SYSTEMIC EMBRYOLOGY

Systemic Embryology: Development of Heart and Lung

1. Describe the formation of primitive heart tube

The primitive heart tube forms from the lateral plate mesoderm, specifically the splanchnic mesoderm, which differentiates into the cardiac mesoderm. The cardiac mesoderm undergoes a process called cardiac looping, where it elongates and forms a tube.

• Step 1 → Cardiac mesoderm differentiates from splanchnic mesoderm
• Step 2 → Cardiac mesoderm undergoes cardiac looping
• Step 3 → Primitive heart tube forms

2. Describe the formation of the atria and ventricles of the heart

The atria and ventricles develop from the primitive heart tube through a process called chamber formation. The atria develop from the proximal part of the primitive heart tube, while the ventricles develop from the distal part.

• Step 1 → Atria develop from proximal part of primitive heart tube
• Step 2 → Ventricles develop from distal part of primitive heart tube
• Step 3 → Chamber formation completes

3. Explain the embryological basis of major congenital anomalies of heart

Major congenital anomalies of the heart include atrial septal defect (ASD), ventricular septal defect (VSD), patent ductus arteriosus (PDA), and tetralogy of Fallot (TOF). These anomalies occur due to abnormal development of the heart during embryogenesis.

• ASD: Abnormal closure of foramen ovale
• VSD: Abnormal closure of interventricular septum
• PDA: Failure of ductus arteriosus to close
• TOF: Combination of VSD, pulmonary stenosis, right ventricular hypertrophy, and overriding aorta

4. Describe formation of lung

The lung develops from the lateral plate mesoderm, specifically the pleuropericardial folds, which fold inwards and form the lung bud. The lung bud undergoes branching morphogenesis, where it divides into smaller buds that eventually form the bronchi and bronchioles.

• Step 1 → Pleuropericardial folds form from lateral plate mesoderm
• Step 2 → Pleuropericardial folds fold inwards to form lung bud
• Step 3 → Branching morphogenesis occurs
• Step 4 → Bronchi and bronchioles form