Embryology

Question 1

What starts the beginning of the heart tube?

Answer 1

Blood islands induced by underlying endoderm -> secrete VEGF

Question 2

How do the heart tubes receive bloodflow?

Answer 2

Inflow/inferior: Sinus venosus (collects from yolk sac, placenta, body) -> Vitelline veins

Outflow/superiorly: dorsal aortas fuse into aortic sac

Question 3

How is the singular primitive heart tube formed?

Answer 3

Lateral folding of embryo

Question 4

List the 4 segments (between the aortic sac and sinus venosus) of the primitive heart tube from cranial –> caudal

Answer 4

Truncus arteriosus, Bulbus cordis, primitive ventricle, primitive atrium

Question 5

After looping, how does the atrium communicate with the ventricle?

Answer 5

Atrioventricular canal

Question 6

Explain the transition that the L and R sinus horns undergo

Answer 6

Equal size at first -> venous return shifts R -> R atria absorbs R sinus horn, L sinus horn recedes

Question 7

Which atria develops from more of the primitive atrium?

Answer 7

R atria

Question 8

Explain why atria have differing textures

Answer 8

Rough: primordial atrium

Smooth: vessels have been pulled in
R atria: vena cava
L atria: pulmonary veins

Question 9

Why is inflow dorsal to outflow?

Which ventricle (R or L) is closest to the inflow/outflow tract?

Answer 9

Atrium dorsal to bulbous cordis during looping.

The primordium of the R ventricle is closest to outflow tract

The primordium of the L ventricle is closest to inflow tract

Question 10

What is the auricle?

Answer 10

Remainder of rough/primitive pt of atria

Question 11

What is the oblique pericardial sinus and when does it form?

Answer 11

Forms as L atria expands and absorbs pulmonary veins

“cull de sac”

Question 12

Which aortic arch is missing from the arched vessels?

Answer 12

Aortic arch 5

*Sprouts from aortic sac, bilaterally symmetrical system of arched vessels

Question 13

What does the 4th, 6th and 3rd aortic arch form?

Answer 13

4th:
R: R subclavian
L: aortic arch

6th aortic arch: Recurrent laryngeal nerve
R: R pulmonary artery
L: L pulmonary artery and ductus arteriosus

3rd: internal carotid arteries

Question 14

Describe the process of septation between the atria

Answer 14

1. Septum primum grow towards endocardial cushions, narrowing foramen primum
2. foramen secundum forms in septum primum, foramen primum closes
3. septum secundum develops downwards to R of septum primum, leaves a shunt between called foramen ovale

Question 15

Briefly describe the process of ventricular septation

Answer 15

Muscular IV septum grows up, leaving IV foramen

Aorticopulmonary septum rotates and fuses with muscular IV septum -> forms membranous IV septum and closing IV foramen

Question 16

What does the Aorticopulmonary septum do?

Answer 16

separates ascending aorta and pulmonary trunk

Question 17

What separates the primitive ventricle from the bulbus cordis?

Answer 17

Bulboventricular sulcus

Question 18

What does the following form?

a) truncus arteriosus
b) bulbus cordis
c) primitive ventricle/atria
d) L sinus horn
e) R sinus horn
f) endocardial cushions
g) primitive pulmonary vein

Answer 18

a) ascending aorta and pulmonary trunk
b) Smooth parts of L and R ventricle
c) Trabeculated pt of both ventricles/atria
d) coronary sinus
e) sm part of R atria
f) atrial septum, membranous IV septum, semilunar valves
g) Sm pt of L atria

Question 19

What forms the SA and AV node?

Answer 19

SA: wall of sinus venosus (R atria), myocardial cells organize/synchronize

AV node: myocardial cells specialize in the AV septum

Question 20

What causes patent foramen ovale and what can it cause?

Answer 20

failure of septum primum and secundum to fuse post birth

*-> paradoxical emboli

Question 21

What are the 4 congenital defects associated with Tetralogy of fallot?

Answer 21

Ventricular septal defect, pulmonary valve stenosis, misplaced aorta, RV hypertrophy