Testicular Morphology and Function

Question 1

location and general functions of the spermatic cord

Answer 1

-Spermatic cord extends from the inguinal ring to its attachment on the dorsal pole of testis. It suspends testis in the scrotum
-Spermatic cord provides the pathway to and from the body for the testicular vasculature, lymphatics and nerves

Question 2

important components contained in the interior of the spermatic cord

Answer 2

-cremaster muscle
-testicular artery
-veins of pampiniform plexus
-ductus deferens

Question 3

how many sperm can be produced per second (eg. in bull)

Answer 3

35,000 to 200,000 seprms/sec

Question 4

typical sequence of spematogenesis in mammals

Answer 4

-Spermatononia (A1-A4, I and B) undergo a series of mitotic divisions and the last mitotic division gives rise to primary spermatocytes that enter meiosis. This series of mitotic divisions allows for continual proliferation of spermatogonia and replacement of A1 spermatogonia

-After meiosis, haploid spherical spermatids differentiate into spermatozoa. Meiosis and differentiation take place in the adluminal compartment.

Note that each generation of cells is attached by intercellular cytoplasmic bridges. Thus, each generation divides synchronously in cohorts. Some cells degenerate during this process.

gonia > 1 cyte > 2 cyte > tid > sperm

Question 5

duration of spermatogenesis?

Answer 5

depends on species, eg.
bull - 60 days
stallion - 55 days
boar - 40 days

Question 6

after manufacturing in the testis, where do sperm go next? How do they change during this phase

Answer 6

to the epididymis - head, body, then tail
>duration in each part depends on species

Species / Head / Body / Tail / Total
Boar / 3 / 4-9 / 9-14
Bull / 2 / 2 / 10 / 14
Ram / 1 / 3 / 8 / 12
Stallion / 1 / 2 / 6 / 9

In head - non-motile, not fertile, low disulfide cross-linking
In body - some expression of motility and fertility, moderate to high disulfide crosslinking
In tail - normal motility and high degree of disulfide cross-linking

> spematozoa in distal tail can be transported into an ejaculatory position

Question 7

Does calculating sperm numbers in an ejaculate tell you if spermatogenesis is normal or not? Why? What timelines are important to consider here?

Answer 7

• Calculating sperm numbers in an ejaculate
  – DOES NOT always accurately reflect normal or abnormal spermatogenesis
  – Fate of males being evaluated is often fraught with error > bad decisions
• 2 to 4 wks delay before effects of deleterious events (heat stress, shipping, fever, exposure to toxins) can be observed.
• 6 to 12 wks required before restoration of normal spermatogenesis can be accomplished post treatment or exposure to deleterious events.

Question 8

Broadly, what is seminal plasma and where does it come from?

Answer 8

Secretions produced by the epididymis and accessory sex glands that contribute the non-cellular liquid part is known as seminal plasma
Seminal plasma is produced by:
* Epididymis
* Ampulla
* Vesicular glands
* Prostate gland
* Bulbourethral glands

Question 9

what are the chemical characteristics of seminal plasma? what does it contain?

Answer 9

• Buffered, nutrient, protective transport medium * pH 7.2-7.8
• Contents:
  – electrolytes
  – proteins
  – citric acid
  – enzymes
  – buffers
  – energy sources
  – prostaglandins
  – antibacterials, zinc

Question 10

Accessory Sex glands of Bull

Answer 10

-Ampulla
-Vesicular glands
-prostate gland

Question 11

Accessory sex glands of stallion

Answer 11

-ampulla
-vesicular glands
-prostate gland
-Bulbourethral glands

Question 12

difference in vesicular glands between bull and stallion

Answer 12

Bull- Compact lobulated
Stallion- Pyriform glandular sacs

Question 13

difference in prostate gland between bull, boar, and stallion?

Answer 13

Bull- Small, predominantly internal
Boar- Large, internal & external
Stallion-Two lateral lobes, large, external

Question 14

accessory sex glands of the boar

Answer 14

-vesicular glands
-prostate gland
-Bulbourethral glands

Question 15

what is the bulbourethral gland of the boar responsible for?

Answer 15

the gel-like component of boar semen

Question 16

accessory sex glands of the dog

Answer 16

-ampulla
-prostate gland

Question 17

Testicular endocrine and spermatogenic function is optimal when scrotal temperature maintained at:

Answer 17

3-4°C below the body temperature

Question 18

what mechanism is responsible for thermoregulation in the scrotum?

Answer 18

• Counter-current heat exchange in the pampiniform plexus controls the scrotal temperature

Question 19

what unique mechanisms do rams have for thermoregulation of the testis?

Answer 19

-proposed scrotal sweating and thermal polypnea pathways

-thermosensitive neurons in hypothalamus send signals to sweaat glands on scrotal skin
-thermosensitive neurons in scrotum send signals to respiratory center in brain, which then results in panting (polypnea)

> this reflex pathway resulting in polypnea is not activated until scrotal temp reaches about 39C

Question 20

what is the physiology/mechanism of penile erection and protrusion?

Answer 20

-sexual stimulation (optical, olfactory)
-seingal to pelvic nerves
>increase PSNS, decrease SNS stimulation
>increase ACh > increase cGMP
>vasodilation
>blood accumulation
>increased pressure on veins
>blood retention

Question 21

major steps in ejaculation, and preparation of sperm for this

Answer 21

1. intromission
2. sensory stimulation of glans penis (temperature and pressure)
3. sudden and powerful contraction of urethralis, bulbospongiosus, and ischiocavernosus muscles
4. expulsion of semen

> > to prep sperm:
1. sensory stimulation (optic, olfactory, tactile, auditory)
2. stimulation of nerves in the supraoptic and paraventricular nuclei
3. release of oxytocin from posterior pituitary
4. contraction of smooth muscle in distal tail of epididymis and ductus deferens
5. transport of spermatozoa into an ejaculatory position