Heart Development Flashcards
What makes up the first heart field?
Endothelial Precursor Cells (EPCs) clusters in splanchnic mesoderm + adjacent mesoderm
For the first heart field, EPC clusters in splanchnic mesoderm differentiate into?
Endothelial cells
Once the EPC clusters in the first heart field differentiate into endothelial cells. What will they form?
2 Endocardial tubes
What takes place to move the 2 Endocardial tubes towards the midline?
Lateral body folding
The 2 Endocardial tubes will ____ to form the simple tubular heart
Fuse
What 3 layers does the primitive heart (tube) walls consist of from innermost to outermost?
- Endocardium
- Cardiac jelly
- Myocardium
What is the cardiac jelly made of?
Extracellular matrix
Inflow of blood into the primitive heart is done by what 3 veins?
- Common cardinal vein
- Vitelline vein
- Umbilical vein
The 3 veins that bring blood to the primitive heart empty into sinus horns. Describe the pathway through the primitive heart from there.
Sinus Horns Sinus Venosus (L and R sinus horns) Primitive atrium AV region Primitive ventricle Outflow tract Aortic sac
Function of Dorsal Mesocardium?
Suspends the heart tube
What does the rupturing of the dorsal mesocardium create?
Transverse sinus (seen in adults)
What are the remnants of the dorsal mesocardium?
Proepicardial organ
What will cells in the proepicardial organ form?
Epicardium
What structural changes occur as the heart tube continues to grow?
Cardiac looping
Before cardiac looping takes place, describe the order of the heart tube from inferior to superior
Sinus horns Sinus venosus Primitive atrium Primitive ventricle Outflow tract Aortic sac
With cardiac looping, the primitive atrium will move where?
Cranially and dorsally to sit between the outflow tract and the dorsal pericardial wall
With cardiac looping, the outflow tract bends which way to create what?
Bends to the right to create the right ventricle
With cardiac looping, what is added to the cranial end?
Myocardium
With cardiac looping, what is created when myocardium is added to the cranial end?
- Conus Arteriosus
2. Truncus Arteriosus
Outflow of both ventricles occurs at the?
Conus Arteriosus
Outflow - aorta and pulmonary artery occurs at the?
Truncus Arteriosus
Development of a ______ lengthens the heart tube at both ends and is also required for cardiac looping
Second heart field
Where does the second heart field form?
Both ends of the rupturing dorsal mesocardium
What cell type in the PA region is necessary to maintain cardiogenic mesoderm proliferation in the second heart field?
NCCs
With the second heart field, what tissue type is proliferating?
Cardiogenic mesoderm
Ventricular inversion
Primitive ventricle folds to the right and the outflow tract folds to the left
= results in a right-sided, left ventricle
Heterotaxia
Any abnormal left-right development
Situs inversus
COMPLETE reverse symmetry of the heart AND GI organs!!
Is situs inversus asymptomatic?
YES
Situs ambiguous
Reversal of SOME organs (partial)
What is a type of situs ambiguous?
Visceroatrial heterotaxia
Visceroatrial heterotaxia
Right-sided heart with NORMAL GI tract
Is situs ambiguous (visceroatrial heterotaxia) asymptomatic?
NO - can be life - threatening
The sinus venosus opens into the?
Primitive atrium
The sinus venosus shifts toward the ____
Right
All that remains of the left sinus horn becomes the?
Coronary sinus
As the atrium enlarges, the sinus venosus only opens into the right atrium and is now called?
Sinoatrial orifice
The Right Common Cardinal Vein becomes the?
Superior vena cava
The Right Vitelline vein becomes?
Part of the Inferior vena cava
Tissue flaps develop on either side of the opening of the sinoatrial orifice and are known as?
Venous valves
The fold of the left sinus horn is a valve of?
Coronary sinus
Left valvular fold is a valve of?
Inferior Vena Cava
What form the SA node?
Right sinus horn and Right common cardinal vein
What form to partition the heart into 4 chambers and by what 2 mechanisms?
Septa
- Differential growth
- New tissue - endocardial cushion tissue
Differential growth makes which septa and what portion of them?
Atrial septum and Interventricular septum
- Muscular portions
Differential growth never fully _____ lumen
Closes
Describe how endocardial cushion tissue is made
- Myocardium secretes molecules into cardiac jelly
- Induces formation and proliferation of new mesenchymal cells derived from endocardium
= Endocardial cushion tissue
Endocardial Cushion Tissue makes what portion of septa and ridges in outflow tract?
Fibrous portions
AV septum separates?
Atrium from ventricle
What fuse to create the AV septum?
Superior and inferior endocardial cushion tissues
Endocardial cushion tissues also form what valves?
Tricuspid and Bicuspid valves
Conotruncal ridges in the outflow tract are made of what 2 things?
- NCCs
2. Endocardial cushion tissue
Why must the conus arteriosus be divided by a conotruncal ridge?
So blood exits the left and right ventricle through different vessels
What does the division of the truncus arteriosus by a conotruncal ridge create?
Aorta and Pulmonary artery
Persistent AV canal
Failure of AV septum fusion (superior and inferior endocardial cushion tissue) and NO AV valves
What disease is a persistent AV canal associated with and what are a few symptoms?
Down’s syndrome
- Intolerance to exercise, shortness of breath, cardiac congestion
During gestation, the blood entering the right atrium must bypass the lungs and enter the left atrium. Septa form that extend from the atrial wall to the?
AV region
Septum primum receives contribution from?
Dorsal Mesenchymal Protrusion (DMP)
Septum primum - Ostium primum
Hole near the AV region of the septum
- It is filled in and closed by DMP and endocardial cushion tissue
Septum primum - Ostium secundum
New hole forms near the superior region of the septum
Septum secundum is ____ than the Septum primum
Thicker
As the Septum secundum grows what does it overlap?
Ostium secundum
An opening that remains in the septum secundum?
Formen Ovale
Where is the foramen ovale?
Just above the AV septum in the septum secundum
What overlaps the foramen ovale?
Septum primum
What creates a 1-way flutter valve allowing right atrial blood into the left atrium but not the reversal?
Septum primum
After birth, pressures on the left side of the heart are»_space;> pressures on the right side of the heart. This pushes septum primum up against septum secundum and eventually?
Seals - closes foramen ovale
Describe the pathway of events for atrial septal defects if blood is allowed to move from left to right
Increased blood to right ventricle Increased blood to the lungs Lung damage Pulmonary resistance Right ventricle hypertrophy Blood moves from right to left = cyanosis
Ostium 2 (high atrial defect)
Hole due to excessive absorption of septum primum or inadequate development of septum secundum
Ostium 1 (low atrial defect)
Failure to fill in ostium primum with DMP and cushion tissue
What causes cyanosis?
Mixing of deoxygenated and oxygenated blood due to low O2 saturation of blood
Signs of cyanosis?
Clubbing of fingers
Bluish tint to skin, fingernail beds, lips
Fatigue
The AV canal shifts to the?
Right
AV canal shifts through what mechanism?
Myocardialization - outer myocardial wall thinned and further remodeling through apoptosis
Double outlet right ventricle
Both aorta and pulmonary artery exit the right ventricle accompanied by a VSD (ventricular septal defect)
Double outlet right ventricle is due to?
Insufficient AV canal shifting or cardiac looping
Conotruncal ridges are made of?
Cushion tissue
Conotruncal ridges spiral down ______ to ventricular septum
Outflow tract
Conotruncal ridges fuse to form?
Conotruncal septum
What are the cells involved in the conotruncal ridges?
NCCs and Endocardial cushion tissue
What does the Conotruncal septum divide?
Outflow tract:
Right ventricle -> Pulmonary artery
Left ventricle -> Aorta
What does complete closure/separates of outflow tract require?
Downgrowth of AV septum
Formation of conotruncal ridges
Interventricular muscular septum formation
