Oogenesis - Reproductive - Medbullets Step 1

Overview
- Oogenesis
  - development of mature oocytes, or haploid gametes capable of fertilization by sperm

Oogenesis
- Pre-natal oogenesis
  - oogenesis, or maturation of oocytes, begins in fetal life
    
    primordial germ cells migrate from fetal hind gut to gonadal ridge
    
    primordial germ cells differentiate to oogonia
    
    in fetal ovary, oogonia proliferate by mitotic divisions
    
    by week 20, proliferation ends and oogonia numbers peak at 7 million
    
    oogonia (2N, diploid) differentiate to primary oocytes (2N, diploid)
    
    primary oocytes begins meiosis I and arrest in prophase I
    
    primary oocytes arrest in "dictyotene stage" until just before ovulation
    
    primary oocyte is surrounded by pre-granulosa cells in primordial follicle
- Post-natal oogenesis
  - oogenesis, or maturation of oocytes, continues in post-puberty adult life
    
    in follicular (proliferative) phase of menstrual cycle, development of primordial follicles yields one dominant, pre-ovulatory Graafian follicle
    
    primary oocyte (2N, diploid) differentiates to secondary oocyte (2N, haploid)
    
    primary oocyte completes meiosis I, yielding secondary oocyte and first polar body
    
    secondary oocyte begins meiosis II and arrests in metaphase II
    
    at ovulation, Graafian follicle ruptures and releases secondary oocyte
    
    in response to fertilization, secondary oocyte completes meiosis II, yielding mature ovum (N, haploid) and second polar body
    
    ovum nucleus condenses and forms female pronucleus that fuses with male pronucleus to form zygote

Action	Numeric Key	Letter Key	Function Key
Show Bullets		S	Enter (frontside only)
20%	1	N
40%	2	H
60%	3	F	Enter (backside only)
80%	4	E
100%	5	M
Toss	0	T