Microvessels in the human orbit in relation to the connective tissue system.

In the connective tissue system of the human orbit, the microvascular bed mainly arises from and drains into relatively large-calibre arteries and veins. The microvascular system shows a density increase from the apical region of the orbit towards the hind part of the eye-ball. Some of the microvessels are long, often arranged in loops. The smallest-sized vessels, branches of these long microvessels, show a dichotomous branching pattern and are in general confined to one adipose tissue compartment. Besides a "metabolic" function, the microvascular system, due to its compartmentalized structure, makes theoretically possible selective blood-filling of one or more adipose tissue compartments. If this does in fact occur, the microvascular bed, in co-operation with the orbital connective tissue "organ", could serve an important biomechanical function in controlling and regulating eye-ball movements. At microvascular level, the orbital vascular system is intensively interconnected with the extra-orbital vascular system. In the next article some histological aspects of the orbital connective tissue system will be described.