When does the human heart form in body?

The human heart begins its development in the early stages of embryonic development, around the third week of gestation. Here is a brief timeline of the formation of the human heart:

1. Cardiac Crescent: During the third week of gestation, a group of cells called the mesoderm forms a primitive heart tube known as the cardiac crescent.

2. Linear Heart Tube: The cardiac crescent then folds into a linear heart tube, which starts pulsating and contracting, marking the beginning of the circulatory system.

3. Septation: The linear heart tube undergoes a process called septation, where it divides into four chambers: two atria (upper chambers) and two ventricles (lower chambers).

4. Valve Formation: As the heart develops, valves start to form within the chambers to regulate the direction of blood flow. The atrioventricular valves (tricuspid and mitral/bicuspid valves) control blood flow between the atria and ventricles, while the semilunar valves (pulmonary and aortic valves) regulate blood flow from the ventricles to the arteries.

5. Looping and Rotation: The heart undergoes a complex series of looping and rotation movements, which position the atria and ventricles in their final anatomical arrangement.

6. Blood Vessel Development: Blood vessels, including the major arteries and veins, develop alongside the heart to form the circulatory system. The heart pumps blood through the vessels to deliver oxygen and nutrients throughout the body.

7. Maturation: Over the course of embryonic and fetal development, the heart continues to mature and develop. By the end of the first trimester (week 12), the basic structures and functions of the heart are established.

Overall, the formation of the human heart is a complex and vital process that occurs early during embryonic development and continues to develop throughout gestation.