Testicular Morphology and Function Flashcards
function and location 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
structures contained in the spermatic cord
within visceral vaginal tunic:
-testicular artery
-veins of pampiniform plexus
-ductus defrens
within parietal vaginal tunic:
-cremaster muscle
-cord is surrounded by spermatic fascia
what is an overview of the process of sperm production all the way to ejaculation
- high speed manufacturing in testis
>35,000 to 200,000 sperm/second - membrane changes, nuclear and flagellar stabilization, motility, etc. and fluid absorption in head and body of epididymus
- storage of sperm for 5 to 10 ejaculations in epididymus tail. Smooth muscle contractions upon sexual stimulation.
- metabolic substrates, surface coatings, transport in accessory sex glands
- ejaculation through the penis
compartments of the seminiferous tubules and what they contain
interstitial compartment:
-leydig cells, connective tissue
basal compartment:
-spermatogonium
-sertoli cells
adluminal compartment:
-spermatocytes
-spermatids
what are the stages that make up spermatogenesis? what are their features?
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
what is the cycle of seminiferous epithelium?
-spermatogonia enter, spermatozoa move on
-four generations are required during this progressions:
>’gonia > primary ‘cyte > secondary ‘cyte > ‘tid
sperm processing in the epididymus
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
clinical interpretation of ejcaulate requires knowledge of what?
timing of spermatogenesis
-species specific
do sperm numbers in ejaculate reflect spermatogenesis? 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.
duration of spermatogenesis?
depends on species, eg.
bull - 60 days
stallion - 55 days
boar - 40 days
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
