Alveolus

ALVEOLUS (from the Latin alveolus, diminutive of alveus—an oblong depression, small cavity, cell), a term introduced by Vesalius to denote depressions resembling the cells of a honeycomb (alveolae dentales) along the free edge (limbus alveolaris) of the lower and upper jawbones, lined with periosteum (periodontium), into which the roots of the teeth are, as it were, driven; depending on the number of roots (see Teeth), the sockets can be simple, separated from one another by an interalveolar septum, or subdivided into compartments by interalveolar septa according to the number of roots. The number of alveoli after the eruption of the wisdom tooth, in the adult state, is equal to 16 for each jaw. Upon the loss of a tooth or its extraction, the socket is resorbed. In a newborn, there are, in addition to 20 sockets for the deciduous teeth, 1 on each side of both jaws for the first permanent small molar; the sockets for the wisdom tooth sometimes begin to develop at the age of about 5 years. Later, the term alveoli pulmonales appeared to denote the minute, air-containing vesicles in a breathing, healthy lung, numbering approximately 7–17 billion, located around the funnel-shaped expanded ends of the finest bronchi (ductuli alveolares). The diameter of the spherical pulmonary alveoli, or vesicles (Malpighi called them vesiculae, cellulae pulmonales), which increases during inhalation and decreases during exhalation, is generally 0.2–0.3 mm in an adult. The base of the pulmonary vesicle is formed by a thin, structureless membrane, permeated with numerous elastic fibers; its inner surface is lined with a single-layered flat "respiratory" epithelium; cilia begin to disappear even in the finest bronchi (see). A dense network of capillaries is located around the pulmonary alveolus. Here, the blood is freed from carbon dioxide and saturated with oxygen.

P. Karuzin. Alveolar—having a cellular structure (macroscopically or microscopically). This term is used to denote everything related to dental sockets: limbus or processus alveolaris—the edge of the jawbones, studded with sockets; foramen, jugum alveolare, arteria, vena, nervus alveolaris—the socket opening, eminence, artery, vein, and nerve. Furthermore, glands are called alveolar if the ends of their branching excretory ducts are studded with vesicles (the production of secretion occurs in the epithelial lining of the latter). In addition, the term "alveolar" characterizes a number of tumors (for example, alveolar cancer, alveolar sarcoma) and, in general, everything related to or connected with alveoli. The alveolar structure of protoplasm, the theory of Bütschli (1878, 1892), according to which all protoplasm has a cellular structure, resembling the structure of foam, wherein the cells of this foamy structure contain a more liquid substance—enchylema. Bütschli saw confirmation of his theory in the fact that artificial foams, prepared by him from oil emulsions and soap solutions, showed a similarity to the structure and movement of living protoplasm. New colloid-chemical data have strongly limited the significance of this widely disseminated theory (see Amoeboid movements, Protoplasm).