According to the National Institutes of Health, the submucosa is a layer of tissue that lies under the mucosa, an inner lining of some organs and body cavities that makes mucus. It is seen in the respiratory, gastrointestinal, and genitourinary tract.
In the respiratory system, the submucosa houses seromucous glands, which secrete both a viscous, mucous substance and a more watery, serous substance. These two substances have distinct and important functions: the serous substance helps make air more human as we breathe in and the mucous substance traps particles to help keep the lungs free of harmful particles and bacteria.
In the GI tract, the submucosa contains large blood vessels, lymphatic vessels, and nerves. An important nerve center that helps control digestive functioning (called the Meissner’s plexus) is located in the submucosal layer.
The submucosal layer of the urethra contains a vascular plexus that helps create pressure important to the urination process. The submucosal layer of the female uterus can sometimes see the growth of fibroids that can cause difficulties during pregnancy. According to Brigham and Women’s Hospital, if uterine fibroids are detected in the submucosal layer, they should be removed.