noun, plural: lacunae
(histology) The small cavity containing an osteocyte in bone, or a chondrocyte in cartilage; a minute cavity containing a nucleate cell
(botany) An air space in plant tissues
(general) A small depression, empty space, or cavity
Of, pertaining to, or relating to a lacuna
Lacuna is a Latin word derived from lacus meaning lake. Thus, in biology, it is a term pertaining to a small depression or cavity and supposedly containing a nucleate cell. In histology or anatomy, lacuna (plural: lacunae) refers to the small cavity in the substance of the bone containing an osteocyte. Osteocyte is an entrapped osteoblast in the matrix. It may also be used to refer to the small cavity containing a chondrocyte in a cartilage tissue. The latter is called cartilage lacuna. In the bone, the lacunae are located between the lamellae. When viewed under an ordinary microscope, they appear as spots in the bone tissue. They are opaque and have a fusiform shape. They are occupied by an osteocyte and are connected to each other by canaliculi (small canals or ducts). In cartilages, the chondrocytes occupy lacunae. Surrounding the chondrocyte is the so-called capsule. In botany, lacunae pertain to the air spaces in plant tissues.
Word origin: Latin lacūna (“ditch, gap”), lacus (“lake”)