Neonatology CA Flashcards
What is gestational age
Time from the beginning of the womens last menstrual period
What is embryonic age
Time from fertilisation
How do you calaculate genstational age
Embryonic age + 14 days
How many chromosomes does a gamete have
23
What is the process of cleavage during formation of blastocyst
Rapid mitotic cell divisions that create a morula consisting of the blastomeres
Explain the changes in cytoplasmic volume of the zygote during celavage
The cytoplasmic volume doesn’t change during cleavage. Rather, the large volume of the zygote cytoplasm is divided into increasingly smaller cells
What are the three layers of a blastocyst
Inner cell mass (embryoblast) for forms the foetus
Fluid filled hollow (blastocyst cavity)
Outer layer (trophoblast) which forms part of the placenta
What does a blastocyst secrete once fully developed
Immunosuppressant protein called early pregnancy factor
When does implantation occur in foetal development
6 days after fertilization
What is the zona pellucida
This is the extra cellular matrix that surrounds the blastocyst and is maintained through the formation of the morula while it travels to the uterus/endometrium
What does the blastocyst embed itself into in the beginning of implantation
Endometrium in the uterus
What are the two layers that the implanted blastocyte forms into
Outer layer - syncytiotrophoblast - erodes through endometrial tissue via apoptosis enabling the blastocyst to further embed into the endometrium
Inner layer - cytotrophoblast - new cells of the inner layer of the blasyocyst which form villi that project to the syncytiotrophoblast
What releases human chorionic gonadotropin and what is its mode of action
syncytiotrophoblast cells - hCG stimulates the corpus luteum of the ovary to produce progesterone to maintain the preganancy
How does the amniotic cavity form
As implantation progresses, the amniotic cavity forms within the blastocyst on the opposite side of the inner cell mass
What is the fate of the blastocyst cavity as implantation progresses
This forms into the primary umbilical vesicle and ultimately the secondary umbilical vesicle (or yolk sac)W
What is the chorionic cavity in implantation
This surrounds the structure that is imbedded into the endometrium at the final stage of implantation
When does gastrulation occur
Embryonic week 3
What is the bilaminar embryonic disc
This is the double sides layer of cells that separates the blastocyst cavity and amnionic cavity
What are the three layers of the trilaminar embryonic disc
Ectoderm, mesoderm and endoderm
What process occurs to make the third streak in the trilaminar embryonic disc
Invagination
How is the notochord developed in foetal development
Forms cranially from the primitive pit (trilinear embryonic disc) until it reaches the prechordal plate
What is the prechordal plate
small column where the ectoderm and endoderm are fused
What is neurulation
Formation of the neural tube
What does the neural plate then go on to develop into
Central nervous system