Comparative Male Repro Anatomy (Mod. 5)

Equine Repro Anatomy

What “type” of penis is the equine penis? What are 3 of the most notable features?

Type: Musculocavernous type penis; like dog and cat

Notable features:

• Mushroom shaped; has an expansion of corpus spongiosum over dorsal surface at tip

• This ^ is where the GLANS are… has 3 regions:

  • Neck (collum glandis)

  • Head (corona glandis)

  • Dorsal process over corpus cavernosum (SEE IMAGE)

• Urethral opening is located at the head of the corona glandis

  • Sits in CENTRAL FOSSA GLANDIS (or ditch)

  • Urethral process sticks out from this (looks like a little button)

Describe the basic equine penis anatomy… what would you see in a cross section?

Very similar to canine penis…

• Paired crura of corpus cavernosum forming the body dorsally… corpus spongiosum surrounding urethra ventrally

  • Corpus spongiosum is also supported underneath by bulbospongiosus muscle

Big difference: retractor penis muscle underneath

• Eventually fuses as we move farther down the penis

As we move farther down penis, crura fuse together as well… dorsal process of the glans also starts to be seen (made of corpus spongiosum as well)

Describe the anatomy of the prepuce… how does it compare to the canine? What is its main difference? What is the difference between the preputial ORIFICE and the preputial RING?

Is much more complex than the canine and ruminant prepuce…

Most notable difference: has an additional fold in wall, allowing for marked lengthening of the penis upon erection

• Has a “telescoping effect”… the inner sleeve that projects out with the penis has a preputial ring

  • The outer opening of the prepuce it then called the preputial orifice

See image for orientation of these features

Describe the erection process of the stallion…

Very similar to canine as well, same 2 stage process

1) Engorgement of cavernous spaces through increased blood flow, venous occlusion to prevent drainage, allowing blood pressure to reach arterial pressure

2) Contraction of ischiocavernosus muscle (muscle around crura) forces blood into cavernous spaces above arterial blood pressure

Describe the characteristics of the equine scrotum… very basic

Simply located beneath the pubic bone

• Scrotal skin is thin, with sebaceous (sweat) glands for thermoregulation

• Central groove or raphe is visible, extends from perineum to the prepuce

  • Gives scrotum “divided” look, L and R sides

Describe the characteristics of the equine testes… again, very basic, don’t need to go in depth

• When cut in half, no mediastinum visible

  • Can see it in carnivores as a small, white line through parenchyma, but not visible in stallions

  • Still has rete testes and a collection point, but no mediastinum visible

ELLIPSOIDAL IN SHAPE

Describe the equine inguinal canal… how does it compare to carnivores, and what problems can come with it?

Inguinal canal is WIDE

• Increases potential for herniation of internal organs

Can still experience cryptorchidism

• Can either be temporary (delay caused by quick increase in testicle size) or permanent

What are the 4 main accessory glands of equines? Describe their characteristics / functions

1) Ampulla -

• Seen in stallion as a widening of the terminal vas deferens as it attaches to prostate (20cm in length)

• Acts as a storage reservoir for sperm and contributes some ejaculatory fluid

2) Seminal vesicles -

• Look like additional bladders in the stallion… located adjacent to the neck of the urinary bladder

• Paired, 12cm long

• Produces a significant contribution of fluid to semen

3) Prostate -

• Compact and bilobed; smaller proportionally in comparison to the canine

• Again, found at the neck of the bladder, surrounding proximal urethra

• Is the main contributor to semen

4) Bulbourethral gland -

• Is paired in the stallion, and quite small

• Responsible for pre-ejaculatory fluid