Oral Histology Slides - Papilla of tongue, Maxillary sinus, Parakeratinised epithelium, Vermillion border of lip, Serous and Mixed gland, Bone, muscle and Fat cells

Here are some of  the histologic slides of various tissue preparations of oral cavity and maxillary sinus prepared in the Department of Oral Pathology, College of Dental Surgery(CODS) , BPKIHS Dharan Nepal

1. Serous Gland
Salivary glands consists of secretory end pieces called acini which may either be of serous nature or mucuous nature. Some mucous acini are found to be capped by serous cells giving a bonnet or crescent shaped appearance which gives rise to the structures called demilunes.

Serous acini are formed by eight to twelve pyramidal cells arranged in a circular pattern to form a narrow central lumen. The basal portion of the cell has a spherical nucleus and the apical part near the lumen contains abundant granules.The RER (rough endoplasmic reticulum) is seen in abundance basal and lateral to the nucleus as serous cells are mostly involved in secreting proteinaceous contents. The ductal system is narrower as compared to that of mucous gland.

2. Mixed Gland
Mixed salivary glands contain both serous and mucous acini. Mucous glands also contain pyramidal cells arranged in circular fashion like that in serous acini but these cells are fewer and shorter. The flattened nuclei lies at the basal portion of the cell and the cytoplasm appears emptyunder routine histological stains. However it is stained strongly by special stains like PAS ( Periodic acid Schiff) or alcian blue. The mucous cells capped by serous cells forming a characteristic demilunes can also be seen. Submandibular gland is a mixed major salivary gland.
3. Vermillion Border of lip
Vermillion zone or red zone of lip is the area between the skin of the lip and mucous membrane. The distinct line that separates the skin and vermillion zone is called vermillion border.
The transition of  type of epithelium from orthokeratined stratified squamous epithelium of skin to non keratinized stratified squamous epithelium of labial mucosa takes place gradually through the parakeratinized vermillion zone. 
The epithelium is thinner and the underlying connective tissue layer contains longer papilla in vermillion zone as compared to the skin. Due to the thin layer of epithelium and richly supplied blood vessels, the vermillion zone appears red. As there are no any sebaceous or sweat glands like skin to prevent it from drying, the lips become dry frequently.

4. Parakeratinized epithelium
Parakeratinization is a peculiar feature of oral mucous membrane.The darkly stained region above the epithelium is due to keratin. The keratinization is not as much as that in orthokeratinized epithelium and in histological section, the rete ridges are less numerous and shorter in parakeratinized stratified squamous epithelium as compared to that of orthokeratinized epithelium. Parakeratinized epithelium is found in most of the gingiva and the vermillion zone of the lips.

5. Circumvallate Papilla
The dorsal surface of the tongue is rife with  papilla.
The papilla may be filiform, fungiform, foliate or circumvallate. The circumvallate papilla are the ones which are found just anterior to the sulcus terminalis which separates anterior  two third and posterior one third of the tongue.

The superficial surface of circumvallate papilla is keratinized whereas the lateral walls of the trench are non keratinized. The trench contains the openings of minor salivary glands and the lateral wall contains numerous taste buds.

6. Fungiform Papilla
These are also a type of papilla found in the dorsum of tongue. The papilla is not as large as circumvallate papilla. Its name is derived from its resemblance to the shape of mushroom, i.e. umbrella shaped. It also contains taste buds.