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SENSORY SYSTEM

Part 2. SENSORY SYSTEM. Lecture for medical students. Organs of Hearing, Equilibrium and Taste. Department of histology, cytology and embryology KhNMU. Organ of Hearing and Equilibrium is located in the ear. Ear consists of: External ear – receives the sound waves

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SENSORY SYSTEM

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  1. Part 2 SENSORY SYSTEM Lecture for medical students Organs of Hearing, Equilibrium and Taste Department of histology, cytology and embryology KhNMU

  2. Organ of Hearing and Equilibriumis located in the ear. • Ear consists of: • External ear – receives the sound waves • Middle ear – transmits vibrations of tympanic membrane • Inner ear = labyrinth – contains receptors for hearing and equlibrium

  3. External, Middle, Inner Ear

  4. External EarAuricle, external auditory meatus, tympanic membrane(individual) (ceruminous glands, earwax) ( fibrous membr. mucous inner)

  5. Middle Earis thetympanic cavity in the temporal bone,malleus, incus, stapes • contains ossicles:

  6. Middle Ear • is the air space • bony ossicles are connected with joints • malleus is connected with ear drum • stapes closes the oval window, leading to the inner ear Middle Ear is connected with nasopharynx by eustachian tube

  7. Middle Ear. Auditory (Eustachian) tube auditory tube

  8. Inner ear = labyrinth is located in the temporal bone, contains cochlea(organ of hearing), vestibule and semicircular canals(organ of equilibrium)

  9. Inner EarVestibule, semicircular canals, cochlea

  10. Inner ear = Bony labyrinth • is fillled with perilymph • (similar in ionic content to extracellular fluid) • in it is located: • Membranous labyrinth is filled with endolymph • (similar to intracellular fluid)

  11. Section of the inner ear C SC V Cochlea (C),vestibule (V), semicircular canal (SC).

  12. Cochlea SV The bony cochlea has at its center the bony pillar - modiolus (M) containing spiral nerve ganglion (G). Bony canal does 2-3 spiral turns around modiolus. SM Sl ST G M G

  13. One section of the coclea spiral canal SV VM CD Limbus Sln OC S lig BM m ST Vestibular membrane (VM) and basilar membrane (BM) divide canal into scala vestibuli (SV), cochlear duct (CD) and scala tympani (ST).

  14. SVCDST VM BM

  15. Coclear ductis three angular VAS VM OC Limbus S lig BMSL The lateral wall of thecochlear duct is formed by the stria vasculrias(vas), which produces endolymph.

  16. Stria vascularis Within the stria vascularis you can see capillaries (c), an unusual feature of this epithelium. vas c

  17. One section of the spiral canal SV VM CD Limbus Sl n OC S lig BM m ST Organ of Corti (OC)is on the basilar membrane. It is peripheral part of organ of hearing

  18. Organ of Corti OC TM OHC Limbus IHC On the osseous spiral lamina locates limbusfrom which extends the tectorial membrane (TM)

  19. Organ of Corti OC TM OHC Limbus IHC Under the tectorial membrane locate the three rows of outer hair cells (OHC) – columnar shaped. The single inner hair cell (IHC) is seen medial - pear shaped.

  20. OHC Organ of Corti OC tm sl IHC phc bm pc t bsl High mag. At the centre of OC the pillar cells (pc) form tunnel (t). Hair cells are supported by phalangeal cells (phc).

  21. tectorial membraneouter hair cells inner h.c. outer phalanger cells inner ph.c. pillar cells Organ of Corti

  22. H SV At the top of the cochlear canal the scala vestibuli connects with the scala tympani - Helicotrema CD ST G M G

  23. Helicotrema SV CD ST

  24. Scala vestibuli ends with the oval window, scala tympani with the round window, located in between middle and inner ear oval window cochlear duct round window

  25. Spiral ganglion G The basal parts of hair cells synapse with dendrites of afferent n. cells of the spiral ganglion,locating in the osseous spiral lamina, extending from the modiolus.

  26. Mechanism of hearing: under sound tympanic membrane vibrates, ossicles push oval window.

  27. Mechanism of hearing: perilymph moves through helicotrema to round window, calls movement of endolymph of cochlear duct and tectorial membrane which irritates hair cells. Dendrites of spiral ganglion cells take impulse. cochlear duct

  28. H The fibers of the basilar membrane are the shortest at the basal turns – percept high-frequency sounds. - are the longest at the apical turns – percept low-frequency sounds. Inner hair cells percept weak sounds, outer - intense sounds. SV CD ST G SV M G

  29. Pathology • Hearing loss: conductive sensorineural • Otosclerosis

  30. Ogran of equilibrium endolymph bsc Utricle AC Semicircular canal Vestibule M Perilymph Semicircular canals and vestibule. Perilymph, endolymph. Within the ampullated end of the bony semicircular canal (bsc) is the ampullary crest (AC). The flat macula (M) is in the utricle and saccule of the vestibule.

  31. Inner EarVestibule, semicircular canals, ampulla

  32. Ampullary crest in the semicircular canals sc AC The sensory epithelium (E) of the cresthas kinocilia and stereocilia and sits on a mound of CT (ct) with nerves(N) leading from it. The crest has a gelatinous cupula (C) resting on top of its receptor(E). Function: C E ct N

  33. Ampullary crest in the semicircular canals • Movements of endolymph causes the deflection of the cupula and arisement of nerve impulse • Cells are stimulated by movements of a head and angular accelerations

  34. Macula of the utricle and succule M Utricle with macula The macula (M) is a flattened collection of sensory hair cells sitting upon their supportive cells. The kinocilium and stereocilia of each sensory cell are embedded in a gelatinous layer with calcified otoliths (arrow) – otolith membrane.

  35. Macula of the utricle and succule O R S A higher magnification of the edge of the macula showing the otolithic layer (O) resting on a gelatinous layer (light arrow) atop the sensory receptor (R) and supporting cells (S).

  36. Otolith membrane Hair cells Supp.cells Nerve endings Macula of the utricle and succule gives information about the force of gravity, linear acceleration and static position of a head – turning, inclination, or in the dark, under the water(Pathology -Vertigo – the sence of rotation without equilibrium)

  37. The membranous labyrinth develops from ectodermal first branchial grooves with contact of neural tube.The vesicles are lined by pseudostraqtified epithelium

  38. Differentiation of inner ear from otic vesicle

  39. Bony labyrinth and connective tissue develop from mesenchyme. Nerve supply develops from neural tube

  40. Organ of Taste • There are taste buds in the epithelium of the tonque papillae. • There are 4 taste sensations: sweet, biter, acid and salty

  41. cv Papillae of the tongue • Tongue. Dorsal surface • Each papilla contains many oval taste buds (tb) on the lateral surfaces. • Each taste bud is opened with taste pore ve tb low

  42. Taste bud • Tongue, papilla with taste buds There are 3 types of cells in taste bud: 1. basal are stem cells, 2. elongated supporting cells 3. actual taste cells. Taste cells are also elongated cells whose microvilli extend into the taste pore which opens to the surface; these cells are contacted by sensory nerves from below. fp tb high med

  43. Taste sensations • Tip of the tongue - sensitive to sweet and salt • Lateral edges - sensitive to sour • Posterior portion - sensitive to bitter

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