1. Gustatory and olfactory apparatus and pathways.
Semmelweis University
Department of Anatomy, Histology and Embryology
2nd year
Kocsis Katalin

2. Sensory pathways sensory homunculus Sensation: conscious
unconscious (spinocerebellar pathways)
Conscious:
- vision (50%)!
hearing and balance
touch, skin sensation
- smell
- taste
„internal” sensation
In human smell and taste sensation are less dominant
sexual activity – feromons
sensory homunculus

3. Olfactory pathway: from the nasal cavity directly to the rhinencephalon
bilateral projection: localisation of the smell
Gustatory pathway: to the thalamus cortex (Brodmann’s 43)
afferent from the brain stem: visceral reflex response (like gastric juice production)

4. Gustatory system

5. Papillae circumvallatae
Gustatory system
Papillae foliatae
Papillae fungiformes

6. Gemma gustatoria (taste buds)

7. Forás: Röhlich Pál: Szövettan
porus gustatorius
receptor
supporting cells
receptors
supporting cells
undifferentiated (basal or „stem” cells
Receptors: dendrite-like short processes on the apical plasma membrane, stereocilia: chemoreceptors ( saliva and mucin).
Life time: very short (10-60 days).
Taste bud
„stem” cells
Schwann sheath
afferent fibers
basement membrane
Forás: Röhlich Pál: Szövettan

8. Signal transduction

9. Four (five, six) basic tastes:
Saulty and sour: directly through the apical ion channels
1. Salty: – ions binding on the microvilli (inorganic ions)
2. Sour: – acids: protons (H+ ions) interact with microvilli
Sweet and bitter: receptor-coupled „second messenger” pathway
3. Sweet – G-protein coupled, receptor-mediated transduction pathway; activation of adenyl cyclase → increase the level of cAMP; cAMP activates a PKA (protein kinase) → phosphorylation of the basolateral K+ channel → close → depolarization Ca-channels open
4. Bitter – IP3 (inozitol-3-phosphate) pathway → Ca2+ release
New and candidate basic tastes
5. Umami (yammi, glutamate-rich)
6. ? Fatty (oily) / starch-taste

10. Sensation of basic tastes, arrangement of specific taste buds
bitter
sour
salty
sweet

11. Sensation of basic tastes, arrangement of specific taste buds

12. Sensory pathway of taste sensation
n. VII.
chorda tympani
n. IX.
n. X.
tongue anterior 2/3: (n. lingualis (V/3))
chorda tympani (n. VII)
ganglion geniculi
nucleus tractus solitarii
tongue anterior 1/3:
n. glossopharyngeus (rr. linguales)
ganglion inferius
nucleus tractus solitarii
tongue root
n. vagus (rr. linguales)
ganglion inferius (nodosum)
nucleus tractus solitarii

13. Sensory pathway of taste sensation

14. nucl. tractus solitarii (VII, IX, X) special visceroafferens
Brain stem nucleus
nucl. tractus solitarii (VII, IX, X)
special visceroafferens

15. Cortical projection 43
n. tr. solitarii → thalamus VPM (parvicellular part VPM pc) → taste sensory cortex (lower part of the postcentral gyrus + operculum and inner surface of the insula (Brodman 43)

17. Olfactory organ

18. Smell sensation Bulbus olfactorius (CNS) Fila olfactoria
(lamina cribrosa)
Forrás: Sobota - Atlas of Human Anatomy
Liquor space of the CNS and the lymphatic vessels of the nasal cavity are in connection with each other through the lamina cribrosa: drugs can enter to the CNS by bypassing the blood/brain barrier

19. Organum olfactum bulbus olfactorius tractus olfactorius
Thalamusban nincs átkapcsolás
Primer bipoláris érzéksejtek axonjai (fila olfactoria): nervus olfactorius
bulbus olfactorius tractus olfactorius
Nagy konvergencia 1000:1
de nincs térképszerű megfeleltetés.
Nincs „rózsillat-receptor”, minden
glomerulus hozzájárul az észlelt szaghoz
A primer érzéksejtek aktivitása változik, belégzés végén maximális,
fokozza éhség, izgatottság, félelem

20. Histological structure of the olfactory region
Tunica mucosa:
lamina epithelialis: 3 types of cells:
receptors: primary olfactory neurons; life time: days (only neurons known to proliferate during adult life)
basal cells: proliferating cells; daughter cells differentiate into mature neurons
supporting cells
lamina propria: Bowmann‘s glands: odorant binding protein (OBP)
regulation: parasympatetic (cholinergic – VIP fibers)
sympathetic (ß-adrenergic fibers)
Afferent fibers (from n. V.): (unmyelinated fibers, nerve endings)
stimulation: local release of substance P: modifies the sensitivity of the neurons

21. Olfactory region Receptors: primary sensory cells: bipolar cells
cilia
cilia
Receptors: primary sensory cells: bipolar cells
contain OBP (odorant binding protein) receptors on their plasma membrane
axon-like processes - fila olfactoria – bulbus olfactorius
the number of them: 2 x 107
life time: days
more than 100 receptor molecules
bulb-like ending
supporting cell
receptor
basal cells
basement membrane
Schwann cells
axon

22. Signal transduction Receptor:
individual receptors respond to large number of odorants
and single odorant will stimulate large number of receptors
each receptor contains many different receptor molecules
olfactory receptor molecules have a broad spectrum of sensitivity and able to respond to many odorant
G protein coupled, 7 transmembrane domain
encoded by more than 1000 genes (in mouse)
variable odorant binding sequences
huge receptor „repertoir”

23. Forrás: Szentagothai J, Réthelyi M: Funkcionális anatómia
olfactory epithelium
olfactory glomerulus
mitral cells tufted cells
inhibitory granule cells
Nucleus olfactorius anterior
efferent fibers
Forrás: Szentagothai J, Réthelyi M: Funkcionális anatómia
medial
lateral
contralateral olfactory bulb
L: prepiriform cortex (base of the frontal lobe, uncus), amygdala
M: substantia perforata anterior, hypothalamus

24. Olfactory bulb 6 layers: 1.) olfactorius n. fibers
2.) glomerular layer: periglomerular cells
3.) ext. plexiforme layer: processes of the mitral cells and tufted cells
4.) mitral cells layer
5.) inner plexiforme layer: granule cells
6.) central fiber core to olfactory tract

25. Olfactory bulb: afferents
Primary afferents: olfactorius n. peptiderg (pl. carnosine) synapses with mitral, tufted and periglomerular neurons (convergence: about 1000 receptors to 1 mitral cell)
Other afferents come: locus ceruleus (noradrenerg), reticular formation: raphe nuclei (serotononerg), medial septal nucleus (cholinerg), contralateral olfactory bulb
Olfactory bulb: efferents
Axons of the mitral cells: uncus, amygdala, ipsilateral olfactory cortex (glutamate, aspartate)
Processes of the tufted cells: substantia perforata ant., contralateral olfactory bulb (substance P, dopamine, cholecystokinin, encephaline)

26. Stria olfact. lateralis
Tractus olfactorius
Trigonum olfactorium
Stria olfact. lateralis
Stria olfact. medialis
bifurcate:
lat.: sulcus lat.
med.: limen insulae
(anterior to the uncus)
medial surface of
the frontal lobe
to subcallose area

27. Olfactory cortex paleopallium (rhinencephalon) bulbus olfactorius
tractus olfactorius
trigonum olfactorium
striae olfactoria med. et lat.
substantia perforata anterior
Broca-féle diagonal band
primer olfactory cortex (lobus piriformis):
gyrus ambiens, gyrus semilunaris

29. Central pathway from the olfactory bulb to the neocortical olfactory area

30. hippocampus és amygdala
Connections of olfactory system
gyrus cinguli
fornix
Complex pathway
No connection with the thalamus!
Projects to the most ancient cortical region.
Strong relationship with the limbic system.
Smell stimuli: regulate the basic emotional reactions.
corpus mamillare
hippocampus és amygdala

31. Vomeronasalis organ (Jacobson's organ)
in the mucosa of the nasal cavity
feromon-sensitive: sexual behaviour
accessory olfactory bulb: amygdala
„13th / 0th cranial nerve”: n. terminalis
well developed in newborns
in 60% of the adult population: regress

32. References
Röhlich Pál: Szövettan, SOTE Képzéskutató, Oktatástechnológiai és Dokumentációs Központ, Budapest, 1999
Szentagothai J, Réthelyi M: Funkcionális anatómia, Medicina, 1989
Sobota - Atlas of Human Anatomy, 20th edition, Urban and Schwarzenberger, 1993
Kahle: SH Atlasz
Willis DW: The Special Senses in Berne RM et al.: Physiology, 5th edition, Elsevier Inc., 2004
Burt AM: Textbook of Neuroanatomy, Saunders Company 1993
Vígh B: Szisztémás anatómia, Rendszeres Orvosi Bonctan, Alliter, 2005