sikiökaudelta

Sikiökausi, also known as the fetal stage, refers to the period of development in mammals following the embryonic stage. In humans, this stage begins around the ninth week of gestation and continues until birth. During the sikiökausi, the developing organism, now called a fetus, undergoes significant growth and maturation of its organs and systems.

Key developments during the sikiökausi include the formation of all major body parts, such as fingers, toes, and facial features. The nervous system continues to develop, and the fetus begins to move and respond to external stimuli. Organ systems like the digestive and urinary systems become functional. Bones begin to harden, and the fetus starts to gain weight.

The sikiökausi is characterized by rapid growth in size and weight. External genitalia become distinguishable, and by the end of this period, the fetus is typically capable of surviving outside the womb with medical assistance, although significant risks remain. The length of the sikiökausi varies depending on the species, with human gestation lasting approximately 40 weeks from the last menstrual period. This phase is crucial for preparing the fetus for life outside the uterus.