Male Reproductive Organs.docx

Scrotum The location and orientation of the testes varies per species. In dogs and boar, the testicles will be located near the anus. Bulls and rams will have scrotums with a longer neck, causing their scrotum to be located near their thighs. This location makes them more susceptible to injury or sn...

Scrotum The location and orientation of the testes varies per species. In dogs and boar, the testicles will be located near the anus. Bulls and rams will have scrotums with a longer neck, causing their scrotum to be located near their thighs. This location makes them more susceptible to injury or snake bites. Cat’s scrotums are very caudally oriented. The scrotum’s function is to support the testis. The scrotum has a dual chambered pouch that is separates left and right halves by a septum. Each halve contains a testis, epididymis, and distal portion of the spermatic chord. The dartos muscle wrinkles the scrotum for temperature control. The scrotum layers include the: Outer layer (and smooth muscle layer): Skin and dartos (they are attached together) Middle layer: external and internal spermatic fascia This is located deep to the skin and dartos. Inner layer: parietal and visceral tunic cavity, and vaginal cavity The vaginal cavity is located in between both tunic cavities, with the parietal tunic cavity being external to it, and the visceral tunic cavity being more internal, in comparison. The vaginal tunic is located deep to the spermatic fascia. Testes (testicles- male gonads) They migrate from their developmental location, near the kidneys, to the outside of the body, the scrotum. They have an ovoid shape and are covered by a tough fibrous capsule, known as the tunica albuginea. The testes have a function of spermatogenesis and endocrine function with testosterone secretion. Epididymis The function of the epididymis is to be the site of maturation and storage of spermatozoa. The epididymis is 1 long coiled duct that is composed of 3 parts. The 3 parts are the: head, body, tail. The tail is the most distal portion of the epididymis, and the head is the most proximal portion, with the body being the middle portion of the epididymis. Sperm enters the head from the testes. The tail is continuous with the ductus deferens. Ductus deferens (plural: ducti deferentes) The ductus deferens enters the abdominal cavity as part of the spermatic chord. It crosses the lateral aspect of the urinary bladder to enter the pelvic urethra. If the ductus deferens is visible while looking at dog, it indicates that the viewer is looking at the right testicle (or at a medial view), if it is in front of the testicle. Male urethra The pelvic urethra is located within the pelvic cavity and receives the opening of the ducti deferentes. The penile urethra exits the caudal aspect of the pelvis and is apart of the penis structure. The end of the urethra is the external urethral orifice. Accessory Sex Glands (4 total) The accessory sex organs are responsible for the production of seminal plasma. The accessory sex glands include the: Prostate gland This is the only visible accessory sex gland in dogs. It surrounds the pelvic urethra. Ampulla Vestibular glands Bulbourethral glands Penis: General Info The penis is the male copulatory (used for sexual intercourse) organ and is composed of 3 parts: root body, glans. The root is anchored to the ischial arch and is the most proximal part of the penis. The glans is the most distal part of the penis, within dogs. The glans consists of the bulbous glandis (BG), pars longa glandis (PGL), and os penis (OP). Penis: Erectile Tissues The penis erectile tissue includes the: Corpus cavernosum This is the main erectile tissue. This will ossify to become the os penis. Corpus spongiosum This surrounds the penile urethra. Proximally (at the root), it expands as the bulb of the penis. Distally, it continues as the glans (apex) of the penis. Penis: Musculocarvernous vs Fibroelastic Erection happens when the retractor penis muscle relaxes, and the erectile tissue fills with blood. 2 types of options for this process include: Musculocavernous There is a large amount of erectile tissue. Commonly found in dogs, humans, stallions. The penis engorges and grows in length as the erectile tissue fills with blood. Fibroelastic There is a limited amount of erectile tissue (that is not well developed). Typically has a very long penis. It contains a sigmoid flexure (has an S-shape) Commonly found in bull, boar, rams The penis does not change in girth, but the sigmoid flexure straightens/smooths out when the erectile tissue is filled with blood. This can give the appearance of growth in length, but there is NO growth that is taking place. Penis: Os penis The os penis is only within dogs. It is a visceral bone. The os penis has a urethral groove on the ventral aspect to provide protection for the urethra. The urethral groove is where the urethra travels through. The urethral groove is what can cause the need for surgical removal of bladder stones, because if the stone is bigger than the groove then it will not be able to pass through. Prepuce The prepuce is the fold of skin covering the glans penis. The external lamina has haired skin on the outer surface. The internal lamina terminates at the fornix where it becomes continuous with the skin of the glans.