CVS development Flashcards
When does the formation and looping of the primitive heart tube take place?
Week 4 after fertilisation
What event forms the primitive heart tube?
Lateral folding of the embryo
What event moves the primitive heart tube and diaphragm into the thoracic region?
Cephalo-caudal folding of the embryo
Name the 5 regions of the primitive heart tube:
1) Aortic roots
2) Truncus arteriosus
3) Bulbus cordis
4) Ventricle
5) Atrium + Sinus venosus
What causes the primitive heart tube to loop?
- Continued elongation of the tube, but within constricting pericardial sac
Where is the primitive heart tube tethered?
At cranial and caudal ends
What happens to the cephalic portion of the primitive heart tube during looping?
Moves ventrally, caudally, and to the right
What happens to the caudal portion of the primitive heart tube during looping?
Moves dorsally, cranially and to the left
Name the parts of the primitive heart tube which gives rise to the right atrium:
- Most of the primitive atrium
- Sinus venosus
What structures form the left atrium?
- Small portion of primitive atrium (forms left auricle)
- Proximal parts of pulmonary veins
The recurrent laryngeal nerves are branches of which cranial nerve?
Cranial nerve X (Vagus nerve)
Which recurrent laryngeal nerve becomes looped around the ductus arteriosus?
Left recurrent laryngeal nerve
What is the first process in septation of the heart?
The junction between the atrium and ventricle becomes constricted, creating a narrow atrioventricular canal
Name the cushions which form in the atrioventricular canal, and divide the heart into left and right canals:
Endocardial cushions
Describe inter-atrial septation:
- Septum primum grows down towards endocardial cushions
- Ostium secondum forms in the septum primum
- Septum secondum grows down in a crescent shape (hole = foramen ovale)
Is the foramen ovale in the septum primum or secundum?
Septum secundum
Why is the foramen ovale shunt so important to foetal life?
- Allows blood to flow from right atrium to left atrium
- Allows blood to bypass the lungs
- Protects underdeveloped lungs
Describe inter-ventricular septation:
- Muscular portion grows upwards towards endocardial cushions, leaving a small primary interventricular foramen
- Membranous portion derived from the endocardial cushions fill the gap
What is the most common defect of inter-ventricular septation?
Undeveloped/faulty membranous portion
What are the 2 different parts to the inter-ventricular septum?
1) Superior membraneous portion
2) Inferior muscular portion