Population and structure of nerve cells in mouse submandibular ganglion.

The anatomy of the mouse submandibular ganglion, and population and fine structure of nerve cells were studied by light and electron microscopy. The submandibular ganglion is a plexus containing up to forty ganglia along the main and the smaller excretory ducts of the submandibular gland. Measurements of the volume of nerve cell bodies display a pattern of distribution with two main peaks, suggesting the presence of large and small types of the intraganglionic neuron. The large neurons mainly have axo-dendritic synapses in which the postsynaptic element is a small spine-like process, while axo-somatic synapses are more common in the small neurons. In some small neurons nuclear chromatin is unusually conspicuous, and accumulations of vesicles of fairly uniform size occur within the cell body. Decentralized ganglia contain almost no synapses showing the absence of definite interneurons.