Sac

〈生〉囊,液囊英释中释nA sac is a small part of an animal's body, shaped like a little bag. It contains air, liquid, or some other substance.

1 embryo sac,胚囊

2 yolk sac,（等于yolk bag）卵黄囊

3 lacrimal sac,[解]泪囊

4 air sac,气囊；肺泡；肺胞囊

5 yolk sac tumor,卵黄囊瘤；卵巢内胚层窦瘤

1 The lungs consist of millions of tiny air sacs..肺包含数百万个小肺泡。