This epithelium is derived from an embryonic germ layer of endoderm. Blood vessels are always found within connective tissues, never within epithelia. Connective tissues derive from embryonic mesenchyme and their principal cells, fibroblasts, secrete the ECM, including collagens and GAGs. EM of brush border. The brush border consists of actin-containing microvilli.
Epithelial cells have an intrinsic apical-basal polarity.
Here the apical surface, facing the lumen, is specialized for absorption. Mucosal epithelium for goblet cell - unicellular mucous gland. Apical surface specialized for secretion. Low magnification of the intestine. This slide also shows the pancreas - epithelia is glandular, pancreas is an exocrine gland with ducts leading to intestinal lumen 11.