| Research Abstract |
In all the endocrine glands, the secretory materiais are released into the connective tissue space, and then enter tlie capillary lumen by passing throilgli the endothelial fenestrations. In the thyroid gland, the population density ind the nijmber of the endothelial fenestrations are changeable and flexible according to the secretory activity of the gland. Both tlie number and density are markedly increased in long-term heperfunctional state of the thyroid gland and decreased in long-term hypofunctional state.
Three-dimensional aspects of tlie thyroid g)-and determined by scanning electron microscopy of corrosion casts show that each follicle of tile thyroid is sijrroiinded by a network of very frequently branclicd b-l-oo(I capillaries. The c, -ipillary network looks like a basket encapsulating the follicle in monkeys, dogs, rats and mice. In tlie hyperfunctional state, the capillaries in cacti basket are markedly dilated, and numerous sproutings and anastomoses with one another are observed, while in tlie hypofunctional state the capillaries covering each follicle become very narrow in diameter, and very poorly distributed as compared with those of normal and hyperfunctional animals.
The sproutings and anastomoses of tlie blood capillaries in liyperfunctinil state of the thyroid gland is considered to be due to qxjantity of TSII, though its(letail. ed mechanism is not has not been solved. The fibrolasts, pericytes, and blood platelets might have a great role for tlie mitosis, growth and sporunting of the endothelial cell. I wish to emphasize that the microvascular system in tlie thyroid gland is flexible and changeable, , in(I shows a p-l-, isticity in tlirce-dimenstonil im, , igcs, distribution patterns, and endothelial morptiol-ogics, m, liich rcflects tIlC functional state of the gland.
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