Cardiac Embryology (Part 2): Topic 6 Flashcards
When does heart folding occur?
Day 23-28
Heart undergoes a series of folding that leads to the formation of what?
Bulboventricular loop
Heart Tube grows rapidly in length, especially what section?
The midsection (Bulbus Cordis and Ventricle)
Because the two ends of the heart tube ends are fixed, the heart tube is forced to do what?
Bend in order to adapt itself into the pericardial space; forms a U-shape, then forms an S-shape.
How is the heart tube oriented when it is bending?
Oriented so that the atrium and sinus venosus lie superior to the bulbus cordis, ventricle and dorsal aorta/aortic sac
Heart Folding: Atria initially paired- forms what?
Common atrium
Heart Folding: Atrioventricular junction remains narrow. Forms what?
AV Canal; connects common atrium and ventricle
Bulbus Cordis is narrow, expect what? What will this form?
Proximal 1/3; will form trabeculated part of the RV
Heart Folding: Junction between the ventricle and the bulbus cordis externally is what?
Bulboventricular sulcus; remains narrow and is called the primary interventricular foramen
Atrial portions of the Heart Tube dilate and form what?
Common atrium
Atrium “climbs up” what? What does it take with it?
The dorsal pericardial wall; takes atrioventricular junction with it
Atrioventricular junction remains narrow and is now called what? Forms the communication between what?
AV Canal; forms the communication between the atrium and the primitive ventricle
What is the junction of the ventricle and bulbus cordis called?
Intraventricular foramen
What two areas does the diverticular appear at Day 24?
- Along the front of the endocardial tube
2. Just proximally and distal to the primary interventricular foramen
Early embryonic ventricle is what?
The primitive LV
Proximal 1/3 of the bulbus cordis is what?
The primitive RV
What gives the densely trabeculated appearance?
The diverticula
The trabeculae inside the heart leads to what?
Valves, chordae tendinae, papillary muscles, and atrioventricular valves
Abnormalities in Cardiac looping is responsible for which cardiac defects?
Ventricular inversion (corrected transposition)
Juxtaposition of the atrial appendages
Double outlet right ventricle
BC
Bulbus cordis (RV)
AS
Aortic sac
TA
Truncus arteriosus
CC
conus cordis
SV
sinus venosus
As the primitive atria grow, the truncus arteriosus is positioned in what depression?
A depression between the roof of the right and left primitive atria
During atrial septation, the left atrium begins to form what?
Sprouts of the pulmonary veins that grow towards the lungs
What day does cardiac septation?
Starts at Day 27
How long does cardiac septation last?
Lasts 10 days (Day 27-day 37)
During septation, the embryo grows how much?
5mm to 16-17mm
Describe the changes in external appearance during the formation of the cardiac septa.
None
What is the name of the narrow channel that connects the primitive right and left ventricles at day 27?
Interventricular Formaen
How does blood reach the primitive LV ?
Via small opening from the primitive atria (AV canal)
During ventricular development, what 2 important processes occur simultaneously that result in the “chamberization” of the ventricles?
- Division of the AV canal into a right and left av orifice vai the endocardial chusions
- ventricular septations
Where do endocardial cushions develop?
Develop in the atrioventricular and conotruncal regions
Endocardial cushions assist in the formation of what?
The atrial and ventricular (membranous septa), AV Canals, Valves, Aortic and pulmonary channels
At the end of week 4, atrioventricular endocardial cushions appear where?
At the AV Canal; 2 lateral AV cushions appear on the right and left side of the canal
When is the complete division of the canal into the right and left AV orifices final?
At the end of week 5
What is the role of the endocardial cushion? What eventually occupies the resulting canals?
- Form a barrier between the atria and ventricles
- Right-left division of the canal
The resulting canals are eventually occupied by the mitral and tricuspid valves
When does ventricular septation occur?
At the end of Week 4
The ventricular septum is formed by what?
The outgrowth of the muscular ridge at the interventricular foramen; 2 primitive ventricles expand; medial wallas become apposed and merge
How does the ventricular septum grow?
Upward from the apex of the heart to the base of the heart
What is the space above the membranous septum called?
Interventricular foramen
When does the interventricular foramen shrink?
When the conus septum is complete
What closes the foramen during ventricular septation?
Outgrowth of tissue form the endocardial cushion along the top of the muscular interventricular septum closes the foramen; fuses with the abutting part of the conus septum
At what day do the paired atria fuse together to form a common atrium
AT day 27-28
Atrial septation occurs simultaneously and in cooperation with what?
Ventricular septation
Atrial septation lasts how many days?
Approx 10 days
What is the first portion of the septum primum?
Sickle-shaped crest grows from the roof of the common atrium
What is the ostium primum?
Formed by the opening between the lower rim of the septum primum and the endocardial cushions
what forms the ostium secundum?
Apoptosis (cell death) makes perforations in the upper part of the septum primum
When do opposing ridges appear in the truncus?
By the 5th week
What divides the truncus into aortic and pulmonary channels?
Aorticopulmonary septum
Semilunar Valaves
Small tubercles found on main truncus swellings; tubercles hollow out on the upper surface
At what day are the valves fully developed?
Day 55
