Sense Organs Gustatory & Olfactory Apparatus ENGnikolai.lazarov.pro/lectures/2014-2015/dental... · Sense organs Golgi -Mazzoni corpuscles: in the subcutaneous tissue of the human

Sense OrgansSense Organs

1.1. Sense organs Sense organs –– classification classification 2.2. Sensory receptors:Sensory receptors:

�� unencapsulated unencapsulated –– free nerve endingsfree nerve endings�� encapsulated encapsulated

3.3. Gustatory apparatusGustatory apparatus4.4. Olfactory apparatusOlfactory apparatus

Prof. Dr. Nikolai LazarovProf. Dr. Nikolai Lazarov 2

�� ff ive senses:ive senses:�� touchtouch�� tastetaste�� smellsmell�� ssightight�� hearinghearing

�� specialized cells specialized cells –– receptors for specific stimulireceptors for specific stimuli:� confined to the head region� receptors are not free endings of sensory neurons

Human sense organsHuman sense organsSense organsSense organs

Five Senses IconsFive Senses IconsFive Senses IconsFive Senses IconsFive Senses IconsFive Senses IconsFive Senses IconsFive Senses Icons


�� 3 main groups 3 main groups –– Sherrington, 1906Sherrington, 1906::

�� exteroceptorsexteroceptors

�� proprioceptorsproprioceptors

�� interoceptorsinteroceptors

�� by sensory modality:by sensory modality:

�� baroreceptorsbaroreceptors – respond to pressure

�� chemoreceptorschemoreceptors – chemical stimuli

�� mechanoreceptorsmechanoreceptors – mechanical stress

�� nociceptorsnociceptors – pain perception

�� thermoreceptorsthermoreceptors – temperature (heat, cold or both)

�� by location:by location:

�� cutaneous receptorscutaneous receptors

�� muscle spindlesmuscle spindles

�� by morphologyby morphology:

�� free nerve endingsfree nerve endings

�� encapsulated receptorsencapsulated receptors

Sensory receptors Sensory receptors –– classification classification Sense organsSense organs

C.S. SherringtonC.S. Sherrington18571857––19521952


Sense of touchSense of touchSense organsSense organs

�� four kinds of touch sensationsfour kinds of touch sensations ::�� light tlight t ouchouch (contact)(contact)

�� coldcold

�� heatheat

�� painpain


Unencapsulated receptorsUnencapsulated receptorsSense organsSense organs

�� free nerve endingsfree nerve endings:� unencapsulated receptors� unspecialized, detect pain� most widely distributed� most numerous in the skin,

mucous&serous membranes, muscle, deep fascia,viscera walls

�� peritrichial (palisade) peritrichial (palisade) endings of hair folliclesendings of hair follicles� nerve plexus

around hair follicle� very light touch


�� tactile discs of Merkeltactile discs of Merkel:� slowly adapting type I mechanoreceptorsmechanoreceptors

– pressure and vibration at low frequencies, around 5 to 15 Hz

� found in the basal layers of:� glabrous skin� hairy skin ("touch domes“, "hair disks" )

� in oral and anal mucosa� in the mammary gland� specialized epithelial cells of Merkel,

“Tastzellen”� embryonic origin – nerve crest, epidermal� APUD cells – neuroendocrine function� specific granules

� Merkel nerve endings (tactile disks)

�� Merkel cellMerkel cell––neurite complexneurite complex

Unencapsulated receptorsUnencapsulated receptorsSense organsSense organs

Friedrich Merkel Friedrich Merkel (1845(1845--1919)1919)


�� Receptors without a lamellar inner coreReceptors without a lamellar inner core::�� Ruffini corpuscles (endings) Ruffini corpuscles (endings) �� Grandry corpusclesGrandry corpuscles

�� Receptors with an asymmetrical Receptors with an asymmetrical lamellated inner core:lamellated inner core:�� tactile corpuscles of Meissnertactile corpuscles of Meissner�� end bulbs (of Krause) end bulbs (of Krause) – ‘genitalgenital’’ corpusclescorpuscles�� GolgiGolgi--Mazzoni corpusclesMazzoni corpuscles

�� Receptors with a symmetrical Receptors with a symmetrical lamellated inner core:lamellated inner core:�� Pacinian (VaterPacinian (Vater--Pacini) corpusclesPacini) corpuscles�� Herbst corpusclesHerbst corpuscles

�� Muscle receptors:Muscle receptors:�� neurotendinousneurotendinous organ (Golgiorgan (Golgi tendontendon organ)organ)�� neuromuscular spindles:neuromuscular spindles:

�� intrafusal fibersintrafusal fibers�� extrafusal fibersextrafusal fibers

Encapsulated receptorsEncapsulated receptorsSense organsSense organs


Cutaneous receptorsCutaneous receptorsSense organsSense organs

�� tactile corpuscles of Meissnertactile corpuscles of Meissner::� unmyelinated nerve endings in the dermis of

glabrous skin� palm, fingers and lips

� responsible for sensitivity to light light touchtouch

�� rapidly adapting receptors rapidly adapting receptors sensing vibrations lower than 50 (20-40) Hz

�� end bulbs of Krause:end bulbs of Krause:� in the mucous membrane of the lips and tongue� also found in the penis and the clitoris –

‘genitalgenital’’ corpusclescorpuscles� responds to pressure –

pressoreceptorspressoreceptors� formerly – cold receptors cold receptors

(thermoreceptors)(thermoreceptors)



�� Pacinian (VaterPacinian (Vater--Pacini) corpuscles:Pacini) corpuscles:� oval-shaped and lamellated� the largest cutaneous receptors – approximately

1 mm in length (2x4 mm)� bulb-like nerve endings in the subcutaneous tissue

of the skin:� palms and soles� joints and genitals

� capsule of 20 to 60 concentric lamellae� inner core of modified Schwann cells� afferent nerve fiber – parts:

� myelinated� unmyelinated preterminal� nerve ending

� rapidly adapting (phasic) mechanoreceptorsmechanoreceptors(vibration and pressure) with optimal sensitivity 150-300 Hz



�� GolgiGolgi--Mazzoni corpuscles:Mazzoni corpuscles:� in the subcutaneous tissue

of the human fingertips � similar in morphology

to Pacinian corpuscles� senses vibratory pressure and touchvibratory pressure and touch

�� Ruffini endings Ruffini endings –– 0.50.5--2 2 mm:mm:

� end organs in the subcutaneous connective tissues of the fingers

� ovoid capsule within which the sensory fiber ends with numerous collateral knobs

� responds to superficial pressure –slowly adapting mechanoreceptorsmechanoreceptors

� early thought to be thermoreceptorsthermoreceptors(mediate the sense of warmthwarmth)


Muscle receptorsMuscle receptorsSense organsSense organs

�� neurotendinous organs (Golgi tendon organs):neurotendinous organs (Golgi tendon organs):� located at the insertion

of skeletal muscle fibers into the tendons�� proprioceptiveproprioceptive – reflex regulation

of muscle tension�� neuromuscular spindles:neuromuscular spindles:

�� intrafusal fibersintrafusal fibers� nuclear-bag fibers� nuclear-chain fibers

�� extrafusal fibersextrafusal fibers�� proprioceptors proprioceptors –– detect changes

in the length of the muscle


Gustatory apparatusGustatory apparatusSense organsSense organs

NB:NB: about 50 fibers innervate a single taste bud!about 50 fibers innervate a single taste bud!

�� peripheral gustatory organsperipheral gustatory organs ::

�� taste buds taste buds

(gustatory caliculi(gustatory caliculi) ) –– 20002000--9000:9000:

�� vallate papillae vallate papillae –– most numerousmost numerous

� plentiful in the posterior posterior ⅓⅓ of the tongueof the tongue

�� fungiform papillaefungiform papillae

�� soft palate, epiglottis and pharynxsoft palate, epiglottis and pharynx

�� nono structuralstructural differencedifference amongamong tastetaste buds:buds:�� gustatory (taste) poregustatory (taste) pore – 2-3 µm� collection of 5050--100 epithelial cells100 epithelial cells� contain long microvillimicrovilli

extend through a taste pore� contain two types of

gustatory receptor cellsgustatory receptor cells• with and without dense-cored granules

�� supportingsupporting (non-sensory) cellscells�� basal cellsbasal cells – undifferentiated,

form new receptor cells every 10-14 days


Gustatory apparatusGustatory apparatusSense organsSense organs

�� traditionally four basic qualities traditionally four basic qualities of taste:of taste:�� sweetnesssweetness�� bitternessbitterness�� sournesssourness�� saltinesssaltiness

�� fifth basic tastefifth basic taste�� umamiumami (“deliciousnessdeliciousness”) –

non-salty sensations evoked by some amino acids – glutamate

NB:NB: the sense of taste is a form of direct chemoreception!the sense of taste is a form of direct chemoreception!


� taste information reaches the cerebral cortexcerebral cortex:(the lowest part of (the lowest part of gyrus postcentralisgyrus postcentralis, parietal operculum = area, parietal operculum = area 4343))

� primarily through the facialfacial (anterior ⅔; lingual nerve � chorda tympani) and glossopharyngealglossopharyngeal (posterior ⅓) nervesnerves

� some taste information through the vagus nervevagus nerve

� sensory neurons synapse in the medulla – solitary tract nucleussolitary tract nucleus� IIIrd neurons in the ventral posterior medial nucleus of thalamusventral posterior medial nucleus of thalamus

Taste pathwaysTaste pathwaysSense organsSense organs


�� the sense of smell (olfaction):the sense of smell (olfaction):� receptors are part of the olfactory epithelium

�� olfactory mucosa olfactory mucosa – 3 cell types:� cell bodies of olfactory receptor cellsolfactory receptor cells

(40 million in human olfactory epithelium)

�� supporting cellssupporting cells – columnar cells

�� basal cellsbasal cells – form new receptor neurons (4-8 weeks)

�� olfactory (Bowmanolfactory (Bowman’’s) glandss) glands –– in lamina propriain lamina propria

Olfactory apparatusOlfactory apparatusSense organsSense organs

NB:NB: The smell receptors are sensitive toThe smell receptors are sensitive toThe smell receptors are sensitive toThe smell receptors are sensitive toThe smell receptors are sensitive toThe smell receptors are sensitive toThe smell receptors are sensitive toThe smell receptors are sensitive to seven types of sensationseven types of sensationseven types of sensationseven types of sensationseven types of sensationseven types of sensationseven types of sensationseven types of sensation::

camphor, musk, flower, mint, ether, acrid, or putrid!camphor, musk, flower, mint, ether, acrid, or putrid!


Olfactory neuroepitheliumOlfactory neuroepithelium� non-myelinated axons of the

olfactory epithelium:� gather into 18-20 bundles –

filaments of the olfactory nerve (CNI)� pass through the cribriform plate of the

ethmoid bone � attach to the olfactory bulbs

Sense organsSense organs


Olfactory bulbOlfactory bulbSense organsSense organs

� transmits smell information from the nose to the brain:� supported and protected by the cribriform plate

� multi-layered cellular architecture:� glomerular layer� external plexiform layer � mitral cell layer � internal plexiform layer � granule cell layer

� olfactory bulb – synaptic glomeruli:� nucleus of termination of cranial nerve I� mitral, granule and periglomerular cells� initial part of rhinencephalon


Olfactory tractOlfactory tract� consists of:

� axons of the mitral and tufted cells� centrifugal axons from the opposite bulb

� anterior olfactory nucleusanterior olfactory nucleus:� medium-sized multipolar neurons� their axons continue into the olfactory

striae and trigone�� olfactory striaeolfactory striae:

� lateral olfactory stria � limen insulae� medial olfactory stria � diagonal band of Broca

�� anterior perforate substanceanterior perforate substance�� olfactory tubercleolfactory tubercle – reduced in man

Sense organsSense organs


�� primary olfactory cortexprimary olfactory cortex:�� prepiriform cortex prepiriform cortex –– lateral olfactory gyrus lateral olfactory gyrus �� gyrus ambiensgyrus ambiens

�� periamygdaloidperiamygdaloid areaarea –– laterallateral olfactoryolfactory striastria �� gyrus semilunarisgyrus semilunaris

�� secondary olfactory cortexsecondary olfactory cortex:�� entorhinal areaentorhinal area, cranial part of parahippocampal gyrus

Olfactory cortex (piriform lobe)Olfactory cortex (piriform lobe)Sense organsSense organs


Thank youThank you……

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Sense Organs Gustatory & Olfactory Apparatus ENGnikolai.lazarov.pro/lectures/2014-2015/dental... · Sense organs Golgi -Mazzoni corpuscles: in the subcutaneous tissue of the human