S9-10) Embryology Flashcards
What is embryology?
Embryology is the study of the molecular, cellular and structural factors involved in the progression from a single cell to a baby in 9 months
Describe the process of oogenesis
Where does fertilisation normally occur?
The ampullary region of the fallopian tube
Sperm must be introduced into the female reproductive tract within 5 days before ovulation.
How long are the sperm and secondary oocyte viable?
- Sperm are viable for 5 days
- Secondary oocyte is viable for 12-24 hours
Why is there a need for capacitation?
- Sperm are initially incapable of fertilisation
- Capacitation allows the tail of the sperm to move faster, causing the oocytes plasma membrane to alter
Describe the process of fertilisation
Define the following terms:
- Embryonic age
- Gestational age
- Embryonic age: time since fertilisation
- Gestational age: time since last menstruation (embryonic age minus 2 weeks)
Define the following terms:
- Germinal stage
- Embryonic period
- Foetal period
- Germinal stage: time from fertilisation to the end of the 2nd week
- Embryonic period: time from the 3rd to end of the 8th week
- Foetal period: time from the beginning of the 9th week to birth at 38 weeks
Before the blastocyst can implant it has to lose the zona pellucida.
What is this process called and why does it happen?
Hatching is the process in which the blastocyst emerges from its zona pellucida as the zona pellucida prevents the morula/blastocyst adhering to the oviduct and enlarging
Distinguish between histiotrophic nutrition and haemotrophic nutrition
- Histiotrophic nutrition is the nutrition provided to the embryo which is not from the maternal blood and is important in humans up to the 12th week
- Haemotrophic nutrition is the nutrition provided by the mother’s blood and is important in humans from 12th week on
Where and when does the blastocyst implant?
Why is this important?
- Normal implantation of the blastocyst occurs in the posterosuperior wall of the uterine cavity on the 6th day
- The implantation site determines the site of formation of the placenta
Identify 7 abnormal implantation sites
Differentiate between the following terms:
- Trophoblast
- Synctiotrophoblast
- Cytotrophoblast
- Trophoblast is a layer of tissue on the outside of a mammalian blastula, supplying the embryo with nourishment
- Syncytiotrophoblast are cells that merge together in the trophoblast
- Cytotrophoblast are cells in the trophoblast
What is the bilaminar disc?
- The bilaminar embryonic disc refers to the epiblast and the hypoblast, evolved from the embryoblast
- These two layers are sandwiched between the primitive yolk sac and the amniotic cavity
Differentiate between the following terms:
- Hypoblast
- Epiblast
- Hypoblast is a tissue type, lying beneath the epiblast, that forms from the inner cell mass and consists of small cuboidal cells
- Epiblast is the outermost layer of an embryo before it differentiates into ectoderm and mesoderm
Differentiate between the follow structures:
- Amniotic cavity
- Yolk sac
- Chorionic cavity
- Amniotic cavity is the closed sac between the embryo and the amnion, containing the amniotic fluid
- Yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast adjacent to the embryonic disk
- Chorionic cavity is the space surrounding the primary yolk sac and amniotic sac (not around connecting stalk)