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Essentials of Human Anatomy

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Essentials of Human Anatomy Special Senses Dr Fadel Naim Ass. Prof. Faculty of Medicine IUG Optic Disc Optic disc lacks photoreceptors. Called the blind spot because ... – PowerPoint PPT presentation

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Title: Essentials of Human Anatomy


1
Essentials of Human Anatomy
Special Senses
Dr Fadel Naim Ass. Prof. Faculty of Medicine IUG
2
Special Senses
  • sensory receptors are within large, complex
    sensory organs in the head
  • smell in olfactory organs
  • taste in taste buds
  • hearing and equilibrium in ears
  • sight in eyes

3
Sense of Smell
  • Olfactory Receptors
  • chemoreceptors
  • respond to chemicals dissolved in liquids
  • Olfactory Organs
  • contain olfactory receptors and supporting
    epithelial cells
  • cover parts of nasal cavity, superior nasal
    conchae, and a portion of the nasal septum

4
Olfactory Receptors
5
Olfactory Nerve Pathways
  • Once olfactory receptors are stimulated, nerve
    impulses travel through
  • olfactory nerves olfactory bulbs
    olfactory tracts limbic system (for
    emotions) and olfactory cortex (for
    interpretation)

6
Olfactory Stimulation
  • olfactory organs located high in the nasal
    cavity above the usual pathway of inhaled air
  • olfactory receptors undergo sensory adaptation
    rapidly
  • sense of smell drops by 50 within a second
    after stimulation

7
Sense of Taste
  • Taste Buds
  • organs of taste
  • located on papillae of tongue, roof of mouth,
    linings of cheeks and walls of pharynx
  • Taste Receptors
  • chemoreceptors
  • taste cells modified epithelial cells that
    function as receptors
  • taste hairs microvilli that protrude from taste
    cells sensitive parts of taste cells

8
Taste Receptors
9
Taste Sensations
  • Four Primary Taste Sensations
  • sweet stimulated by carbohydrates
  • salty stimulated by salts
  • sour stimulated by acids
  • bitter stimulated by many organic compounds

Spicy foods activate pain receptors
10
Taste Nerve Pathways
  • Sensory impulses from taste receptors travel
    along
  • cranial nerves to
  • medulla oblongata to
  • thalamus to
  • gustatory cortex (for interpretation)

11
Hearing
Ear organ of hearing
  • Three Sections
  • External
  • Middle
  • Inner

12
External Ear
  • auricle
  • collects sounds waves
  • external auditory meatus
  • lined with ceruminous glands
  • carries sound to tympanic membrane
  • terminates with tympanic membrane
  • tympanic membrane
  • vibrates in response to sound waves

13
Middle Ear
  • tympanic cavity
  • air-filled space in temporal bone
  • auditory ossicles
  • vibrate in response to tympanic membrane
  • malleus, incus, and stapes
  • oval window
  • opening in wall of tympanic cavity
  • stapes vibrates against it to move fluids in
    inner ear

14
Auditory Tube
  • eustachian tube
  • connects middle ear to throat
  • helps maintain equal pressure on both sides of
    tympanic membrane
  • usually closed by valve-like flaps in throat

15
Inner Ear
  • complex system of labyrinths
  • osseous labyrinth
  • bony canal in temporal bone
  • filled with perilymph
  • membranous labyrinth
  • tube within osseous labyrinth
  • filled with endolymph

16
Inner Ear
  • Three Parts of Labyrinths
  • cochlea
  • functions in hearing
  • semicircular canals
  • functions in equilibrium
  • vestibule
  • functions in equilibrium

17
Cochlea
  • Scala vestibuli
  • upper compartment
  • leads from oval window to apex of spiral part
    of bony labyrinth
  • Scala tympani
  • lower compartment
  • extends from apex of the cochlea to round window
  • part of bony labyrinth

18
Cochlea
  • Cochlear duct
  • portion of membranous labyrinth in cochlea
  • Vestibular membrane
  • separates cochlear duct from scala vestibuli
  • Basilar membrane
  • separates cochlear duct from scala tympani

19
Organ of Corti
  • group of hearing receptor cells (hair cells)
  • on upper surface of basilar membrane
  • different frequencies of vibration move
    different parts of basilar membrane
  • particular sound frequencies cause hairs of
    receptor cells to bend
  • nerve impulse generated

20
Auditory Pathway
Cochlear branch of CN VIII
To cochlear nucleus of medulla
  • To inferior colliculus of opposite side of
    midbrain
  • To thalamus
  • To auditory cortex

21
Vestibular Complex
  • Semicircular canals with ampullae (mutually
    perpendicular)
  • Saccule and utricle ( fill up vestibule)

22
Two Receptor Organs Maculae of Vestibule (or
macula of saccule plus macula of utricle)
23
Macula
  • responds to changes in head position
  • bending of hairs results in generation of nerve
    impulse

24
Crista Ampullaris
  • sensory organ of ampulla
  • hair cells and supporting cells
  • rapid turns of head or body stimulate hair cells

25
Equilibrium
  • Rotation of the head causes endolymph within the
    semicircular canal to push against the cupula
    covering the hair cells, resulting in bending of
    their stereocilia and the initiation of a nerve
    impulse.

26
Equilibrium
  • Dynamic Equilibrium
  • semicircular canals
  • sense rotation and movement of head and body
  • Static Equilibrium
  • vestibule
  • sense position of head when body is not moving

27
The Sense of Vision
  • Visual receptors (photoreceptors) in the eyes to
    detect light, color, and movement.
  • Accessory structures of the eye.
  • provide a superficial covering over its anterior
    exposed surface (conjunctiva)
  • prevent foreign objects from coming into contact
    with the eye (eyebrows, eyelashes, and eyelids)
  • keep the exposed surface moist, clean, and
    lubricated (lacrimal glands)

28
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29
Lacrimal Apparatus
  • lacrimal gland
  • lateral to eye
  • secretes tears
  • canaliculi
  • collect tears
  • lacrimal sac
  • collects from canaliculi
  • nasolacrimal duct
  • collects from lacrimal sac
  • empties tears into nasal cavity

30
Structure of the Eye
  • hollow
  • spherical
  • wall has 3 layers
  • outer fibrous tunic
  • middle vascular tunic
  • inner nervous tunic

31
Cavities and Chambers of the Eye
  • The internal space of the eye is subdivided by
    the lens into two separate cavities.
  • anterior cavity
  • posterior cavity

32
Cavities and Chambers of the Eye
  • The anterior cavity is
  • the space anterior to the lens and posterior to
    the cornea
  • The iris of the eye subdivides the anterior
    cavity further into two chambers.
  • anterior chamber is between the iris and cornea
  • posterior chamber is between the lens and the
    iris

33
Vitreous Humor
  • Posterior cavity is posterior to the lens and
    anterior to the retina.
  • Transparent, gelatinous vitreous body which
    completely fills the space between the lens and
    the retina.

34
Optic Disc
  • Optic disc lacks photoreceptors.
  • Called the blind spot because no image forms
    there.
  • Just lateral to the optic disc is a rounded,
    yellowish region of the retina called the macula
    lutea containing a pit called the fovea centralis
    (the area of sharpest vision).
  • contains the highest proportion of cones and
    almost no rods

35
Visual Pathways
  • Each optic nerve conducts visual stimulus
    information.
  • At the optic chiasm, some axons from the optic
    nerve decussate.
  • The optic tract on each side then contains axons
    from both eyes.
  • Visual stimulus information is processed by the
    thalamus and then interpreted by visual
    association areas in the cerebrum.

36
Extrinsic Eye Muscles
  • Superior rectus
  • rotates eye up and medially
  • Lateral rectus
  • rotates eye laterally
  • Medial rectus
  • rotates eye medially
  • Inferior rectus
  • rotates eye down and medially
  • Superior oblique
  • rotates eye down and laterally
  • Inferior oblique
  • rotates eye up and laterally

37
THE END
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