Arteries and veins
The human vascular system is a closed network with a total length of more than 100,000 km, which is 2.5 times the length of the equator. Blood flows from the heart through arteries, through veins to the heart, and in capillaries the exchange of substances between blood and tissues occurs.
Structure of the vascular wall
The wall of arteries and veins consists of three layers:
- Intima (inner membrane) - endothelium, smooth lining
- Media (tunica middle) - smooth muscle cells and elastic fibers
- Adventitia (outer shell) - connective tissue
Arteries have thick muscular walls that can withstand high pressure. Veins are thin-walled, but contain valves that prevent backflow of blood.
Aorta and its branches
Aorta is the main artery of the body, with a diameter of about 3 cm. It leaves the left ventricle and gives off branches to all organs:
- Ascending aorta → coronary arteries (heart)
- Aortic arch → brachiocephalic trunk, left common carotid, left subclavian (head and arms)
- Descending aorta → thoracic and abdominal branches (organs and walls of cavities)
- Bifurcation → common iliac arteries (pelvis and legs)
Venous system
All venous blood collects in two vena cava:
- Superior vena cava - from the head, neck and upper extremities
- Inferior vena cava - from the lower half of the body
A special system is the portal vein (vena portae): blood from the intestines first passes through the liver for neutralization, and then returns to the heart.
Capillaries
Capillaries are the smallest vessels with a diameter of 5–10 microns (less than the thickness of a hair). Their wall consists of a single layer of cells, which allows gases and nutrients to pass freely. The total area of the capillary bed reaches 6,000 m².
Circulation circles
Small circle: right ventricle → pulmonary arteries → pulmonary capillaries (gas exchange) → pulmonary veins → left atrium.
Large circle: left ventricle → aorta → arteries → capillaries (tissue nutrition) → veins → vena cava → right atrium.
An understanding of vascular anatomy is essential for surgeons, intensivists, and ultrasound physicians for safe access and accurate interpretation of examinations.
In the Humio](/) app you can trace the course of the aorta and its branches on an interactive 3D model - zoom in, rotate and highlight individual vessels.