뼈의 혈관순환의 생리병리에 관한 논문
Intraosseous circulation from physiology to disease.pdf
Blood flow within bones is unique in two ways
(1) the blood circulates within a closed cavity in which pressure must remain constant, a feat achieved in part thanks to the considerable distensibility(팽창) of the intraosseous vessels and, above all, veins
(2) the intraosseous circulation allows traffic of minerals between the blood and bone tissue and sends the blood cells produced within the bone marrow into the systemic circulation.
In contrast, the arterioles and capillaries within bones have the same anatomic structure as those located elsewhere in the body and are susceptible to arteriosclerosis, arteritis, or thrombosis. The mechanisms that regulate blood flow within bone are incompletely understood, probably because they are difficult to study in vivo.
The cytokines and growth factors that regulate intraosseous angiogenesis also regulate bone remodeling, and close links exist between the blood supply to bone and bone formation and resorption: most diseases characterized by increased bone resorption are associated with increased bone vascularization. The vascular bud located at the center of bone multicellular units(BMUs) may determine the timing of bone resorption and bone formation.
Avascular bone necrosis and bone infarction may result from acute blood vessel occlusion (thrombosis, lipid emboli, fat cell hypertrophy with compression of intraosseous capillaries), whereas arteriosclerosis may contribute to the development of osteoporosis.
Diagram of the arterial vascularization of a long bone
Diagram of the venous vascularization of a long bone
Normal intraosseous circulation [9]
The physiology of the intraosseous circulation has received far less attention than blood flow in other organs such as the kidney, heart, and brain, where the regulatory mechanisms have been fully elucidated. Intraosseous blood flow can adjust either through changes in the intraosseous blood flow rate (IOBFR) or through stimulation or inhibition of intraosseous angiogenesis, which is growth of new capillaries from preexisting capillaries.
The intraosseous circulation operates under two unique constraints. One is that the bone is a closed
cavity within which pressure must remain constant. Variations in intraosseous pressure (IOP) can cause pain. For instance, the pain related to avascular necrosis of the femoral head is related in part to increased pressure within the bone. When pressure is measured via the trochanteric route, the slightest movement of the guide within the trocant or injection of saline replicates the patient’s pain, whereas vasodilators and core biopsy provide rapid pain relief [9].
Whether the increase in IOP is a cause or a consequence of the necrosis remains unclear. The considerable distensibility
of the intraosseous veins helps to maintain the IOP constant. IOP often changes in the same direction as the IOBFR, and most disease processes that increase IOBFR also increase IOP. The second constraint is that the intraosseous circulation must allow trafficking of calcium, phosphate and other minerals between the bone tissue and the serum and must carry newly formed blood cells from the marrow to the peripheral blood: these two functions are apparently very different, since
one supplies nutrients to a tissue that supports and protects the body, whereas the other contributes to effective production of hematopoietic cells.