Early embryonic development Flashcards
What is a spermatozoon
Mature, motile male sex cell with a head, mid-piece and tail
What does the head of the spermatozoon contain
The nucleus and
an acrosome, which contains
enzymes required for the
penetration of the zona
pellucida of the oocyte
Where are secondary oocytes found
In the ovary, arrested in metaphase II of meiosis I
What is the cytoplasm of ovulated secondary oocyte surrounded by
Plasma membrane, zona pellucida and corona radiata
Describe oogenesis
- Each month from puberty to menopause, one primary oocyte undergoes meiosis I, divides into first polar body and secondary
oocyte (arrested in metaphase II) - Secondary oocyte has 23 chromosomes
- It is the secondary oocyte that is ovulated
What is ovulation
The discharge of usually a single secondary oocyte from the ovary as a result of increase in LH
What happens when secondary oocyte is fertilised
Meiosis II is completed
What do fimbriae of uterine tubes do
They “sweep” the ovulated secondary oocyte into the uterine tube
What do peristaltic waves of uterine tube musculature and cilia do
They bring the secondary oocyte into the ampulla of the uterine tube
What is fertilisation
Fertilization is the fusion of haploid sperm and haploid oocyte to form a diploid zygote
Where does fertilisation take place
Usually in the
ampulla, but can take place in any part of the uterine tube
What must spermatozoa undergo to acquire fertilisation capability
Capacitation and the acrosome reaction
Describe the 3 phases of the spermatozoon penetrating the oocyte
- Phase 1: Capacitation (~7 hours) - Passing through the corona radiata
- Phase 2: Acrosome reaction - Penetration of the zona pellucida
- Phase 3: Penetration of the oocyte membrane by one spermatozoon, which loses its own plasma membrane
How does the spermatozoon penetrate the corona radiata
By hyaluronidase
