Embryology Of The Heart Flashcards
What is an early phase of embryonic development and when does it occur?
Gastrulation
3rd week
What happens during gastrulation?
During this phase the embryoblast develops into a trilaminar (three layered structure) called gastrula and forms three germ layers
What are the 3 germ layers called?
Ectoderm
Mesoderm
Endoderm
What does the ectoderm form?
Outer layer - structures in contact with outside of the body
Skin, NS (peripheral & central), cardiac crest cells
(Pituitary, mammary and sweat glands)
What does the mesoderm form?
All muscle, cardiovascular system, cartilage and bone, urogenitial system
What does endoderm form?
Liver, pancreas, endocrine organs, GI epithelial lining
When does the folding of the primitive heart tube occur & what happens each day?
Pre day 19 - heart is formed by cells that form a ‘horse shoe’ shape, called the cardiogenic region
Day 19 - 2 endocardial tubes form
Day 20/21 - the tubes fuse to form the primitive heart tube
What are the 5 parts of the heart tube?
Trunchus arteriosis Bulbus cordis Primitive ventricle Primitive atrium Sinus venosus
What happens by day 22?
The heart begins to beat
What happens by day 23?
The heart tube begins to fold
Which way does each section fold?
Bulbus cordis - folds inferiorly, anteriorly & right
Primitive ventricle - shifts left
Primitive atrium & sinus venosus - more superiorly & posteriorly
What does the trunchus arteriosis form?
Aorta & aortic arches
What does the bulbus cordis form?
Proximal aorta and pulmonary trunk
What does the primitive ventricle form?
Left ventricle
What does the primitive atrium form?
All of left atrium, part of right atrium, left and right auricles
What does the sinus venosus form?
Part of right atrium, vena cava, coronary sinus
What is the asymmetry in the heart due to?
Cilia wafts molecules R —> L (why muscle wall in L is thicker)
Adaptation to increase molecule conc on left
What happens in septation?
Superior & inferior endocardial cushions grow and meet at central atrioventricular canal
Where does the superior& inferior grow from?
Superior - grows from bottom up
Inferior - grows from top down
What does the superior continue up to do?
Divide Left and right atria (interatrial septum)
What is the embryologist deficit (gap) in the atria?
Foramen ovale (allows blood to flow freely through left and right atria)
What happens at birth to the foreman ovale?
Closed off and becomes fossa ovale
What does the inferior continue down to divide?
Separate the left & right ventricle, interventricular septum
Has an upper and lower membranous part
What do the aortic arches develop/branch off?
When does it occur?
Trunchus arteriosis
27 days to 7 weeks
What does the Trunchus arteriosis continue upwards to form?
Aortic sac
How many aortic arches are there?
6
What does the first branch form?
Maxillary artery
What does the second branch form?
Hyoidal
& stapedial
What does the third branch form?
Common carotids
Proximal portion of internal carotid artery
What does the fourth branch form?
Left - aortic arch
Right - Right subclavian branches
What does the fifth branch form?
Nothing, regresses
What does the 6th branch form?
Right - pulmonary trunk
Left - ductus arteriosis
