2) Embryology

Question 0

What does folding of the embryo do to the developing heart?

Answer 0

Lateral = Creates heart tube from 2 primitive endocardial tubes (come from blood islands)
Cephalocaudal = Brings heart tube into the thoracic region from cranial end

Question 1

Name the sections of the primitive heart tube from cranial to caudal? (6)

Answer 1

Aortic Roots
Truncus Arteriosus
Bulbus Cordis
Ventricle
Atrium
Sinus Venosus

Question 2

Describe looping of the primitive heart tube?

Answer 2

Tube constrained by the pericardial cavity
Bending during day 23 to day 28
Cephalic portion - Ventral, caudal and to the right
Cranial portion - Dorsal, cranial and to the left

Question 3

Functions of looping? (5)

Answer 3

1) Primitive right ventricle is closest to outflow tract
2) Primitive left ventricle is closest to inflow tract
3) Atrium is placed dorsal to bulbus cordis (inflow is below outflow)
4) Produces transverse pericardial sinus - arteries in front of veins
5) Atrium communicates with ventricle via atrioventricular canal

Question 4

Describe the developmental stages of the Sinus Venosus?

Answer 4

1) Right and left sinus horns equal in size
2) Venous return shifts to the right and left sinus horn recedes
3) Right sinus horn absorbed by the enlarging right atrium

Question 5

Describe the development of the atria?

Answer 5

RA develops from: most of the primitive atrium, sinus venosus and receives venous drainage from the body (VC) + heart (coronary sinus)
LA develops from: small part of primitive atrium, absorbs proximal parts of pulmonary veins, receives oxygenated blood from lungs

Question 6

How is the oblique sinus formed?

Answer 6

As left atrium expands it absorbs the pulmonary veins

“Cul de Sac”

Question 7

Describe the main differences of the foetal circulation?

Answer 7

Lungs are non-functional (uses shunt to bypass the lungs)
Receives oxygenated blood from the mother via the placenta
Returns deoxygenated blood back to the placenta

Question 8

Explain the foetal circulation?

Answer 8

O2 blood from Placenta -> bypass liver -> IVC -> RA -> LA -> LV -> Aorta -> Body -> Deoxygenated blood back to the placenta

Question 9

How are the Great Vessels formed?

Answer 9

Arterial systems begins as bilaterally symmetrical system of arches
Undergo extensive remodelling to create major arteries leaving the heart
Aortic arch 5 has no derivatives only 1-4 and 6 are connected to aortic sac attached to the primitive heart tube

Question 10

Aortic Arch derivative of the 4th arch?

Answer 10

R = Proximal part of right subclavian artery
L = Arch of the Aorta

Question 11

Aortic Arch derivative of the 6th arch?

Answer 11

R = Right pulmonary artery
L = Left pulmonary artery and ductus arteriosus

Question 12

Factors influencing the course of the nerve on the left and right side of the 6th aortic arch? (2)

Answer 12

1) Caudal shift of heart and expansion of developing neck region
2) Need for foetal shunt between pulmonary trunk and aorta

Question 13

Corresponding nerves for Aortic arch 4?

Answer 13

Recurrent laryngeal nerve (CN 10)
Right - descends to T1-T2
Left - descends to T4-T5

Question 15

Describe the course of the recurrent laryngeal nerves over the 4th aortic arches?

Answer 15

Right nerve - hooks around arch and turns back on itself

Left nerve - hooks around the shunt between the pulmonary trunk and aorta