Untitled Quiz

Development of the Heart

• The cardiovascular system is the first functioning system, with the heart starting to contract by day 22 of gestation.
• The heart develops from two heart tubes that fuse to form a single heart tube.
• The heart tube shows 5 expansions: sinus venosus, common atrium, common ventricle, bulbus cordis, and truncus arteriosus.
• The heart tube undergoes cardiac looping, forming a U-shape, then an S-shape, and finally taking the shape of the heart chambers.

Sinus Venosus

• The sinus venosus consists of a body and two horns, each receiving three veins: umbilical vein, vitelline vein, and common cardinal vein.
• The derivatives of the sinus venosus are the posterior wall of the right atrium and the coronary sinus.

Development of the Atria

• The right atrium develops from the common atrium, right half of the atrioventricular canal, and sinus venosus.
• The left atrium develops from the common atrium, left half of the atrioventricular canal, and pulmonary veins.

Formation of the Interatrial Septum

• The interatrial septum is derived from the septum primum and septum secundum.
• The gap between the septum secundum and septum primum is called the foramen ovale, which closes just before birth.

Development of the Ventricles

• The ventricles develop from the bulbus cordis and common ventricle.
• The interventricular septum is formed, comprising a muscular part and a membranous part.

Truncus Arteriosus

• The truncus arteriosus divides into the ascending aorta and pulmonary trunk by the aortico-pulmonary septum.

Congenital Anomalies of the Heart

• Dextrocardia: the apex of the heart is directed to the right.
• Atrial septal defects (ASD): a mixing of oxygenated and deoxygenated blood leading to cyanosis.
• Ventricular septal defects (VSD): presence of a foramen in the muscular/membranous part.
• Tetralogy of Fallot: a combination of VSD, pulmonary stenosis, right ventricular hypertrophy, and overriding aorta.
• Transposition of great arteries (TGA): aorta arises from the right ventricle, and pulmonary trunk from the left ventricle.

Fetal Circulation

• Oxygenated blood from the placenta passes through the left umbilical vein to the left branch of the portal vein and then to the inferior vena cava (IVC) via the ductus venosus.
• Deoxygenated blood from the upper part of the body enters the right atrium from the superior vena cava (SVC).
• Blood circulation changes after birth, including the closure of the foramen ovale, ductus arteriosus, ductus venosus, left umbilical vein, and umbilical arteries.

Applied Anatomy

• Patent ductus arteriosus (PDA) causes mixing of oxygenated and deoxygenated blood, leading to cyanosis.