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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


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 bone) in superior nasal epithelium at midline

  • 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 bone) in superior nasal epithelium at midline

Eye movement simulator

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

Human Anatomy, Frolich, Head II: Throat/Larynx


Extrinsic eye muscles
Extrinsic eye muscles bone) in superior nasal epithelium at midline

III (Oculomotor)

Human Anatomy, Frolich, Head II: Throat/Larynx


M&M, fig. 16.4 bone) in superior nasal epithelium at midline

Human Anatomy, Frolich, Head II: Throat/Larynx


Support maintenance of eye
Support/Maintenance of Eye bone) in superior nasal epithelium at midline

  • 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 bone) in superior nasal epithelium at midline

  • 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 bone) in superior nasal epithelium at midline

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 bone) in superior nasal epithelium at midline

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 bone) in superior nasal epithelium at midline

  • 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


M&M, fig. 16.4 bone) in superior nasal epithelium at midline

Human Anatomy, Frolich, Head II: Throat/Larynx


Detail aperture and focus
Detail: Aperture and focus bone) in superior nasal epithelium at midline

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 bone) in superior nasal epithelium at midline

  • 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 bone) in superior nasal epithelium at midline

  • 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 bone) in superior nasal epithelium at midline

M&M, fig. 16.10

Human Anatomy, Frolich, Head II: Throat/Larynx


Ear hearing
Ear/Hearing bone) in superior nasal epithelium at midline

  • 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 bone) in superior nasal epithelium at midline

  • 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 bone) in superior nasal epithelium at midline

  • 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 bone) in superior nasal epithelium at midline

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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