cap·sule / ˈkapsəl; ˈkapˌsoōl/ • n. a small case or container, esp. a round or cylindrical one. ∎ a small, soluble case of gelatin containing a dose of medicine, swallowed whole. ∎ a top or cover for a bottle, esp. the foil or plastic covering the cork of a wine bottle. ∎ short for space capsule. ∎ [as adj.] fig. (of a piece of writing) shortened but retaining the essence of the original: a capsule review of the movie. ∎ Anat. a tough sheath or membrane that encloses something in the body, such as a kidney, a lens, or a synovial joint. ∎ Biol. a gelatinous layer forming the outer surface of some bacterial cells. ∎ Bot. a dry fruit that releases its seeds by bursting open when ripe, such as a pea pod. ∎ Bot. the spore-producing structure of mosses and liverworts, typically borne on a stalk. DERIVATIVES: cap·su·lar / ˈkapsələr/ adj. cap·su·late / ˈkapsələt; -ˌlāt/ adj.
1. (of prokaryotes) The gelatinous, outer surface layer to the cell (also known as the sheath in cyanobacteria), which is composed primarily of polysaccharides. In pathogenic bacteria, and possibly in others, it appears to serve a protective function against the defensive mechanism of the host, since such bacteria become non-infective in its absence.
2. The spore-bearing structure of a moss or liverwort. In most mosses the capsule may be spherical, cylindrical, oval, or pear-shaped, and is borne on a stalk or seta; the seta in turn is anchored to the gametophyte by an absorptive region called the foot. The capsule is protected, at least initially, by a calyptra. In most cases the capsule has a mouth initially covered by a lid; when the spores inside the capsule are mature, the lid falls off and the spores are released, to be dispersed by wind. (Compare SPHAGNUM and ANDREAEIDAE.) In liverworts the capsule is usually ovoid or spherical and has no lid. On ripening, the capsule usually splits into four ‘valves’, which open out to release the spores.
3. A dry fruit, normally dehiscent.
1. (in botany)
a. A dry fruit that releases its seeds when ripe; it is formed from several fused carpels and contains many seeds. The seeds may be dispersed through pores (as in the poppy), through a lid (as in plantain), or by the splitting and separation of the individual carpels (as in the crocus). Various other forms of capsules include the silicula and siliqua.
b. The part of the sporophyte of mosses and liverworts in which the haploid spores are produced. It is borne on a long stalk (seta) and sheds its spores when mature (see peristome).
2. (in microbiology) A thick relatively rigid gelatinous layer completely surrounding the cell wall of certain bacteria (see glycocalyx). It appears to have a protective function, making ingestion of the bacterial cell by phagocytes more difficult and preventing desiccation.
3. (in animal anatomy)
a. The membranous or fibrous envelope that surrounds certain organs, e.g. the kidneys, spleen, and lymph nodes.
b. The ligamentous sheath of connective tissue that surrounds various skeletal joints.
1. The gelatinous, outer surface layer of a prokaryotic cell (also known as the sheath in cyanobacteria), which is composed primarily of polysaccharides. In pathogenic bacteria, and possibly in others, it appears to serve a protective function against the defensive mechanism of the host, since such bacteria become non-infective in its absence.
2. The spore-bearing structure of a moss or liverwort.
3. A dry fruit, normally dehiscent.
1. a membrane, sheath, or other structure that encloses a tissue or organ. joint c. the fibrous tissue, including the synovial membrane, that surrounds a freely movable joint.
2. a soluble case, usually made of gelatin, in which certain drugs are administered.
3. the slimy substance that forms a protective layer around certain bacteria.