Apical cell undifferentiated

The neural tube is a pseudostratified epithelium, with cells extending between the apical and basal surfaces of the epithelial wall. The neuroepithelium contains undifferentiated populations of stem cells and radial glia (see Ch. 29). With time, both of these cell types give rise to the three main lineages for neurons, astrocytes and oligodendrocytes. After the final mitotic division, neurons migrate away from the ventricular surface of the neural... 

The other well-known member of this superfamily is CEA or carcinoem-bryonic antigen. CEA is a widely used tumor marker, especially for monitoring patients with diagnosed colorectal cancer (M5). It is a high-molecular-weight (Afr 200,000, approximately) glycoprotein containing about 60% carbohydrate. In normal colonic cells and in well-differentiated colon carcinomas, the distribution of CEA is apical. However, in undifferentiated colonic tumors, CEA is present on all of the cell membrane (J3). Whether this altered subcellular localization of CEA mediates cancer spread is presently unclear. 

A monolayer of multiple cell types comprises the intestinal epithelium. Entero-cytes, the absorptive cells, are the main focus in drug delivery issues. In addition to enterocytes, there are undifferentiated crypt cells, mucus-secreting goblet cells, and M cells, which sample the gut lumen for the lymphatic system.6 However, it is the columnar villar enterocyte that forms the primary barrier to absorption. An extensive network of microvilli on the apical surface of villar enterocytes provides a vast amount of surface area for absorption of nutrients, pharmaceuticals, and xenobiotics.6,7... 

Cytoarchitectonic study. 6th-month fetuses The cerebral cortices of various areas were not well differentiated or developed, only three layers being distinguishable. Cortex nerve cells consisted almost entirely of undifferentiated neuroblasts. No mitoses were found. With Golgi s silver impregnation, apical dendrite budding was seen, but not the basal dendrites. No myelination was revealed in the cortex with Weil s stain. 

Intermediate cells have been described in the respiratory epithelium of a wide variety of species. The cells are called intermediate because they lack either secretory granules or cilia and their apical processes are few and short (Fig. 70). In this respect they are undifferentiated and capable of transformation into any of the epithelial cell types. The electron density of the cytoplasm is variable, presumably electron dense if it is to form a secretory or electron-lucent it is to form a ciliated cell. The cell is found both in proximal and distal airways. 

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