Human Anatomy, Part 2 - K. A. Dyubenko, A. K. Kolomiyytsev, Yu. B. Chaykovsky 2008

Specialized Part
Cardiovascular System, systema cardiovasculare – General Overview
Arteries – Structure of Arteries

Based on their functional purpose and the histological Structure of their walls, Arteries are divided into three types: elastic, muscular, and mixed (or musculo-elastic) arteries (Fig. 2). The arterial wall consists of three coats (tunics): the inner coat — tunica intima (or interna), which comprises the endothelium, subendothelial layer, and internal elastic membrane; and the middle coat — tunica media, formed by smooth Muscle Cells and elastic fibers. The middle coat is the most developed; it withstands Blood pressure from within and resists the surrounding Muscles and Tissues, preventing them from compressing the artery from the outside (a function known as resistance). Through this resistive function, arteries regulate blood pressure and blood flow intensity. The outer coat — tunica externa (or adventitia) — is represented by loose Connective Tissue, which houses nerve plexuses and the vessel's own nourishing Blood Vessels, the vasa vasorum.

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Fig. 1. General diagram of the human Cardiovascular system

Fig. 2. STRUCTURE OF THE blood vessel wall (diagram).

Elastic arteries, aa. elastotypica (Fig. 2) — these include large blood vessels: the aorta, pulmonary trunk, and pulmonary arteries. Blood moves through them under high pressure (120–130 mm Hg) and at a high velocity (0.5–1.3 m/s). The presence of a significant amount of elastic elements in their walls provides elasticity, allowing them to expand during Heart contraction (systole) and return to their baseline diameter during relaxation (diastole). Elastic arteries primarily perform a transport function.

Muscular arteries, aa. myotypica (Fig. 2) — these include medium- and small-diameter vessels, namely the arteries of Internal Organs, upper and lower limbs, and the Skin. The walls of these arteries contain a substantial number of smooth muscle cells. By contracting, the smooth muscle Cells of the middle coat maintain blood pressure and regulate Blood supply to the microcirculatory bed of organs. These smooth muscle cells are arranged in an oblique spiral, which ensures that upon contraction, the volume of the vessels decreases and blood is propelled into the distal regions. Elastic fibers accompanying the smooth muscle cells at the border of the outer and inner coats merge with their elastic elements.

Thus, a unified elastic framework is formed within the arteries, providing the vascular wall with stretch elasticity and compression resilience. It prevents the arteries from collapsing, which helps maintain their lumen and ensures continuous blood flow.

Mixed or musculo-elastic arteries, aa. mixtotypica — in terms of wall structure, they occupy an intermediate position between muscular and elastic vessels. These include the subclavian, carotid, and femoral arteries.

The internal coat of these vessels is formed by the endothelium, subendothelial layer, and internal elastic membrane. The middle coat of mixed-type arteries consists of smooth muscle cells, spirally arranged elastic fibers, and fenestrated elastic membranes. The outer coat is divided into two layers: the inner layer, which contains isolated bundles of smooth muscle cells, and the outer layer, containing loose Fibrous connective tissue. The outer coat also houses the vasa vasorum and nerve endings.

The branching of arteries into smaller vessels occurs according to three main types: main (stem),散 (dispersed/scattered), and mixed (V. M. Shevkunenko). According to the fundamental law of angiology by P. F. Lesgaft, arteries are characterized by certain regular patterns:

1. Arteries are arranged in accordance with the Skeletal structure of the trunk, which forms The basis of the body, and retain a segmental structure. For example, the aorta runs along THE Vertebral Column, while the posterior intercostal arteries (aa. intercostales posteriores), lumbar arteries (aa. lumbales), and spinal branches (rr. spinales) run along the Ribs.

2. In certain Regions of the body, arteries travel as part of neurovascular bundles, alongside venous and lymphatic vessels, as well as nerves. All of them reach the organs following the shortest possible path.

3. Major body regions are supplied by large arterial vessels (the HEAD and Neck by the carotid and vertebral arteries, the arm by the brachial artery, the thigh by the femoral artery, the forearm by the ulnar and radial arteries, and the leg by the tibial and fibular arteries). Each limb receives one main arterial trunk for nourishment: the Subclavian Artery for the upper limb, and the external iliac artery for the lower limb.

4. Arteries are divided into parietal (parietal) and visceral (nutryni).

5. The majority of arteries are arranged according to THE PRINCIPLE OF bilateral Symmetry (paired Arteries of the soma and viscera).

6. Arteries are located on the flexion surfaces of the body because they stretch and collapse during extension. This placement protects the vessels and reduces the likelihood of injury.

7. The diameter of the arteries delivering blood to organs, as well as the branching pattern of their ramifications, corresponds to the organ's function.

8. Large arteries run within grooves and canals, deep near the bones themselves, covered by Muscles and fascia, which protects them from compression.

9. Arteries penetrate an organ from its medial surface, which faces the source of blood supply.

10. In accordance with the organ's function, arteries form collateral vascular networks (around joints) and arciform or circular anastomoses (around the intestine). There are 4–5 arterial arcades around the Small Intestine and 2 around the Large Intestine.

11. Additional arteries and Veins accompanying relatively large arterial or venous vessels form the para-arterial and paravenous beds (B. A. Dolgo-Saburov, A. T. Akilova).