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The Sensory Organs

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The Sensory Organs The Sensory Organs Sensory organs include the receptors and accessory organs. – PowerPoint PPT presentation

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Title: The Sensory Organs


1
The Sensory Organs
  • ??????? ?????
  • ???

2
The Sensory Organs
  • Sensory organs include the receptors and
    accessory organs. The receptors may be divided
    into three kinds
  • The exteroceptors ???? receive stimuli such as
    touch, temperature, pain, light and sound from
    the external environment
  • The interoceptors ???? pick up information about
    internal environment
  • The proprioceptors ????? receive stimuli from
    muscles, tendons, joints and ligaments

3
The Visual Organ ??
  • Composition eyeball and accessory organs of eye
  • Shape of eyeball
  • Has anterior and posterior poles
  • Equator ?? an imaginary line encircling the
    eyeball, midway between anterior and posterior
    poles
  • Axis of eyeball ?? a line joining the two poles
  • Optic axis ?? a line joining the center of the
    pupil to the fovea centralis

4
Walls of eyeball
Cornea ??
Fibrous tunic of eyeball
Sclera ??
Iris ??
Vascular tunic of eyeball
  • Cilliary body ???
  • Choroid ???

Pars iridica retinae
Pars caeca retinae
Retina ???
Pars ciliaris retinae
Pars optica retinae
5
Fibrous tunic of eyeball (outer)
  • Cornea ?? anterior 1/6, a nonvascular,
    transparent portion, richly supplied by nerves
    because it is curved, the cornea helps focus
    light
  • Sclera ?? (white of eye, opaque portion)
  • posterior 5/6, consisting of fibrous connective
    tissue that forms a tough protective covering for
    eyeball,
  • Contains sinus venosus sclerae ?????which lies
    beneath the junction of cornea and sclera

6
Vascular tunic of eyeball (middle)
  • Iris ??
  • Thin contractile membrane anterior to ciliary
    body, with a central opening, the pupil ??
  • Contains sphincter pupillae ?????(circular
    fibers) and dilator pupillae ????? (radial
    fibers)
  • Cornea and iris meet to form the iridocorneal
    angle ?????

7
  • Cilliary body ???
  • Body a ring-shaped thickening anterior to
    equator, containing smooth muscle fibers called
    ciliary muscle ???
  • Ciliary processes ??? a series of some 6080
    projections producing aqueous humor
  • Ciliary ring ???

8
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9
  • Choroid ???
  • Thin, highly vascular in posterior 2/3 of eye
  • Contains brown pigmented cells and dense
    capillary plexus

10
Retina ???
  • Pars caeca retinae?????
  • Pars iridica retinae ??????
  • Pars ciliaris retinae ???????
  • Pars optica retinae?????
  • Lines the choroidsComposed of two layers
  • An outer pigment cell layer
  • Inner neural layer (four layers)

11
  • The fourth layer consists photoreceptor cells
  • Cone cells ????are color receptors that function
    best during the day
  • Rod cells ????are dark-light receptors that
    function best at night and in dim light
  • The third layer consists of bipolar neurons ????
  • The second layer is formed ganglion cells ???,
    whose axons form optic nerve
  • The first layer consists of nerve axons that
    collect at the optic disk and pass through the
    sclera to form the optic nerve

12
  • Optic disc ???? (blind spot), located medial to
    posterior pole of eye, and consists of optic
    nerve fibers and central artery of retina
  • Macula lutea ??
  • Lies lateral about 3.5 mm to optic disc, a
    shallow depression, it is completely free of
    blood vessels and is yellowish in color
  • Fovea centralis ???, aera of greatest visual
    acuity (concentration of cones), at its center
  • The pigmentted layer absorbs light that passes
    completely through the anterior layer, preventing
    backscatter (blurring of vision)

13
Contents of eyeball
Aqueous humor ??
Lens ???
Vitreous body ???
14
Aqueous humor ??
  • Chamber of eye ??- lies between cornea and lens,
    and divided by iris into anterior and posterior
    chambers
  • Aqueous humor ??
  • A clear watery fluid that fills chamber of eye
  • Continuously secreted by ciliary body into
    posterior chamber
  • Passes through pupil into anterior chamber
  • Then it filters though iridocorneal angle into
    sinus venosus sclerae, this sinus drains via
    anterior ciliary veins into ophthalmic veins

15
Production and circulation of aqueous humor
Ciliary body
Posterior chamber
Anterior chamber
Sinus venosus sclera
Anterior ciliary vein
Ophthalmic vein

Functions
  • Helps focus light
  • Helps maintain constant pressure in eyeball
  • Helps nourish the lens and cornea

16
Lens ???
  • Transparent biconvex structure, covered by an
    elastic transparent capsule
  • Located between iris and vitreous body, and
    suspended behind pupil by ciliary zonule ????
  • Shape changed by the ciliary muscle for near
    vision, the ciliary muscle contracts and the lens
    rounds up, while for distant vision the lens
    flattens out, so that the eye may be focused on
    distant objects

17
Vitreous body ???
  • Consists of colorless, transparent jelly-like
    substance in which there is a meshwork of fine
    fibrils, occupies the vitreous chamber, the space
    between lens and retina
  • Helps maintain the shape of eyeball and supports
    the retina

18
Refractive media of eye????
  • Bend entering light waves and focus them on the
    retina
  • Cornea
  • Aqueous humor
  • Lens
  • Vitreous body

19
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20
Accessory organs of eye ???
Eyelids ??
Conjunctiva ??
Lacrimal apparatus ??
Ocular muscles ????
Connective tissue in the orbit
21
Eyelids ??
  • (from without inwards )
  • Skin, extremely thin
  • Subcutaneous areola tissue, loose and delicate
  • Muscular layer orbicularis oculi
  • Tarsus ??, formed by dense connective tissue in
    which the tarsal glands???embedded
  • Lined by palpebral conjunctiva ???
  • Function to protect, open, and close eye

22
Tarsus ??
23
Conjunctiva ??
  • Three parts
  • Palpebral conjunctiva ??? lining inner
    surface of eyelids
  • Bulbar conjunctiva ??? lining anterior part of
    sclera, up to corneal margin
  • Conjuntival fornix ???(superior and inferior)
    line of reflection of bulbar and palpebral
    conjunctiva
  • Conjunctival sac ???

24
Lacrimal apparatus ??
  • Lacrimal gland ??
  • Oval 2-cm, occupies fossa for lacrimal gland
  • Ducts (610 in number) empty into anterior
    region of superior fornix of conjunctiva
  • Secrets tears, which move across eyeball to
    medial angle,protect and moisten eye

25
  • Lacrimal passages ??
  • Lacrimal puncta ?? opening to lacrimal ductules,
    one on each eylid margin near medial angle
  • Lacrimal ductules ??? one in each lid, pass
    medially, join and enter lacrimal sac
  • Lacrimal sac ?? within fossa for lacrimal sac,
    opening into nasolacrimal duct
  • Nasolacrimal duct ???courses 2 cm inferiorly and
    opens into inferior nasal meatus

26
  • Tear is produced by lacrimal gland
  • Passes through superior conjunctival fornix into
    conjunctival sac
  • Then it is drained through lacrimal punctum,
    lacrimal ductule, lacrimal sac and nasolacrimal
    duct into inferior nasal meatus.

27
Ocular muscles ????
Muscle Action Nerve supply
levator palpebrae superioris Raises upper eyelid ?
Superior rectus Turns eyeball superomedially ?
Inferior rectus Turns eyeball inferomedially ?
Medial rectus Turns eyeball medially ?
Lateral retus Turns eyeball laterally ?
Superior obliquus Turns eyeball inferolaterally ?
Inferior obliquus Turns eyeball superolaterally ?
28
Ocular muscles ????
29
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30
Connective tissue in the orbit
  • Sheath of eyeball ????? a thin
    membrane, which surrounds the eyeball from optic
    nerve to corneoscleral junction, permits the
    eyeball to move in the orbit without friction
  • Adipose body of orbit ??? lies between sheath
    of eyeball and the orbit acts as a protective
    cushion and shock sorber for the eyeball

31
Vessels of eye
  • Ophthalmic artery???
  • Branch of internal artery
  • Branches-central artery of retina ???????
  • Enters optic nerve, passes toward the optic disk
    and then fans out to supply the retina

32
  • Four branches superior and inferior nasal or
    temporal arteriole of retina

33
  • Ophthalmic vein ???
  • Superior ophthalmic vein communicates with facial
    vein anteriorly, exits posteriorly via superior
    orbital fissure to drain into cavernous sinus
  • Inferior ophthalmic vein lies on floor of orbit
    and communicates with pterygoid plexus, exits via
    superior orbital fissure to drain into cavernous
    sinus

34
The Vestibulocochlear Organ
  • ??????? ?????
  • ???

35
General features
  • Three parts
  • External ear ?? collects sound waves
  • Middle ear ?? transmits sound waves
  • Internal ear ?? contains the vestibulocochlear
    organ concerned with equilibration and hearing

36
External ear ??
  • Auricle ??
  • External acoustic meatus ???
  • Tympanic membrane ??

37
Auricle ??
38
External acoustic meatus ???
  • A slender canal that extends from external
    acoustic pore to tympanic membrane
  • Two parts
  • Cartilaginous part- lateral 1/3
  • Bony part-medial 2/3
  • Lined by a layer of thin skin.
  • This S-shaped passage medially, at first forward
    and upward, then backward and, finally forward
    and downward.

39
Tympanic membrane ??
  • A thin oval membrane
  • Two parts
  • Flaccid part ??? upper 1/4
  • Tense part ??? lower 3/4
  • Umbo of tympanic membrane ???
  • Cone of light ??

40
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41
Middle ear ??
  • Tympanic cavity ??
  • Auditory tube ???
  • Mastoid antrum ???and mastoid cells ????

42
Tympanic cavity ??
  • An air-containing cavity locates within petrous
    portion of temporal bone

43
Walls
Roof
Medial wall
lateral wall
Posterior wall
Anterior wall
Floor
44
  • Walls
  • Roof or tegmental wall ???? formed by tegmen
    tympani, separates tympanic cavity from middle
    cranial fossa
  • Floor or jugular wall ????separates the cavity
    from superior bulb of internal jugular vein
  • Anterior wall or carotid wall ????separates
    tympanic cavity from carotid canal, superiorly
    lies two openings
  • Upper opening for tensor tympani muscle
  • Lower opening for auditory tube, which
    communicates with nasopharynx

45
  • Posterior wall or mastoid wall ???
  • Aditus of mastoid antrum
  • Pyramid ???
  • lateral wall or membranous wall ??-tympanic
    membrane with epitympanic recess superiorly

46
  • Medial wall or labyrinthine wall ???
  • Promontory ?
  • Fenestra vestibuli ???
  • Fenestra cochleae ??covered by secondary tympanic
    membrane ????
  • Prominence of facial canal ?????

47
Acute otitis media
Perforation, inflammation or trauma
48
  • Auditory ossicles ???
  • Consists of chain of three bones
  • Malleus ??
  • Incus ??
  • Stapes ??
  • Articulate by synovial joints
  • Transmit vibration of tympanic membrane to
    footplate of stapes in fenestra vestibule.
  • Muscles of auditory ossicles
  • Tensor tympani ????
  • Stapedius ???

49
Auditory tube ???
  • About 34 cm long, extends from nasopharynx
    posteriorly, laterally, and upward to tympanic
    cavity
  • Two parts
  • Bony part posterolateral 1/3
  • Cartilaginous part medial 2/3
  • Functions to equalize air pressure on either side
    of tympanic membrane
  • In childhood, it is shorter, wider and more
    horizontal than in adult

50
Mastoid antrum ???and mastoid cells ????
  • Mastoid antrum??? a small chamber between
    tympanic cavity and mastoid cells
  • Mastoid cells???? contain a group of air cells
    within mastoid process of temporal bone

51
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52
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53
Internal ear ??
  • General features
  • Lies within the petrous portion of temporal bone
  • Key contents of internal ear
  • Bony labyrinth ??? contains perilymph
  • Membranous labyrinth ???is filled with
    endolymph and contains the sensory organs

54
Bony labyrinth ???
  • Cochlea ??
  • Vestibule ??
  • Bony semicircular canals ????

55
  • Cochlea ??
  • It somewhat resembles a snails shell
  • Consists of
  • Modiolus ??
  • Cochlear spiral canal ????makes two and one-half
    spinal turns around the modiolus
  • Osseous spiral lamina ????
  • Scala vestibuli ???
  • Scala tympani ??

56
  • Vestibule ??
  • Hollow bony space
  • Contains utricle ???and saccule ??

57
Bony semicircular canals ???? (anterior,
posterior, and lateral) posteriorly
  • Semicircular duct in each
  • Canal at right angles to each other
  • Dilated ampulla in each canal,called bony
    ampullar ???

58
Membranous labyrinth ???
  • Cochlear duct ??
  • Utricle and saccule ??????
  • Semicircular ducts ????

59
  • Cochlear duct ??
  • Contains spinal organ ??? (of Corti), the sound
    receptors lies on tympanic wall of cochlear duct

60
  • Utricle and saccule ??????
  • Contain macular utricli ????and macular sacculi
    ???, end organs of balance, which respond to
    linear acceleration and deceleration, static of
    gravity

61
  • Semicircular ducts ????
  • Each duct has a membranous ampullae ???
  • Containing crista ampullaris ???, receptors of
    balance that respond to rotational acceleration
    in three different planes

62
Conduction of sound
Sound waves
Cochlear nerve
Air-conduction of sound
63
Bony- conduction of sound
Sound waves
Skull
Bony labyrinth
Perilymph
Endolymph within cochlear duct
Spinal organ
Cochlear nerve
64
Internal acoustic meatus ???
  • Extends from internal acoustic pore to fundus of
    internal acoustic meatus
  • Facial, vestibulocochlear nerves and vessles of
    labyrinth pass through the fundus of internal
    acoustic meatus
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