intro to embryology Flashcards
1
Q
weeks 0-3
A
conceptus/embryo
2
Q
weeks 3-8
A
embryonic period. critical time most problems occur also the most development
3
Q
weeks 9-40
A
foetal period. growth rather than development
4
Q
phases of embryogenesis
A
- Gametogenesis
- Fertilisation
- Cleavage
- Gastrulation
- Formation of a body plan
- Organogenesis
5
Q
what is gametogenesis
A
formation of a gamete. consisting of mitosis and meiosis leading to genetic variation
6
Q
what is a gamete
A
- A gamete is a cell with a complement of 23 chromosomes (half of a typical somatic cell)
- Haploid (23 chromosomes)
7
Q
what id oogenesis
A
formation of female gamete
8
Q
when does oogenesis take place
A
- Starts in development (of embryo) and ends at menopause.
- By week 28-30: Primary oocytes begin meiosis but arrest in prophase until puberty.
- Reproductive life span determined in fetal life (already has all eggs from birth)
9
Q
spermatogenesis
A
- Formation of male gametes
- Occurs at puberty and continues throughout life - Each cycle takes ~64-74 days
10
Q
production rate of spermatogenesis
A
- Production rate: ~6.5 million sperm per gram of testicular tissue/day. Decreases with age
11
Q
who determines sex of baby
A
males. * Outcome 22+X or 22+Y
12
Q
trisomy 21
A
additional copy of chromosome 21. typically caused by nondisjunction
13
Q
when does nondisjunction typically occur
A
75% of nondisjunction occurs during oocyte formation
14
Q
fertilisation
A
union of gametes. fusion of sperm and oocyte
15
Q
cleavage
A
- Period of rapid mitotic cell division
- No increase in size
- Formation of Morula then Blastocyst (blastocyte splits into 2 parts 1 forming the placenta the other forming the embryo)
