Embryology Flashcards
What are the phases of embryonic development?
Pre-embryonic 0-3 weeks
Embryonic 4-8 weeks
Foetal 9-40 weeks
What happens during each week in the pre-embryonic phase?
Week 1 - zygote is formed, divides to form blastocyst.
Moves through uterine tube to reach uterine cavity
Week 2 - implantation occurs in the endometrial layer and the placenta begins to develop. Cells that later form the embryo form a bilaminar disc
Sacs, membranes and cord to nourish the embryo start to form
Week 3 - formation of germ layers (gastrulation), formation of neural tube (neurulation), development of somites and early development of CVS
What name is given to the initial mass of cells in early division?
Morula
What cavity develops in the morula in the early stages?
What term is given to the outer lining of cells?
Blastocystic cavity
Outer lining = trophoblasts
Together = blastula and then blastocyst when inner cell mass forms
What is the chorion?
Layer of trophoblast that surrounds the entire embryo + placenta
What are the names given to the three parts the mesoderm splits into? What do each turn in to?
Paraxial mesoderm - somites
Intermediate Plate mesoderm - urogenital system
Lateral Plate mesoderm - body cavity and coverings
What happens during the embryonic phase?
Folding completes Neural development Heart starts on day 24 Gut formation from endoderm Urogenital system from intermediate mesoderm Body cavities from lateral plate mesoderm 43 pairs of somites (paraxial mesoderm) Limbs
What does each somite divide into?
Dermatome - skin dermis
Myotome - muscles
Sclerotome - skeleton
When and from where does the respiratory tract develop?
4th week
Buds from ventral wall of foregut
What are the different structures in the primitive heart tube? What do they turn into?
Truncus arteriosus - aorta/pulmonary trunk
Bulbus cordis > RV and parts of outflow tract
Ventricle > LV
Atrium > Parts of RA and LA
Sinus Venosus - superior VC, RA
What is tetralogy of fallot?
Pulmonary stenosis - obstruction of RV outflow
VSD
Dextroposition of aorta
What does each embryonic circulatory vessel supply? What do they turn in to?
Vitelline - yolk sac - coeliac + mesenterics
Umbilical - foetus to placenta/reverse - internal iliac + superior vesical (cardinal and vitelline veins drain into umbilical vein)
Cardinal - drains embryo body - VC
What are the shunts in the embryo? What do they become?
Ductus venosus (L umbilical vein > IVC = liver bypass) > ligamentum venosum of the liver Foramen ovale (RA > LA = lung bypass) > closes Ductus arteriosus (pulmonary trunk > aorta = lung bypass) > ligamentum arteriosum
