During organogenesis, major organs such as the heart, brain, kidneys, and lungs begin to form. Each organ system follows a specific timeline and pattern of development:
- The heart starts beating around the 22nd day after fertilization. - The brain and spinal cord begin forming by the end of the 3rd week. - The kidneys and urinary system start to develop around the 4th week. - The lungs begin their development by the end of the 4th week.
