ANS 710 28 Male Reproductive Anatomy

Male genital apparatus

• Paired testes

• Paired duct systems

  • Epididymis

  • Ductus deferens

• Urethra

• Penis

• Skin adaptations

  • Prepuce

  • Scrotum

Testes exocrine function

Gamete production (spermatocytes)

Testes endocrine function

Testosterone, estrogen, etc

Temperature regulations for testes

• Pampiniform plexus

  • Network of testicular veins that allows countercurrent exchange (hot arterial blood cooled down by venous blood)

• Cremaster muscle (poorly developed in toms)

  • Strip of internal abdominal oblique that helps to raise and lower the testicle within the scrotum

• Tunica dartos

  • Layer of smooth muscle beneath scrotal skin that helps raise and lower testicles

• Scrotal skin

  • Sweat glands

Where are testes developed?

In abdomen

Testes Composition

• Thick capsule = tunica albuginea

  • Lobules

    • Seminiferous tubules: Produce sperm cells

  • Mediastinum testis

    • Rete testis

  • Efferent ductules

    • Leads to epididymis

Superficial inguinal ring

• Slit in the aponeurosis of the external abdominal oblique → on the outside of abdominal wall

• 2 crura (borders), 2 commissures (craniolateral & caudomedial)

Deep inguinal ring

• On the inside of abdominal wall

• Boundary → NOT a distinct structure

  • Caudal border of the internal abdominal oblique M

  • Arcus inguinalis (inguinal ligament)

    • Thickened caudal portion of aponeurosis of EAO M

Inguinal canal

Between superficial and deep rings

What is the developing testicle invested in?

Visceral peritoneum

Gubernaculum testis

Mesenchymal tissue from testis through inguinal canal to eventual scrotum

As the gubernaculum testis retracts through the inguinal canal and rings, the ________ _____ will also surround the testicle

parietal peritoneum

Vaginal tunic

• Visceral peritoneum → visceral vaginal tunic

• Parietal peritoneum → parietal vaginal tunic

Virtual space between tunics

• Vaginal canal: Within spermatic cord

• Vaginal cavity: Within scrotum

What becomes the internal spermatic fascia?

Endoabdominal fascia (aka transverse abdominal fascia)

External spermatic fascia

Layer of loose connective tissue deep to scrotal skin

True or False: The vaginal cavity/canal directly communicates with the peritoneal cavity 

True

Risk of open neuter

If the parietal layer of the vaginal tunic is penetrated during castration, then a channel to the peritoneal cavity is opened with the potential for an ascending infection to cause peritonitis

Benefit of closed neuter

If the parietal layer of the vaginal tunic is not penetrated, then no pathway to the peritoneal cavity exists

Scrotal ligament

Between tail of epididymis and tunica dartos

Ligament of the tail of the epididymis

Absent in cats and dogs

Proper ligament of the testis

Tail of epididymis to the testis

Cryptorchidism timeline 

If not resolved by 7 months of age, testicle(s) will need to be removed abdominally (like a spay)

Cryptorchidism: Temporary inguinal retention

Palpable, likely to eventually descend with growth

Cryptorchidism: Permanent inguinal retention

Has passed through the deep inguinal ring but is partly within inguinal canal

Cryptorchidism: Incomplete abdominal retention

Cremaster muscle, epididynmal tail; partially through vaginal ring

Cryptorchidism: Complete abdominal retention

Testis and epididymis

Cryptorchidism significance

• No sperm production (too warm) but still produces testosterone

• Higher risk for cancer

Head of epididymis

• Attached firmly to testis

• Efferent ductules enter here

Body of epididymis

• Only part not firmly adhered to testis

• Testicular bursa: space between the body and the testis

Tail of epididymis

Adhered to internal spermatic fascia

Picture of Epididymis

Ductus deferens

• Continuation of epididymis

• Connects to urethra

  • Colliculus seminalis

    • Ejaculatory ducts

  • Prostate

• Invested in mesentery

Spermatic cord

• Testicular artery, vein, and nerve

  • Pampiniform plexus

• Lymphatics

• Ductus deferens

• Visceral vaginal tunic (remnant of visceral peritoneum)

Mesorchium

Covers vessels and nerves of spermatic cord

Mesoductus deferens

Covers the ductus deferens and attached to mesorchium

Mesofuniculus

Between origin of mesorchium and mesoductus deferens

Dog mesenteric structures picture

Accessory reproductive glands 

Help sperm cells live longer in female reproductive tract with secretions (forms semen)

Dog accessory reproductive glands 

• Ampulla of the ductus deferens (small in dog)

  • Ampullary glands

• Prostate gland

  • Right and left lobes with dense capsule

  • Bulk is around the urethra

  • Small disseminate part within the urethral mucosa

Cat accessory reproductive glands 

• Prostate - small body

  • Prostatic glands within walls of pelvic urethra, not just in body of prostate

• Small bulboeurethral glands

• No ampullae present

Male urethra

Divided into pelvic and penile parts

Pelvic part of male urethra

• Preprostatic - very short

• Prostatic part - urethral crest in dorsal wall

  • Colliculus seminalis: Openings for deferent ducts (aka deferent duct orifices)

Penile part of male urethra

Terminates at external urethral ostium

Root of the penis

2 crura + bulb of the penis

Crura

• Proximal end of each corpus cavernosum penis, that attaches to ischiatic arch

• Each crus has a core of cavernous tissue

  • Corpus cavernosum penis

  • Tunica albuginea

• Covered by ischiocavernosus muscle

Bulb of the penis

• The caudal expansion of the corpus spongiosum penis

  • Corpus spongiosum penis surrounds the caudal part of pelvic urethra and all of the penile urethra

  • Do not confuse with bulbus glandis

  • Covered by bulbospongiosus muscle

Muscles of penis

• Ischiocavernosus

• Bulbospongiosus

• Retractor penis

How far can the body of the dog penis bend during tie?

180 degrees

Os penis (dogs)

• Located within the glans penis

• Attached to terminal CSP

• Urethral groove

  • A place where urinary stones often block urethra

Glans penis in dogs

• The part of the penis that will be introduced into the female repro tract to create the tie

• Parts:

  • Bulbus glandis

    • Large thickening

  • Pars longa glandis

  • Corona glandis

    • Tip of penis

Glans penis in cats

• Penis directed caudoventrally

• Glans with keratinized spines

  • Stimulates ovulation

Prepuce

• External lamina

• Internal lamina

• Paired preputial muscles

External lamina of prepuce

Continuous with the abdominal skin

Internal lamina of prepuce

• Reflects onto penis at the level of the preputial fornix

• Lined by glands and lymphoid tissue

Midventral incision through prepuce

Phimosis

• Constriction of preputial ostium

• Penis can’t come out

Paraphimosis

• Inability to retract penis due to swelling or preputial constriction

  • Ex. hair wrapped around penis

Priapism

Persistent abnormal erection

Penile frenulum

Thin band of connective tissue joining ventral glans penis to corpus of penis or to the prepuce

Persistent penile frenulum

• Clinical signs

  • Excessive licking

  • Urine scald

  • Phallocampsis (curvature of the erect penis)

• Treatment

  • Thin: transect

  • Thick: local anesthesia then cut

Scrotum

• Median raphe (aka groove) → scrotal septum

• Sebaceous and sudoriferous (sweat) glands

• Tunica dartos

Dog testis orientation in scrotum 

Dorsocaudal

Cat testis orientation in scrotum

Obliquely toward anus

Dog scrotum

Mostly hairless

Cat scrotum

Haired