Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download The Eye - My Anatomy Mentor
Document related concepts
Transcript
ACCESSORY EYE STRUCTURES Eyebrows ◦ Shade ◦ Protection from sweat and other substances Eyelids (Palpebrae) Protection from foreign objects Moisten the eyes (blinking) Levator palpebrae superioris muscles raise the eyelids Palpebral Fissure Space between upper and lower eyelids ACCESSORY EYE STRUCTURES Medial and Lateral Canthi ◦ Eye angles Caruncle Fleshy, elevated area in medial canthus Contains sebaceous and sweat glands Eyelashes Reflex blinking when touched Richly innervated ACCESSORY EYE STRUCTURES Tarsal or Meibomian Glands ◦ Embedded in eyelids ◦ Openings posterior to eyelashes ◦ Secrete oil to lubricate eyelids Ciliary Glands Small sebaceous glands Between hair follicles of eyelashes ACCESSORY EYE STRUCTURES Conjunctiva ◦ Mucous membrane ◦ Lines inside of each eyelid (palpebral conjunctiva) ◦ Covers anterior surface of eye except over cornea (bulbar or ocular conjunctiva) palpebral conjunctiva ocular conjunctiva ACCESSORY EYE STRUCTURES Lacrimal Apparatus lacrimal gland ◦ Lacrimal gland + ducts that lacrimal sac drain tears into nasal cavity ◦ Releases dilute saline solution onto eyes Contains mucus, lacrimal antibodies, lysozyme canal ◦ Solution drains via: nasolacrimal Lacrimal puncta duct lacrimal canals lacrimal sac nasolacrimal duct nasal cavity EXTRINSIC EYE MUSCLES Superior Rectus ◦ Moves eyes superiorly Inferior Rectus Moves eyes inferiorly Lateral Rectus Moves eyes laterally Inferior Oblique Moves eyes up and out [R] Lateral View EXTRINSIC EYE MUSCLES Superior Oblique Moves eyes down and out Medial Rectus Moves eyes medially Superior View EYE MUSCLE INNERVATION (LR6SO4)O3 Lateral Rectus Superior Oblique All Others Cranial nerve VI (abducens) Cranial nerve IV (trochlear) Cranial nerve III (oculomotor) Name Cranial Nerve Action Lateral rectus VI (abducens) Moves eye laterally Medial rectus III (Oculomotor) Moves eye medially Superior rectus III (Oculomotor) Moves eye superiorly Inferior rectus III (Oculomotor) Moves eye inferiorly Inferior oblique III (Oculomotor) Moves eye up and out Superior oblique IV (trochlear) Moves eye down and out STRUCTURE of the EYE FIBROUS TUNIC Sclera Cornea STRUCTURE of the EYE VASCULAR TUNIC Ciliary body Iris Choroid STRUCTURE of the EYE SENSORY TUNIC Outer Retinapigmented Inner neural layer STRUCTURE OF THE EYE Ora serrata Suspensory ligament Cornea Pupil Iris Ciliary body Sclera Choroid STRUCTURE of the EYE Anterior Segment Posterior chamber Anterior chamber Lens Vitreous humor STRUCTURE of the EYE Optic disc Optic nerve Optic disc Fovea centralis Macula lutea STRUCTURE of the EYE Canal of Schlemm Central artery & vein PHYSIOLOGY OF VISION: REFRACTION Refraction ◦ Bending of light rays ◦ Light rays change speed as they pass through substances of different densities ◦ Light is refracted in 3 areas of the eye: Cornea Entrance of lens Exit of lens Distant vision Close vision PHYSIOLOGY OF VISION: REFRACTION lens bulges Lens shape can change ◦ Can be used to refract light to a specific distance ◦ Allows light to focus on retina ◦ No focusing is necessary for distant objects (over 6m away) Close vision lens flattens Distant vision FOCUSING FOR NEAR VISION Accommodation Constriction of Pupils Convergence of Eyeballs ◦ Ciliary muscle contracts ◦ Suspensory ligaments release tension on lens ◦ Lens thickens and bulges to focus image on retina ◦ Constrictor muscle in iris makes pupil smaller ◦ Focuses light in a finer point ◦ Medial rectus muscles contract ◦ Each eye moves medially ◦ Focuses on near object VISION: DISORDERS OF REFRACTION Emmetropia ◦ Normal vision Myopia Nearsightedness Object focuses in front of the retina Eyeball is too long Hyperopia Farsightedness Object focuses behind the retina Eyeball is too short PHOTORECEPTION: THE RETINA Pigmented Layer ◦ Outer layer of retina ◦ Dark pigment to prevent light from scattering Neural Layer pigmented layer neural layer Inner layer of retina Contains photoreceptors Modified neurons called rods and cones Composed of three layers THE RETINA: INNER NEURAL LAYER Three Layers ◦ Photoreceptor layer Bipolar cell layer Ganglion cell layer THE RETINA: INNER NEURAL LAYER Photoreceptor Layer ◦ Rods and cones adjacent to the outer pigmented layer Rods cone More numerous rod Used in dim light Used for peripheral vision Do not detect color Cones Less numerous Provide color vision Used for acute vision Light NEURAL LAYER: RODS AND CONES Rods and Cones ◦ Contain an inner and outer segment ◦ Outer segment Receptor region Contains visual pigments inner segment outer segment NEURAL LAYER: BIPOLAR CELLS Bipolar Cells ◦ Just inside the photoreceptor cell region ◦ Pass impulse from the receptor cells to the inner ganglion cells Light NEURAL LAYER: GANGLION CELLS Ganglion Cells ◦ Innermost retinal layer ◦ Generate an action potential in response to photoreceptor and bipolar cells ◦ Action potential travels to optic nerve (composed of axons from these cells) Light VISUAL PIGMENTS Retinal ◦ Light absorbing molecule ◦ Made from Vitamin A ◦ Combines with proteins call opsins to form 4 types of visual pigments ◦ When bound to opsin, retinal is bent ◦ When light strikes retinal it causes the molecule to straighten and release opsin ◦ Series of reactions result in electrical impulses down the optic nerve PHOTODISSOCIATION OF RHODOPSIN Retinal 1 4 2 Rhodopsin 3 Energy Light active site STIMULATION OF PHOTORECEPTORS Excitation of Rods ◦ Visual pigment in rods is rhodopsin (retinal + a form of opsin) ◦ Stored in discs in outer segments of rods ◦ Light strikes rhodopsin retinal changes shape releases opsin ◦ Triggers a reaction that initiates an impulse ◦ Retinal is converted back to its original form in the pigmented layer of the retina ◦ Rhodopsin is reformed when the retinal attaches to opsin again STIMULATION OF PHOTORECEPTORS Excitation of Cones ◦ 3 types of Cones Each contains a pigment with a different opsin Each pigment is sensitive to a different wavelength of light Each detects a different color of light (red, green and blue) Breakdown and regeneration of visual pigments in the cones is the same as for rhodopsin Threshold for activation of cones is much higher so they respond to intense light VISION DISORDERS Night Blindness ◦ Nyctalopia ◦ Caused by impairment of rod function ◦ Most commonly caused by Vitamin A deficiency Color Blindness ◦ Due to lack of one or more cone types at birth ◦ Most commonly red/green color blindness VISUAL PATHWAY Right eye Left eye Optic nerve Optic chiasma Optic tract Lateral geniculate body of thalamus Optic radiations Visual cortex
