Development of the heart Flashcards
Understand the basic development of the heart. Describe how fetal circulation differs from that of the neonate. Understand the circulatory adaptations at birth. Describe some common congenital abnormalities of the heart.
What is the special about the development of the heart?
It is one of the earliest organs to develop, differentiate and function.
What does the heart develop from at day 18?
From the cranial end of the neural tube from cardiogenic mesoderm (lateral plate)
What does the cardiogenic mesoderm contain?
Blood islands of haemangioblasts and myoblasts.
What happens at 20 days?
The angioblast cell clusters form left and right endocardial tubes which are continually dorsally with the aorta and caudally with the vitello-umbilical vein.
What happens at 21 days?
The left and right endocardial tubes fuse together into a primitive heart tube.
What happens at 22 days?
The heart starts to beat and more structures begin to form such as: sinus venosus, paired primitive atria, atrioventricular sulcus, primitive ventricle, interventricular sulcus, bulbus cordis
What is the function of the sinus venosus?
Inflow
What is the function of the atrioventricular sulcus?
To separate the atria from the primitive ventricle
What is the function of the primitive ventricle?
becomes the left ventricle
What is the function of the interventricular sulcus?
Divides primitive ventricle from the bulbus cordis
What are the parts of the bulbus cordis?
Cranial - truncus arteriosus
Caudal - conus cordis
LV - aortic vestibule
RV - conus arteriosum
What is heart looping and when does it happen?
At 22 days after the structures have formed the heart lengthens but the ends are fixed so it is forced to bulge and twist in the pericardial sac
How does the septum form in the atrio-ventricular canal and when?
At 28 days 2 mesenchymal tissue swellings appear from the canal walls to form endocardial cushions. They grow and fuse dividing the canal into right and left.
What is the septum primum
On day 28 the septum primum appears (a tissue crescent) and grows from the dorsal atrial wall to the endocardial cushion.
How do the atria partition?
Before the septum primum is formed, the foramen ovale is open as the right atrium has a higher pressure. However at birth the left atrial pressure increases as the pulmonary vein empties into it and the septum primum is forced against the septum secundum so that they fuse together closing the foramen ovale and forming the common atrial septum.