Spermatogenesis Flashcards
1
Q
Testicular anatomy
A
- Spermatogenesis occurs in seminiferous tubules
- Rete testis receives drainage from seminiferous tubules
- Rete testis empties into epididymis
- Epididymis function is to store sperm, help sperm mature, has 3 regions
- Head: concentration
- Body: maturation
- Tail: storage
- Spermatogenesis occurs from basement membrane inward to seminiferous tubule lumen
- Blood-testis barrier formed by tight junctions between Sertoli cells
- Physical barrier between blood vessels and seminiferous tubules
- Prevents some proteins and toxic agents from entering seminiferous tubules
- Differentiating germ cells (with 1N haploid DNA) are potentially antigenic/recognizable as foreign - barrier sequesters these cells from the blood environment
2
Q
Spermatogenesis and spermiogenesis
A
- Spermatogenesis occurs in a cyclical fashion that is continuous: at any given time or place in the seminiferous vesicle, different stages of spermatogenesis will be seen (about 60 different stages in humans)
- Defined as 3 stage process by which spermatogonial stem cells give rise to spermatozoon:
- Proliferative phase: spermatogonia mitotically divide = 1 primary spermatocyte + 1 copy of self
- Meiotic phase: spermatocytes undergo meiosis that reduce the chromosome number by half
- Spermiogenic phase / spermiogenesis: haploid spermatid differentiated into mature spermatozoa
3
Q
Spermiogenesis
A
- Haploid spermatid differentiated into mature spermatozoa
- Golgi phase = G apparatus produces acrosomal vesicles - most prominent cytoplasmic inclusion
- Cap phase = acrosomal vesicle migrate to one end of spermatid, capping sperm
- Acrosomal phase
- Maturational phase
- Spermiation is final step of spermatogenesis in Sertoli cell, in which sperm is released from Sertoli cell into the epididymis (via rete testis)
4
Q
Functions of Leydig (interstitial) cells
A
- Produce androgens including 95% of testosterone; stimulated to do so by LH
- T synergizes with FSH to stimulate formation of ABP in Sertoli cells
- Synthesis of StAR, SCP, SAP
- Help cholesterol get into cell and make steroids
- Required for spermiogenesis
- Have LH receptors (Gs)
5
Q
Functions of Sertoli (supporting) cells
A
- Form blood testis barrier via tight juntions
- Produce ABP - dramatically increase effectiveness of testosterone
- Nurture gametes (47 spermatozoa per Sertoli cell)
- Have FSH receptors (Gs)
- Produces estrogens from T via aromatase
- Produces inhibin and other growth factors
- Support Leydig cells with other growth factors + inhibin
6
Q
Hormonal control of spermatogenesis
A
- Spermatogenesis stimulated by testosterone, under control of HPT axis