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Ch. 15 Special Senses: Vision Slides mostly © Marieb & Hoehn 9 th ed. Other slides by WCR.

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Presentation on theme: "Ch. 15 Special Senses: Vision Slides mostly © Marieb & Hoehn 9 th ed. Other slides by WCR."— Presentation transcript:

1 Ch. 15 Special Senses: Vision Slides mostly © Marieb & Hoehn 9 th ed. Other slides by WCR

2 © 2013 Pearson Education, Inc. The Eye and Vision 70% of body's sensory receptors in eye Visual processing by ~ half cerebral cortex Most of eye protected by cushion of fat and bony orbit

3 © 2013 Pearson Education, Inc. Accessory Structures of the Eye Protect the eye and aid eye function –Eyebrows –Eyelids (palpebrae) –Conjunctiva –Lacrimal apparatus –Extrinsic eye muscles

4 © 2013 Pearson Education, Inc. Eyebrow Eyelid Eyelashes Site where conjunctiva merges with cornea Palpebral fissure Lateral commissure Iris Eyelid Surface anatomy of the right eye Pupil Sclera (covered by conjunctiva) Lacrimal caruncle Medial commissure Figure 15.1a The eye and accessory structures.

5 © 2013 Pearson Education, Inc. Figure 15.1b The eye and accessory structures. Levator palpebrae superioris muscle Orbicularis oculi muscle Eyebrow Tarsal plate Palpebral conjunctiva Tarsal glands Cornea Palpebral fissure Eyelashes Bulbar conjunctiva Conjunctival sac Orbicularis oculi muscle some structures shown in sagittal section Lateral view;

6 © 2013 Pearson Education, Inc. Conjunctiva Transparent mucous membrane Produces a lubricating mucous secretion Lines eyelids & covers sclera Lacrimal Apparatus Makes & drains tears Lacrimal gland Above lateral end of eye Secretes tears Nasolacrimal duct Drains tears into nasal cavity

7 © 2013 Pearson Education, Inc. Figure 15.2 The lacrimal apparatus. Lacrimal sac Lacrimal gland Excretory ducts of lacrimal glands Lacrimal punctum Lacrimal canaliculus Nasolacrimal duct Inferior meatus of nasal cavity Nostril

8 © 2013 Pearson Education, Inc. Extrinsic Eye Muscles Six straplike extrinsic eye muscles –Originate from bony orbit; insert on eyeball –Steer the eyes Four rectus muscles –Superior, inferior, lateral, medial rectus –Steer eye up, down, side-to-side Two oblique muscles –Superior and inferior oblique –Rotate eyeball about the central visual axis

9 © 2013 Pearson Education, Inc. Figure 15.3a Extrinsic eye muscles. Superior oblique muscle Superior oblique tendon Superior rectus muscle Lateral rectus muscle Inferior rectus muscle Inferior oblique muscle Lateral view of the right eye

10 © 2013 Pearson Education, Inc. Figure 15.3b Extrinsic eye muscles. Trochlea Axis of rotation of eye Inferior rectus muscle Medial rectus muscle Lateral rectus muscle Common tendinous ring Superior oblique muscle Superior oblique tendon Superior rectus muscle Superior view of the right eye

11 © 2013 Pearson Education, Inc. Figure 15.3c Extrinsic eye muscles. Muscle ActionControlling cranial nerve Summary of muscle actions and innervating cranial nerves Lateral rectus Medial rectus Superior rectus Inferior rectus Inferior oblique Superior oblique Moves eye laterally Moves eye medially Elevates eye and turns it medially Depresses eye and turns it medially Elevates eye and turns it laterally Depresses eye and turns it laterally VI (abducens) III (oculomotor) IV (trochlear)

12 © 2013 Pearson Education, Inc. Structure of the Eyeball Wall of eyeball contains three layers –Fibrous –Vascular –Inner Internal cavity filled with fluids called humors Lens separates internal cavity into anterior and posterior segments (cavities)

13 © 2013 Pearson Education, Inc. Figure 15.4a Internal structure of the eye (sagittal section). Ora serrata Ciliary body Ciliary zonule (suspensory ligament) Cornea Pupil Anterior pole Anterior segment (contains aqueous humor) Lens Scleral venous sinus Posterior segment (contains vitreous humor) Diagrammatic view. The vitreous humor is illustrated only in the bottom part of the eyeball. Sclera Choroid Retina Macula lutea Fovea centralis Posterior pole Optic nerve Central artery and vein of the retina Optic disc (blind spot) Iris

14 © 2013 Pearson Education, Inc. Fibrous Layer Outermost layer; dense avascular connective tissue Two regions: sclera and cornea 1. Sclera Opaque, white Protects eyeball; anchors extrinsic eye muscles Continuous with dura mater of brain posteriorly 2. Cornea Transparent anterior part of fibrous layer Bends light as it enters eye Numerous pain receptors contribute to blinking and tearing reflexes

15 © 2013 Pearson Education, Inc. Vascular Layer (Uvea) Middle (pigmented) layer Three regions: choroid, ciliary body, and iris 1. Choroid region Most of uvea; posterior portion of uvea Supplies blood to all layers of eyeball Brown pigment absorbs light to prevent light scattering, which would cause unclear images 2. Ciliary body Ring of tissue surrounding lens: ciliary muscles (parasympathetic) control lens shape, ciliary zonule (suspensory ligament) holds lens in position 3. Iris Colored part of eye Pupil—central opening regulates amount of light entering –Sphincter pupillae (parasympathetic) constrict –Dilator pupillae (sympathetic) dilate

16 © 2013 Pearson Education, Inc. Figure 15.5 Pupil constriction and dilation, anterior view. Sphincter pupillae muscle contracts: Pupil size decreases. Iris (two muscles) Sphincter pupillae Dilator pupillae muscle contracts: Pupil size increases. Parasympathetic + Sympathetic +

17 © 2013 Pearson Education, Inc. Inner Layer: Retina Originates as outpocketing of brain; 2 layers –Outer Pigmented layer Single-cell-thick lining Absorbs light and prevents its scattering –Inner Neural layer Transparent Composed of three main types of neurons –Photoreceptors, bipolar cells, ganglion cells Signals spread from photoreceptors to bipolar cells to ganglion cells Quarter-billion photoreceptors: rods & cones Optic disc (blind spot) –No photorecetprs where optic nerve leaves eye

18 © 2013 Pearson Education, Inc. Figure 15.6a Microscopic anatomy of the retina. Neural layer of retina Pathway of light Optic disc Central artery and vein of retina Pigmented layer of retina Choroid Sclera Optic nerve Posterior aspect of the eyeball

19 © 2013 Pearson Education, Inc. Figure 15.6b Microscopic anatomy of the retina. Photoreceptors Rod Cone Ganglion cells Bipolar cells Axons of ganglion cells Amacrine cell Horizontal cell Pathway of signal output Pathway of light Cells of the neural layer of the retina Pigmented layer of retina

20 © 2013 Pearson Education, Inc. Photoreceptors Rods –Dim light, peripheral vision receptors –More numerous, more light-sensitive than cones –No color vision or sharp images; numbers greatest at periphery Cones –Bright light, high-resolution, color vision –Macula lutea : mostly cones Fovea centralis: Tiny pit in center of macula; all cones; sharpest vision

21 © 2013 Pearson Education, Inc. Figure 15.7 Part of the posterior wall (fundus) of the right eye as seen with an ophthalmoscope. Central artery and vein emerging from the optic disc Optic disc Macula lutea Retina

22 © 2013 Pearson Education, Inc. Internal Chambers and Fluids Lens and suspensory ligaments separate eye into anterior and posterior segments Posterior segment contains vitreous humor –Transparent, gel-like, lasts a lifetime Anterior segment contains aqueous humor & has two chambers –Anterior chamber, cornea to iris. –Posterior chamber, iris to lens. Aqueous humor: clear fluid, slowly made & slowly drains, supplies nutrients and oxygen to lens and cornea Glaucoma: blocked drainage of aqueous humor increases pressure, compresses retina and optic nerve  blindness

23 © 2013 Pearson Education, Inc. Figure 15.4a Internal structure of the eye (sagittal section). Ora serrata Ciliary body Ciliary zonule (suspensory ligament) Cornea Pupil Anterior pole Anterior segment (contains aqueous humor) Lens Scleral venous sinus Posterior segment (contains vitreous humor) Diagrammatic view. The vitreous humor is illustrated only in the bottom part of the eyeball. Sclera Choroid Retina Macula lutea Fovea centralis Posterior pole Optic nerve Central artery and vein of the retina Optic disc (blind spot) Iris

24 © 2013 Pearson Education, Inc. Lens Biconvex, transparent, flexible, avascular Changes shape to precisely focus light on retina Ciliary muscle contracts: lens gets rounder Cataracts –Clouding of lens. Risk factors: age, diabetes mellitus, smoking, frequent exposure to bright sunlight –Lens can be replaced surgically with artificial lens


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