Hialina

Hialina, or hyaline in English, is a term used in histology and pathology to describe a glassy, eosinophilic, homogeneous material that stains with standard light microscopy and resembles glass. The word derives from the Greek hyalos meaning glass.

In tissues, hyaline change refers to the accumulation of a glassy, eosinophilic substance within cells or the extracellular matrix. Hyaline cartilage is a well-known example of this material in connective tissue; its matrix is rich in type II collagen and proteoglycans, giving it a smooth, translucent appearance. Hyaline cartilage forms the articular surfaces of joints as well as parts of the respiratory tract, such as the nasal septum, larynx, and trachea.

Pathology uses the term hyalinosis or hyaline degeneration to describe deposition of homogeneous, glassy material in vessel walls or other structures. Hyaline arteriolosclerosis, often seen with aging, diabetes, or hypertension, involves thickened, glassy-appearing vessel walls. Hyaline membranes are eosinophilic, glassy layers that line alveoli in certain lung conditions, most notably hyaline membrane disease (neonatal respiratory distress syndrome) and some forms of acute lung injury.

Hyaline material can also appear in the kidney and other organs as accumulations of proteinaceous or extracellular matrix components, contributing to organ dysfunction. Diagnosis relies on histological examination and, when needed, additional staining to characterize the composition of the hyaline substance.

See also: hyaline cartilage, hyaline membrane disease, hyalinosis, hyaline arteriolosclerosis.