Introduction to Embryology: Fertilization, Implantation and Formation of Bilaminar Embryo Flashcards
what are the major stages of embryonic development?
1) ) Pre-0implantation
2) Embryonic period
3) Fetal period
What weeks are considered the embryonic period?
wks 2-8
What weeks are considered the fetal period?
wks 9-38
Which period is the most dramatic one where the basic body plan is laid down?
Embryonic period
What occurs during the fetal period?
morphogenesis- generation of form & organogenesis- generation of organs
–>Massive increase in size and weight, rotation of limbs, ossification of bones, proportion of body and differention of external genitalia
What is Teratology?
the study of abnormal development of embryos and the causes of congenital malformations
T/F: 2/3 of major malformation end up spontaneously aborted
True
What are factors that cause developmental malformations?
Genetic, Environmental and Multifactoral
~50% are multifactoral or unknown
T/F: most abnormalities occur in children of normal parents with no known risk factors?
True
Describe the concept of the critical period in embryogenesis?
WKS 4-6
The critical period for a particular organ or structure is when cell division in that structure is most rapid and therefore when the structure will be most sensitive to the action of teratogens
Where does fertilization usually occur?
in the ampulla of fallopian tube
Describe the pathway of the oocyte as it leaves the ovary?
oocytes are ovulated from ovary enter fimbria fertilize in ampulla differentiate into a blastocyst implant in endometrium
What is the layer around the oocyte that is Acellular and used for protection against polysperm?
Zona pellucida
What is the area around the zona pellucida that is made of follicle cells and provides protection, nutrition and sperm maturation?
corona radiata
Describe the zona reaction
once the cells penetrates the zona pellucid –> the zona converts from gel like to leathery and prevents additional fertilization
T/F: Polyspermy is lethal.
True
A fertilized diploid individual cell is called?
Zygote
A zygote starts to divide (8x) and there is symmetric cleaving which form a?
Morula
Is the zona still intact in the morula stage?
YES!
Is there growth in the morula stage?
NO!
When the zona breaks down and fluid rushes into spread the cells apart, it forms the?
Blastocele
The blastocyst continues to grow and the outer cell layer is called the trophoblast, which gives rise to?
Placenta
The cells that accumulate towards the dorsal part of the Blastocyst form the inner cell mass which gives rise to?
Embryo
What is meant by conceptus?
everything that arises from the zygote
