Part Ⅳ

Sensory Organs SHANDONG UNIVERSITY Liu Zhiyu

The Sensory Organs

The receptors may be divided into three kinds: • exteroceptors :receive stimuli such as touch,

temperature, pain, light and sound from the external environment

• interoceptors :pick up information about internal environment

• proprioceptors : 分 receive stimuli from muscles, tendons, joints and ligaments

Sensory organs include

• receptors

• accessory organs

The Visual Organ consist of

eyeball

chapter 1 The Visual Organ

accessory organs of eyeball

Section 1 Eyeball

Ⅰ. Shape of eyeballanterior and posterior poles

anterior pole

posterior pole

Axis of eyeball :a line joining the two poles

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

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

Ⅱ.Structure of eyeball 1. Walls of eyeball

Fibrous tunic of eyeball

Cornea

Sclera

Vascular tunic of eyeball

Retina

Pars iridica retinae

Pars ciliaris retinae

Pars optica retinae

Pars caeca retinae

Iris

Cilliary body

Choroid

Wall of eyeball

(1) Fibrous tunic

(outer layer)

Cornea : anterior 1/6 ； a nonvascular, transparent

portion ； supplied richly by nerves;

because it is curved, the

cornea helps focus light.

Ⅱ

Walls of eyeball

(1) Fibrous tunic

Sclera: posterior 5/6, consists of fibrous

connective tissue having

protection and

surpporting

for eyeball, posteriorly it contineus

with the sheath of optic n.

Sinus venous sclerae

sclera

cornea

sinus venous sclerae :

lies beneath the junction of cornea and sclera, and is irregular circular canal.

cribriform plate of sclera

iris lies the anterior part of the vascular tunic, and is a thin contractile membrane with a central opening, the pupil

(2) Vascular tunic (middle layer):

Wall of eyeball

iridocorneal angle

sphincter pupillae

dilator pupillae

eyeball

a) ciliary ring b) ciliary processes : 60~80, producing aqueous humor

ciliary zonules

Ciliary body : Behind the iris ， may be divided into

ciliary muscle ciliary zonules

d)secrete the aqueous humor

eyeball

choroid

Thin, highly vascular in posterior 2/3 of eye Contains brown pigmented cells and dense capillary plexus

function：

Nutrition

Absorb the disperse light

(3) Internal tunic of eyeball—

retina

a. Pars caeca retinae:

b. Pars optica retinae:

pars iridica retinae

pars ciliaris retinae

division: ora serrata

Wall of eyeball

Photoreceptor cells

pigment epithelial layer nervus layer ： consist of three layers of cells

The retina consists of two layers:

Cone cell

Rod cell

2) structure:

Pigment cell layer

Cone cell

Rod cell

Wall of eyeball

bipolar cell

ganglion cell whose axons form the optic n. fibers

Pigment cell layer

Cone cells

Rod cells

Bipolar neuron

Ganglion cell

Wall of eyeball

Optic disc (blind spot), located medial to posterior pole of eye, and consists of optic nerve fibers and at where there are central a.and v. of retina

Macula lutea

– Lies lateral about 3.5 mm to optic disc, a shallow depression, and is yellowish in color

Wall of eyeball

– Fovea centralis is an aera of greatest visual acuity and is completely free of blood vessels (concentration of cone cells).

The pigment epithelial layer absorbs light that enter the eyeball preventing backscatter (blurring of vision)

Wall of eyeball

(1)  Aqueous humor

1) Chamber of eye :

lies between cornea and

lens, and divided by iris

into：

2. Contents of eyeball

anterior chamber

posterior chamber

 

Contents of eyeball

2) Aqueous humor

•A clear watery fluid that fills

chamber of eye ， secreted by

ciliary body.

Functions

• Helps focus light

• Helps maintain constant pressure in eyeball

• Helps nourish the lens and cornea

secreted by the ciliary body

Production and circulation of aqueous humor:

sinus venosus sclera

posterior chamber pupil

anterior chamber  iridocorneal angle

anterior ciliary vein ophthalmic vein

sinus venosus sclera

(2)  Lens

position ： lis behind the

iris ， anterior to the vitreous

body

Contents of eyeball

shape ：

Transparent biconvex structure, covered by an elastic transparent capsule which is connected by the ciliary zonules(suspensory lig.)to the ciliary process

Structure:

lens capsule

cortex of lens

lens nucleus

Contents of eyeball

Its shape is 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

(3)  Vitreous body

Consists of colorless,

transparent jelly-like substance in

which there is a meshwork of fine

fibrils, occupies the space

between lens and retina

Helps maintain the shape of eyeball and supports the retina

Contents of eyeball

Cornea

aqueous humor

lens

vitreous body

(4) Refractive media: include

Bend entering light waves and focus them on the

retina

Contents of eyeball

Section2. Accessory organs

①Skin

②subcutaneous adipose

tissue

③musclar layer :

orbicularis oculi

④tarsus ： formed

by dense connective

tissue (tarsal glands)

⑤ palpebral conjunctiva

Ⅰ.  Eyelids: upper and lower ， consist of 5 layers,

3 parts:• Palpebral conjunctiva : lining inner surface of eyelids; • Bulbar conjunctiva : lining anterior part of sclera; •

Ⅱ.Conjunctiva :

thin mucous membrane

Accessory organs of eye

Conjunctival fornix (superior and inferior):

the reflected part of the conjunctiva from the superior and inferior eyelids onto the eyeball. Conjunctival sac

Accessory organs of eye

Ⅲ.Lacrimal apparatus

1. Lacrimal gland :

2. Lacrimal passages :  

lacrimal punctum: on each eyelid margin near medial angle

lacrimal ductules : in each lid, pass medially, join and enter lacrimal sac

Lacrimal sac : in fossa for lacrimal sac, opening into nasolacrimal duct

Nasolacrimal duct : opening into inferior nasal meatus

Accessory organs of eye

Ⅳ.Extraocular m. : 7 levator palpebrae superioris: elvates the upper eyelid.

Obliquuses : 2

Superior obliquus

 Inferior obliquus

Rectuses: 4 superior rectus

inferior rectus

medial rectus

lateral rectus

 

Muscle Action N. supply

levator palpebrae superioris elvates upper eyelid Ⅲ

Superior rectus turns eyeball superomedially Ⅲ

Inferior rectus turns eyeball inferomedially Ⅲ

Medial rectus turns the eyeball medially Ⅲ

Lateral retus turns the eyeball laterally Ⅵ

Superior obliquus turns eyeball inferolaterally Ⅳ

Inferior obliquus turns eyeball superolaterally Ⅲ

Accessory organs of eye

Accessory organs of eye

Accessory organs of eye

Ⅴ. Connective Tissues in the Orbit

1. adipose body of orbit lies between sheath of eyeball and the orbit acts as a protective cushion and shock sorber for the eyeball

2. orbital fasciae

a. periorbita

b. fascial sheath of eyeball

c. sheath of ocular muscles

d . orbital septum

Ⅰ. Vessels of eye 1. Artery

(1)Ophthalmic a.: Arises from the internal carotid a.

Branches: 1) central a. of retina

Enters optic nerve, passes toward the optic disk and then fans out to supply the retina

Section 3. The vessels and nerves of eye

1) central a. of retina

branches:

The vessels and nerves of eye

superior nasal arteriole of retina inferior nasal arteriole of retina superior temporal arteriole of retina inferior temporal arteriole of retina

3) long posterior ciliary a .

;

4) anterior ciliary a.

2) short posterior ciliary a.:

Choroidal artery

The vessels and nerves of eye

Ⅱ.Vein

(1 ） central v. of retina

(2 ） vortex vein

(3 ） anterior ciliary veins

(4 ） Ophthalmic v.

a)Superior ophthalmic v.

b) Inferior ophthalmic v

The vessels and nerves of eye

optic nerve: oculomotor n. trochlear n. abducent n.

Ⅲ.Nerves

ophthalmic n.

facial n.

The vessels and nerves of eye

inferior temporal arteriole of retina

superior nasal arteriole of retina

inferior nasal arteriole of retina

superior temporal arteriole of retina

Ciliary Processes

Sphincter PupillaeDilator Pupillae

Sinus venosus sclerae

ciliary zonule

Ciliary Muscle Iridocorneal angle

Lens

chapter14 The Visual Organ

  

aqueous humor lens vitreous body

Eyeball

accessory organs of eyeball

fibrous tunic ：

vascular tunic ：

retina

walls

composition

iris

ciliary body

choroid

cornea sclera

choroidal part: pars opticaretinae

pars ciliaris

pars iridiacpars caeca retinae