wear your heart on your sleeve. to make your feelings and opinions obvious to other people John's always worn his heart on his sleeve, so there's no doubt who he'll be supporting. See also: heart, on, sleeve, wear. Related vocabulary: wear something on your sleeve.
In many bivalves and snails, and in cephalopods, part of the mantle is modified into a siphon, which can be used to pump water through the mantle cavity for respiration, feeding and/or jet propulsion. Freshwater and marine mollusks have gills (called ctenidia) for respiration, located in the mantle cavity. In most bivalves, these are enlarged and serve to trap food particles as well (Morton 1983).
Gills. The purpose of a fish's gills are to enable it to obtain oxygen from the water. A fish's gills contain special membranes that absorb oxygen and also release carbon dioxide. Basically a fish's gills has the same function as a person's lungs-the gills are where gas exchange occurs. Water has oxygen dissolved in it, which the fish needs to survive. The fish takes water in through its mouth and this water passes over the gills. The gills contain lots of blood vessels.