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Module 5: GI > Histology of the Oral Cavity > Flashcards

Histology of the Oral Cavity Flashcards

1
Q

What are the layers of the GI tract?

A

Lumen

Mucosa

Submucosa

Inner Circular Muscle

Outer Circular Muscle

Serosa (Adventitia replaces serosa in some areas)

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2
Q

What are the layers of mucosa?

A

Epithelium lining villi

Lamina propria

Muscularis mucosa

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3
Q

What are enteroendocrine cells?

A

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)
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4
Q

How does the parasympathetic nervous system affect the GI tract?

A
  • 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
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5
Q

What does the vagus nerve innervate in the GI tract?

A

Esophagus

Stomach

Pancreas

Upper large intestine

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6
Q

What does the pelvic nerve innervate in the GI tract?

A

Lower large intestine

Rectum

Anus

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7
Q

How does the sympathetic nervous system affect the GI tract?

A
  • 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

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8
Q

What is the enteric nervous system?

A

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
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9
Q

What glands are found in the mucosal gland layer of the lip (mucosal surface)?

A

Labial salivary glands mostly secrete mucous

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10
Q

What are the histological layers found on the mucosal layer of the lip?

A

Top –> Bottom:

Mucosal epithelium: non-keratinized simple squamous epithelium

Lamina propria

Mucosal glands

Orbicularis Oris: muscular layer

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11
Q

What are ameloblasts?

A

Ameloblasts are the layer of a tooth that, during development, produce enamel.

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12
Q

What are odontoblasts?

A

Neural crest-derived cells of tooth adjacent mesenchyme that produce dentin

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13
Q

What is cementum?

A

A bonelike material that coverst he root of the tooth secreted by cementocytes

  • Unlike bone, cementum is avascular
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14
Q

What are the different types of tongue papillae?

A
  • Filiform
  • Fungiform
  • Foliate
  • Circumvallate
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15
Q

What are filiform papilae?

A
  • 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
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16
Q

What are fungiform papillae?

A
  • 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
17
Q

What are circumvallate papillae?

A
  • **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)
18
Q

What are foliate papillae?

A
  • 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
19
Q

What is the structure of a taste bud?

A
  • Taste pore: small opening onto the epithelial surface at the apex of the taste bud

3 principal cell types:

  • Neuroepithelium
  • Supporting cells
  • Basal cells
20
Q

What are characteristics of the neuroepithelial cells of taste buds?

A
  • 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)
21
Q

What are characteristics of the supporting cells of taste buds?

A
  • 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
22
Q

What are characteristics of basal cells of taste buds?

A
  • Small cells located in basal portion of taste bud
  • They are stem cells for neuroepithelial (sensory) cells and supporting cells
23
Q

What are the five basic taste bud stimuli?

A

Sweet

Salty

Bitter

Sour

Umami

24
Q

Which tastes are detected by receptors and which by ion channels?

A

Receptors:
Bitter
Sweet
Umami

Channels:
Sour
Salty

25
Q

What is the mechanism of taste receptors?

A

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

26
Q

What is the mechanism of sour taste?

A
  • 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

27
Q

What is the mechanism of Salty taste?

A
  • 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
28
Q

What does saliva contain?

A

Water

Ions (K, Na, Bicarb, Cl)

Enzymes and other glycoproteins

Antibacterial agents

Immunoglobulins

Cells (including lymphocytes, ‘shed’ epithelia)

…more…

Module 5: GI (19 decks)

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