Human Embryology Flashcards
Why is embryology studied?
- history of prenatal origin
- understand birth defects
- to understand adult anatomy
- understand adult illness’s and origins
What are the embryological periods?
1st, 2nd, 3rd trimesters and pre-embryonic period
What is the embryonic period? (organogenesis)
beginning of 4th week to end of 8th week
What are the 3 germ layers and what do they give rise to
Ectoderm, Mesoderm, Endoderm
give rise to specific tissues and organs
what is the period of the foetus?
beginning of 3rd month to birth
What is gametogenesis?
process of production of male and female gametes from the primordial germ cells (PGC) via meiotic cell divisions
What are male and female gametogenesis called?
male - spermatogenesis
female - oogenesis
What are the principal goals of gametogenesis?
reduces chromosomal number of gametes from 46 (paired) to 23 (unpaired)
enhance genetic variability
starts at puberty in males and from fetal life in females
What do chromosomal abnormalities lead to?
birth defects, spontaneous abortions, fertility
What is fertilisation?
process of male and female gametes fuse to form a zygote
restores diploid number of chromosomes
what is capacitation?
a sperm conditioning process within the female reproductive tract in preparation for fertilisation - only capacitated sperm can pass corona cells
what is acrosome reaction?
release of enzymes needed to penetrate the zona pellucida (layer of ovum)
what is the cortical reaction?
the oocyte releases lysosomal enzymes from cortical granules making the plasma membrane impenetrable to other sperm
what is the zona reaction?
structure and composition of the zona pellucida is altered preventing polyspermy
what causes male infertility?
how can it be treated?
quality and quantity of spermatozoa
assisted reproductive technology (ART)
what causes female infertility?
multiple physiological and anatomical factors
what is and when does cleavage happen
within week of fertilisation
rapid repeated mitotic cell division of zygote to produce blastomeres
what is the purpose of cleavage?
form multicellular embryo (morula) from the single large zygote
what is the process of compaction
inner (embryoblast) and outer (trophoblast) cell masses forming and polarity being established