Heart Development Flashcards
at what week does heart development begin
week 3
the first sign of heart formation is a solid horseshoe shaped endothelial cord within the _____________
cardiogenic mesoderm
cardiogenic mesoderm is derived from what type of mesoderm
splanchnic mesoderm
describe the heart formation process known as vasculogenesis
angioblasts form cell clusters which turn into islands lined with endothelial cells, which form channels that fuse = solid horseshoe endothelial cord
when does the solid horseshoe shaped endothelial cord start to canalize
week 4
prior to the head fold, where is the primordial heart tube in reference to the opopharyngeal membrane
heart is rostral
what causes the formation of the horseshoe shaped endothelial cord to become the primordial heart tube (endocardial tube)
lateral body folding causes endothelial cord to fuse at the midline
what causes the primardial heart tube to move caudal to the oropharyngeal membrane
cranial caudal folding (head fold)
where is the primordial heart tube in reference to the pericardial cavity before and after head folding
before - ventral to pericardial cavity
after - dorsal to pericardial cavity
what vessel delivers oxygen to the fetal primordail heart from the mother ?
umbilical vein and cardinal vein
what is the function of the umbilical arteries in fetal circulation
output of deoxygenated blood back to mother
how oxygenated is the blood of the umbilical a. and v. in fetal circulation
umbilical v - partially deoxy
umbilical a. completely deoxygenated
what is the mesentary the suspends the primordial heart tube, when does this degenerate, and what does it form/become
dorsal mesocardium
- degenerates at day 22-28
- becomes transverse pericardial sinus in adult heart (known as the great vessel area)
what are the layers of the primitive heart tube from deep to superficial
- endocardium
- cardiac jelly
- myocardium (cardiac m.)
- epicardium (visceral pericardium_
as the heart tube elongates craniocaudally it forms dilations and constrictions. What are the 4 from dilations cranial to caudal
- Bulbus cordis
- primordial ventricle
- primordial atrium
- sinus venosus
what are the 2 components of the bulbus cordis and what do they become in the adult heart
- truncus arteriosus —-> pulmonary trunk and aorta
- conus cordis —-> right ventricle
what does the primordial ventricle become in the adult heart
left ventricle
what does thr primordial atrium become in the adult heart
- R and L auricles
- portions of atria
what does the sinus venosus become in the adult heart
coronary sinus and sinus venarum
what are the 2 main constrictions in the elongating heart tube during development, and what do the become in the adult heart
- bulboventricular sulcus —> primary interventricular foramen
- atrioventricular sulcus —> atrioventricular canal
when does the heart begin to beat
day 22 or 23
explain the orientation of how the cranial loop forms from the elongated heart tube, when does this occur
cranial end shifts ventral, caudal and to the right
caudal end shifts dorsal and superiorly
the formation of the the heart loop all occurs with the ________ cavity
pericardial
explain the path of circulation through the primordial heart starting at the sinus venosus
sinus venosus —> primordial atrium —> atrioventricular canal —> primordial ventricle (left ventricle) —-> interventicular foramen —-> right ventricle —-> conus cordis —> truncus arteriosus —> aortic sac —> pharyngeal arches —> dorsal aortae
when does the partitioning of the heart occur (partitioning into seperate atria and ventricles)
week 4-7
in the partitioning of the heart, what cells near the atrioventricular canal revert back to the mesenchymal state and proliferate, and why is this importnant
endothelial cells
-proliferation causes endocardium to bulge forming dorsal and ventral endocardial cushions
what is the importance of the dorsal and ventral endocardial cushions
As cushions get bigger they fuse forming the
-atrioventricular septum
once the atriooventricular septum is formed from the endocardial cushions, what remains to allow for circulation to continue
separate R and L atrioventricular canals
in partitioning of the atrium, what are the original two septa that fuse to form the interatrial septum
- septum primum
- septum secundum
of the septum of the interatrial septum, which develops first, and where does it develop from
septum primum
-develops from roof of primordial atrium like a moon crescent coming down
as septum primum continues to grow inferiorly it will fuse with ____________.
endocardial cushion
what is the opening left b/w septum primum and the endocardial cushions after fusion occurs
foramen primum
how does foramen secundum form ?
As perforations in septum primum
where is foramen secundum located in reference to foramen primum
cranial or higher than foramen primum
how does foramen ovale form ?
As septum secundum grows inferiorly to fuse w/endocardial cushions, it leaves an opening called foramen ovale
where does septum primum grow in relation to septum secundum
septum secundum grows to the right of primum, and grows much thicker
Blood circulation in the fetus after partitioning has occured flows strictly from R to L atria b/c it can avoid the pulmonary circuit. What 2 openings does blood flow through to do this ?
Goes R to L thorugh foramen ovale and foramen secundum
when does foramen primum close ?
gradually closes off as foramen secundum forms
when does the pulmonary bypass STOP ?
First breath of baby
After birth and the first breath, what happens to foramen ovale ?
Pressure in L atria exceeds R atria so by force foramen ovale is fused against septum secundum and it closes off.
-Becomes fossa ovalis
what is fossa ovalis
depression in wall of adult R atria - remmnant of foramen ovale in primordial circulation
what are the portions of the interventricular septum and what is the role of each
muscular portion - grows cranially towards endothelial cushions but doesnt fuse
membranous portion - fuses
where is the membranous portion of the interventricular septum derived from ?
mesenchyme of the endocardial cushion tissue
what is the most commom congenital heart defect
ventricular septal defect
- failure of interventricular septum to form
- results in mixing of arterial and venous blood*
