The Sensory Organs

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The Sensory Organs

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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

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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

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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
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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

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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 ?????

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• 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 ???

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

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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)

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• 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

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• 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)

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Contents of eyeball
Aqueous humor ??
Lens ???
Vitreous body ???
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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

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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

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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

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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

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Refractive media of eye????

• Bend entering light waves and focus them on the
  retina
• Cornea
• Aqueous humor
• Lens
• Vitreous body

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Accessory organs of eye ???
Eyelids ??
Conjunctiva ??
Lacrimal apparatus ??
Ocular muscles ????
Connective tissue in the orbit
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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

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Tarsus ??
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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 ???

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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

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• 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

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• 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.

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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 ?
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Ocular muscles ????
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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

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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

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

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• 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

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The Vestibulocochlear Organ

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• ???

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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

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External ear ??

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

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Auricle ??
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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.

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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 ??

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Middle ear ??

• Tympanic cavity ??
• Auditory tube ???
• Mastoid antrum ???and mastoid cells ????

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Tympanic cavity ??

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

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Walls
Roof
Medial wall
lateral wall
Posterior wall
Anterior wall
Floor
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• 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

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

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

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Acute otitis media
Perforation, inflammation or trauma
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• 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 ???

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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

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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

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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

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Bony labyrinth ???

• Cochlea ??
• Vestibule ??
• Bony semicircular canals ????

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• 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 ??

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

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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 ???

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Membranous labyrinth ???

• Cochlear duct ??
• Utricle and saccule ??????
• Semicircular ducts ????

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

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

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

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Conduction of sound
Sound waves
Cochlear nerve
Air-conduction of sound
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Bony- conduction of sound
Sound waves
Skull
Bony labyrinth
Perilymph
Endolymph within cochlear duct
Spinal organ
Cochlear nerve
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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