tkanki

Tkanki (singular: tkanka) are structural and functional units that form the bodies of multicellular organisms. In biology, tkanka refers to groups of specialized cells and their extracellular matrix that cooperate to perform specific tasks. Tkanki are traditionally classified into four broad categories: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. Each category contains several subtypes with characteristic cell shapes, arrangements, and functions.

Epithelial tissue lines surfaces and cavities, provides protection, absorption, secretion, and sensation. It includes simple and stratified epithelia and various glandular forms. Connective tissue supports, binds, and fills spaces; it includes loose and dense connective tissues, cartilage, bone, blood, and adipose tissue. Muscle tissue contracts to produce movement and includes skeletal, smooth, and cardiac muscle. Nervous tissue carries electrical signals and supports neural processing, comprising neurons and glial cells.

Tissues originate from embryonic germ layers (ectoderm, mesoderm, endoderm) and consist of cells embedded in an extracellular matrix made of proteins, polysaccharides, and minerals. The exact composition and organization determine tissue properties and functions. Histology studies tissue structure using microscopic staining techniques to distinguish cell types and matrix components.

In organisms, tissues organize into organs (such as the skin, heart, or liver) that form organ systems. The arrangement and interaction of different tissues underpin physiology and development. Tissues can regenerate after injury, with responses varying by tissue type; some tissues show high regenerative capacity, others repair through scar formation.

In medicine and research, tissue sampling and biopsy analyze tissue structure for diagnosis. Abnormal tissue organization, inflammation, degenerative changes, or neoplasia reflect disease processes. The study of tkanki provides essential insights into biology, anatomy, and pathology.