Anatomy & Physiology Of The Eye

ANATOMY & PHYSIOLOGY of the EYE 马

静

郑州大学第一附属医院眼科教研室 The First Affiliated Hospital of Zhengzhou University

Contents 

The Eye Ball

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The Orbit

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The Ocular Adnexa

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The Visual Pathway

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Blood and Nerve Supply

一、 the Eye Ball 

The Wall ： Outer Layer —— cornea & sclera Middle Layer ——Iris 、 Ciliary body 、 Choroid Inner Layer —— Retina

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The Contents ： Aqueous, Lens, Vitreous body

The Outer Layer of the Eye Ball Function ： protecting maintain the shape of the eyeball 

cornea： anterior 1/6 transparent

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sclera： posterior 5/6 white ， opaque

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limbus

Cornea  

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Insert into the sclera at limbus Average 0.52mm thick in the center, 0.65mm at the periphery anterior 1/6

transparent Five distinct layers ： 

Epithelium Bowman’s layer Stroma Descemet’s membrane endothelium 

Tear membrane

Cornea 

Physilogical function ： Refracting media: +43D Transparent: Avascularity Tear membrane: lubrication, keeping wet, protecting, nutrition The epithelium: regeneration The endothelium: maintaining the essential deturgescence of the stroma, susceptible to injury, undergoing loss of cells with age, its repair is limited to enlargement and sliding of the existing cells Bowman’s layer: could not regenerate, haze

Sclera 

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The fibrous outer layer, consisting almost entirely of collagen, Dense and white, Continuous with the cornea and the dural sheath of the optic nerve Inserted or penetrated by rectus mucles, posterior ciliary arteries and nerves, vortex veins, anterior ciliary arteries and veins Lamina cribrosa: the posterior scleral foramen were acrossed by bands of collagen and elastic tissue, between

Sclera 

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Three layers ： episclera: contains blood vessels Stroma:parallel and interlacing collagen bundles lamina fusca: brown pigment layer on the inner face Physiologic Function protection maintaince nuitrition

limbus The place that cornea insert into sclera Anterior chamber angle  Schwalbe’s line  Schlemm’s cannal  Trabecular meshwork  Scleral spur  Collect channels and aqueous veins

C I A

Middle layer 一、 

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Anterior extension of the ciliary body A flat surface with a centrally situated round aperture---the pupil Lies in contiguity with the anterior surface of the lens sphincter and dilator muscles in the stroma Two havily pigmented layers on the posterior surface:represent anterior extensions of

iris

Iris frontal view 

Iris 

Function: Controls the amount of light entering the eye Pupillary size is principally determined by a balance between constriction due to parasympathetic activity transmitted via the third cranial nerve and diation due to sympathetic activity

Middle layer 

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Roughly triangular in crosssection Extends forward from the anterior end of the choriod to the root of the iris a corrugated anterior zone: pars plicata(2mm) A flattened posterior zone: pars plana(4mm) Two layers of epithelium: internal nonpigmented layer

二、

Ciliary body

Ciliary body function 

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The ciliary processes and their covering epithelium are responsible for the formation of aqueous The ciliary musles: composed of a combination of the longitudinal, circular and radial fibers; to contract and relax the zonular fibers, this alters the tension on the capsule of the lens, --- focus adjustment The longitudinal fibers insert into the trabecular meshwork to influente its pore size --- adjusting the IOP nutrition

Middle layer 

The posterior segment of the uveal tract, between the retina and the sclera

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Composed three layers of choroidal blood vessels, suprachoroidal space, Bruch’s membrane

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Function: make the “dark room” nourish the retina adjust the temperature

三、

choroid

Inner layer——Retina Ten layers ： ILM neuroretina NF GCL RPE Special structure ： IPL INL macula optic disc OPL Function ： ONL receiving light stimuli OLM forming visual impulse

R&C RPE Choroid

GC Müller Amacrine Bipolar horizont

rod cone

RPE

Optic disc & Macula

黄斑的分区和组织学

黄斑的分区和组织学

Intraocular Space and Contents Intraocular space ： Anterior chamber Posterior chamber Vitreous cavity

Contents ： Aqueous Lens Vitreous body

Aqueous Formation ： ciliary processes and their covering epithelium

Function ： 1 maintain the IOP refraction

2 metobolism

3

Aqueous drainage circle ： ciliary body→posterior chamber→pupil→anterior chamber→trabecular meshwork →Schlemm’canal →collector channels→aqueous veins→episcleral venous system → blood circle

Lens 

Biconvex, avascular colorless and almost completely transparent

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4mm thick and 9mm in diameter

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Suspended behind the iris by zonule, which connects it with the ciliary body

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Aneterior:

posterior:

lens Subcapsular epithelium Lens capsule, cortex, nucleus, The lens gradually becomes larger and less elastic throughout life Long concentric lamellae form suture lines by end-to-end joining their fibers:Yshaped

Vitreous body 

A clear, avascular, gelationous body

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Comprises two-thirds of the volume and weight of the eye

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Bounded by the lens, retina, and optic disk

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Hyaloid membrane

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The base of the vitreous

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99% of water, gel-likeform

The Anatomy Outside the Eyeball       

Orbit Extraocular Musles Visual Pathway Conjunctiva Eyelids Lacrimal Aparatus Blood and Nerve Supply

Orbit   

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A pyramid shape of four walls The optic nerve located at the top point The medial walls of the two side are parallel and are separated by the nose The lateral and the medial walls forma an angle of 45 degrees A right angle between the two lateral walls The eyeball occupies 1/5 of the orbit volume, the other space is tamponed by fat and musles

Orbit 

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7 bones ： frontal, sphenoid, zygomatic, maxilla, palatine, ethimoid, lacrimal 4 walls ： Roof, Lateral, Floor, Medial Neighbours: frontal lobe of brain frontal, maxillary, ethmoid and sphenoid sinus Fossa of lacrimal sac Lacrimal fossa Trochlear fovea

Orbital Apex:

The entry portal for all nerves and vessels, and the site of origin of all extraocular muscles Optic foramen & Optic cannal: optic nerve, oph. artery, sympathic Superior orbital fissure:Between the body and the greater and lesser wings of the sphenoid bone. Superior oph.vein, lacrimal,frontal and trochlear nerves; superior and inferior divisions of the oculomotor nerve, abducens, nasociliary nerve, inferior orbital fissure:between the lateral and floor of the orbit. Maxilla nerve, inferior orbital vessels, etc. annulus of Zinn: ring tondon,

Extraocular musles 

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4 rectus: superior(7.5mm), lateral(7mm), inferior(6.75mm), medial(5.5mm) 2 oblique: superior, inferior Functions: Eye movement: adduct, abduct, depress, elevate, torsional synergic and antagonistic movement Stereoscopic vision

经

Visual Pathway Optic nerve: Consists of about 1X106 axons that arise from the GCs of the retina. About 40mm long. Including 4 courses: intraocular(1mm), orbital (2530mm), intracanalicular (4-9mm) and intracranial (10mm) segment. The sheaths of the ON emerges from the posterior surface of the globe, and ends at the intracranial segment after a short distance within the cranium. It divides the ON fibers into bundles. Fulfilling the

Visual Pathway After the photoreceptors (rods and cones) receive the light stimulation ， they change the light power into the membrane electric potential and form the visual impulses. Then the neural impulses are transferred to the bipolar cells, then ganglion cells. The impulses were send to the lateral geniculate body along the axons of the ganglion cells which travels by the optic chiasm and the optic tract. At the lateral geniculate body, a changing of neuron would be done. Then the new axons reaches the visual center at the occipital lobe via optic radiation.

Visual pathway & Light reflection

The Pupil Reflex Pathway 

light reflex one side photoreceptors---visual pathway---lateral geniculate body---arm of superior colliculus---pretectal nuclei(change neurons)---both sides E-W nuclei--oculomotor nerve---ciliary ganglion(change neurons)--short ciliary nerve---sphincter

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Near Reflex one side photoreceptors---visual pathway---visual center--- both sides E-W nuclei and medial rectus muscle nuclei---oculomotor nerve---sphincter, ciliary muscle and medial rectus muscle

Eyelid (Palpebrae) 

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The palpebrae are modified folds of skin that can close to protect the anterior eyeball Blinking helps spread the tear film, protect the cornea and conjunctiva from dehydration The posterior lid margin is in close contact with the globe, with small orifices of meibomian glands supplying lid for the tear membrane ：

Eyelid 

Structures of eyelids

Skin layer: thin, loose, ealstic Orbicularis Oculi Muscle: For the close of lids, supplied by facial nerve Areolar Tissue: Tarsal Plates:main supporting structure, dense fibrous tissue, attached to orbital margin by palpebral ligaments, contains meibomian gland Palpebral Conjunctiva: mucous membrane, adheres

Movement of the Eyelid 

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Opened by Lid Retractors: Formed by a musculofascial complex, with both striated and smooth muscle components Levator palpebrae superioris and Müller’s musle in upper lid Inferior rectus muscle in lower lid Closed by Orbicularis Oculi Muscle: the portion over the orbital septum id eht preseptal portion, the segment outside the lid is called the orbital portion

Eyelid

眼轮匝肌正面观

Conjunctiva 

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Thin transparent mucous membrane that covers the postrior surface of the lids (the palpebral conjunctiva)and the anterior surface of the sclera(the bulbar conjunctiva) Palpebral conjunctiva:firmly adherent to the tarsus Bulbar conjunctiva: loosely attached to the orbital septum in the fornices and is folded many times, this allow the eye to move. Superior and inferior fornics: Semilunar Fold(located at the inner canthus) and caruncle: Accessory lacrimal glands(Krause, Wolfring) resemble the lacrimal gland in structure Goblet cells in the conjunctival epithelium secret mucus, which is necessary for proper dispersion of the prexorneal tear film

Conjunctiva

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7 骨： 额、蝶、筛、腭、 泪、上颌、颧

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4 壁： 上、下、内、外 主要结构： 视神经孔和视神经管 眶上裂 眶下裂 眶上切迹 泪腺窝 滑车窝 泪囊窝

Lacrimal Apparatus 

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Lacrimal Gland ： Orbital portion: in the lacrimal fossa in the anterior upper temporal sgement of the orbit Palpebral portion located above the temporal segment fo the superior conjnctival fornix Lacrimal secretory ducts open to the superior conjunctival fornix Accessory lacrimal glands Lacrimal Passage: upper and lower puncta, canaliculi, lacrimal sac, nasolacrimal duct

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Lacrimal punctum: at the medial end of the posterior margin of the lid, a small elevationwith a central small opening , serve to carry the tears down through the cannaliculue to the lacrimal sac

Artery supply of the eye Central Retinal A. Lacrimal A. Long posterior ciliary A. Internal carotid A.---Ophthalmic A.--- Short posterior ciliary A. Muscle branchs Supraorbital A. Dorsal nasal A. Angular A. External carotid A. ---Facial A.--- Superficial temporal A. Infraorbital A.

血 液 供 应

Nerve Supply of the Eye 

Motor N. ： III 、 IV 、 VI 、 VII cranial nerve (oculomotor, trochlear, abducent and facial nerve)

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Sensory N.:

1. Optic N.

Long C. N. Nasociliary N.

2. Ophthalmologic N. Lacrimal N.

Long root of C.G. C.G. Short C. N.

Frontal N. 

Parasympathetic N.: E.W.nuclei oculomotor short root of C.G. Sympathetic N.: Cervical sympathetic plexus

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