0512 - Embryology of the Heart - EG Flashcards
Briefly describe the stages of growth over the first week once an egg is fertilized.
Fertilized egg undergoes mitotic cell division to form daughter cells (blastomeres), increasing in size over the first 4 days, then becomes a blastocyst over days 5&6, which has an outer trophoblast layer, with blastomeres segregating themselves to one side which becomes the embryoblast and the rest of the space being filled with fluid, to form the blastocyst cavity. By the end of the week the blastocyst implants in the uterine wall.
What are the functions of the trophoblast?
to produce human chorionic gonadotropin (hCG) to support the corpus luteum maintain the uterine lining and to invade the uterine and pull the blastocyst into the uterine wall.
What happens in the second week after fertilisation?
The embryoblast splits into the bilaminar germ disc of the primary ectoderm and primary endoderm. The blastocyst remodels into an amniotic cavity and chorionic cavity.
What happens in the third week after fertilisation?
Gastrulation - the formation of a trilaminar germ disc as epiblast cells ingress through the primitive streak to form intraembryonic mesoderm.
When does the heart start to develop?
in the third week (17-19 days)
Outline the basic stages of heart development. in (#week)
(3w) development of primitive heart tube; (4w) heart tube folds and loops; (5w) formation of septum primum, ostium primum, and secundum, ventricular septum and AV valves start to form; (7w) foramen ovale forms intraventricular foramen closes; (8w) aortic and pulmonary tract and ventricles fully separated; (9w) semilunar valves completed.
What are the blood shunts in foetal circulation?
(1) umbilical vein to IVC through ductus venosus (2) RA to VA through foramen ovale (3) pulmonary trunk to aorta through ductus arteriosus (8) to placenta via umblical arteries
