Cardio Devo Flashcards
Where are Cardiac Precursors located?
Where are the specification and migration signals from?
Splanchnic Mesoderm
Anterior Endoderm
What is acardia and its cause?
Lack of heart formation due to mutation in Nkx2.5 (Tinman)
What do precursor cells in the heart field express?
Nkx2.5
Where is the endocardial heart tube located?
Bilaterally adjacent to foregut
How is the ventral heart formed? How are the heart primordia united?
Heart initially is cranial to the brain but folding in the cranial-caudal plane pulls the heart down to be ventral and inferior to head
Folding in the transverse plane unites the heart primordia in the midline
What is ectopia cordis? What causes it?
Heart is outside of body
Anterior thoracic wall fails to close properly
What is the pentalogy of cantrell?
- Ectopia cordis
- Ventricular septal defect
- Sternal cleft
- Diaphragmatic hernia
- Omphalocele
These all common to a body wall closure defect
What is important to know about the classical concept of heart tube formation?
It’s wrong.
What does the primitive heart tube become? What neighbors the primitive heart tube? Do the primitive heart segments become the mature chambers?
Primitive left ventricle
The arterial and venous poles which result in the other primitive heart segments
Do the primitive heart segments become the mature chambers? ⇒ No
Where is the secondary heart field located? What does it originate from? What is the master gene for it? What is its purprose?
Medial and dorsal to the primary heart field
Originates from splanchnic mesoderm
Isl-2 is master gene
Allows for elongation of the Primiitive heart ventricle, outflow region, primordial atrium, AV canal, sinus venosus
What are the layers of the primitive heart tube? What is the external fourth layer?
From inside to outside:
Endocardium
Cardiac jelly - ECM of GAGs and glycoproteins
Myocardium
Proepicardilal organ coming from coelomic epithelium and
What do cardiogenic precursors become?
- Mesoderm:
- Endocardial Endothelial cell which also form Cushion cells
- Atrial myocyte
- Ventricular myocyte which also forms Purkinje Fibers
- Neural Crest: Aortic Smooth Muscle Neuron
- Proepicardium:
- Coronary smooth muscle
- Endothelial cell
- Fibroblast
Where does venous inflow enter? What are the major veins, what do they drain, and is the blood oxygenated?
Venous inflow enters sinus venosus
Umbilical veins - Placental blood, O2 rich
Vitelline veins - Gut blood, O2 poor
Common cardinal veins - Blood from head and trunk, O2 poor
Where does arterial outflow start? Where does the aortic sac flow to?
Arterial outflow from primitive RV
- Aortic sac - Pharyngeal arch arteries
What is the first step in chamber formation and partitioning?
Cardiac looping
When does the primitive heart tube begin to loop? Which direction does it loop toward? Where is the apex of the loop located?
Looping begins soon after heart tube formation
Loops typically to right
Apex of loop located between primitive and right ventricle
What does right torsion help result in? What happens to the chambers during looping?
Right torsion helps form the inner and outer curvatures
During looping atria and ventricle chambers expand due to ballooning
What is dextrocardia? What is the cause of this? What is it typically associated with?
Right-sided mirror image heart
Turns left due to a cilia abnormality which doesn’t force the heart to twist to the left
Associated with situs inversus (all of abdominal organs flipped), 5-10% have other cardiac abnormalities (TGA)
What are changes resulting from early phase looping and torsion?
- Proper anatomical relationships between segments
- Outflow and inflow regions brought together
- Outflow region forms and elongates into proximal and distal regions
- Distal outflow region continuous with aortic sac
What changes result from late phase looping and torsion?
Caudal and cranial limbs contact at AV canal level via bending at inner curvature
Proximal portion of the outflow region is “wedged” into the AV canal (due to twisting/torsion)
What is the timeline of heart beating?
Begins to beat at 21-22 days: Initially back and forth flow
Flow becomes unidirectional by day 26
2 separate streams leave the heart by day 28
Timeline of development of right atrium
Definitive right atrium forms from primitive right atrium and parts of sinus venosus
Day 22 - Right horn of SV connects to right side of primitive atrium, left horn to left side of atrum
Day 24 - A common SV opens into atrium via the sinoatrial opening, sinoatrial opening flanked by right and left valves
Weeks 5-8: SV is absorbed into the right atrium and venous connections to the SV are lost or remodeled
- Left (proximal) and right umbilical and left vitelline vein atrophy
- Left SV becomes a tributary of the right SV
- Anastomosis forms between the left and right anterior cardial veins
Where do each of these come from?
- Coronary Sinus
- Crista Terminalis
- Valve of the IVC
- Valve of CS
- Smooth Area of RA
- . IVC terminal portion
- SVC
- Auricle
- Left horn of SV
- Rt valve of SV
- Rt valve of SV
- Rt valve of SV
- Absorption of SV, primarily the Rt. Horn
- Rt Vitelline Vein
- Rt Common Cardinal and Proximal Anterior Cardinal Vein
- Primordial Atrium
What is the formation of the definitive left atrium?
Absorption of the pulmonary veins and the primitive
