Quiz 3 - Cardiac Embryology (ONLY TESTED SECTIONS) Flashcards Preview

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Flashcards in Quiz 3 - Cardiac Embryology (ONLY TESTED SECTIONS) Deck (35):

where does the heart form?

-visceral layer of the lateral plate mesoderm at the cranial end of the embryo (the "cardiogenic region")


angiogenic cell clusters

-coalesce to form two tubes
1. endocardial tubes (lateral)
2. dorsal aortae (medial)

*the endocranial tubes and dorsal aortae maintain a connection cranially


during folding, what happens in regard to the endocardial tubes?

-yolk sac is incorporated into the embryo, allowing the endocardial tubes to come together in the ventral midline of the embryo, where they fuse into a single primary heart tube, except at their caudal end.
-meanwhile, dorsal aortae have remained in their original position (dorsal and towards the medial aspect of the embryo)


the developing heart is initially ____ to the septum transversum (diaphragm)



longitudinal folding of the embryo does what in regard to the endocardial tubes?

-forces them into the thoracic region of the embryo
-also causes the developing heart to come to lie cranial to the septum transversum


after longitudinal folding, the heart is initially located ____ to the pericardial cavity



series of constrictions and expansions in the heart tube (21 days)

-starting at the caudal (venous/inflow) end these are the:
-sinus venosus
-primitive atrium
-atrioventricular sulcus
-primitive ventricle
-interventricular sulcus
-bulbus cordis


why is the heart tube forced to bend and twist on itself as it grows?

-because the cranial and caudal ends of the heart tube are anchored in the pericardial cavity


what does the forced patterned folding of the heart form?

-the cardiac loop, which in normal folding of the heart tube results in the ventricles coming to lie inferior and anterior to the atria


transverse cardiac sinus

-formed during cardiac looping
-represents the space between the inflow and outflow tracts of the primitive heart tube
-in an adult, there remains a passage between the venous (inflow) and arterial (outflow) tracts of the heart (e.g. between the aorta & pulmonary trunk [anterior] and the SVC [posterior]) called the TRANSVERSE PERICARDIAL SINUS.

**if you clamp this during cardiac surgery it will clamp off all arterial flow out of the heart


primary heart tube after looping

-after cardiac looping, there is still a single primitive atrium and a single primitive ventricle connected by a narrow AV canal.


separation of the heart into left and right circulations

4 stages which occur nearly simultaneously
1. division and shifting of AV canal
2. partitioning of the primitive atrium
3. partitioning of the primitive ventricle
4. division of the outflow tract (conus cordis and truncus arteriosus)


separation of the heart into left and right circulations
1. shifting of AV canal

-neural crest cells migrate into the developing heart and cause swelling of the endocardial mesenchyme (swollen areas = endocardial cushions)
-superior and inferior endocardial cushions eventually fuse and separate the AV canal into L and R canals
-abnormalities of endocardial cushions contribute to many cardiac malformations


separation of the heart into left and right circulations
2. partitioning of the primitive atrium

-first, a C-shaped piece of tissue called the septum primum grows from the dorsal wall of the primitive atrium towards the endocardial cushions. the opening formed by the free edge of the septum primum is the ostium primum.
-as the septum primum is fusing with the endocardial cushions (and closing the ostium primum), cell death occurs in the superior part of the septum producing an opening called the ostium secundum
-thus, even tho a septum forms, blood can still pass b/w the two atria
-meanwhile, another septum begins to form immediately to the right of the septum primum, the septum secundum


unlike the septum primum, the septum secundum...

-never forms a complete partition in the atrial cavity
-the opening that remains is called the foramen ovale
-blood flows b/w atria via foramen ovale and ostium secundum


separation of the heart into left and right circulations
3. partitioning of ventricles

-the interventricular septum has both a muscular and a membranous portion
-muscular component: made up of muscular tissue that grows from the floor of the ventricles towards the endocardial cushions
-membranous component: formed by further growth of the endocardial cushions and downgrowth from the aorticopulmonary septum.


separation of the heart into left and right circulations
4. division of the outflow tract

-major outflow tracts of the ventricles are divided by R and L truncoconal ridges that grow from the walls of the conus cordis and truncus arteriosus. They meet in the midline and fuse with endocardial cushions and muscular interventricular septum, forming the aorticopulmonary (spiral) septum
-the septum develops as a spiral, so this is why the pulmonary trunk and aorta twist around each other in the adult heart


fetal lungs are ____ until birth

-fluid-filled (non-functional)
-no reason to circulate blood thru them, so R-L shunts reroute fetal blood from pulmonary to systemic circulations
-fetal pulmonary circulation pressure = systemic circulation pressure


fetal pulmonary and systemic circulations linked by 3 shunts

1. foramen ovale: shunts blood from R to L atrium
2. ductus arteriosus: shunts blood from pulmonary artery to descending aorta
3. ductus venosus: shunts oxygenated blood from umbilical vein directly to the IVC, bypassing the liver


which shunt helps blood flow bypass liver in fetus?

ductus venosus


arterial and venous blood are ______ in fetal circulation



adult circulation

1. lo pressure pulmonary
2. hi pressure systemic

**no mixing of blood


what happens when the infant takes its first breath?

-the lungs expand, the pulmonary vessels open, and the resistance of pulmonary vasculature drops (increasing pulmonary blood flow)


opening of pulmonary circulation causes what changes to the septum primum?

-increased intra-atrial pressure forces the septum primum against the septum secundum, functionally closing the foramen ovale
-fusion of the septum primum and secundum (formation of fossa ovalis) occurs later


what happens to the ductus arteriosus after first breath?

-also closes after the lungs expand, to form the ligamentum arteriosum


what happens to the ductus venosus after birth?

-degenerates and forms the ligamentum venosum.


which fetal circulatory shunts are closed after birth?

-all three


obstetrical clamping of the umbilical vessels

-cuts off flow from the placenta
-the umbilical vessels close, forming the medial umbilical ligaments (remnants of the umbilical arteries) and the ligamentum teres hepatis (remnant of the umbilical vein)


patent foramen ovale (PFO)

-most common form of atrial septal defects (ASD)
-pts may have no symptoms or may have lower arterial blood oxygen content due to R-L shunting of atrial blood
-untreated: can result in pulmonary hypertension (if blood moves from LA to RA) with consequent RH hypertrophy
-another complication is increased susceptibility to arterial embolism. --> increases risk of tissue ischemia, including stroke



-results when the heart tube folds to the right instead of the left
-pts often present with a reversal of many organs (situs inversus)


ventricular septal defects (VSD)

-most common in membranous part of the interventricular septum


transposition of the great vessels

-aorta stems from RV
-pulmonary trunk stems from LV


patent ductus arteriosus (PDA)

-allows for abnormal circulation of blood b/w the aorta and pulmonary artery
-can result in backflow of systemic circulation blood into the pulmonary circulation
-untreated: can result in congestive heart failure (CHF)
-since ductus arteriosus closes following expansion and oxygenation of lungs, premature and hypoxic newborns are at higher risk for PDA


coarctation of the aorta

-severe constriction of the aorta in the region of the ductus arteriosus
-pre-ductal: above entrance of DA; DA persists
-post-ductal: below entrance of DA; DA obliterates


teratology of Fallot

-has 4 anatomical components
1. VSD
2. pulmonic stenosis (can be valvular or pulmonary)
3. over-riding aorta (aortic valve not restricted to LV)
4. RV hypertrophy