HISTOLOGY Quiz: Colon and Pinna Connective Tissues
Document Summary
The colon has the typical histological structure as the digestive tube: mucosa, submucosa, muscularis, and serosa/adventitia. The mucosa is lined by simple columnar epithelium (lamina epithelialis) with long microvilli. It is covered by a layer of mucus which aids the transport of feces. The mucosa does not contain villi but many crypts of lieberkuhn in which numerous goblet cells and enteroendocrine cells are found. The connective tissue layer (lamina propriae mucosae) is filled with macrophages, plasma cells, and other immune cells. The submucosa comprises blood vessels, lymph nodes, and particularly fat tissue. The inner circular musculature of the muscularis is strongly pronounced whereas the outer longitudinal musculature is practically only found in the taeniae. The external ear includes the auricle (pinna) and the external ear canal; both have a lining of keratinized stratified squamous epithelium. The outer ear functions to direct sound energy and vibrations into the ear canal to the tympanic membrane.
