Male Carnivore INTERNAL Genitalia (Mod. 5)

Describe the “outer capsule” of the testes… what is it also known as?

Tunica albuginea

• Predominantly connective tissue

• Large vessels can be seen on its surface… pattern of vessels is characteristic between species

Describe the parenchyma of the testes… what is it? What is it made of? What are other notable features? (think of the central groove…)

The parenchyma is the tissue of the testes

• Made primarily of interstitium; comprised of Leydig cells and has a connective tissue/vascular framework

  • Supports seminiferous tubules

• IS LOBED… lobules formed by invaginations of capsule

Notable features:

• Central groove running through testicle, called the Mediastinum Testis

  • This contains the Rete Testis, a space where the seminiferous tubules drain into

Now knowing what you do about the parenchyma and the structures it holds, describe the path of sperm…

Sperm produced in seminiferous tubules → drains into mediastinum testis → drains to rete testes → small efferent ductules carry sperm to head of epididymis

Describe the epididymis… what is its function? What are the three parts it is composed of, and what are their functions?

A firm, palpable ridge that lies dorsally to the testes

Function: Allows sperm storage and maturation

• Travels from head → body → tail → ductus deferens

Head:

• Firmly attached to testes… receives the efferent ductules, which COMBINE to form the convoluted epididymal duct

Body:

• Loosely attached to the surface of the testes… creates a space between it and testicle called the testicular bursa

Tail:

• Firmly attached to testes as well… epididymal duct exits here to form the ductus deferens / vas deferens

What are the 3 main testicular attachments / ligaments? Describe them. What is their significance clinically?

1) Proper ligament of testis - Attaches TAIL of epididymis to testes

2) Ligament of tail of epididymis - attaches TAIL to PARIETAL VAGINAL TUNIC

3) Scrotal ligament - attaches vaginal tunic to scrotum

When castrating, will need to break these down, EXCEPT FOR PROPER LIGAMENT!!!!! Can be left alone

What 5 structures are found within the spermatic cord?

1) Deferent duct (vas deferens)

2) Deferent Artery + Vein - Small blood vessels; supply vas deferens

3) Large Testicular Artery + Vein

4) Lymphatic structures

5) Testicular nerves - predominantly SYMPATHETIC

What structure is ALSO associated with the spermatic cord, but is OUTSIDE of it?

Cremaster muscle

• Sits outside vaginal tunic

Describe the deferent duct (ductus deferens, vas deferens, same thing); what is its function? Where does it lead into?

Function: Carries sperm to urethra

• Travels through spermatic cord

• Runs through inguinal ring, then crosses over the dorsal neck of bladder

• Enters the PROSTATE and joins with the urethra

What is the pampiniform plexus of the testicles? What is its function?

An elaborate complex of veins that is arranged right at the base of the spermatic cord

• Wraps around the distal convoluted testicular artery

Function: heat exchange mechanism + venous drainage

• Arterial blood coming down to the testes is cooled as it passes through the pampiniform plexus, which is draining slightly cooler blood from the testicles

• This helps reduce the temperature of the blood entering the testicles, keeping the sperm safe

• At the same time, the arterial blood warms the cooler blood being drained as it goes up the spermatic cord and back into the body

What is the cremaster muscle, and what is its function?

Is a strip of muscle originating from the internal abdominal oblique

• Caudal to dep inguinal ring (so further into the body)

• Runs along vaginal tunic; inserts onto tunic as well

Function: when contracted, brings testis closer to body to increase testicular heat

What is the structure that REGULATES TESTICULAR DESCENT?? (hint: funny name)

Describe it and its structure, including its 3 main layers.

Gubernaculum testis

• A mesenchymal structure that extends from abdominal testes in immature males… runs through inguinal canal and opens into scrotum

• Forms the vaginal tunic when it makes balls drop

  • Gubernaculum swells and shortens, which opens the inguinal canal wide enough to draw testes down

Three main layers:

1) Pars propria - visceral layer; extends up to catch the testes

2) Pars vaginalis - parietal layer; lines the INSIDE of the SCROTUM

3) Pars infravaginalis - distal to invagination, but is the junction between the other two layers (see image)

What are the two main INTERNAL reproductive organs?

1) Urethra

2) Accessory Reproductive Glands

• Ampullary glands (NOT IN CATS)

• Prostate

• Bulbourethral glands (NOT IN DOGS)

Describe the male urethra… what are its two “regions” its divided into?

Urethra runs from bladder to tip of penis

Its two regions:

1) Pelvic urethra - portion that runs through pelvic canal

2) Penile urethra - runs through penis

Describe the pelvic urethra… where does it insert? What is the “dorsal ridge”? Where is it oriented in the body?

Starts at the bladder, but is contained in the prostate initially

Has a “dorsal ridge” called the seminal colliculus

• Projects into the lumen

• This is where the VAS DEFERENS and PROSTATIC DUCTS open up into to release sperm + semen

Lies along the pelvic floor (see image) with a muscular sleeve called the urethralis

Describe the penile urethra (very simple)… where does it run through?

Runs through penis between cavernous tissues

THEN runs through ventral groove of OS Penis

What are the ampullary glands?

Dilations of the terminal vas deferens before entering the prostate (see image)

• Lies dorsal to the bladder

Function: Lined with glandular tissue → contributes to a small amount of ejaculate

• Has a capsule and a layer of septa w/ smooth muscle… assists in the expulsion of fluid (small structure, so not a lot of force)

Describe the prostate… what is its function? Why is it so important? What are its two main components?

Function: Produces the bulk of seminal fluid

Has two parts:

1) Vestigial disseminated part WITHIN URETHRAL MUSCOSA

• So tissue within the wall of the urethra; “microscopic prostatic tissue”

2) The large compact part around the proximal urethra

• Is bi-lobed (see image)

Describe the structure of the larger portion of the prostate gland:

Divided into left and right lobes by a dorsal groove and internal septum

Is located at the neck of the bladder; surrounds the proximal urethra

• In dogs, urethra completely surrounded

• In cats, ventral area of urethra free

INTERNALLY, there are multiple small ducts that drain into the urethra by the seminal colliculus (dorsal groove on pelvic urethra)

What is the most common cause of prostatic enlargement in dogs? What are some other possible causes?

Most common cause: Benign Prostatic Hyperplasia

• Hormonally induced

• Seen in almost every dog that is still intact around 5-6 years old

• May compress the rectum or urethra

  • Causing constipation

Other causes:

• Neoplasia (cancer)

• Inflammation (prostatitis)

• Cystic disease

***** RARELY SEEN IN CATS