Embryology Flashcards
What are the 2 methods used to date pregnancy
Menstraul age and fertilisation age
How do menstraul age and fertilisation age differ
Menstraul age takes the first 2 weeks into account
When is the most vulnerbale point in uman development for mutations
week 3-8
What does TORCH stand for
Toxoplasmosis, other, rubella, cytomegalovirus, herpes
What are the causes for birth defects called
Teratogens
What is the effect of thalidomide on birth defects
causes shortened or ab sent limbs
Effect of alcohol on birth defects
Causes foetal alcohol syndrome - intellectual disability
Follic acid deficiency
Causes malformations in the CNS - spina bfida and anencephaly
Other teratogens
Radiation
Maternal disease
What is gametogenesis
Formation of the gametes
Capacitation of the sperm
Maturation of sperm cell occurs in the reproductive tract
Acrosome reaction
enzymes released that allow the sperm to penetrate the zona pellucida
Zona reaction
Following sperm penetration, 2nd fertilisation is stopped by making the zona pellucida impenetrable
What occurs after fertilisation
Nucleus of the spem enters the oocyte to form a zygote
What is cleavage
rapid cell division, the cells actually get smaller
What is a morulla
Ball of 16-32 cells made by cleavage
What makes up the morulla
Inner cell mass are embryoblasts
Outer cell mass are trophoblasts
What happens to the morulla
Cleavage continues and forms a fluid filled cavity called a blastocyst on day 5
what happens in days 5-6
Implantation ONTO the uterine wall
What is hatching
the process by which the zona pellucida is removed and the blastocyst is implanted into the endometrium
Describe the differentiation of the trophoblast into syncytiotrophoblast
Syncytiotrophoblast cells are the ones that burrow their way into the uterine lining and go on to form support structures
Describe the differentiation of the embryoblast into epiblast and hypoblast – bilaminar disc
Epiblast and hypoblast cells go on to form the embryo. Becoming bilaminar is when the embryo starts to become organised
Appreciate the importance of the epiblast and hypoblast in establishing the dorsal/ventral axis of the embryo
Epiblast form the dorsal surface and the hypoblast cells form the ventral surface
Describe the process of full implantation of the blastocyst
After 9 days the embryo is fully implanted into the uterine lining. A coagulation plug forms over the area of entry.
The formation of the amniotic cavity and the primary yolk sac
Amniotic cavity forms a small fluid-filled cavity in the epiblast. Hypoblast cells cover the blastocyst to form the primary yolk sac.
Formation of definitive yolk sac on the 13th day
Hypoblastcells continue to migrate around the primary yolk sac and push the old hypoblast cells out of the way to form a new cavity
What is the extraembryonic mesoderm and what cavity does it form
a layer of connecive tissue derived from yolk sac cells that eventually covers the amniotic cavtity. It eventually develops to form the chorionic cavity
How is uteroplacental circulation established
Syncytiotrophoblasts break down the wall of the mothers capillaries . Blood seeps into the trophoblastic lacuna
Describe the production of human chorionic gonadotrophin and its importance in pregnancy testing
Syncytiotrophoblast cells secrete a hormone. The hormome is needed to maintain the endometrium so it is tested for.