Week 10 - Histology of Oral Mucosa Flashcards
What is histology
the study of the microscopic anatomy of cell and tissues of plants and animals
What are different tissues of the oral cavity
- Oral mucosa
- Teeth (enamel, dentine and pulp)
- Periodontal tissues (alveolar bone, periodontal ligament, cementum and gingiva)
- Salivary glands (major and minor salivary glands)
- Bone
- muscles
- nerves
What are the 3 main parts of the oral mucosa
- Oral epithelium
- Lamina propria (connective tissue)
- Submucosa
What type of cell comprises oral epithelium
stratified squamous
What are the 2 types of oral epithelium
- Keratinized
- Non-keratinized
What are the cell layers in keratinized oral epithelium
- stratum corneum (cornified cell layer)
- stratum granulosum (granular cell layer)
- stratum spinosum (prickle cell layer)
- stratum Basal
What are the main characteristics of the stratum corneum (cornified cell layer)
- nuclei and organelles disintegrated
- cells filled with keratin
- desmosomes disappear to allow cells to be shed away
What are the main characteristics of stratum granulosum
3-5 cell layers above the stratum spinosum
* Contain large number of keratohyalin granules
What are keratohyalin granules
Keratohyaline granules help to form the matrix of keratin fibres of the stratum corneum layer - they help bind the keratin fibers of the stratum corneum layer
What are the characteristics of stratum spinosum
- several cell layers thick
-Contains several tonofilaments (fine proteins), they also bundle to form a tonofibril - Desmosomes increase in number and become more obvious - therefore gives a prickly appearance
What are the main characteristics of stratum basale
- Single layer of cuboidal cells
- Adjacent to lamina propria
- Almost constant mitosis producing daughter cells where 1 become the superior cell layers, while the other remains as a stem cell
- Cells are connected by desmosomes, hemidesmosomes, intermediate, tight and gap junctions-
What are the cell junctions found in the stratum basale (5)
- desmosomes
- hemidesmosomes
- Intermediate junctions (adherents junctions)
- gap junctions
- tight junctions
What are desmosomes
- provides cell to cell adhesion (adjacent cells)
- Provides adhesion through intermediate filaments (type of protein)
What are hemidesmosomes
- Stud like structures found in keratinocytes that attach to the extracellular matrix
- Attaches cells to the basal lamina (where as desmosomes attach to adjacent cells)
- Uses intermediate filaments to create adhesion
What are intermediate junctions (adherents junctions)
- These are cell to cell adhesions and cell to extra cellular adhesions
- Uses actin filaments to provide adhesion (actin filaments are the same as intermediate filaments but they a smaller)
What are gap junctions
- They are communicating junctions which allow the direct chemical communication between adjacent cell cytoplasm through diffusion
- This occurs through a special type of protein
What are tight junctions
Main function is to prevent leakage of solutes and water and seals between the epithelial cells
What are the 2 types of keratinized oral epithelium
- ortho-keratinized
- para-keratinized
What is ortho-keratized oral epithelium
keratinized oral epithelium which has no nuclei or organelles
What is para-keratinized oral epithelium
Keratinized oral epithelium where the cells may retain nuclei but they are small and shrunken.
Where is para-keratinized oral epithelium found
gingiva
What is non-keratinized oral epithelium
- Cells are non-keratinized at the surface
- No keratohyalin granules
- More organelles in the surface layer
What are the cell layers of non-keratinized oral epithelium
- Superficial cell layer (stratum superficial)
- Intermediate Layer (stratum intermedium)
- Basal cell layer
What are some non keratinocyte cells
Melanocyte
langerhan cells
merkel cells
What are melanocytes
- derived from neural crest cells
- located in the basal cell layer
- Melanin is produced and packaged into vesicles - melanosomes
- Difference in skin colour reflects the activity and size of melanosomes, not the number of cells
What are langerhans cells
- Located in the layers above the basal layer
- Derived from bone marrow precursors
- Immune function
- Responsible for anti-tumour immunity, graft rejection and contact hypersensitivity reactions
What are merkel cells
- Found in the basal cell layer
- Closely apposed to nerve fibers
- It is a specialized neural pressure sensitive receptor cell
- Responds to touch sensation
What are key differences between keratinized and non keratinized epithelium
- Different cell layers
- Non-keratinized don’t have keratohyalin granules
- the top layer of non-keratinised has nuclei in its cells
What are the 2 layers of the lamina propria
- papillary layer
- reticular layer
What is the papillary layer of the lamina propria
-upward projections of connective tissue = connective tissue papillae
-downward projections of epithelium = rete ridges or rete pegs
What are connective tissue papillae
upward projections of connective tissue
What are rete ridges or rete pegs
downward projections of epithelium
What is the reticular layer of the lamina propria
It is located below the papillary layer which consists of more of a matrix
What is the epithelial connective tissue interface/ basement membrane
Layer of cells in between the oral epithelium and lamina propria which helps connects these tissues
What does the epithelial-connective tissue interface/ basement membrane consist of
Lamina Lucida = immediately under the epithelium
Lamina dense = electron dense and composed of network of type IV collagen
What is the submucosa
- Deepest layer
-A layer of loose fatty glandular tissue - Contains vessels and nerves
- Separates the oral mucosa form underlying bone or muscle
Where is submucosa found
Present in cheeks, lips and part of hard palate - the palate is hard because it doesn’t have a lot of submucosa - on the other hand the soft palate is abundant with submucosa
Where is the submucosa not found
not found in the gingiva
What is the oral mucoperiosteum
- The oral mucosa is directly attached to the underlying bone - there is no submucosa layer
- It provides a firm inelastic attachment
Where is the oral mucoperiosteum found
Present in gingiva and parts of the hard palate
