Week 1 - Carnivore External Genitalia (Male)

What makes up the male reproductive tract? (generic)

• Two testes

• Paired gonadal tracts

  • epididymis, ductus deferens

• Accessory glands

  • ampulla, vesicular glands (seminal vessels), prostate, bulbourethral glands

• Urethra

• Penis

What are the main functions of the male repro tract?

Production of gametes (spermatozoa), androgenic hormones (testosterone), and semen

• Also to introduce sperm into the female repro tract

What is the function of semen?

Supportive fluid keeping sperm alive as it travels through the female reproductive tract

What makes up the external part of the male repro tract?

• Testes

• Scrotum

• Penis

• Prepuce

What are some notable features of the canine penis?

• Made of musculo-cavernous tissue

• internal bone - os penis

• bulbus glandis swells

What are the 3 erectile tissues in the root of the canine penis?

• Left crura

• Right crura

• Bulb of penis

They converge and combine to form body of penis

What is the corpus cavernosum? (canine)

• makes up crura of penis

• distensible erectile tissue

• distal end becomes os penis

What is the corpus spongiosum? (canine)

• formed from vascular sleeve around urethra

• begins at bulb of penis

• expands distal to corpus cavernosum to form glans

• larger blood spaces than corpus cavernosum

What is the os penis?

• bone in the canine penis

• has a ventral groove that contains & protects the urethra

• formed from distal end of corpus cavernosum

• is the place where majority of bladder stones get stuck & causes obstructions

What are the 2 main glands in the canine penis?

• Bulbus glandis

  • swells during erection & mating (the tie), firmly attached to os penis

• Pars longa glandis

  • elongated, responsible for initial penetration, helps maintain rigidity during erection, not as firmly attached to os penis, has urethra orifice at tip

What is the preputial layers? What are the 2 layers?

The invagination of abdominal skin, where the penis sits when not erect

• Lamina externa: outer layer - basically just skin

• Lamina interna: inner layer - covers the free end of the penis

What are some preputial problems? (canine)

• Congenital narrowing of preputial orifice - Phimosis

  • Prevents extrusion of penis

• Paraphimosis

  • Inability to retract penis - impaired circulation

What are the 4 main muscles associated with canine penis?

• Bulbospongiosus: continuation of urethralis muscles

• Ischiocavernosus: paired powerful muscles that contract to force blood into corpus cavernosum during erection

• Ischiourethralis: small muscle that blocks/closes dorsal vein during erection

• Retractor penis: smooth muscle, draws penis back into prepuce

What makes up the artery of the penis? (canine)

• First branch: dorsal artery of penis - supplies the glans & a little to prepuce

• Second branch: deep artery of penis - supplies corpus cavernosum

• Third branch: artery of bulb - supplies corpus spongiosum

What is the importance of the fibrous ring along the dorsal vein?

Part of the ischiourethralis muscle, when it retracts the ring constricts and stops drainage through the dorsal vein - important for erection

What are the stages of canine penile erection

• First stage: increase blood flow, stop of blood outflow via fibrous ring & valves

• Second stage: contraction of ischiocavernosus & bulbospongiosus muscles, squeeze more blood into cavernous spaces

Difference of feline penis compared to canine

• Penis remains in embryonic position with apex directed caudoventrally

• Prepuce thick & quite short

• Preputial orifice faces caudally

• Glans is small with less division & covered in small keratinized spines (spines trigger ovulation)

What are the external features of the scrotum?

• Location: intermediate for canine, perineal for feline

• Thin skin

• Copious sweat & sebaceous glands

• Hair covering variable

What are the internal features of the scrotum?

• Skin lined internally by fibromuscular layer (called dartos)

  • contraction of this layer causes testicles to be drawn closer to body

• Internal septum divides scrotum into left & right halves

• Layered fascia supports outer layer of testes

What is the vaginal tunic?

Encloses spermatic cord and the structures that supply testes (vas deferens & testicular vessels)

What is the inguinal canal?

Potential space between body wall - allows passage of testes & testicular vessels & vas deferens

• allows transmission of testes to scrotum as animal develops