Testicular Morphology and Function Flashcards
location and general functions of the spermatic cord
-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
important components contained in the interior of the spermatic cord
-cremaster muscle
-testicular artery
-veins of pampiniform plexus
-ductus deferens
how many sperm can be produced per second (eg. in bull)
35,000 to 200,000 seprms/sec
typical sequence of spematogenesis in mammals
-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
duration of spermatogenesis?
depends on species, eg.
bull - 60 days
stallion - 55 days
boar - 40 days
after manufacturing in the testis, where do sperm go next? How do they change during this phase
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
Does calculating sperm numbers in an ejaculate tell you if spermatogenesis is normal or not? Why? What timelines are important to consider here?
- 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.
Broadly, what is seminal plasma and where does it come from?
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
what are the chemical characteristics of seminal plasma? what does it contain?
- Buffered, nutrient, protective transport medium * pH 7.2-7.8
- Contents:
– electrolytes
– proteins
– citric acid
– enzymes
– buffers
– energy sources
– prostaglandins
– antibacterials, zinc
Accessory Sex glands of Bull
-Ampulla
-Vesicular glands
-prostate gland
Accessory sex glands of stallion
-ampulla
-vesicular glands
-prostate gland
-Bulbourethral glands
difference in vesicular glands between bull and stallion
Bull- Compact lobulated
Stallion- Pyriform glandular sacs
difference in prostate gland between bull, boar, and stallion?
Bull- Small, predominantly internal
Boar- Large, internal & external
Stallion-Two lateral lobes, large, external
accessory sex glands of the boar
-vesicular glands
-prostate gland
-Bulbourethral glands
what is the bulbourethral gland of the boar responsible for?
the gel-like component of boar semen
accessory sex glands of the dog
-ampulla
-prostate gland
Testicular endocrine and spermatogenic function is optimal when scrotal temperature maintained at:
3-4°C below the body temperature
what mechanism is responsible for thermoregulation in the scrotum?
- Counter-current heat exchange in the pampiniform plexus controls the scrotal temperature
what unique mechanisms do rams have for thermoregulation of the testis?
-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
what is the physiology/mechanism of penile erection and protrusion?
-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
major steps in ejaculation, and preparation of sperm for this
- 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
