Labia oris

Description of the slide

• border of the oral cavity
• primary substrate - skeletal muscle (here sparse collagenous connective tissue - endomysium)
• subcutaneous, submucosal connective tissue - here we can find numerous glands
• lip surface:

1. Outer side - On the upper side is the epidermis, the lips are covered by the skin, where we find the multi-layered squamous epithelium. The next layer is the dermis, a sparse collagenous connective tissue. This side also often contains skin adnexa such as hair follicles, sebaceous glands (branched alveolar glands, layered squamous epithelium in the ducts) or sweat glands (simple tubular coiled glands, two-layered cuboidal epithelium in the ducts).
2. Transition zone of the lip - It is formed by thin skin without pigment. On the slide we observe the transition of stratified squamous stratified epithelium from cornified to non-cornified. The pigment eleidin is found in the surface cells, which ensures the transparency of the epithelial cells and thus the blood from the blood vessels. In this zone, there is an abundance of sparse collagenous connective tissue that runs out in high papillae. A rich network of blood capillaries can be observed in these. As on the outer side of the lip, sebaceous glands can be seen here, but now without hair follicles.
3. Inner side - On the inner side of the lip we find a multi-layered squamous epithelium, i.e. a mucous epithelium. Below the epithelium is a second layer of lamina propria mucosae, i.e., sparse collagenous connective tissue. The third layer is the tunica submucosa, where small salivary glands, serous or mucinous, are found.

Sources

• MARTÍNEK, Jindřich and Zdeněk VACEK. Histological atlas. 1st ed. Prague: Grada, 2009, 134 p. ISBN 978-80-247-2393-8.
• LÜLLMANN-RAUCH, Renate and Zdeněk VACEK. Histology. 1st Czech edition. Translation by Radomír Čihák. Prague: Grada, 2012, xx, 556 p. ISBN 978-80-247-3729-4.
• Presentation from the website of the Institute of Histology, 1st Faculty of Medicine.