Title: The Sensory Organs
1The Sensory Organs
2The 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
3The 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
4Walls of eyeball
Cornea ??
Fibrous tunic of eyeball
Sclera ??
Iris ??
Vascular tunic of eyeball
Pars iridica retinae
Pars caeca retinae
Retina ???
Pars ciliaris retinae
Pars optica retinae
5Fibrous 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
6Vascular 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 ???
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9- Choroid ???
- Thin, highly vascular in posterior 2/3 of eye
- Contains brown pigmented cells and dense
capillary plexus
10Retina ???
- 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)
13Contents of eyeball
Aqueous humor ??
Lens ???
Vitreous body ???
14Aqueous 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 maintain constant pressure in eyeball
- Helps nourish the lens and cornea
16Lens ???
- 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
17Vitreous 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
18Refractive media of eye????
- Bend entering light waves and focus them on the
retina - Cornea
- Aqueous humor
- Lens
- Vitreous body
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20Accessory organs of eye ???
Eyelids ??
Conjunctiva ??
Lacrimal apparatus ??
Ocular muscles ????
Connective tissue in the orbit
21Eyelids ??
- (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
22Tarsus ??
23Conjunctiva ??
- 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 ???
24Lacrimal 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.
27Ocular 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 ?
28Ocular muscles ????
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30Connective 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
31Vessels 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
34The Vestibulocochlear Organ
35General features
- Three parts
- External ear ?? collects sound waves
- Middle ear ?? transmits sound waves
- Internal ear ?? contains the vestibulocochlear
organ concerned with equilibration and hearing
36External ear ??
- Auricle ??
- External acoustic meatus ???
- Tympanic membrane ??
37Auricle ??
38External 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.
39Tympanic 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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41Middle ear ??
- Tympanic cavity ??
- Auditory tube ???
- Mastoid antrum ???and mastoid cells ????
42Tympanic cavity ??
- An air-containing cavity locates within petrous
portion of temporal bone
43Walls
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 ?????
47Acute 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 ???
49Auditory 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
50Mastoid 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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53Internal 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
54Bony 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 ??
57Bony 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 ???
58Membranous 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
62Conduction of sound
Sound waves
Cochlear nerve
Air-conduction of sound
63Bony- conduction of sound
Sound waves
Skull
Bony labyrinth
Perilymph
Endolymph within cochlear duct
Spinal organ
Cochlear nerve
64Internal 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