Comparative Male Reproductive Anatomy

Perineal hernia

escape of pelvic viscera due to weakness or atrophy of muscles of pelvic diaphragm

presents as swelling to side of anus

Male perineal anatomy

1 = coccygeus —> depresses tail
2 = levator ani —> depresses tail
3 = retrococcygeus —> continuous with rectus
4 = external anal sphincter

What are the blue arrow and orange arrow pointing to?

Blue = sacrotuberous ligament
Orange = anal sac —> lies between internal & external anal sphincters

What is this structure?

Rectum

Dog Penis Anatomy

Name 1-3 and all other parts

1 = ureter
2 = cremaster muscle
3 = glans penis
B = bladder
P = prostrate
DD = ductus deferens
BG = bulbus glandis
T = testes

What are the three parts of a penis?

Base (root) - attaches to ischial arch

Shaft - main proportion

Glans penis - end tip (variable morphology between species)

What are the two basic penile anatomy models?
Which species exhibit these?

Musculocavernous - dog & stallion

Fibroelastic - boar, bull & ram

Key features of musculocavernous penis

Erection dependent upon sinusoids that fill with blood
No sigmoid flexure

What is unique about a dog's bulbus glandis?

Allows them to face in opposite direction during intraomission

Mechanism of erection in musculocavernosus penises

- increased arterial blood inflow
- sinusoids dilate (parasympathetic NANC neurones)
- restricted venous flow
- increased intrapenile pressure
- penis diameter increases (in horse & dog)

Name tissues within glans penis

TA = tunica albugenia
CC = corpus cavernosum
OP = os penis
PU = penile urethra
CS = corpus spongiosum

Fibroelastic penis key features

- limited erectile tissue from dense tunica albuginea
- sigmoid flexure —> S-shaped configuration along shaft allows to be retracted within sheath until erection

- erection is stiffening without significant change in diameter

- sigmoid flexure maintained by pair of retractor penis muscles

Mechanism of erection in a fibroelastic penis

relaxation of retractor penis muscles & blood filling corpus cavernosum & corpus spongiosum

What species does this penis belong to? What are its key features?

Bull

retractor penis holds sigmoid flexure

retractor penis m. is a lot bigger

Name the parts of the bull penis

What species does this penis belong to? What are its key features?

Boar

Fibroelastic

Sigmoid flexure is prescrotal

corkscrew shape enables it to lock within sow cervix

Name muscles 1-4 associated with the penis (dog)

1 = Urethralis —> striated, surrounds pelvic urethra, moves semen into penile urethra
2 = Ischiocavernosus —> paired, short muscles in root of penis
3 = Bulbospongiosus —> overlaps root of penis, extends down caudal & ventral surfaces to cover bulbourethral glands
4 = Retractor Penis —> smooth muscle

Comparative glans anatomy of boar & stallion

Boar

No glans - terminates in spiral

Locks into sows cervix —> forces ejaculation into uterus

Stallion

Urethral process is sunk into deep fossa glandis

Comparative glans anatomy of bull & ram

Bull

penis tapers to a point

Ram

similar but has vermiform appendage (worm-like urethral process —> extention of urethra)

No bulbus glandis or os penis (unlike dog)

Anatomy of the tom cat glans penis

Cornified spines - stimulate reflex ovulation
Dependent upon androgens (disappear in neutered animals)

Describe urethral calculi (stones)

From bladder

Can get caught in penile urethra —> unable to pass urine

Common “pinch points” where urethral calculi obstruction occurs in:

Dogs

Bulls

Rams

Dogs —> base of os penis

Bulls —> proximal end of sigmoid flexure/ischial arch

Rams —> vermiform appendage

What is the function of the accessory sex glands?

Produces seminal plasma —> correct pH, ionic content and with nutrients for survival

small in immature animals & animals castrated prior to puberty

Post-pubertal castration leads to atrophy of glandular component

Label the accessory sex glands of the stallion

1 = ampulla —> enlargments of ductus deferens, open directly into pelvic urethra
2 = vesicular glands
3 = prostrate —> consists of compact body & diffuse tissue within wall of pelvic urethra
4 = bulbourethral gland

Comparative scrotum anatomy of bulls, stallions and boars

Bull

long/pendulous marked neck

Stallion

globular with poorly defined neck

Boar

subanal, close to caudal thigh surface

Which testes belong to which species

1 = bull
2 = stallion
3 = boar

Comparative kidney anatomy:
Cats/Dogs/Sheep
Cows
Pigs
Horses

Kidney bean shaped

12 lobed shape

Dorsoventrally flattened

L & R different shapes —> more cranial kidney (i.e. right kidney) more heart shaped

Which species have all 4 male accessory glands present?

Cow, Horse & Sheep

In what situation is the rupture of the bull penis most likely to occur?

At natural service if the female suddenly drops down

Why does the scrotum of bulls (and many other species) not heal well?

They contain lots of sebaceous glands