Histology of the Oral Cavity Flashcards
What are the layers of the GI tract?
Lumen
Mucosa
Submucosa
Inner Circular Muscle
Outer Circular Muscle
Serosa (Adventitia replaces serosa in some areas)
What are the layers of mucosa?
Epithelium lining villi
Lamina propria
Muscularis mucosa
What are enteroendocrine cells?
Endocrine-paracrine cells of the gut
- sensitive to luminal contents
- Release hormones
- Can act locally (i.e. secrete Gastrin by G cells acting on parietal cells)
- Can act on more distance organs (i.e. Secretin secreted in duodenum acting on pancreatic duct cells)
How does the parasympathetic nervous system affect the GI tract?
- Part of extrinsic innervation, it is usually excitatory on functions of the GI tract
- Carried by the vagus and pelvic nerves
- Preganglionic parasympathetic fibers synapse in myenteric and submucosal plexuses
- Cell bodies in the ganglia then send info to smooth muscle, secretory cells, and endocrine cells
What does the vagus nerve innervate in the GI tract?
Esophagus
Stomach
Pancreas
Upper large intestine
What does the pelvic nerve innervate in the GI tract?
Lower large intestine
Rectum
Anus
How does the sympathetic nervous system affect the GI tract?
- Part of extrinsic innervation, it is usually inhibitory on functions of the GI tract
- Fibers originate in spinal cord between T8 and L2
- Preganglionic sympathetic cholinergic fibers synapse in prevertebral ganglia
- Postganglionic sympathetic adrenergic fibers leave the prevertebral ganglia and symapse in myenteric and submucosal plexuses. (direct innervation of blood vessels and some smooth muscle also occurs)
–> cell bodies of plexuses then innervate smooth muscle, secretory cells, and endocrine cells
What is the enteric nervous system?
Intrinsic innervation
of the GI tract
- Coordinates and relays info from parasympathetic and sympathetic nervous systems to GI tract
- Uses local reflexes to relay info within the tract
Myenteric plexus: controls motility
- *Submucosal plexus:** controls secretion and blood flow
- receives info from chemoreceptors and mechanoreceptors
What glands are found in the mucosal gland layer of the lip (mucosal surface)?
Labial salivary glands mostly secrete mucous
What are the histological layers found on the mucosal layer of the lip?
Top –> Bottom:
Mucosal epithelium: non-keratinized simple squamous epithelium
Lamina propria
Mucosal glands
Orbicularis Oris: muscular layer
What are ameloblasts?
Ameloblasts are the layer of a tooth that, during development, produce enamel.
What are odontoblasts?
Neural crest-derived cells of tooth adjacent mesenchyme that produce dentin
What is cementum?
A bonelike material that coverst he root of the tooth secreted by cementocytes
- Unlike bone, cementum is avascular
What are the different types of tongue papillae?
- Filiform
- Fungiform
- Foliate
- Circumvallate
What are filiform papilae?
- Smallest and most numerous papillae in humans
- Conical, elongated projections of connective tissue that are covered with highly keratinized stratified squamous epithelium
- NO taste buds
- Mechanical function only
What are fungiform papillae?
- Mushroom shaped projections located on dorsal surface of tongue.
- Project above the filiform papillae and ar just visible to unaided eye
- More numerous near tip of tongue
- Taste buds are present on stratified squamous epithelium of papillae
What are circumvallate papillae?
- **Large, dome shaped structures ** that reside in mucosa just anterior to sulcus terminalis
- Human tongue has 8-12 of these
- Each papillae is surrounded by moatlike invagination lined with stratified squamous epithelium that contains numerous taste buds
- Ducts of lingual salivary (von Ebner’s) glands empty serous secretion into base of moats (theoretically to flush taste buds)
What are foliate papillae?
- Papillae that consist of parallell low ridges separated by deep mucosal clefts
- They are aligned at right angles to the long axis of the tongue
- Many taste buds are in the epithelium of the walls facing neighboring papillae and small serous glands empty into the clefts
What is the structure of a taste bud?
- Taste pore: small opening onto the epithelial surface at the apex of the taste bud
3 principal cell types:
- Neuroepithelium
- Supporting cells
- Basal cells
What are characteristics of the neuroepithelial cells of taste buds?
- They are the sensory cells and most numerous in the taste bud.
- Elongated cells that extend from the basal lamina of epithelium to the taste pore
- At base, form a synapse with the processes of afferent senory neurons of CN VII, IX, or X (depending on location on tongue)
What are characteristics of the supporting cells of taste buds?
- Also elongated cells that extend from basal lamina to the taste pore
- Like neuroepithelial cells, contain microvilli on apical surface and possess tight junctions, but do not symapse with nerve
What are characteristics of basal cells of taste buds?
- Small cells located in basal portion of taste bud
- They are stem cells for neuroepithelial (sensory) cells and supporting cells
What are the five basic taste bud stimuli?
Sweet
Salty
Bitter
Sour
Umami
Which tastes are detected by receptors and which by ion channels?
Receptors:
Bitter
Sweet
Umami
Channels:
Sour
Salty
What is the mechanism of taste receptors?
Receptor activation –> G protein stimulates phospholiase C –> release of inositol 1,4,5-triphosphate (IP3) –> IP3 activates taste-specific Na+ Channels –> influx of Na+ into cell –> Depolarization of plasma membrane and activation of voltage -gated Ca2+ channels –> Ca2+ releases NTs which generates an AP on the post-synaptic afferent nerve
What is the mechanism of sour taste?
- It is generated by H+ protons that are formed by hdrolysis of acidic compounds
- H+ protons block K+ channels
–> Influx of H+ activates voltage-sensitive Ca2+ channels
–> Ca2+ triggers migration of synaptic vesicles, their fusion, and transmitter release, which results in generating AP in sensory nerve fiber
What is the mechanism of Salty taste?
- Na+ enters the neuroepithelial cells through specific amiloride-sensitive Na+ channels
- Na+ entering the cell depolarizes the membrane and activates voltage-sensitive Na+ channels and voltange-sensitive Ca2+ channels
- As in Sour tatse, Ca2+ triggers migration and release of synaptic vesicles, resulting in AP activation of gustatory afferent nerve cell
What does saliva contain?
Water
Ions (K, Na, Bicarb, Cl)
Enzymes and other glycoproteins
Antibacterial agents
Immunoglobulins
Cells (including lymphocytes, ‘shed’ epithelia)
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