Ultrastructural Study on the Development of The Aorticopulmonary Body in Human Fetuses

ABSTRACT

The development of aorticpulmonary bodies was studied by electron microscope in human fatuses ranging from 40mm to 260mm crowm-rump length. The aorticpulmonary bodies were observed in the wall of the aorta, and of the pulmonart trunk and arteries. At 40mm fetus, the aorticopulmonary bodies were composed of clusters of primitive glomus cells, primative supporting cells, unmyelinated nerve fibers, and capillaries. The primitive glomus cells possessed large nuclei, dense-cored vesicles, many Golgi complexes, rough endoplasmic reticulum, and, multivesicular bodies, the primitive supporting cells were agranular with attenuated cytoplasmic processed which partially ensheathed the primitive glomus cells. Synaptic contacts between the axon terminals and the aoma of primitive glomus cells were first observed. The primitive glomus cells increased somewhat in size and number by 90mm fetus, but retained essentially the same characteristics as at the earlier stage. Desmosome-like contacts between glomus cells and adjacent cells were commonly seen. At 160mm fetus, the glomus cells had increased accumulations of all organells and numerous dense cored vesicles. The supporting cells completely invested the glomus cells. Two types of nerve terminals were observed. One type contained small agranular vesicles which was identified as cholinergic axon terminal. The other contained a majority of small granular vesicles which was classfied as adrenergic axon terminal. Synaptic contacts between the cholinergic axon terminals and the soma of the glomus cell were observed. During next prenatal stage up to 260mm fetus the glomus cells and the supporting cells resembling those in adult were present. It is concluded that the ultrastructural features of these aorticopulmonary bodies are similar to those of the carotid body. It is therefore suggested that the aorticopulmonary bodies of the human fetures have a chemorecepter function similar to that of the carotid body.