1A hollow, flexible structure resembling a bag or pouch.

一枝有墨水袋的自来水笔。

1. 1.1 A cavity enclosed by a membrane within a living organism, containing air, liquid, or solid structures.
   囊
   Example sentencesExamples

   • ‘Surfactant keeps the tiny air sacs in the lungs open,’ Hein says.
   • The yolk sac was completely absorbed, but the site of attachment was still visible.
   • Fistulas commonly extend from the rectal sac to the perineum or genital tract in a female, or to the urinary tract in a male.
   • If chemicals are splashed into the eye, the eye and the conjunctival sacs should be washed out immediately with copious amounts of water.
   • For example, the tiny air sacs in lungs expand more than seven times when you inhale.
   • The ink sac can make cleaning the squid a bit messy, but all it needs is a good rinse and it's gone.
   • Tests have also shown that if a needle is placed into the sac and touches the baby, the baby feels pain and will immediately move away.
   • Worst bit: having to take out the squid's ink sac.
   • This is particularly noticeable in the knee and hip where we have big fluid sacs.
   • These protein and lipid molecules are then transported inside lysosomes -- minute, balloon-like sacs within the cell.
   • In human beings, the testis is located outside the body in the scrotal sac.
   • And I think the blisters resemble pomelo pulp sacs.
   • At 8:30 AM, the obstetrician manually broke the patient's amniotic fluid sac in an effort to speed up labor.
   • In the field of biology, biochemists have been studying vesicles, the small membrane sacs found within cells.
   • Each anther cone was gently agitated to release the pollen sacs into the dye solution.
   • The amniotic sac that contains your baby begins to form about 12 days after conception.
   • Fish make the popping noises by sending air through different chambers of their swim bladders, the inflatable sacs that help fish float.
   • Scientists also suspect that air pollutants might dampen the growth of alveoli, tiny air sacs in the lungs.
   • Sepia comes from the Greek word for the rich reddish-brown pigment obtained from a fluid that is secreted by the cuttlefish from their ink sac.
   • The female was fed one cricket per day until an egg sac was produced.
2. 1.2 The distended membrane surrounding a hernia, cyst, or tumor.
   （包住疝、囊肿或肿瘤的）肿胀膜
   Example sentencesExamples

   • They are swollen, fluid-filled sacs which often become enlarged and painful.
   • This procedure meant cutting directly into the back of the knee, tying the damaged artery above and below the aneurysm and scraping out the blood-filled sac.
   • PCOS is a hormone problem that can cause the ovaries to become enlarged and develop fluid-filled sacs.
   • On physical examination, a swollen, fluid-filled sac is noted and palpated over the olecranon.
   • Essentially, an ovarian cyst is nothing more than a fluid-filled sac, like a blister, on an ovary.
   • In the vicinity of this mass, there was a hernia sac.
   • If there is a recurrence (which unfortunately does often happen) then operative removal of the cyst and its sac becomes necessary.
   • As people get older, fluid-filled sacs, called ‘cysts,’ can form in the kidneys.
   • Prior to this Claudius Amyand, physician to Queen Anne, in 1736 successfully removed an acutely inflamed appendix from inside the hernial sac of a young boy.
   • A cyst is a fluid-filled sac that can grow in any part of the body.
   • In the distal folds of the hernia sac, a small erosion was noted.
   • A breast cyst is a fluid-filled sac, like a tiny balloon, inside the breast.
   • If the leak persists or the aneurysmal sac enlarges, intervention becomes necessary.
   • A visit to the local hospital did not improve matters as the doctor inadvertently punctured a small sac in his elbow which required extensive treatment back in Melbourne.
   • Alternatively, they can be drained with a needle and syringe, although the sac of the hydrocele may fill with fluid again after a few months.

(in the US) Strategic Air Command.

(in the RAF) Senior Aircraftman or Senior Aircraftwoman.