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Neuro > Gustatory & Olfactory System Histology > Flashcards

Gustatory & Olfactory System Histology Flashcards

1
Q

Describe gross anatomy of posterior 1/3 of tongue

A

Displays aggregations of lymphatic tissue, the lingual tonsils

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2
Q

Describe histology of dorsal surface of tongue

A

Nonkeratinized stratified squamous epithelium supported by lamina propria associated with muscle core of tongue

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3
Q

What are the intrinsic muscles of the tongue?

A

Superior longitudinal
Inferior longitudinal
Transversus linguae
Verticalis linguae

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4
Q

Serous and mucous glands extend across the lamina propria and the muscle. Where do their ducts open into?

A

Crypts and furros of lingual tonsils and circumvallate papillae

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5
Q

Describe lingual papillae

A

Mucosal projections on dorsal surface of tongue

Formed by a highly vascular connective tissue core an a covering of stratified squamous epithelium

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6
Q

What are the four types of lingual papillae?

A

Filiform papillae: narrow conical and most abundant
Fungiform papillae: mushroom-shaped, has taste buds
Circumvallate papillae: has taste buds
Foliate papillae: leaf-shaped and rudimentary in humans

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7
Q

Describe geographic tongue

A

Thought to be oral manifestation of psoriasis (dermatological condition which causes patches of dry, flakey, itchy skin)
Manifests as area of erythema, with atrophy of filiform papillae of tongue, surrounded by serpiginous, white, hyperkeratotic border

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8
Q

Serous (Ebner’s) glands in the connective tissue are in contact with underlying muscle and are associated with foliate and circumvallate papilla. What do they secrete?

A

Lingual lipase and Von Ebner’s gland protein (VEGP)

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9
Q

What does Von Ebner’s gland protein (VEGP) do?

A

Undertakes selective binding of sapid (flavorful) chemicals and their transport to taste receptors

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10
Q

Describe location of circumvallate papillae

A

In posterior part of tongue, aligned in front of sulcus terminalis
Occupies a recess in mucosa and is surrounded by ciruclar furrow or trench

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11
Q

What are the three components of a taste bud?

A 
Taste receptor cells
Supporting cells (immature taste cells)
Precursor cells (basal cells)
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12
Q

Describe cycle of taste bud

A

Taste receptor cells have a life span of 10-14 days

Precursor cells give rise to supporting (immature taste) cells, which in turn, become mature taste receptor cells

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13
Q

What does the basal portion of a taste receptor cell make contact with?

A

Afferent nerve terminal derived from neurons in sensory ganglia of facial, glossopharyngeal, and vagus nerves

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14
Q

Describe the biochemistry of taste

A

Taste is initiated when soluble chemicals (tastants) diffuse through taste pore and interact with G-protein gustducin linked to receptors TR1 and TR2 in apical microvilli of taste receptor cells
GTP binds to Galpha and activates ion channels in taste receptor cells
Ionic changes cause either depolarization or hyperpolarization of cells
An increase in intracellular Ca2+ triggers release of neurotransmitters at afferent synapse with afferent nerve terminal

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15
Q

Nerve fibers innervate types I-III taste buds, and all three function in discrimination of taste. About __ fibers innervate a single taste bud

A

50

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16
Q

Facial nerve carries the five taste sensations (sweet, sour, bitter, salty, umami), while glossopharyngeal nerve may carry ____

A

Sweet and bitter

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17
Q

Where are the sweet, salty, and sour taste receptors on the tongue?

A

Sweet (sugars): tip of tongue
Salty (sodium): posterior and lateral to tip of tongue
Sour (acidic, H+): on anterior 2/3 of dorsum and along lateral margin

18
Q

Describe individuals with sensitive form of hTAS2R38 taste receptor gene

A

They rate kohlrabi (which contains glucosinolates that inhibit iodine uptake by thyroid) as more bitter than do people with less sensitive form of gene
Depending on version of gene, there are different sensitivities

19
Q

Describe umami

A

Taste of monosodium glutamate
Linked to specialized receptor for L-glutamate and other amino acids
Distribution of receptors is unknown
Glutamate signals presence of proteins and causes intake of proteinious foods
Glutamate Is found in meats, cheeses, several vegetables, and is often added to processed food as a flavor enhancer
Can promote food consumption (could help elderly and ill at risk for malnutrition)

20
Q

Describe taste perception of taste buds

A

Each taste bud can discern all five tastes but appear to concentrate on two
Taste buds on palate register primarily bitter and sour, while posterio pharynx & epiglottis register all five
Receptor cells are tuned to respond to single taste modalities and are innervated by individually tuned nerve fibers
Each taste quality is specified by activity of non-overlapping cells and fibers

21
Q

Describe fat and receptor CD36

A

CD36 recognizes texture of fat
Also functions to facilitate uptake of fatty acids
May possibly increase preference for fatty foods
Altered C36 decreases desire for fatty foods

22
Q

Describe origin, sensory innervation, and innervation of taste buds for anterior 2/3 of tongue

A

Origin: median tongue bud, lateral lingual swellings
Sensory: lingual nerve (branch of CNV)
Taste: facial nerve (CNVII)

23
Q

Describe origin, sensory innervation, and innervation of taste buds of posterior 1/3 of tongue

A

Origin: hypopharyngeal eminence
Sensory: glossopharyngeal nerve (IX)
Taste: glossopharyngeal nerve. Vagus (X) near base of tongue

24
Q

Describe origin and innervation of muscles of tongue

A 
Develop from mesoderm of occipital myotomes that migrate into developing tongue
Hypoglossal nerve (XII)
25
Q

Most sensory information that is thought of as taste is actually __

A

Olfactory sensation by olfactory mucosa

26
Q

Describe histology of nasal cavity

A

Lined by pseudostratified columnar epithelium with goblet cells
Lamina propria contains both serous and mucous glands to moisten inspired air and trap particulate contaminants
Lamina propria also contains extensive vascular plexus (swell/cavernous bodies)
Contains mast and plasma cells (IgA, IgE, IgG)

27
Q

Describe how nasal mucosa causes air hydration

A

Secretions of serous & mucous exocrine glands & Goblet cells moisten surface of nasal cavity
Add water vapor to inspired air

28
Q

Describe how nasal mucosa causes air filtration

A

Conchae interrupt air flow and create turbulence
Particulate matter thrown against conchae and adheres to its moist surface
Cilia move mucus/matter into nasopharynx

29
Q

Describe how nasal mucosa causes temperature regulation

A

Superficial vascular plexus (swell bodies) within lamina propria
Can warm or cool inspired air

30
Q

Describe olfactory epithelium

A

Pseudostratified columnar epithelium
Restricted to roof of nasal cavity: upper surface of superior conchae
Contains three cell types: olfactory cells, supporting (sustentacular) cells, an basal cells
Underlying lamina propria also contains lymphoid cells

31
Q

Describe olfactory cells

A

Bipolar sensory neurons that span thickness of epithelium
Dendrite extends to free surface and dilates to form olfactory vescile
Projects, along with cilia, above epithelial surface
Proximal process extends basally, becomes a non-myelinated axon, and forms bundles of nerve fibers: the fila olfactoria

32
Q

Describe the supporting (sustentacular) cells for olfactory

A

Columnar cells with oval nuclei (apical one-third of cell)
Apical surface has microvilli submerged in seromucous fluid layer
Contain light yellow pigment that gives olfactory epithelium its color
Provide physical support, nourishment, and electrical insulation for olfactory cells

33
Q

Describe production of olfactory cells

A

Basal cells are mitotically active stem cells, producing daughter cells that differentiate into immature olfactory cells that then turn into mature olfactory cells
Olfactory cells proliferate during adult life, and life span of cells is about 30-60 days

34
Q

Describe the process of olfaction

A

Cilia contain odorant receptors (OR).
Each olfactory receptor cell expresses only one OR gene
Olfactory serous glands (glands of Bowman) secrete a serous fluid in which odoriferous substances are dissolved
Secretory fluid contains odorant-binding protein (OBP) with high binding affinity for a large number of odorant molecules
OBP carries odorants to receptors present on surface of cilia and removes them after they have been sensed

35
Q

What are the protective substances secreted by olfactory serous glands (glands of Bowman)?

A

Lysozyme an IgA

36
Q

Describe axons and dendrites of olfactory cells

A

Axons from olfactory cells with the same OR terminate in one to three glomeruli present in olfactory bulb
Dendritic endings of predominantly mitral cells extend into glomeruli
Axons of mitral cells form olfactory tract

37
Q

What is anosmia?

A

No sense of smell
Lack of neurons in brain (mitral cells) that receive input from olfactory neurons
Olfactory bulb does not develop

38
Q

What can cause small genitalia/sterility?

A

Lack of gonadotropin releasing hormone (GnRH), secreted by hypothalamus
GnRH is required for secretion of luteinizing hormone (LH), required for gonadal development and genital maturation

39
Q

Describe Kallman Syndrome

A

X-linked disease characterized by anosmia, small genitalia, and sterile gonads
Caused by failure of GnRH-secreting neurons and olfactory neuron growth cones to migrate into brain

40
Q

What is the defective gene for Kallman Syndrome?

A

KAL-1, which codes for anosmin 1
Anosmin 1 is a cell adhesion protein that is expressed in olfactory system and medial walls of primitive cerebral hemispheres

41
Q

GnRH-secreting neurons do not originate in hypothalamus. Where do they originate?

A

Originate in olfactory epithelium (vomeronasal organ) and migrate into brain
Axons of olfactory neurons must contact developing brain to stimulate olfactory bulb development

42
Q

Describe gross anatomy of the anterior 2/3 of tongue

A

Consist of core mass of skeletal muscle oriented in 3 directions:
Longitudinal, transverse, and oblique

Neuro (13 decks)

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