Development Of Cardiovascular System

Question 1

When is the cardiovascular system active?

Answer 1

By the beginning of 4th week when the placenta is unable to meet the needs of the embryo

Question 2

Development of the heart begins…

Answer 2

Formation of primitive heart tube following folding of the embryo during end of third week
Lateral folding creates heart tube by bringing together 2 precursor regions, then cephalocaudal folding positions the heart tube in the future thorax
Initially, heart tube suspended within pericardial cavity by membrane then degenerates to allow further growth
Heart tube continues to elongate, begins lopping around day 23. Bulbous cordis moves centrally, caudallly and to the right
Primitive ventricle (caudal portion) moves dorsally, cranially and to the left

Question 3

Six regions of primitive heart tube

Answer 3

Aortic roots (arterial poles)
Truncus arteriosus
Bulbous cordis
Ventricle
Atrium
Sinus venosus (venous poles)

Question 4

Atria

Answer 4

At 4th week, sinus venosus causes inflow of blood to primitive heart, empties into primitive atrium. Receives venous blood from right and left sinus horns
Venous return then shifts to right side of heart causing left sinus horn to recede and form coronary sinus (drainage of venous blood from heart itself). Enlarged right sinus horn absorbed by growing right atrium, eventually forms part of inferior vena cava in adult
In left atrium, four pulmonary veins incorporated into left atrium forming smooth inflow portion of left atrium and oblique pericardial sinus

Question 5

Aortic arches

Answer 5

Early arterial system begins as a bilateral symmetrical system of arched vessels which undergo extensive remodelling to create the major arteries that exit the heart

Question 6

1st arch

Answer 6

Contributes to the maxillary, hyoid and stapedial arteries

Question 7

2nd arch

Answer 7

Contributes to the maxillary, hyoid and stapedial arteries

Question 8

3rd arch

Answer 8

Forms the common carotid artery and part of the proximal internal carotid artery

Question 9

4th arch

Answer 9

Right arch forms the right subclavian artery
Left arch forms part of the arch of the aorta

Question 10

5th arch

Answer 10

Either never forms, or forms incompletely and regresses

Question 11

6th arch

Answer 11

Right arch forms the right pulmonary artery
Left arch forms the left pulmonary artery and the ductus arteriosus

Question 12

Arches corresponding nerve during development

Answer 12

Recurrent laryngeal nerve (a branch of CN C) which is associated with the 6th arch
Right recurrent laryngeal nerve - initially hooks around the right 6th aortic arch. When the distal part of right 6th arch disappears, moves up to hook around the right subclavian artery (4th arch)
Left recurrent laryngeal nerve - hooks around 6th aortic arch. Distal part of left 6th aortic arch persists as the ductus arteriosum, nerve remains in this position