The Sensory Organs

The Sensory Organs Sensory organs include the receptors and

accessory organs. The receptors may be divided into three kinds:

The exteroceptors 外感受器 : receive stimuli such as touch, temperature, pain, light and sound from the external environment

The interoceptors 内感受器 : pick up information about internal environment

The proprioceptors 本体感受器 : receive stimuli from muscles, tendons, joints and ligaments

The Visual Organ 视器Composition: eyeball and

accessory organs of eyeShape of eyeball Has anterior and posterior

poles Equator 赤道 : an

imaginary line encircling the eyeball, midway between anterior and posterior poles

Axis of eyeball 眼轴 : a line joining the two poles

Optic axis 视轴 : a line joining the center of the pupil to the fovea centralis

Walls of eyeball

Fibrous tunic of eyeball

Cornea 角膜Sclera 巩膜

Vascular tunic of eyeball

Iris 虹膜Cilliary body 睫状体Choroid 脉络膜

Retina 视网膜Pars iridica retinae

Pars ciliaris retinae

Pars optica retinae

Pars caeca retinae

Fibrous tunic of eyeball (outer)

Cornea 角膜 : anterior 1/6, a nonvascular, transparent portion, richly supplied by nerves; because it is curved, the cornea helps focus light

Sclera 巩膜 (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 巩膜静脉窦 which lies beneath the junction of cornea and sclera

Vascular tunic of eyeball (middle)

Iris 虹膜 Thin contractile membrane

anterior to ciliary body, with a central opening, the pupil 瞳孔

Contains sphincter pupillae 瞳孔括约肌(circular fibers) and dilator pupillae 瞳孔开大肌 (radial fibers)

Cornea and iris meet to form the iridocorneal angle 虹膜角膜角

Cilliary body 睫状体 Body a ring-shaped

thickening anterior to equator, containing smooth muscle fibers called ciliary muscle 睫状肌

Ciliary processes 睫状突 : a series of some 60~80 projections producing aqueous humor

Ciliary ring 睫状环

Ciliary Processes

Sphincter PupillaeDilator Pupillae

Sinus venosus sclerae

ciliary zonule

Ciliary ring

Ciliary Muscle Iridocorneal angle

Lens

Choroid 脉络膜 Thin, highly vascular in

posterior 2/3 of eye Contains brown

pigmented cells and dense capillary plexus

Retina 视网膜 Pars caeca retinae 视网膜盲部

Pars iridica retinae 视网膜虹膜部 Pars ciliaris retinae 视网膜睫状体部

Pars optica retinae 视网膜视部 Lines the choroids Composed of two layers

An outer pigment cell layer Inner neural layer (four

layers)

The fourth layer consists photoreceptor cells Cone cells 视锥细胞 are color receptors that function best during the day Rod cells 视杆细胞 are dark-light receptors that function best at night and

in dim light The third layer consists of bipolar neurons 双极细胞 The second layer is formed ganglion cells 节细胞 , 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

Pigment cell layer

Cone cells

Rod cells

Bipolar neurons

Ganglion cells

Optic disc 视神经盘 (blind spot), located medial to posterior pole of eye, and consists of optic nerve fibers and central artery of retina

Macula lutea 黄斑 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 中央凹 , 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)

Contents of eyeballAqueous humor 房水

Lens 晶状体

Vitreous body 玻璃体

Aqueous humor 房水 Chamber of eye 眼房－ lies

between cornea and lens, and divided by iris into anterior and posterior chambers

Aqueous humor 房水 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

Ciliary body Posterior chamber Anterior chamber

Sinus venosus sclera Anterior ciliary vein

Ophthalmic vein

Iridocorneal angle

Pupil

Production and circulation of aqueous humor

Functions

• Helps focus light• Helps maintain constant pressure in eyeball• Helps nourish the lens and cornea

Lens 晶状体 Transparent biconvex structure, covered by an elastic transparent capsule Located between iris and vitreous body, and suspended behind pupil by

ciliary zonule 睫状小带 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

Vitreous body 玻璃体 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

Refractive media of eye 折光装置Bend entering light waves and focus them on the retina

Cornea Aqueous humor Lens Vitreous body

Accessory organs of eye 眼副器Eyelids 眼睑Conjunctiva 结膜Lacrimal apparatus 泪器Ocular muscles 眼球外肌Connective tissue in the orbit

Eyelids 眼睑（ from without inwards ） Skin, extremely thin Subcutaneous areola

tissue, loose and delicate Muscular layer: orbicularis

oculi Tarsus 睑板 , formed by

dense connective tissue in which the tarsal glands 睑板腺 embedded

Lined by palpebral conjunctiva 睑结膜

Function: to protect, open, and close eye

Tarsus 睑板

Conjunctiva 结膜 Three parts

Palpebral conjunctiva 睑结膜 : lining inner surface of eyelids

Bulbar conjunctiva 球结膜 : lining anterior part of sclera, up to corneal margin

Conjuntival fornix 结膜穹(superior and inferior): line of reflection of bulbar and palpebral conjunctiva

Conjunctival sac 结膜囊

Lacrimal apparatus 泪器Lacrimal gland 泪腺 Oval 2-cm, occupies fossa

for lacrimal gland Ducts (6~10 in number):

empty into anterior region of superior fornix of conjunctiva

Secrets tears, which move across eyeball to medial angle,protect and moisten eye

Lacrimal passages 泪道 Lacrimal puncta 泪点 opening

to lacrimal ductules, one on each eylid margin near medial angle

Lacrimal ductules 泪小管 : one in each lid, pass medially, join and enter lacrimal sac

Lacrimal sac 泪囊 within fossa for lacrimal sac, opening into nasolacrimal duct

Nasolacrimal duct 鼻泪管courses 2 cm inferiorly and opens into inferior nasal meatus

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.

Ocular muscles 眼球外肌Muscle Action Nerve supply

levator palpebrae superioris

Raises upper eyelid Ⅲ

Superior rectus Turns eyeball superomedially Ⅲ

Inferior rectus Turns eyeball inferomedially Ⅲ

Medial rectus Turns eyeball medially Ⅲ

Lateral retus Turns eyeball laterally Ⅵ

Superior obliquus Turns eyeball inferolaterally Ⅳ

Inferior obliquus Turns eyeball superolaterally Ⅲ

Ocular muscles 眼球外肌

Connective tissue in the orbit Sheath of eyeball 眼球筋膜鞘 : 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 眶脂体 : lies between sheath of eyeball and the orbit acts as a protective cushion and shock sorber for the eyeball

Vessels of eye

Ophthalmic artery 眼动脉 Branch of internal artery Branches － central artery

of retina 视网膜中央动脉 Enters optic nerve, passes

toward the optic disk and then fans out to supply the retina

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

Ophthalmic vein 眼静脉 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

The Vestibulocochlear Organ

General features

Three parts External ear 外耳 : collects

sound waves Middle ear 中耳 :

transmits sound waves Internal ear 内耳 : contains

the vestibulocochlear organ concerned with equilibration and hearing

External ear 外耳 Auricle 耳廓 External acoustic meatus 外耳道 Tympanic membrane 鼓膜

Auricle 耳廓

External acoustic meatus 外耳道 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.

Tympanic membrane 鼓膜 A thin oval membrane Two parts

Flaccid part 松弛部 : upper 1/4

Tense part 紧张部 : lower 3/4

Umbo of tympanic membrane 鼓膜脐 Cone of light 光锥

Middle ear 中耳 Tympanic cavity 鼓室 Auditory tube 咽鼓管 Mastoid antrum 乳突窦 and mastoid cells 乳突小房

Tympanic cavity 鼓室 An air-containing cavity

locates within petrous portion of temporal bone

WallsRoof

Floor

lateral wallMedial wall

Posterior wall

Anterior wall

Walls Roof or tegmental wall 鼓室盖壁 formed by tegmen tympani,

separates tympanic cavity from middle cranial fossa Floor or jugular wall 颈静脉壁 separates the cavity from

superior bulb of internal jugular vein Anterior wall or carotid wall 颈动脉壁 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

Posterior wall or mastoid wall 乳突壁 Aditus of mastoid antrum Pyramid 锥隆起

lateral wall or membranous wall 膜壁－ tympanic membrane with epitympanic recess superiorly

Medial wall or labyrinthine wall 迷路壁 Promontory 岬 Fenestra vestibuli 前庭窗 Fenestra cochleae 蜗窗 covered by secondary tympanic membrane 第二鼓膜 Prominence of facial canal 面神经管凸

Acute otitis media Perforation, inflammation ortrauma

Auditory ossicles 听小骨 Consists of chain of three

bones: Malleus 锤骨 Incus 砧骨 Stapes 镫骨

Articulate by synovial joints Transmit vibration of

tympanic membrane to footplate of stapes in fenestra vestibule.

Muscles of auditory ossicles

Tensor tympani 鼓膜张肌 Stapedius 镫骨肌

Auditory tube 咽鼓管 About 3~4 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

Mastoid antrum 乳突窦 and mastoid cells 乳突小房 Mastoid antrum 乳突窦 :

a small chamber between tympanic cavity and mastoid cells

Mastoid cells 乳突小房 : contain a group of air cells within mastoid process of temporal bone

Internal ear 内耳General features Lies within the petrous

portion of temporal bone Key contents of internal ear

Bony labyrinth 骨迷路 contains perilymph Membranous labyrinth

膜迷路 is filled with endolymph and contains the sensory organs

Bony labyrinth 骨迷路 Cochlea 耳蜗 Vestibule 前庭 Bony semicircular canals 骨半规管

Cochlea 耳蜗 It somewhat resembles a

snail’s shell Consists of

Modiolus 蜗轴 Cochlear spiral canal 蜗

螺旋管 makes two and one-half spinal turns around the modiolus

Osseous spiral lamina 骨螺旋板

Scala vestibuli 前庭阶 Scala tympani 鼓阶

Vestibule 前庭 Hollow bony space Contains utricle 椭圆囊 and saccule 球囊

Semicircular duct in each Canal at right angles to each other Dilated ampulla in each canal ， called bony ampullar 骨壶腹

Bony semicircular canals 骨半规管(anterior, posterior, and lateral) posteriorly

Membranous labyrinth 膜迷路 Cochlear duct 蜗管 Utricle and saccule 椭圆囊和球囊 Semicircular ducts 膜半规管

Cochlear duct 蜗管 Contains spinal organ 螺旋器 (of Corti), the sound

receptors lies on tympanic wall of cochlear duct

Utricle and saccule 椭圆囊和球囊 Contain macular utricli 椭圆囊斑 and macular sacculi 球囊斑 ,

end organs of balance, which respond to linear acceleration and deceleration, static of gravity

Semicircular ducts 膜半规管 Each duct has a membranous ampullae 膜壶腹 Containing crista ampullaris 壶腹嵴 , receptors of balance

that respond to rotational acceleration in three different planes

Conduction of sound

Air-conduction of sound

Sound wavesCochlear nerve

Bony- conduction of sound

Sound waves Skull Bony labyrinth Perilymph

Endolymph within cochlear duct Spinal organ

Cochlear nerve

Internal acoustic meatus 内耳道 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