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What major physical changes occur in a human embryo during the seventh and eighth weeks after conception?
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human development
Growth of the human fetus from the fourth month to the ninth month of pregnancy.
During the seventh and eighth weeks of development, the human embryo undergoes significant morphological changes as it transitions toward a recognizably human form.
By the end of the second month, the embryo reaches a length of approximately 30 mm (1.2 inches), marking the conclusion of the embryonic stage and the beginning of the fetal period. Key developments during this timeframe include:1
- External Features: The head, which is initially bent at an acute angle, continues to develop alongside the formation of olfactory pits. The external ears become more defined, forming around grooves located between the mandible and the second branchial arch.1
- Limb Development: Limb buds elongate and flatten at their distal ends. Constrictions appear on these buds, clearly separating paddlelike hand or foot plates from the cylindrical segments attached to the body wall, with upper limbs showing more advanced development than the lower pair.1
- Internal Organs: The heart and the rapidly growing liver become the primary ventral prominences of the body.1
- Structural Integration: The umbilical cord establishes itself as a distinct entity, positioned on the abdominal wall.1