4. Development of the Cardiovascular System Flashcards
Where is the heart tube suspended in embryonic development?
In the pericardial cavity by a membrane that later degenerates.
What are the parts of the primitive heart tube?
Aortic roots, trunks arteriosus, bulbous cordus, ventricle, atrium, sinus venosus.
What occurs in looping of the primitive heart?
The heart tube continues to elongate, so has to bend to fit in the space. The cephalic portion bends ventrally, caudally and to the right. The caudal portion bends dorsally, cranially and to the left.
What does looping of the primitive heart achieve?
It puts everything in the right place:
Primordial of right ventricle closest to outflow tract.
primordial of left ventricle closest to inflow tract.
Atrium dorsal to bulbus cordis, so inflow is dorsal to outflow.
How do the atrium and ventricle communicate after looping?
Via the atrioventricular canal.
How does the sinus venosus develop?
The right and left sinus horns begin of equal size. The venous return shifts to the right hand side so the left sinus horn recedes. The right sinus horns is absorbed by enlarging right atrium.
What does the right atrium develop from?
From most of the primitive atrium. Receives venous drainage from the body and the heart.
What does the left atrium develop from?
A small portion of the primitive atrium, from absorbing proximal parts of the pulmonary veins. It receives oxygenates blood from the lungs.
When is the oblique sinus formed?
When the left atrium expands and absorbs the pulmonary veins.
Describe foetal circulation.
Oxygenated blood empties into the right atrium from the mother via the placenta and umbilical vein. The blood by-passes the lungs as they are non functional at the moment. The blood returns to the placenta via the umbilical arteries.
What are the aortic arch derivatives?
4th arch - right is proximal part of right subclavian artery, left is arch of aorta.
6th arch - right is right pulmonary artery, left is left pulmonary artery and ductus arteriosus (connection ebtween pulmonary artery and aorta).
What are the recurrent laryngeal nerves?
The nerves corresponding to the 6th artery from the aortic arch. They turn back on themselves and innervated the larynx.
Where does the left recurrent laryngeal nerve hook?
Around the shunt between the pulmonary trunk and aorta.
What does folding of the embryo do the the developing heart?
Lateral folding creates the heart tube and cephalcaudal folding brings the tube into the thoracic region.
