Development Of The Heart Flashcards
The heart develops from
paired endothelial strands - angioblastic cords (Solid cord of cells),
in the splanchnic mesoderm in relation to pericardial coelom (part of the intraembryonic
coelom),
Heart begin to develop during —week of development
3rd
The angioblastic cords canalize to form————-, which fuse to form——-
endocardial heart tubes
tubular heart.
To begin with fused endocardial heart tube is ventral to the———- and cranial to the———-
pericardial cavity
oropharyngeal membrane.
with head fold formation, pericardial cavity and tubular heart come to lie——-, in the future neck region
ventral to the foregut
pericardial cavity is ventral to the heart tube.
That why the heart is related ventral and anterior to esophagus
K
The heart tube invaginates into the———from its——
pericardial cavity
dorsal side.
With the formation of lateral folds, left and right endocardial heart tubes fuse to form
median fused tubular heart.
Invagination of the fused endocardial heart tube into pericardial cavity is such that lining Of pericardial cavity applied to the heart tube will form
visceral layer of serous pericardium (Epicardium),
lining of the rest of the pericardial cavity will form
parietal layer of serous pericardium
cavity of the original pericardial coelom will form the
pericardial cavity.
Mesenchymal tissue around the pericardial cavity forms the
fibrous pericardium.
lie outside the pericardial cavity
The cranial (Arterial) and caudal (venous) ends of the heart tube
The fused endocardial heart tube (Tubular heart) splits into left and right parts and also gets divided into
primitive atrial and
ventricular chambers.
Venous end of the heart tube (Sinus venosus) gets absorbed into the
right atrium.
Arterial end of the heat tube (Truncus arteriosus) divides into.
ascending aorta and pulmonary trunks
Blood flow in primitive heart
Sinus venosus Sinostrial valve Primordial atrium Atrioventrcular Ventricle Bulbous cord is Truncus arteriosus Aortic sac Dorsal aorta
The simple tubular heart develops enlargement
Atria and ventricles
The simple tubular heart develops enlargement (Atria and ventricles) and constrictions
bulboventricular sulcus and
atrioventricular sulcus
The simple tubular heart develops enlargement and constrictions and folds in such a way that,
ventricles lie in front of (Ventral) the atria, - and sinus venosus behind (dorsal) to atria.
atrioventricular canal is a
single wide communication between primordial atrium and primordial ventricle
Two thickenings, ventral and dorsal endocardial cushions develop in the atrioventricular canal in ventral and dorsal position.
T
These endocardial cushions grow towards each other and fuse to form
fused endocardial cushion
fused endocardial cushion which divides
the atrioventricular canal into right and left atrioventricular canals.
———grows towards fused endocardial cushion form the roof of the primitive atrium.
Septum primum
The passage between the lower end of the septum primum and fused endocardial cushion is the
foramen primum
foramen primum which
shunts blood from right atrium to left atrium
As the septum primum fuse with endocardial cushion, perforations appear in the upper part of the septum primum, to form
foramen secundum
foramen secundum which
shunts the blood from right atrium to left atrium as the foramen primum is now closed.
septum secundum develops on
the right side of septum primum. grows towards endocardial cushion
septum secundum it overlaps the foramen secundum such that an oval opening formed between them
Foramen ovale,
Foramen ovale, bounded by
lower free margin of septum secundum and upper free margin of septum primum
With further growth of septum secundum, it overlaps the septum primum on right side and convert the foramen ovale into a
slit-valve like opening.
When the blood pressure is increased in the right atrium (due to blood flow from sinus venosus into right atrium) flap like valve of foramen ovale (Septum primum), will deviate towards
left allowing the blood to flow to left atrium.
After birth when the pressure in the left atrium is increased (due to blood returning to it from lungs through pulmonary veins), it will push the valve of foramen ovale (septum primum) against the thick free margin of the septum secundum there by closing the foramen ovale.
T
The sinus venosus at the venous end of the heart tube receives blood from body of the
embryo (Cardinal veins), yolk sac( Viteline veins) and placenta (Umbilical vein).
sinus venosus opens into to primitive atrium on its
posterior wall.
Sinus venous will be absorbed into the wall of right atrium where it forms the
sinus venarum-smooth part of the right atrium.
The pulmonary veins develop as an
outgrowth
The pulmonary veins develop as an outgrowth from the- to—
atrial wall to the left of the septum primum.
As the left atrium expands, the pulmonary veins are absorbed into the atrial wall such that,
two initial branches of pulmonary vein now open separately into left atrium.
With further expansion of left atrium, pulmonary veins were further absorbed into atrial wall so that secondary branches of pulmonary veins (four in number) open directly into the left atrium.
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