Lecture 3 -- Comparative Male Reproductive Anatomy

Which two muscles act as tail depressors?

• Coccygeus

• Levator ani

What is the rectococcygeus muscle?

A smooth muscle continuation of the rectum that extends toward the tail

What is a musculocavernous penis?

• Smooth muscle with large cavernous spaces

• Erection occurs when the corporeal sinusoids fill with blood

• No sigmoid flexure

Which species belongs to?

Horse

• Tunica albuginea is thicker than dog’s

• No bone separating the corpus cavernosum

Cow

• Dense tunica albuginea

• Little erectile tissue

  • Can barely see the corpus cavernosum

Which species have musculocarvernous penis?

Dogs and horses

What is the bulbus glandis?

• Unique to dogs that:

  • Allows dogs to mate before full erection

  • Enables the male to turn around while copulating

  • Works with the os penis to penetrate the female reproductive tract

What is a fibroelastic penis?

• Fibrous and elastic tissue with small cavernous space

• Non expandable dense tunica albuginea

  • Limited erectile tissue

• Arranged with sigmoid flexure

Which species have fibroelastic penis?

Ruminants and pigs

What is sigmoid flexure?

An S-shaped bend along the shaft of the penis

• Allows the penis to retract within the sheath until erection

What maintains the sigmoid flexure?

Paired retractor penis muscles

• Attach dorsally to the coccygeal vertebrae

• Attach ventrally to the ventrolateral sides of the penis

Where is the sigmoid flexure located in the boar?

In the pre-scrotal (prepubic) region of the penis

• Since the scrotum of boar is tightly up into the anus, the sigmoid flexure is right in front of the scrotum

Where is the scrotum and penis located in the cat?

• Their scrotum lies just below the anus

• The penis is located immediately beneath the anus. During mating, the penis projects backward, extending out behind the animal.

The penis shown in this picture belongs to which species? What are the key characteristics?

Ram (Sheep)

• Tapers to a point

• Has vermiform appendage (Worm-like urethral process)

The penis shown in this picture belongs to which species? What are the key characteristics?

Bull (Cow)

• Taper to a point

The penis shown in this picture belongs to which species? What are the key characteristics?

Stallion

• Urethral process is sunk into a deep fossa glandis

The penis shown in this picture belongs to which species? What are the key characteristics?

Boar (Pig)

• Free end terminates in a spiral

  • Lock into the sow’s cervix

  • Forces ejaculate into the uterus

• No distant glans

The penis shown in this picture belongs to which species? What are the key characteristics?

Tom cat

• Has cornified 角質化 spines

  • Stimulate reflex ovulation

• Androgen dependent

  • Gradually disappear in neutered animals

What is the pathway of semen expulsion during ejaculation

1. Intromission

2. Sensory stimulation of glans penis (Temperature and pressure) go through the spinal cord

3. Spinal cord then sends signals via motor neurons back to bulbospongiosus, ischiocarvernosus and urethralis muscle

4. Expulsion of semen

What are “stones” that can get caught in the penile urethra and block urine flow called?

Urethral calculi

Where do urethral obstructions commonly occur in different species?

• Dogs: Base of the os penis

• Bulls: Proximal end of the sigmoid flexure / ischial arch

• Rams: Vermiform appendage

What is the main function of accessory sex glands?

Produce seminal plasma (non cellular fluid portion of semen)

How do accessory sex glands develop?

• Small in immature animals or animals castrated before puberty

• Post-pubertal castration → Atrophy of glandular component, but some structure is maintained

What are the common accessory sex glands in domestic male animals?

1. Ampulla

   • Paired enlargement of ductus deferens that open directly into pelvic is urethra

2. Prostate

   • Single gland near the junction between pelvic urethra and bladder

   • Consists of compact body and diffuse tissue within wall of pelvic urethra

3. Bulbourethral gland

   • Paired glands located on either side of pelvic urethra near ischial arch

4. Vesicular gland = Seminial vesicles

   • Paired glands located dorso-cranial to the pelvic urethra

   • Sit closest to the bladder

List the accessory sex glands in different species.

Describe the scrotum in bull, small ruminants, stallion and boar

Bull and small ruminants

• Long. pendulous with a marked neck

Stallions

• Globular shape with poorly defined neck

Boar

• Subanal, lying close to the caudal surface thighs