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HEAD III: Special Senses. Taste Smell Vision Hearing/Balance. TASTE: how does it work?. Taste buds on tongue on fungiform papillae (“mushroom-like projections) Each “bud” contains several cell types in microvilli that project through pore and chemically sense food

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head iii special senses
HEAD III: Special Senses
  • Taste
  • Smell
  • Vision
  • Hearing/Balance

Human Anatomy, Frolich, Head II: Throat/Larynx

taste how does it work
TASTE: how does it work?
  • Taste buds on tongue on fungiform papillae (“mushroom-like projections)
  • Each “bud” contains several cell types in microvilli that project through pore and chemically sense food
  • Gustatory receptor cells communicate with cranial nerve axon endings to transmit sensation to brain

M&M, Fig. 16.1

Human Anatomy, Frolich, Head II: Throat/Larynx

five taste sensations
Five taste sensations
  • Sweet—front middle
  • Sour—middle sides
  • Salty—front side/tip
  • Bitter —back
  • “umami”—posterior pharynx

M&M, Fig. 16.1

Human Anatomy, Frolich, Head II: Throat/Larynx

cranial nerves of taste
Cranial Nerves of Taste

Anterior 2/3 tongue: VII (Facial)

Posterior 1/3 tongue: IX Glossopharyngeal)

Pharynx: X (Vagus)

M&M, Fig. 16.2

Human Anatomy, Frolich, Head II: Throat/Larynx

smell how does it work
Smell: How does it work?
  • Olfactory epithelium in nasal cavity with special olfactory receptor cells
  • Receptor cells have endings that respond to unique proteins
  • Every odor has particular signature that triggers a certain combination of cells
  • Axons of receptor cells carry message back to brain
  • Basal cells continually replace receptor cells—they are only neurons that are continuously replaced throughout life.

Human Anatomy, Frolich, Head II: Throat/Larynx

slide6
Olfactory epithelium just under cribiform plate (of ethmoid bone) in superior nasal epithelium at midline

M&M, Fig. 16.3

Human Anatomy, Frolich, Head II: Throat/Larynx

vision
Vision
  • Movement of eye—extrinsic eye muscles and location in orbit
  • Support of eye—lids, brows, lashes, tears, conjunctiva
  • Lens and focusing—structures of eyeball and eye as optical device
  • Retina and photoreceptors

Human Anatomy, Frolich, Head II: Throat/Larynx

movement of eye
Movement of eye

Eye movement simulator

(http://cim.ucdavis.edu/eyes/version1/eyesim.htm)

Human Anatomy, Frolich, Head II: Throat/Larynx

extrinsic eye muscles
Extrinsic eye muscles

III (Oculomotor)

Human Anatomy, Frolich, Head II: Throat/Larynx

slide10

M&M, fig. 16.4

Human Anatomy, Frolich, Head II: Throat/Larynx

support maintenance of eye
Support/Maintenance of Eye
  • Eyebrows: shade, shield for perspiration
  • Eyelids (palpebrae): skin-covered folds with “tarsal plates” connective tissue inside
    • Levator palpebrae superioris muscle opens eye (superior portion is smooth muscle—why?)
  • Canthus (plural canthi): corner of eye
    • Lacrimal caruncle makes eye “sand” at medial corner
    • Epicanthal folds in many Asian people cover caruncle
    • Tarsal glands make oil to slow drying
  • Eyelash—ciliary gland at hair follicle—infection is sty
  • Eyelashes—touch sensitive, thus blink

Human Anatomy, Frolich, Head II: Throat/Larynx

support of eye conjunctiva
Support of Eye--conjunctiva
  • Mucous membrane that coats inner surface of eyelid (palpebral part) and then folds back onto surface of eye (ocular part)
  • Thin layer of connective tissue covered with stratified columnar epithelium
  • Very thin and transparent, showing blood vessels underneath (blood-shot eyes)
  • Goblet cells in epithelium secrete mucous to keep eyes moist
  • Vitamin A necessary for all epithelial secretions—lack leads to conjunctiva drying up—”scaly eye”

Human Anatomy, Frolich, Head II: Throat/Larynx

support of eye tears
Support of eye--tears

M&M, fig. 16.5

  • Lacrimal glands—

superficial/lateral in orbit, produce tears

  • Lacrimal duct (nasolacrimal duct) —

medial corner of eye carries tears to nasal cavity (frequently closed in newborns—opens by 1 yr usually)

  • Tears contain mucous, antibodies, lysozyme (anti-bacterial)

Human Anatomy, Frolich, Head II: Throat/Larynx

eye as lens optical device
Eye as lens/optical device

M&M, fig. 16.7

Light path: Cornea  Anterior segment  Pupil  Lens  Posterior segment  Neural layer of retina  Pigmented retina

Human Anatomy, Frolich, Head II: Throat/Larynx

eye as optical device structures
Eye as optical device--structures
  • Sclera (fibrous tunic): is tough connective tissue “ball” that forms outside of eyeball
    • like box/case of camera
    • Corresponds to dura mater of brain
  • Cornea: anterior transparent part of sclera (scratched cornea is typical sports injury); begins focusing light
  • Choroid Internal to sclera/cornea
    • Highly vascularized
    • Darkly pigmented (for light absorption inside box)
  • Ciliary body: thick ring of tissue that encircles and holds lens
  • Iris: colored part of eye between lens and cornea, attached at base to ciliary body
  • Pupil: opening in middle of iris
  • Retina: sensory layer that responds to light and transmits visual signal to brain

Human Anatomy, Frolich, Head II: Throat/Larynx

slide16

M&M, fig. 16.4

Human Anatomy, Frolich, Head II: Throat/Larynx

detail aperture and focus
Detail: Aperture and focus

APERTURE

  • Pupil changes shape due to intrinsic autonomic muscles
    • Sympathetic: Dilator pupillae (radial fibers)
    • Parasympathetic: sphinchter pupillae

M&M, fig. 16.8

(animation of lens

http://artsci.shu.edu/biology/Student%20Pages/Kyle%20Keenan/eye/lensmovementnrve.html)

  • FOCUS
  • Ciliary muscles in ciliary body pull on lens to focus far away
  • Elasticity of lens brings back to close focus
  • Thus, with age, less elasticity, no close focusfar-sighted

Human Anatomy, Frolich, Head II: Throat/Larynx

detail eye color
Detail: eye color
  • Posterior part of iris always brown in color
  • People with brown/black eyes with pigment throughout iris
  • People with blue eyes—rest of iris clear, brown pigment at back appears blue after passing through iris/cornea

Human Anatomy, Frolich, Head II: Throat/Larynx

details retina and photoreceptors
Details: Retina and photoreceptors
  • Retina is outgrowth of brain
  • Neurons have specialized receptors at end with “photo pigment” proteins (rhodopsins)
    • Rod cells function in dim light, not color-tuned
    • Cone cells have three types: blue, red, green
    • In color blindness, gene for one type of rhodopsin is deficient, usually red or green
  • Photoreceptors sit on pigmented layer of choroid. Pigment from melanocytes--melanoma possible in retina!!
  • Axons of photoreceptors pass on top or superficial to photoreceptor region
  • Axons congregate and leave retina at optic disc (blind spot)
  • Fovea centralis is in direct line with lens, where light is focused most directly, and has intense cone cell population (low light night vision best from side of eye)
  • Blood vessels superficial to photoreceptors (retina is good sight to check for small vessel disease in diabetes)

Human Anatomy, Frolich, Head II: Throat/Larynx

retina and photoreceptors
Retina and photoreceptors

M&M, fig. 16.10

Human Anatomy, Frolich, Head II: Throat/Larynx

ear hearing
Ear/Hearing
  • Outer Ear: auricle is elastic cartilage attached to dermis, gathers sound
  • Middle ear: ear ossicles transmit and modulate sound
  • Inner ear: cochlea, ampullae and semicircular canals sense sound and equilibrium

M&M, fig. 16.17

Human Anatomy, Frolich, Head II: Throat/Larynx

middle ear
Middle Ear
  • External auditory canal ends at tympanic membrane which vibrates against malleus on other side
  • Inside middle ear chamber
    • malleusincus stapes which vibrates on oval window of inner ear
  • Muscles that inhibit vibration when sound is too loud
    • Tensor tympani m. (inserts on malleus)
    • Stapedius m. (inserts on stapes)

M&M, fig. 16.19

Human Anatomy, Frolich, Head II: Throat/Larynx

inner ear labyrinth
Inner Ear/Labyrinth
  • Static equilibrium, linear motion
    • Utricle, saccule are egg-shaped sacs in center (vestibule) of labyrinth
  • 3-D motion, angular acceleration
    • 3 semicircular canals for X,Y,Z planes
  • Sound vibrations
    • Cochlea (“snail”)

M&M, fig. 16.20

Auditory Nerve (Acoustic) VIII receives stimulus from all to brain

Vestibular n.—equilibrium

Cochlear n.—hearing

Human Anatomy, Frolich, Head II: Throat/Larynx

cochlea how it works
Cochlea--how it works

Which is more incredible?

Retina or spiral organ?

  • Spiral organ is receptor epithelium for hearing
  • Range of volume and tone that are perceived astonishing
  • Basilar membrane running down middle
    • Thicker at start, vibrates with lower sounds
    • Thinner at end, vibrates at higher sound
  • (in figure shown uncoiled, in life is spiral in shape)

M&M, fig. 16.24

Human Anatomy, Frolich, Head II: Throat/Larynx

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