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Flashcards in Heart Development Deck (44):

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

-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



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***