개혓바닥 포즈 썸네일형 리스트형 늘었다 줄었다 하는 미국여자 유방 풍선껌을 불때마다 늘었다 줄었다 하는 유방 호흡기관의 원리 동영상 내용 The human respiratory system exchanges oxygen from the air, for carbon dioxide produced by the body. The center of the system is the lungs, two elastic cone-shaped sacks that nearly fill the chest cavity. The actual mechanism where the gas exchange occurs is the alveoli, a tiny cluster of air sacks. When we inhale through our nose and mouth, air passes thr.. 더보기 이전 1 다음
