By measuring telomeres, some scientists believe they can determine biological age, which doesn't always equal chronological age. That means some people may be biologically older or younger than their age, said Jerry Shay, professor and vice chairman of cell biology at UT Southwestern Medical Center in Dallas.
It is of ectodermal origin and is continuous with the skin at various body openings such as the eyes, ears, nose and mouth, the urethral opening and the anus. Some mucous membranes secrete mucus, a thick protective fluid. The function of the membrane is to stop pathogens and dirt from entering the body and to prevent bodily tissues from becoming dehydrated.
mucous cells, which produce a very mucus-rich secretion Acini in the parotid glands are almost exclusively of the serous type, while those in the sublingual glands are predominantly mucus cells. In the submaxillary glands, it is common to observe acini composed of both serous and mucus epithelial cells. In the histologic sections of canine salivary gland shown above, the cells stained pink are serous cells, while the white, foamy cells are mucus-secreting cells. Secretion of saliva is under control of the autonomic nervous system, which controls both the volume and type of saliva secreted.