During inspiration, the diaphragm moves down, expanding the thoracic cavity, resulting in a decreased intra-thoracic pressure and a subsequent expansion of the lungs.

吸气过程中，膈肌向下移动，胸腔扩张，导致胸腔内压力降低，随后肺部扩张。

As the inferior vena cava passes through both abdominal and thoracic cavities, an increase in abdominal pressure together with a decrease in thoracic pressure squeeze the blood upward- toward the heart.

当下腔静脉同时通过腹腔和胸腔时，腹腔压力增加和胸腔压力降低会将血液向上挤压—流向心脏。