Answer:
At 20 weeks gestation, the cellular structure of the __________ of the fetal lungs is complete.
Step-by-step explanation:
The alveoli are tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place. These structures play a crucial role in respiration, allowing for efficient gas exchange between the lungs and the bloodstream. The development and maturation of alveoli are essential for the proper functioning of the respiratory system.
By 20 weeks gestation, the cellular structure of the alveoli has reached a stage of completeness. However, it is important to note that full lung development and the ability to function independently typically occur closer to the end of pregnancy, around 34 to 36 weeks gestation. At this stage, the surfactant, a substance that helps keep the alveoli open and prevents lung collapse, is also adequately produced.