Heart Development Flashcards
In the adult heart, blood with low oxygen concentration enters the (left/right), while oxygenated blood enters the (left/right) side.
low oxygenated (venous blood) = right oxygenated (arterial) = left
Do lungs function during fetal life?
No
In fetal life, oxygenated blood from _____ to _____
From placenta to RA
In early embryo, what start to differentiate into endothelial cells? What do they form?
Mesenchymal cells – form primitive blood cells (will eventually anastomose to form vascular system)
Where does the formation of primitive blood cells occur in early embryo?
At the wall of the yolk sac outside of the embryo proper
How does heart primordium form?
Differentiation of endothelial tubes withs ome blood cells
Where does heart primoridum originally form? What will occur due to location?
Originally placed above neural plate (above what will be brain). Requires tremendous movement and developmental rearrangement to relocate future heart
Growth of what organ is tremendous at stage of relocating the future heart?
Brain
During relocation of the future heart, what occurs so primitive heart changes position to what will become the definitive thorax?
Folding of the embryo
The endocardial tube is surrounded by what layer?
Epimyocardium–where functioning heart cells will be. (heart surrounded by myocardium wall, then outside will have epimyocardium)
The endocardial tube is initially connected to this structure, which will vanish
dorsal mesocardium
During endocardial heart tube development, you get paired endocardial heart tubes which will eventually fuse to form a single heart tube. What did these initial two tubes start as?
Angiogenetic cell clusters
What are the two ends of the heart tube?
Arterial and venous end
In between the arterial and venous end, what does the heart tube have? What is weird about the structures?
Primitive ventricles and atrium except they are in the incorrect order! (Ventricle on top of atrium). Will need further rearrangement
In the formation of the loop, what happens as result of bending the tube?
The atrium (bottom) will get pushed up and behind
What is the symmetry like in the fetal heart? How is this different from the adult heart?
Everything is symmetrical in the arterial and venous sides, even when the loop is introduced. They are asymmetrical in the adult heart.
After formation of the loop, what is formed?
Primitive canal (AV canal)
What will grow out to divide the canal in half?
Endocardial cushions
A primitive atrium and ventricle develop via the fusion of what?
Endocardial cushions –at this point, it resembles the adult heart more than ever before!
What are the endocardial (AV) cushions, and where do they come from? Function?
Subset of cells in the primordial heart. Major role in proper heart septation
The endocardial cushion gives rise to these two important structures of heart that are critical to proper formation of a 4-chambered heart
heart’s valves and septa
The endocardial cushions consists of these two:
dorsal and ventral
When do the endocardial cushions fuse into one?
Fusion occurred after atrium came up above ventricle during tube bending
Before birth, in which atrium is there higher pressure?
Higher pressure in Right atrium, lower in left.
How do you divide the atrium into two?
Via the septum primum and secundum
Describe action of septum primum. Why is there still no division?
Comes down from top, towards the fused endocardial cushion. Just as it’s about to meet the endocardial cushion, the initial segment at top will degenerate, so there is still no division
What does the septum primum form due to its growing/degeneration of top? How does help in transition process of blood source?
A hole/valve develops from R to L top side of heart. If higher pressure in R atrium than left, you get blood flowing across. When L pressure is higher than R, it slams shuts like a trap door. Makes use of this when want to change source from umbilical vein to pulmonary vein
Describe action of septum secundum
Will grow down where septum primum failed to seal off the two atrium.
What does the septum secundum functionally form?
A one way valve – if pressure is higher in RA, then blood will move from RA to LA by pushing the leaflet
What is on either side of the fused endocardial cushion?
A right and left atrioventricular canal
After the atrium is divided into two, is the atria and ventricle divided yet?
No, but there is a blueprint
What divides into the aorta and pulmonary trunk?
Truncus arterioris (just below the aortic arches on top)
What is one of the most common abnormalities?
Ventricular septum-divides the ventricles
What divide the tube intwo two compartments?
Ridges that grow outward, will come off different parts of the tube
How do ridges form the ventricular spetum
Ridges growing downward that divided the common trunk will come down to the fused endothelial cushion, leading to the muscular part of the intraventricular foramen
How does a ventricular septal defect occur?
Improper fusing of the bulbar ridges
How does division of the ventricles occur? (2 parts)
- muscular intraventricular septum will grow up to endocardial cushions, stops going all the way and leaves a hole
- membranous portion is developed on top to finish off the divison
Different regions of the heart develop under control of different ____
transcription factors
Arterial end of the heart will have a series of aortic arches that develop symmetricaly/asymmetrically
symmetrically
There will be selective degeneration and differential elaboration of aortic arches that cause asymmetric differentiation. Important ones to know:
- fourth arch = ?
- sixth arch = ?
4th - aorta
6th - pulmonary
Analagous to the aortic system, the venous system starts off symmetrical. But in adult, we know that all venous blood from SVC and IVC go to the RA> How does this occur? (4)
- Anastomoses will form between R and L side
- shunt of venous system develops (poorly understood)
- degeneration of selective structures
- changes in liver
trace the circulation of oxygenated blood before birth:
from ___ –> ___ –> enters liver and ____, the latter which enables bypass of the liver to enter the ____ via ____
From placenta –> umbilical vein –> enters liver and DUCTUS VENOSUS –> inferior vena cava –> RA
How does level of oxygenated blood carried by IVC and SVC differ before birth?
IVC carries highly oxygenated while SVC carries low in oxygen (no source of O2 in superior)
Pulmonary vascular resistance before birth is (high/low)
High. Won’t get blood flow from RA–>RV–>pulmonary trunk –> lungs
Ductus arteriosus is a shunt to bypass ___ to ____
pulmonary trunk to aorta (further relieves very high vascular resistance in pulmonary trunk
As states earlier, pressure is higher in RA than LA during fetal life. How does this effect blood flow?
Higher RA pressure will shunt blood to LA (via one way valve,) down to LV. The blood will then get pumped out to the aorta. This is good–oxygenated blood will get pumped out to rest of body
-note that some will get into RV and get pumped out
Lungs require this for proper development
Surfactant. Lipid molecule that reduces surface tension of the lungs–so they can inflate
What happens to pulmonary vascular resistance after birth? Effect?
Dramatically decreases, so it’s easier to get blood to and back from the lungs. Can now pump blood from right ventricle to lungs
How does the atria pressure dynamics change after birth? How does this effect the one way valve?
LA pressure will increase–will shut the one way valve
After birth, the following transformations occur in the three fetal shunts:
umbilical vein –> ?
ductus venosus –> ?
ductus arteriosus –> ?
umbilical vein –> ligamentum teres
ductus venosus –> ligamentum venosum
ductus arteriosus –> ligamentum arteriosum
What happens to the foramen ovale?
Shuts to form a fossa–complete separation between the two atriums of the heart
Mixing of blood high in oxygen with blood low in oxygen within heart (Before/After) birth. Explain both scenarios
Before. Oxygenated blood carried by umbilical vein through ductus venosus to IVC to RA. Get deoxygenated from SVC
After birth-oxygenated blood enters LA via pulmonary vein –no mixing of blood within heart
iCMs (induced cardiomyocytes) +
Importance in future approaches to adult heart disease?
resemble cardiomyocyte cells. Get reprogramed by TF’s (Gata4, MEF2c, TBx) from fibroblasts. Have spontaneous contraction and action potentials]
can’t regenerate heart cells very well when lose them during heart attack, so can do transplantation in vivo.
What gives rise to the aortic arches?
Truncus arteriosus (common outflow channel for RV and LV)
blood from left ventricle enters aorta which passes to the right (in front of/behind) the pulmonary artery
behind
Blood from the RV enters the pulmonary artery which passes (in front of/behind) the aorta, turning (anteriorly/posteriorly) on the left side of mediastinum
in front of the aorta, passes posteriorly
3 fetal shunts and function:
- foraman ovale: allows blood flow from RA to LA
- ductus arteriosus: blood that got into RV to bypass pulmonary circulation
- ductus venosus: blood from umbilical vein to IVC, bypassing liver
