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

Special Part
Cardiovascular System, systema cardiovasculare – General Overview
Arteries – Concept of Anastomoses and Vascular Collaterals

Arteries are characterized by the presence of interconnections between them or their branches, known as vascular anastomoses, within Organs and various Regions of the body. An anastomosis, or vas anastomoticum (from the Greek anastomos meaning to furnish with a Mouth), is any connecting tertiary vessel that joins two other vessels.

The majority of anastomoses are located in the distal regions of The Vascular System. The following types of anastomoses are distinguished: 1) arterio-arterial; 2) arteriovenous; 3) veno-venous (for example, caval-caval and portacaval), which will be discussed in a separate section (see p. 73); and 4) arteriolovenular at the level of the Hemomicrocirculatory bed.

Arterio-arterial anastomoses are connections between arteries originating from different arterial trunks. These anastomoses provide an alternative (collateral) pathway for Blood supply to organs, which is observed around The Stomach, intestines, glands, and joints.

Intersystemic Arterial Anastomoses—connections between branches of different arteries—and intrasystemic anastomoses—between Branches of the same artery—are also distinguished.

Arterio-arterial anastomoses serve as supplementary pathways for the blood supply to organs or specific body regions. When the main trunk is damaged, they take over the organ's blood supply. This also occurs under extreme conditions (such as vessel compression by a tumor, Thrombosis of the main trunk, or ligation of the main trunk during surgical interventions).

Arteriovenous anastomoses (or shunts), known as anastomosis arteriovenosa, are Blood Vessels that connect the arterial bed directly to the venous bed, bypassing the capillaries. They function to regulate regional peripheral Circulation. The Dutch anatomist Frederik Ruysch (1838–1909) was the first to draw attention to them (1872–1876), defining them as permanent structures comprising arterial and venous segments. According to Claude Bernard, arteriovenous anastomoses perform a 'mechanical' function, whereas modern views hold that they participate in thermoregulation, Blood Pressure Regulation, blood redistribution, and The transfer of kinetic energy from the arterial segment to the venous segment (V. V. Kupriianov).

In addition to anastomoses between arteries and their branches, and between arteries and Veins, there are direct connections between arterioles and venules, known as arteriolovenular anastomoses (AVAs). Blood flows through these anastomoses from arterioles into venules, bypassing the capillary bed. For more details on arteriolovenular anastomoses, see p. 8.

Vascular collaterals. A collateral vessel is a secondary, alternative pathway (from the Latin collateralis, meaning side-by-side or alternative). It provides an alternative route for blood flow around a primary major vessel. Collaterals develop both during temporary circulatory challenges and in cases where blood flow ceases due to pathological conditions (thrombosis, injury, surgery). Vascular collaterals ensure Blood Circulation in both the arterial and venous systems. They also exist in The Lymphatic system. Vascular collaterals become critically important when blood flow is impaired in major vessels and their branches due to arterial compression (by a tumor) or venous obstruction, or following the ligation or removal of a blood vessel. Significant contributions to The Study of vascular collaterals were made by P. F. Lesgaft, V. N. Shevkunenko, and V. N. Tonkov. Depending on their Location, vascular collaterals are classified as extra-organ or intra-organ. Extra-organ collaterals connect branches of large arteries or tributaries of large veins either within the branching basin of a single vessel (intrasystemic vascular collaterals) or divert blood from the branches or tributaries of other vessels (intersystemic vascular collaterals). For example, within the basin of the External Carotid Artery, intrasystemic vascular collaterals are formed by connections between its various branches and the branches of the subclavian and Internal Carotid Artery systems. An additional source for The formation of vascular collaterals is the perivascular auxiliary network, which consists of small arteries and veins located adjacent to larger vessels.