3 – Male Reproductive System I Flashcards
Sperm journey
- High speed manufacturing
- Nuclear and flagellar stabilization, motility (head and body of epididymis)
- Warehouse and shipping (tail of epididymis)
- Final alteration and packaging
- Delivery system
Thermoregulation of testis
- 4-6 degrees C cooler than body
- Short periods of high temperature is probably tolerated
o If more than 8 hours = reduce sperm MOTILITY and cause DNA damage
Cooling is a function of
> creamster muscle
scrotal skin
tunica dartos (lots of SM fibers)
vascular countre-current (pampiniform flexus)
Pampiniform plexus
- Venous network wrapped around the testicular artery
Pampiniform plexus has an effect in:
o Heat exchange
o Pulse pressure reduction
Pulse over time could cause damage to testes
Mechanism is not clear
*maybe the testicular artery is more elastic?
o Transfer of testosterone
Rete testis
- Pigs and bulls: central
- Horses and humans: superficial
Leydig (interstitial endocrine) cells
- Produce testicular androgens
o Lots of estrogen in pig and horse - Occupies most volume in pigs
- Large polymorphous acidophilic (pink) cells w/round nucleus
3 distinct Leydig cell populations
- Fetal Leydig
- Infantile/early postnatal Leydig
- Adult Leydig
- Fetal Leydig
a. Sex determination to shortly after birth
- Infantile/early postnatal Leydig cells
a. Only in some species
b. Very short-lived
- Adult Leydig cells
a. From puberty thru adult life
Seminiferous cords/tubules
- Convoluted double-ended loops (2m in mice, 5kim in bulls)
Seminiferous cords/tubules consists of
o Lamina propria
Made up of basal lamina surrounded by peritubular cells
o Sertoli cells
o Spermatogenic cells
Seminiferous cords
o Immature and lack a lumen
o 70-90um
o Sertoli and gonocytes (early generation of germ cells)
Seminiferous tubules
o More developed and have a lumen
o 150-300um
o Sertoli and multiple generation of germ cells
Peritubular myoid cells (PTMCs)
- 1-5 layers of contractile cells surrounding the basal lamina
- Contain abundant actin filaments and cytoskeleton proteins
- Resemble myofibroblasts (ex. bull) or SM fibers (ex. boar)
- *contractile action assists in propulsion of sperm and testicular fluid
o Along seminiferous tubules toward rete testis
Sertoli (sustentacular) cells
- Oval nucleus w/prominent nucleolus near base
- Adult cells differ and lose mitotic capability
- Large elongated cells w/irregular outlines touching basal membrane
- Even spaced in tubule
Sertoli (sustentacular) cells ROLES
o Provide nutrients and signals to dividing germ cells
o Move germ cells along to lumen
o Secrete testicular fluid into lumen for sperm transport
o Phagocytize faulty germ cells and their excess cytoplasm
o Produce chemical mediators to regulate spermatogenesis
Sertoli cells’ junctional complexes
- Sertoli-Sertoli tight junction
- Sertoli-spermatid junction
- Sertoli-Sertoli tight junction
o Between adjacent cells
o Forms blood-testis barrier
o Divides tubules into basal and adluminal compartments
o *opens like a zipper to allow germ cells to pass from basal to lumen
- Sertoli-spermatid junction
o Specialized with spermatid nucleus
Gonocytes
- Part of male GERMLINE stem cells
o Come after primordial germ cells (PGCs)
o Come before spermatogonia stem cells (SSCs) - Appear at 13.5dpc in rodents and 7wk of gestation in human embryos
o Development is HORMONE-Independent
Gonocytes appear when
- Testis cords are formed
- PGCs have lost alkaline phosphatase (AP) activity and adopted male germ cell fate
Gonocytes classification
- Mitotic fetal gonocytes
- Quiescent gonocytes
- Mitotic postnatal gonocytes
