Embryology of heart Flashcards
Why does the heart form in embryo
Embryo can no longer supply it nutritional and oxygen requirements by diffusion
Heart develops as an efficient method of acquiring oxygen and nutrients from maternal blood and disposing of CO2 and waste products
When the the heart first start to beat and first start to pump blood
First start to beat at 21-22 days and first start to pump blood at 24-25th days
What is Vasculogenesis
Formation of new vascular channel by assembly of individual cell precursors called angioblasts
The major vessels, including dorsal aorta and cardinal veins are formed by this
What is Angiogenesis
Formation of new vessels by budding and branching from pre-existing vessels
How does the cardiogenic region form
Progenitor heart cells migrate through the primitive end streak during gastrulation to form mesoderm and migrate to splanchnic layer of lateral plate mesoderm
Forms horseshoe shaped cluster of cells called primary heart field
The cells are induced by the underlying endoderm to form cadriac myoblasts and blood islands that will form blood cells and vessels
where do proginator heart cells originate
Epiblast, adjacent ti the cranial end in the primitive streak
How does primitive heart tube form?
Lateral folding of the embryo brings the 2 endocardial tubes together to form a single endocardial tube
What unites to form the unpaired descending aorta of the adult
right and left dorsal aortas
why does the heart tube bend?
Bulbus cordis and ventricular parts elongate rapidly
But arterial and venous ends are fixed by pericardium
how are the atria and ventricle partitioned
Endocardial cushions form on the dorsal and ventral walls of the AV canal
Endocardial cushions approach each other and fuse
Divides AV canal into right and left canal
partially seperating primordial atrium and primodial ventricle
What is the septum primum
cresent-shaped membrane that divides common atrium into right and left
What is the foramen primum
Gap between the edge of the septum primum and endocardial cushions
Allows blood to pass from left to right
Gets progressivly smaller and disappeares
What do the small perforations in septum primum form
joined up to form foramen secundum
What is septum secundum
A 2nd thick cresent shaped muscular fold
Adjacent to septum primum
Grows down and overlaps the foramen secundum
How does the valve of the foramen ovale form
degradation of septum primum
Why can blood flow from right to left through foramen ovale
right atrium at higher pressure than left
what happens to foramen ovale after birth
fuses with septum secundum forming fossa ovalis
what is mainly involved in dividing the primordial ventricle
Muscular interventricular septum
How does the interventricualr foramen close
Formation of membranous interventricular septum, which merges with muscular interventricular septum
What opens communication between ventricles and either pulmonary trunk or aorta
fusion of interventricular septum with aorticopulmonary septum
How are the aorta and pulmonary trunk separated
Bulbar ridges and truncal ridges develop in the bulbis cordis and truncus arteriosus respectively
ridges grow and fuse at the same time
causes 180 spiralling of the outflow tract creating the sprial shaped septum that makes the seperation
what are the 3 pairs fo vessels bringing venous blood to the heart
common cardinal veins
umbilical veins
vitelline veins
where does the vitelline vein come from
from yolk sac and developing gastrointestinal tract
how is common cardinal vein formed
formed by the union of the anterior and posterior cardinal veins
where does the blood in the common cardinal vein come from
Posterior cardinal vein - trunk
Anterior cardinal vein - head region
What happens when umbilical vein approaches the liver
Some blood enters liver sinusoids by mixing with portal vein
Rest passes through the ductus venosus behind the liver to enter the IVC
deoxygenated blood brought from lower limb in IVC mixes with the highly oxygenated blood from the placenta
What happens to the oxygenated blood that enters the right atirum
mostly shunted through the foramen ovale
What vessel moves the blood from the pulmonary trunk across to the decending aorta
ductus arteiosus
