Neural membranes, embryonic

Embryonic neural membranes Sialogangliosides Neural cell adhesion molecules Extraneural cells and tissues Human kidney, heart, muscle, pancreas, lung, thyroid, T lymphocytes... 

As its name implies, the neurohypophysis is derived embryonically from nervous tissue. It is essentially an outgrowth of the hypothalamus and is composed of bundles of axons, or neural tracts, of neurosecretory cells originating in two hypothalamic nuclei. These neurons are referred to as neurosecretory cells because they generate action potentials as well as synthesize hormones. The cell bodies of the neurosecretory cells in the supraoptic nuclei produce primarily antidiuretic hormone (ADH) and the cell bodies of the paraventricular nuclei produce primarily oxytocin. These hormones are then transported down the axons to the neurohypophysis and stored in membrane-bound vesicles in the neuron terminals. Much like neurotransmitters, the hormones are released in response to the arrival of action potentials at the neuron terminal. 

Hoffman S, Sorkin BC, White PC, Brackenbury R, Mailham-mer R, et al. 1982. Chemical characterization of a neural cell adhesion molecule purified from embryonic brain membranes. J Biol Chem 257 7720-7729. 

The medulloepithelioma looks like carcinoma but occurs in childhood, an unlikely age for carcinoma. The pseudostratified columnar epithelium of medulloepithe-iioma is crowded with cells that resemble those lining the embryonic neural tube. It rests on a type IV collagen basement membrane and fibrous stroma. The basal layer of the epithelium expresses nestin, vimentin, and microtubule-associated protein type 5 immunoreactiv-ity. Focal differentiation and expression of either GFAP, S-100 protein, NSE (Fig. 20.42), NF protein, CK, or EMA immunoreactivity frequently occur. 

Bone formation may involve either endochondral ossification as in most long bones, or membranous ossification as in the calvaria and the dentaries. The Prxl defects were seen in both types of bones and the affected bones were also diverse in their embryonic origin, as they included facial bones that are derived from neural crest, limb bones that originate from lateral plate mesoderm, and vertebrae that originate from paraxial (somitic) mesoderm. 

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