5 Gametogenesis Flashcards
Where does spermatogenesis occur?
Seminiferous tubules
Spermatogenesis begins as germ cells (spermatogonia) in the basal compartment of the seminiferous tubules. What stages must these spermatogonia go through to become spermatids?
Spermatogonia–> mitosis–> two primary spermatocytes–> meiosis 1 –> secondary spermatocytes–> meiosis 2–> spermatids
Why is it important that spermatids are at different levels of maturation at different sections of the seminiferous tubules? (spermatogenic cycle= 16days in human)
So matured sperm ready to go when time arises
What is the spermatogenic cycle and what is the spermatogenc wave?
Spermatogenic cycle: LENGTH OF TIME taken for reappearance of same stage within given segment of seminiferous tubule
Spermatogenic wave: DISTANCE between groups of spermatids at same level of maturation
What is spermiogenesis? When does this happen?
Process: spermatids become spermatozoa (mature sperm)
Non-motile spermatids become motile- process complete once reached epididymus
When: Spermatids released into lumen of seminiferous tubule
What is sperm ‘capacitiation’?
Process- occurs in female reproductive tract
Process- stimulated by conditions in female genital tract
Top layer of glycoproteins and cholesterol removed from outer membrane of sperm
(important to consider in IVF)
How are primary oocytes created in the ovary?
Germ cells settle in ovary to form oogonia (before birth)
Germ cells–> mitosis–> meiosis–> STOP prophase I–> primary oocyte
What is oogenesis?
Maturation of primary oocytes in ovary
Primary oocytes remain until puberty
What are primordial follicles?
Primary oocytes surrounded by follicular cells (occurs at birth)
What process causes the number of primordial follicles deteriorate after birth?
Atresia (degenerative process)
What occurs in the preantral phase of ooogenesis?
Follicular cells (of primordial follicles)–> granulosa cells-> secrete glycoprotein (zona pellucida)–> primary follicle
What occurs in the antral phase?
Primary follicle–> fluid filled spaces appear between granulosa cells–> secondary follicle–> outer layer : theca interna and theca externas
What happenstl the follicle in the pre-ovulatory phase (after the antra phase) ?
LH surge–> secondary follicle–> completes meiosis I
Many follicles- only one chose to mature fully (one with most FSH bound)
(Graafian follicle)
Graafian follicle –> enters meiosis II before ovulation- (will complete ovulation when fertilisation occurs)
What is the ‘Graafian follicle’?
Secondary follicle chosen to mature fully in pre-ovulatory phase
What happens to the Graafian follicule if fertilisation doesn’t occcur?
Oocyte with degrade about 24hrs later
How is the corpus luteum formed following ovulation? What happens to it is fertilisation doesn’t occur?
Remaining granulosa and theca interna cells= vascualrised- become corpus luteum- secretes oestrogen and progesterone
No fetilisation: degenerates after 14 days- form corpus albicans- mass of scar tissue
What happens to the corpus luteum if fertilisation occurs?
Implanted embryo releases ß-hCG
Maintains corpus luteum until placenta takes over production of progesterone (about 8-10 weeks)
Compare spermatogenesis and oogenesis.
Why is the blood testis barrier (Sertoli cell barrier) inmportant?
What is spermiation?
Spermatids released into lumen of seminiferous tubules
How are the spermatids transported through the seminiferous tubules?
What is Ad spermatogonium and Ap spermatogonium?
What is contained within semen?
