kärlen

Kärlen is a Swedish term meaning “the vessels,” and in medical and anatomical contexts it refers to the body’s network of blood vessels that form the circulatory system. The term encompasses arteries, veins, and capillaries—the conduits through which blood is transported to and from tissues and organs.

Arteries carry blood away from the heart and typically have thick, elastic walls to withstand high pressure. In systemic circulation they usually transport oxygenated blood, while in the pulmonary circuit arteries carry deoxygenated blood to the lungs. Veins return blood to the heart and generally have thinner walls and valves to prevent backflow, collecting blood from capillaries through venules and larger veins. Capillaries are the smallest vessels, with very thin walls that enable the exchange of gases, nutrients, and waste between blood and surrounding tissues. The vascular network is organized into a hierarchical system with large elastic arteries and veins transitioning to muscular arteries, arterioles, capillaries, venules, and veins.

Regulation of Kärlen involves the autonomic nervous system, local metabolic factors, and hormonal signals, which adjust vessel diameter and blood flow according to tissue needs. Clinically, vascular health is assessed through measurements such as blood pressure, and imaging or laboratory tests may evaluate vessel structure and function. Common pathologies affecting the vessels include atherosclerosis, aneurysms, thrombosis, pulmonary embolism, varicose veins, and chronic venous insufficiency, all of which can disrupt circulation and tissue perfusion.

In Swedish medical literature, Kärlen is used to describe the integrated network of blood vessels; in English, the terms “blood vessels” or “vascular system” convey the same concept. See also circulatory system, vascular biology.