Kapilarna

Kapilarna is a term used in Slavic languages to denote capillary-related structures and processes. In biology and medicine it usually refers to capillaries, the smallest blood vessels that connect arterioles with venules. Capillaries form a dense microcirculatory network where exchange of gases, nutrients, and waste occurs between blood and tissues. Their walls consist mainly of a single endothelial cell layer, with a surrounding basement membrane and, in some beds, pericytes.

Anatomy and types: Capillaries are about 5–10 micrometers in diameter. They can be continuous, fenestrated, or sinusoidal, reflecting differences in permeability. Continuous capillaries have uninterrupted endothelium; fenestrated ones contain pores; sinusoidal capillaries are wider with gaps, found in liver, bone marrow, and spleen. Pericytes and tight junctions regulate exchange of fluids, solutes, and cells between blood and tissue.

Capillary action: This describes liquid rise in narrow spaces due to adhesion to surfaces and cohesion within the liquid. It supports water transport in plants and moisture movement in soils, and influences wicking in porous materials. The height, h, can be approximated by h = 2γ cos θ /(ρ g r), where γ is surface tension, θ the contact angle, ρ density, g gravity, and r the capillary radius.

Clinical relevance: Capillary health underpins tissue perfusion and healing. Capillary density and integrity can be affected by diabetes, hypertension, and inflammation, contributing to organ dysfunction. Assessments such as capillaroscopy monitor microvascular changes in health and disease.