Testicular Morphology and Function

Question 1

function and location 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

structures contained in the spermatic cord

Answer 2

within visceral vaginal tunic:
-testicular artery
-veins of pampiniform plexus
-ductus defrens

within parietal vaginal tunic:
-cremaster muscle

-cord is surrounded by spermatic fascia

Question 3

what is an overview of the process of sperm production all the way to ejaculation

Answer 3

1. high speed manufacturing in testis
   >35,000 to 200,000 sperm/second
2. membrane changes, nuclear and flagellar stabilization, motility, etc. and fluid absorption in head and body of epididymus
3. storage of sperm for 5 to 10 ejaculations in epididymus tail. Smooth muscle contractions upon sexual stimulation.
4. metabolic substrates, surface coatings, transport in accessory sex glands
5. ejaculation through the penis

Question 4

compartments of the seminiferous tubules and what they contain

Answer 4

interstitial compartment:
-leydig cells, connective tissue

basal compartment:
-spermatogonium
-sertoli cells

adluminal compartment:
-spermatocytes
-spermatids

Question 5

what are the stages that make up spermatogenesis? what are their features?

Answer 5

proliferation + meiosis + differentiation

proliferation:
-spermatogonia undergo mitosis, often remain connected by intercellular bridge junctional complexes
-last mitotic devision gives rise to primary spermatocytes

meiosis:
-primary spermatocytes undergo meiosis 1, generating secondary spermatocytes

differentiation:
-secondary spermatocytes undergo meiosis 2 to generate spermatids, which develop more features of the mature sperm cell

Question 6

what is the cycle of seminiferous epithelium?

Answer 6

-spermatogonia enter, spermatozoa move on
-four generations are required during this progressions:
>’gonia > primary ‘cyte > secondary ‘cyte > ‘tid

Question 7

sperm processing in the epididymus

Answer 7

head:
-not motile
-not fertile
-proximal cytoplasmic droplet
-low disulfide cross-linking

body:
-some expression of motility after dilution
-some expression of fertility
-translocationg cytoplasmic droplet
-moderate to high degree of disulfide cross-linking
-can bind to oocytes

tail:
-expression of normal motility after dilution
-fertile potential
-distal droplet
-high degree of disulfide cross-linking
-can bind to oocytes

=> sperm in distal tail can be transported into an ejaculatory position

Question 8

clinical interpretation of ejcaulate requires knowledge of what?

Answer 8

timing of spermatogenesis
-species specific

Question 9

do sperm numbers in ejaculate reflect spermatogenesis? why? what timelines are important to consider here?

Answer 9

• 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 10

duration of spermatogenesis?

Answer 10

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

Question 11

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

Answer 11

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 12

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

Answer 12

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

Question 13

Accessory Sex glands of Bull

Answer 13

-Ampulla
-Vesicular glands
-prostate gland

Question 14

Accessory sex glands of stallion

Answer 14

-ampulla
-vesicular glands
-prostate gland
-Bulbourethral glands

Question 15

difference in vesicular glands between bull and stallion

Answer 15

Bull- Compact lobulated
Stallion- Pyriform glandular sacs

Question 16

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

Answer 16

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

Question 17

accessory sex glands of the boar

Answer 17

-vesicular glands
-prostate gland
-Bulbourethral glands

Question 18

what is the bulbourethral gland of the boar responsible for?

Answer 18

the gel-like component of boar semen

Question 19

accessory sex glands of the dog

Answer 19

-ampulla
-prostate gland

Question 20

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

Answer 20

3-4°C below the body temperature

Question 21

what mechanism is responsible for thermoregulation in the scrotum?

Answer 21

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

Question 22

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

Answer 22

-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 23

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

Answer 23

-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 24

major steps in ejaculation, and preparation of sperm for this

Answer 24

intromission
sensory stimulation of glans penis (temperature and pressure)
sudden and powerful contraction of urethralis, bulbospongiosus, and ischiocavernosus muscles
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