Male comparative anatomy Flashcards
What are the two basic models of penis and in which species are they found?
- musculocavernous = dog and stallion
- fibroelastic = ruminants and pigs
What are the 3 basic parts of the penis?
- Base where it is attached to the ischial arch
- Shaft
- Glans penis, specialised at distal end
What is an erection in a musculocavernous penis dependant on?
A large corporeal sinus that fills with blood
What forms an os penis?
The corpus cavernous fusing together
What is the function of the bulbus glandis?
Allows a dog to mate and turn to face their enemies
As it swells it locks the penis in place
What is the erectile tissue surrounding the urethra called?
Corpus spongiosis
What changes occur during the erection of a penis?
- elevated arterial blood inflow
- dilation of corporal sinusoids
- restricted venous outflow
- elevated intrapenile pressure
What is the function of the urethralis muscle?
Striated muscle that surrounds the pelvic urethra and moves semen into the penile urethra
Which muscle overlaps the root of the penis and extends down the caudal and ventral surfaces, covering the bulbourethral glands?
Bulbospongiosus muscle
Where is the ischiocavernosus muscle found?
Paired, short muscles in the root of the penis that insert laterally above the sigmoid flexure and connect the penis to the ischial arch
Which muscle holds the penis inside of the sheath when contracted and where is it found?
Retractor penis muscle
- attached dorsally to the coccygeal vertebrae and ventrally to the ventrolateral sides of the penis
Describe the events that take place that lead to expulsion of semen
- Sensory stimulation of glans penis during intromission
- Impulses are transmitted from the glans penis to the lumbosacral region of the spinal cord by means of the pudendal nerve and hypogastric nerve
- Sudden contraction of the urethralis, Bulbospongiosus and ischiocavernosus muscles causes reflex expulsion of semen
Describe the anatomy of a stallions penis
Musculocavernous penis
Thick tunica albuginea
Large amount of cavernous space which fills with blood during an erection
How is a fibroelastic penis characterised?
By a sigmoid flexure
Which muscle hold the sigmoid flexure?
Retractor penis muscle
How does an erection occur in a fibroelastic penis?
Relaxation of the retractor penis muscle
Corporal sinusoid fills with blood
Where is the sigmoid flexure in the bull?
Pre-scrotal
How is the boar penis adapted for copulation?
Spiral shape which locks into the sows cervix and forces ejaculate into the uterus
What is the worm like process at the end of the rams penis?
Vermiform appendage
What is unique about a tom cats penis?
Has cornified spines to help stimulate reflex ovulation
Gradually disappear in neutered animals
Where are possible places a urethral calculi (bladder stones) can occur in dogs, bulls and rams?
Dogs - base of os penis
Bulls - proximal end of the sigmoid flexure/ischial arch
Rams - vermiform appendage
What is the most common site for rupture of the tunica albuginea?
Where the retractor penis muscles attach to the distal part of the sigmoid flexure
How does rupture of the tunica albuginea occur?
When the tunica albuginea of the corpus cavernosum is stretched beyond capacity
- if a cow does down under a bull during service
What are the 3 ligaments of the testis?
- Proper ligament of the testis
- Ligament of the tail of epididymis
- Scrotal ligament
Which 2 structures does the ductus deferens link together?
The tail of the epididymis and the pelvic urethra
What is the function of the pampiniform plexus?
Counter current heat exchanger
- Regulates testicular temperature allowing sperm maturation
What is produced by accessory sex glands?
Seminal plasma - non-cellular fluid portion of semen
What are the 4 different accessory sex glands?
- Ampulla
- Vesicular glands
- Prostate gland
- Bulbourethral gland
What is the ampulla?
Enlargements of the ductus deferens that open directly into the pelvic urethra
Where does the prostate gland lie?
Close to the junction between the pelvic urethra and bladder
Which species has all 4 accessory sex glands?
Stallion
Which species only has one accessory sex gland? which is it?
Dogs only have a prostate gland
Which accessory sex gland does a boar not have?
Ampulla
Which accessory sex gland does a bull not have?
Bulbourethral gland
