vessels and nerves which nourish the testicles. The ductus deferens are also contained inside the spermatic cords. The ductus runs into the abdominal cavity through the inguinal canal, then leaves the abdomen, running through the prostate and ending at the urethra.
Although the exact function of the prostate gland is unknown, it is thought that it secretes substances necessary to protect and activate the sperm. This accessory sex gland contributes as much as 90% of the fluid that is released when the dog ejaculates.
Once they have matured in the epididymis, the sperm cells enter the ductus deferens, which has strong muscular walls. The muscular walls of the ductus contract to push the sperm into the urethra, which runs the length of the penis. The urethra then releases sperm into the female when the dog ejaculates.
The penis has three portions: the root, the body, and the glans. The root and body are made of spongy tissue surrounding a bone known as the os penis. The glans is soft but swells with blood during sexual stimulation. This swelling is important because it keeps the penis locked into the female dog’s vagina, allowing the dogs to “tie” to each other to promote successful passage of sperm from the male to the female.
Covering the penis is the prepuce, a tubular piece of skin which protects the penis. The prepuce secrets a lubricating liquid known as smegma which keeps the penis moist.
Hormonal control of the male canine reproductive system
The cells of the testicles are under the control of the hypothalamus and pituitary gland of the brain. The hypothalamus releases gonadal releasing factor, which stimulates the pituitary to secrete follicle stimulating hormone and luteinizing hormone. Both hormones travel to the testicles, where FSH stimulates the seminiferous tubules to produce sperm and LH stimulates the Leydig cells to produce testosterone.
Sperm, of course, is used to impregnate female dogs. Testosterone is responsible for the development of male sexual characteristics during puberty. This includes higher muscle mass, thicker bones, more red blood cells, and a higher metabolic rate.
Diseases of the male reproductive tract in dogs
Before a puppy is born, his testicles reside in his abdominal cavity. At birth, they begin to move slowly through the groin area and into the scrotum. The trip should be complete by 6 – 8 weeks of age. In some puppies, one or both of the testicles may fail to descend at all, or may get stuck part of the way through the trip. This condition, known as cryptorchidism or undescended testicle, keeps the testicle trapped in the relatively high temperature of the pelvic cavity, making the affected testicle incapable of producing sperm. Undescended testicles have a higher incidence of tumor development as the dog ages. This condition has a genetic component, so dogs with an undescended testicle should not be bred.
Other problems which may occur in the testicles are inflammation known as orchitis or torsion, which occurs when the testicle becomes twisted on itself. Both of these conditions cause your dog considerable pain as well as infertility. You may notice your dog walking strangely or wanting to lay on cold surfaces to relieve the pain.
The epididymis may become inflamed due to bacterial or viral infections, trauma, or diseases of the immune system.
The most common problem which occurs in the prostate is benign prostatic hypertrophy (BPH). In un-neutered dogs, the continual influence of testosterone causes the prostate to gradually enlarge. The enlargement may block both the urinary tract and the rectum causing the dog to strain when he relieves himself. Other problems of the prostate include infection, cysts, and tumors, which are usually malignant.
The prepuce can also be the site of several disorders. If the opening of the prepuce is abnormally small, the dog may not be able to protrude his penis through the opening, making sexual intercourse impossible. This condition is known as phimosis.
At the other end of the spectrum, if the dog cannot withdraw his penis into the prepuce, the condition is known as paraphimosis. This condition can be treated by applying ice to the dog’s penis to encourage it to become less erect, allowing the dog to retract it.
Priapism is a condition where the dog’s penis remains erect in the absence of sexual activity. This is typically the result of an infection or a spinal cord injury.
The prepuce may become inflamed due to infections, which may include sexually-transmitted diseases.
How will the vet check my dog for reproductive problems?
Your vet will first interview you to find out about the dog’s medical history so he can choose which tests will be most beneficial. It is important that you spend enough time observing your dog’s normal behavior in order to know when something has changed. You are your dog’s best advocate, so make sure you can give your vet an accurate description of any problems you are seeing.
Next, your vet may want to run an analysis of the dog’s blood and urine. This will help her rule out any systemic infections which may be causing the problems. Serologic testing of the blood can indicate the presence or absence of Brucellosis, a bacterial infection that is often the cause of reproductive tract disorders in male dogs.
X-rays of the abdomen can point out problems with internal structures, as can ultrasound inspection of the prostate and testicles.
If a tumor is suspected, your vet may take a biopsy of solid tissues or may aspirate the liquid from a fluid-filled tumor for microscopic analysis.
If you are concerned about your dog’s fertility, your vet may want to examine a sperm sample under the microscope to check for the quantity and quality / motility of the cells. Sperm may be collected by using what is known as a “teaser bitch”, which is just what it sounds like, or by the vet stimulating the dog by hand.
The importance of neutering
Neutering a dog involves the removal of both testicles, making the dog unable to produce sperm. Within a week or two after the surgery, your dog’s scrotal sacs will simply shrink and become unnoticeable. If you value the look of an intact dog, there are prosthetic testicles which can be inserted to maintain the scrotal sac size. The penis is not removed during neutering because it houses the urethra and has a function other than carrying sperm. It also carries urine from the bladder, directing it outside of the body.
Aside from reducing overpopulation problems, there are health reasons for neutering your dog as soon as possible after he joins your family. For example, a neutered dog cannot develop testicular cancer or benign prostatic hypertrophy. There is also some evidence that a neutered dog will be less aggressive than an intact dog.
Vets are becoming aware that it is not beneficial and in fact may be undesireable in the long run for an animal to be sexually altered before it is sexually mature. Most vets will advise that you spay or nueter your dog before her first heat or when he is six months old. It is now advised, and many vets agree and many breeders are applying this in their contract of sale, that you wait until the dog is finished growing before removing any hormones that take part in the dogs development.
Spaying a bitch is more benificial for the bitch than nuetering a male is more benificial for the male; ther is a longer list of risks for females than for the males. Nonetheless males should be nutered if they are not going to be bred to prevent accidental, unwanted and unplanned matings becuase we do not need anymore dogs in this world unless it is for a worthy cause!
You will notice that “pets” tend to be bigger than they ought to be. Not “fatter,” just bigger. If a dog is nutered before he has become matured his body is delayed in “telling him to stop” growing. While this is really not a health concern, there are many health concerns that the dog may expereince latter in life from being sexually altered before sexual maturity, or, in other words, it is not good to remove the hormones that are removed when a pet is altered when the animal is still growing.
It is still true that spaying and nuetering your pet decreases or eliminates the chances of certain health issues related to the reproductive parts but you should wait to do this until the animal is sexually matured. There is no harm in letting the animal mature first.
Shelters and vets that do not agree with this are still paranoid, with good reason, about the risk of more homeless cats and dogs (many of which that have to be killed) due to irresponsible pet owners with intact animals that intentionaly or unintentionaly produce litters, and so they feel altering the animal before it can ever reproduce is the safest measure, and it is for this situation, except it is now being learned that this is not benefical and in fact may be harmful for the animal.
There should be ne problem letting a dog remain intact until it is mature if pet owners and breeders are responsible. THE RESPONSIBILTY IS UP TO THE PET OWNERS AND SHOULD ULTIMATELY BE THE BREEDER’S. DO NOT SUPPORT BREEDERS WHO DO NOT TAKE RESPONSIBILITY OF A PET FOR ITS ENTIRE LIFE, and this means that a breeder will have a contract that states when the animal must be sexually altered, that states whether the animal may be bred or not bred, and the breeder WILL TAKE BACK the dog with no refunds being issued to the owner if the contract is violated. ANYONE selling puppies without a contract regarding sexually altering or properly breeding the animal, among other things, IS NOT REPUTABLE and only cares about selling puppies for a profit; they care nothing about the integrity of the breed nor the situation in the animal shelters and rescues caused by uneducated breeders or people with pets that they decide to breed.
Irresponsible uneducated breeders sell to irresponisble uneducated owners. People buying pets from breeders have an equal impact on the situation of the integrity of a breed and the number of homeless cats and dogs. YOUR MONEY ENABLES A BREEDER OR PET STORE TO CONTINUE WHAT THEY ARE DOING, it is that simple. Do not think that you are “helping a poor puppy that needs a home” because when you provide him a home they will simply breed another one and plop him in the viewing cage and repeat.
Reputable breeders do not sell to pet stores or any online pet dealer because they wish to meet the buyer and decide who the buyer will be: dont buy puppies from pet stores at petco, the mall whatever UNLESS THEY ARE A RESCUE which means that who ever produced the animal is not gettting any money when you purchase the animal. Find a shelter or rescue or reputable breeder instead and do your research so you may identify what a reputable breeder actually is because pet owners are evedently fooled all the time.
SPAY OR NUETER YOUR PET if the breeder was irresponisble enough to allow you to have it without this requirement when you are simply a pet owner. There is no money in breeding dogs if you do it the right way and making money off a stud is a pipe dream because way too much money goes into it before you will have that awesome stud everyone will flock to. Plus any expereinced or successfull breeder knows that not every bitch should be breed with any male, even if he is a champion in six contries, because certain males simply complement certain females. Only backyard breeders will be interested otherwise…because they think “a stud” is simply any intact dog capable of impreginating a female so long as it is the right breed and registered and they think a “proven stud” is any dog that successfully created puppies which really is nothing special….please to do your research and become educated before breeding dogs or buying a dog to breed because there is so much more to it than you may think and I could go on and on here!
I got my little dog from a rescue organization and was told that he was neutered. He was about 4 months old and just 3 pounds at the time, He is now 18 months. I have noticed recently that he is responding to females with erection which includes external exposure of what appear to be testicles at the base of the penis. This seems to cause pain and he does bite at himself. Although he has no scrotum, is it possible that the testicles are indeed still present?
No, Wendy, I would be pretty certain he does not have testicles. What you’re seeing is almost certainly the Bulbus Glandis. You may want to do a search if you’d like more information. In my opinion people – here in the UK at least – are seldom given complete information about neutering, including the fact that neutered dogs CAN still be aroused sexually and CAN even tie with a female, though of course the “mating” wouldn’t produce puppies.
I hope that helps.
I have a question that may sound bizarre but here goes.
Will giving a male dog testosterone to help him breed affect the litter of pups? 7 months ago I bought a rotty from an in home breeder, it was a litter of 11, the mother and father were on the premises, beautiful dogs. My pup as well as 6 of the others whose owners Ive been in contact all say the same thing, the markings are wrong, the ears as well as the nose too long. We cant decide if it was the testosterone or if the female was allowed to breed with something else. The people who bought pups to use for breeding are very disappointed. One couple bought a dog from the same breeder a few years ago, same mother and father and that dog is perfect. That was one reason they bought one from the litter I did. Hoping you can answer my question.
“For example, a neutered dog cannot develop testicular cancer.”
Nonsense. In some cases, neutering can CAUSE cancer. Folks, if you are responsible dog owners, leave your dogs as they are. If you’re the type to let them wander the neighborhood off the leash, neutering would be a good option, but then again, so would you not owning a dog in the first place.
Marc, I totally agree with and fully support everything you say AFTER the word “Nonsense”.
“For example, a neutered dog cannot develop testicular cancer” – or more specifically “…. a CASTRATED dog cannot develop testicular cancer” IS factually correct, though, as castration involves the removal of the testicles, therefore it’s physically impossible to subsequently develop testicular cancer.
My partner didn’t desex his male American bulldog, he’s is not going to breed him and the dog is four years old. This may sound weird but do male dogs need to release their sperm?
http://www.naiaonline.org/pdfs/LongTermHealthEffectsOfSpayNeuterInDogs.pdf
NEED to? No. WANT to? Perhaps. Can be trained to behave properly? Absolutely.