Wk.3 L1 - Cardiovascular Development (Heart)

Question 1

LO

Answer 1

1. Briefly describe the adult heart
2. Describe the stages of embryological development of the heart structures
3. Identify fetal heart regions and structures, and relate them to adult heart

Question 2

Adult Heart

Answer 2

• 4 chambers
• 4 valves

Septum: Wall dividing LHS & RHS

2 Outflows:
- Aorta (Systemic)
- Pulmonaty (lungs)

Question 3

Primitive Heart Tube Formation

Answer 3

~Day 20 Endocardial tubes form

1. By day 22 the Endocardial Tubes fold together to form a single Heart Tube
2. Once Heart Tube forms, it contains 2 cell types:
   - Endothelial cells (inside)
   - Myocardial cells (outside)
   Heart beat starts

Question 4

Heart tube looping

Answer 4

• Endocardial tubes have blood flow from bottom to top of the tubes
  1. The Tubes fuse together to form the heart tube
  2. The Heart tube then starts folding in on itself after day 22
  3. After folding, the Atriums and Ventricles form

Atriums: Bottom of tube folds up
Ventricles: Mid of tube folds down

Question 5

Heart Tube regions

Answer 5

[heft]
5 main regions, precursers for the heart
Aortic arch = Aorta & Systemic system

• Aortic sac
  1.Truncus Arteriosus (TA)
• Endocardial cushion
  2.Bulbus Cordis (BC)
  3.Primitive Ventricle (PV)
• Endocardial cushion
  4.Primitive Atrium (PA)
  5.Sinus Venosus (SV)

Primitive venous system:
- End of venous system where blood entres heart again

Question 6

Endocardial cushions

Answer 6

Between TA & BC and PV & PA

• Endocardial Cushions are populations of mesenchymal cells (inside the tube)
• Regions of the Heart tube that form the internal structures of the heart and drive chamber seperation

Question 7

PA & PV cushions forming the chambers of the heart

Answer 7

Supeior and inferior walls of the heart tube grow in towards eachother and pinch down the middle to seperate the lateral sides

The bridge down the centre is called the Septum Intermedium (AV Septum)
- Blood now flows down the L&R atrioventricular canals

[heft]

Question 8

Heart chamber seperation (PA&PV cushion)

Answer 8

The AV septum acts as a central point

Interventricular septum:
1. Grows from the inferior section of the ventricle up towards the
2. Interventricular Septum joins the AV septum to seperate the L&R ventricles

Foramen Ovule:
1. At the same time, the Septum Premium grows down from the superior section of the atrium and meets superior growths of the AV sepetum in the middle of the atrium
2. The premium septum doesn’t join up with the AV septum to allow blood to flow from the right to left atrium
3. This is because the blood doesn’t go into the lungs yet.

Valves:
- The lateral sides of the heart grow in towards the AV septum to form the two valves seperating the atria and ventricles

Question 9

Outflow tract seperation (TA & BC cushion)

Answer 9

• Seperates the blood leaving the heart (systemic Vs. pulmonary)
• Forms from the TA&BC endocardial cushion
• The endocardial cushion cells grow upwards towards eachother to form a bridge and spiral upwards
• Spiral septation occurs

Question 9

Spiral Septation

Answer 9

[heft]

• Forms the Aorticopulmonary septum and corotruncal septation starts
• Conotruncal septation forms the aorta and pulmonary trunk
• The bridges then fuse together and seperate
• As they seperate, they form two different outflow tracts
• The endocardial cushions growing in from all sides are precursers to the leaflets of the semi-luna valves
• 1 valve for pulmonary trunk
• 1 valve for aortic trunk