ULTRASTRUCTURAL-CHANGES OF THE DEVELOPING BLOOD-VESSELS IN THE CHICK-EMBRYO ADENOHYPOPHYSIS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 13  (3) , 391-406
Abstract
Ultrasturctural changes of the capillaries during development of the adenohypophysis pars distalis were studied in the chicken embryo. Adenohypophysial sinusoids attain their full set-up during the last third of embryonic life. Main features of the differentiation of the capillary wall concern the following: a progressive thinning of the endothelium commencing at the 14th i.d. [inculation day] accompanied by a reduction of the cytoplasmic organelles of its cells from the 16th i.d.; a gradual disappearance of the largely overlapping cytoplasmic projections of adjoining endothelial cells, and a progressive increment of the pores, closed by diaphragms, in their thinnest peripheral extensions; a marked narrowing, from the 14th i.d. on, of the perivascular space, which attains its definitive characteristics only at hatching when the endothelial basement lamina forms. The significance of endothelial porous vacuoles throughout maturation of the vessel wall is discussed, and relationships between histogenesis and vessel development in the chicken adenohypophysis pars distalis are discussed.