Male Anatomy

Question 1

Name the six layers of the scrotum

Answer 1

Tunica Albuginea (consists of collagen, connective tissue and smooth muscle) 
Visceral vaginal tunic 
Parietal vaginal tunic
Scrotal fascia 
Tunica dartos 
Scrotal skin (contains sweat glands)

Question 2

What is the role of the tunica dartos?

Answer 2

It adjusts the height of the testes in response to temperature by long term contraction via androgen control.

Question 3

What role does the scrotal skin play in temperature control?

Answer 3

The skin is innervated by sympathetic nerves which feed back to the hypothalamus, if there is an increase in temperature the hypothalamus will trigger the sweat glands

Question 4

What is the mediastinum?

Answer 4

The central connective tissue core of the testes

Question 5

Where are sperm produced?

Answer 5

In the seminiferous tubules, as they mature they move fro the outside to the inside of the tubes

Question 6

What cells lie on the basement membrane of the seminiferous tubules?

Answer 6

Sertoli cells, they support the germ cells as they mature

Question 7

What is the path of the sperm as they mature

Answer 7

The sperm starts in the seminiferous tubles which consists of the convoluted tuble (where the spermatozoa are produced) and then the straight tubule. From here the sperm move to the rete tubules (in the mediastinum) and then to the efferent ducts which connect to the head of the epididymis

Question 8

Describe the ultrasound appearance of the testes

Answer 8

Mediastinum is central and bright white (hyper echoic)

Question 9

What is the epididymis?

Answer 9

Is one large (30-60m) convoluted duct that consists of the head (caput), body (corpus), tail (cauda)
It is surrounded by smooth muscle that contracts rhythmically and aids the transport of spermatozoa
The main functions of the epididymis is for the reabsorption of fluid and the secretion of proteins

Question 10

What is the epididymis transit time?

Answer 10

The time taken for the spermatozoa to travel from the proximal head to the distal tail of the epididymis

Question 11

What is the function of the ductus deferens?

Answer 11

Connects the epididymis tail to the pelvic urethra

Has a very strong muscular wall for the propulsion of spermatozoa

Question 12

What is the spermatic cord made up of?

Answer 12

Consists of the ductus deferens, testicular artery and vein (pampiniform plexus), and cremaster muscle

Question 13

Where does the testicular artery come from and how does it form the pampiniform plexus?

Answer 13

The testicular artery comes from the abdominal aorta and once it passes through the inguinal canal it becomes very convoluted and is surrounded by veins and this is the pampiniform plexus.

Question 14

What is the function of the pampiniform plexus?

Answer 14

The pampiniform plexus acts as a heat exchanger, pulse pressure eliminator and allows transfer of testosterone from the testicular vein to the artery so maintaining the high level of testosterone in the testis.

Question 15

What is the function of the cremaster muscle?

Answer 15

The cremaster muscle is striated and acts for short term elevation of the testes.

Question 16

Name all the possible accessory sex glands?

Answer 16

Ampulla of the deferent duct, vesicular gland, prostate gland (corpus prostate sits above urethra and disseminate prostate sits in the wall of the urethra) and the bulbourethral gland.

Question 17

What accessory sex glands do stallions have?

Answer 17

Ampulla of the deferent duct, vesicular gland, prostate gland (lacks desseminate part) and the bulbourethral gland.
The stallion has colliculus seminalis, a common duct of the ampulla and vesicular gland. Is the opening of the ejaculatory ducts.

Question 18

What accessory sex glands do boar have?

Answer 18

The boar lacks ampulla however other glands are very large so there is a large volume of ejaculate

Question 19

What accessory sex glands do dogs have?

Answer 19

Dog – only has the ampulla and corpus prostate, which is bilobed

Question 20

What accessory sex glands do bulls have?

Answer 20

Bull – all glands present but a very small prostate corpus which means a small volume of ejaculate
See table of glands

Question 21

What is the function of seminal plasma?

Answer 21

Needed for the dilution and delivery of sperm, it also contains fructose as an energy source in all species except the stallion.
In the sow the seminal plasma coagulates and blocks the cervix thus preventing reflux of semen

Question 22

Name the muscles surrounding the urethra

Answer 22

Urethral muscle – surrounding the pelvic urethra
Bulbospongious muscle – surrounds the bulbourethral glands and the penile urethra
Both are striated muscles important for the transport of semen through the urethra

Question 23

What three regions does the penis consist of?

Answer 23

Consists of the root (with paired crura attached to the ischiatic arch), the shaft (corpus) and the glans.

Question 24

Where does the blood supply to the accessory glands and the penis come from?

Answer 24

The blood supply to the accessory glands and penis come from the internal pudendal artery (terminal branch of the internal iliac artery)

Question 25

Where does the innervation for the penis come from?

Answer 25

The innervation of the penis is from the dorsal penis nerve which arises from the terminal branch of the pudendal nerve

Question 26

Name the three columns of erectile tissue in the penis

Answer 26

Corpus cavernosum (paired): At the base of the crura they make up the main part of the corpus. Surrounded by dense connective tissue (tunica albuginea)

Corpus spongiosum: Surrounds the urethra

Question 27

Name the two types of penis

Answer 27

Fibroelastic (ruminants, pigs)
Lots of fibroelastic tissue in the corpus cavernosum so during erection there is little change in length and girth
The sigmoid flexure relaxes when the retractor penis muscle relaxes

Musculocavernous (stallion, dog)
More muscular/less connective tissue in the corpus cavernosum
Significant increase in length and girth during erection

Question 28

What muscle is more important in animals with a fibroelastic penis?

Answer 28

Retractor penis muscle

Question 29

When will bull and ram testicles descend?

Answer 29

Mid- pregnancy

Question 30

When will boar testicles descend?

Answer 30

Late- pregnancy

Question 31

Which species have horizontal and vertical testes?

Answer 31

Bull and Ram are vertical
Boar and stallion are horizontal
Dog and Tom are horizontal but slightly tilted cranioventrally