Histology Lecture 3a -- Oral Mucosas Flashcards
Describe the epithelium of the skin on the face
Stratified squamous epithelium, keratinized and shows hair follicles, sebaceous glands, and sweat glands
Layer beneath the epithelium of the skin
Connective tissue layer called the dermis
2 layers of the dermis of the skin
Papillary layer
Reticular layer
Describe the organization of the papillary layer
Interdigitated with the rete pegs of the epithelium
Layer contained in the skin epidermis
Stratum granulosum layer with basophilic keratohyalin granules
Define stratum corneum of the skin
Dead cell layer that is orthokeratinized
Define orthokeratinized
The usual or true form of keratinization
Define the red border of lip
A transitional region from dry to wet surface epithelium (dry skin-type epithelium becomes the wet oral mucous membrane or oral mucosa)
What layer is the lamina propria of the oral mucosa continous with at the level of the lips
The dermis of the skin
Describe the keratinization of the lips
Epithelium is partially keratinized, so keratinized near the skin, but non-keratinizaed near the oral mucosa
The keratinized layer is thin, making the epithelium translucent
Describe the dermis/lamina propria of the lips
Rete pegs are very deep and the vessel-containing papillae of the lamina propria extend very close to the lip surface
Describe the anatomical location of the oral mucosa
Entire inside of the mouth except for the gingiva and the dorsal surface of the tongue
Describe the epithelium of the oral mucosa
Stratified squamous epithelium, nonkeratinized
Surface cells of the epithelium are squamou but contain nuclei and desquamate as living cells into the oral cavity
Describe the lamina propria of the oral mucosa
Very vascular (reason for deep red color of mucosa)
Layer beneath the lamina propria of the oral mucosa and its contents
Submucosa, which has small glands that constitute the minor salivary glands (may be serous, mucous or mixed)
Define the anatomical location of gingiva
gums surrounding the teeth and cover the entire hard palate
Define the mucogingival junction
Where the oral mucosa nad gingiva meet at a visible line in the mouth
Describe the epithelium of the gingiva
Modification of the stratified squamous epithelium. Has a stratum germanitavum and a stratum spinosum layer, but no stratum granulosum. Spinosum cells flatten and become keratinized, but do not die. They retain their nuclei until they desquamate.
Define parakeratinization
Type of keratinization found in the gingiva wherein the spinosum cells of the epithelium flatten and become keratinized, but do not die. Instead, they retain their nuclei (thin, flattened and not obvious) until they desquamate. Form a thick regular layer that stains deeply eosinophilic
What layer is the submucosa of the gingiva and hard palate continuous with?
Periosteum lining the alveolar bone or the palatine process of the maxilla (therefore the gingiva does not move freely over the bone)
Define the junctional epithelium of the gingiva
Gingiva reflects onto the tooth surface and the cells become modified for attachment to the tooth surface
What does the formation of the junctional epithelium of the gingiva involve?
Formation of hemidesmosomal attachments to the calcified surface of the tooth (can be to either the enamel or the cementum)
What is the only seal separating the “dirty (bacteria, etc)” oral cavity from the “inside” lamina propria and blood vessels supplying the gingiva?
Hemidesmosomal attachments
2 subdivisions of the palate
Hard palate
Soft palate
What underlies the mucosa of the hard palate?
Bone
What underlies the mucosa of the soft palate?
Skeletal muscle
Describe the mucosa of the palate
Masticatory mucosa similar to that of the gingival (i.e. with a stratified squamous parakeratinized epithlium). Reflects around the soft elastic palate and the uvula where it is a stratified squamous nonkeratinizing epithelium, to become respiratory epithelium (pseudostratified ciliated columnar) on the nasal side of the palate.
How is the mucosa attached to the palatine bone in the hard palate region?
By a mucoperiosteum
Where can salivary glands be found in the palate?
Laterally in the mucosa
Differentiate between the two portions of the tongue
- Free portion = covered entirely by epithelium
- Attached portion = epithelial lining continues with the oral mucosa covering the floor of the mouth
Describe the musculature of the tongue
Striated muscle with fibres that run in all directions and are:
- Intrinsic = origin and insertion from the connective tissue within the tongue
- Extrinsic = origin within the tongue, but an insertion outside the tongue (i.e. larynx)
Describe the contents between the muscle fibres in the tongue
Connective tissue containing fat and minor salivary glands that open by ducts to the epithelial covered surface of the tongue
What is located between the floor of the mouth and the tongue
Sublingual gland, a major salivary gland
Describe the epithelium of the dorsal surface of the tongue
Partially keratinized, modified in the form of papillae (projections from the surface)
4 types of tongue papillae
- Filiform (threadlike) papillae
- Fungiform (mushroom shaped) papillae
- Foliate papillae
- Circumvallate papillae
Tastes that utilize G-protein coupled membrane receptor pathways
- Bitter
- Sweet
- Umami
Tastes that utilize ion channels
- Sour (acid) = proton channel
- Salt = sodium channel
Most numberous type of papillae on the tongue
Filiform papillae
Reason for the tongue’s whitish velvety appearance and feel
Filiform papillae (keratinization of the epithelium)
Disrtibution of filiform papillae on the tongue
Fine ros on either side of the central line bisecting the tongue
Describe the histology of filiform papillae
Cup-shaped or pointed projections of epithelial cells that are usually keratinized on the outside, but not on the inside. Keratinization takes place from a stratum granulosum layer where the granules are eosinophilic.
What do the eosinophilic granules of the stratum granulosum layer in the filiform papillae resemble?
Resemble the trichohyalin granules seen in the internal root sheath of the fair follicle
Describe the filiform papillae in animals such as the cat
- Very well-developed
- Keratinized surface forms a sharp-ended structure with the sharp tip directed posteriorly = raspy feel to tongue and provides pockets that fill with fluid (lap up liquids)
Describe the distribution of fungiform papillae on the tongue
Between the filiform papillare as small ret dots and are more numerous on the sides and tip of the tongue
Describe the histology of fungiform papillae (5)
- Mushroom-shaped
- Lined by a stratified squamous epithelium (non-keratinized)
- Taste buds on top
- Core = lamina propria (primary connective tissue papilla)
- Smaller interdigitated papillae with epithelial papillae = LP close to surface –> red
Define foliate papillae
Folds in the mucosa (rather than actual papillae)
Location of foliate papillae
Predominantly in the posteriolateral portions of the tongue
Describe the development of foliate papillae from birth
Taste buds are present only in the newborn and soon degenerate, as do the papillae
What empties into the base of the furrows of foliate papillae
Von Ebner glands
How is the tongue divided postero-anteriorly?
Anterior two thirds divided from the posterior third by a V-shaped line of papilae, the lingual V.
Describe the form of the lingual V
The apex of the V is directed posteriorly and the arms of the V are formed by 8 - 12 very large circumvallate papillae
What is behind the apex of the lingual V
A blind invagination called the foramen caecum
What is the foramen caecum?
The rudiment of the thyroglossal duct, which is the origin of the epithelial invagination from which the thyroid gland developed
Describe the general structure of circumvallate papillae
- Large structures with a large primary papilla and numberous secondary connective tissue papillae
- Extend just above the surface of the tongue, surroudned by deep crypts
Describe the walls of the crypts surrounding circumallate papillae
The side walls are formed by other tongue papillae on the outside and the smooth walls of the circumvallate papillae themselves, both of which have numerous taste buds in the epithelium.
How do the taste buds of circumvalalte papillae open into the crypt lumen?
Taste pores
Describe how the taste buds in the walls of the circumvallate papillae are stimulates
Substances dissolved in the saliva enter the crypt space and stimulate the sensory cells
What happens to the fluid in the crypts of the circumvallate papillae
Continuous replacement by serous secretions delivered to the bottom of the crypt by way of numerous ducts from serous glands found under the circumvallate papillae
Location of Von Ebner glands
Under the circumvallate papillae
Histological location of taste buds
From the basal lamina through the epithelium to the surface
What forms the taste pore of taste buds?
Squamous epithelial cells
4 types of cells in the taste bud
- Columnar
- Type I dark supporting cells
- Type II light neuroepithelial cells
- Type III intermediate cells
- Basal cell (type IV)
Location of the cells types I to III in the taste bud
From the base of the taste bud, with their microvilli opening into the taste pore
Location of the nuclei of the columnar taste bud cells
Central regions
Location of Type IV basal cells in taste bud
Peripheral to the columnar cells and does not reach the taste pore
Function of Type IV basal cells in taste bud
Stem cell that renews the other cells
Turnover of taste bud cells
10 days
Descirbe the support cells for the taste buds
- Secretory
- Contain secretion granules with a content that resembles the amorphous material surrounding the microvilli in the taste pore
Number of neuroepithelial cells per taste bud
4 - 20 per taste bud
Location of neuroepithelial cells of the taste bud
Dispersed throughout, between the supporting cells
Contents of neuroepithelial cells of the taste bud
Vesicles that resemble synaptic vesicles, which are related to the free nerve endings that enter the taste bud through the basal lamina
Describe the stimulation of taste buds
Substances dissolved in the saliva stimulate the sensory hairs (microvilli) and the impulse produced is conducted to the nerve endings
Function of Von Ebner glands
Removal of the stimulatory substances from the taste buds
