Eye presentation [compatibility mode]


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Eye presentation [compatibility mode]

  1. 1. 7/6/2012 Sight and the eye By Shahzad Bashir RN, BScN (NMC ION) Objectives By the end of this presentation you The Eye will able to: Describe the gross structure of eye. The eye is the organ of sense of sight Structure related to vision It is supplied by optic, Describe the structure and function oculomotor,trochlear, abducent nerves of ear. (2nd,3rd,4th and 6th cranial nerves) Transmission through ear. It is spherical in shape and is about 2.5 Physiology of Hearing and balance cm in diameter. Structure Structure inside the eyeball are the lens,aqueous fluidThere are three layers of tissue in the wall of eye: (humour) and vitreous body The outer fibrous layer: sclera and (humour) cornea The middle vascular layer or uveal tract:choroid, ciliary body and iris The inner nervous tissue layer: retina 1
  2. 2. 7/6/2012 Accessory Structures of the The Fibrous Tunic (layer) Eye Lacrimal apparatus – keeps the Most external layer of the eyeball surface of the eye moist Composed of two regions of connective tissueLacrimal gland – produces lacrimal Sclera – White, opaque region fluid Provides shape and an anchor for eye muscles Lacrimal sac – fluid empties into Cornea – The transparent circular part of front of the eye, it refracts the light to entering in the eye. nasal cavity Limbus – junction between sclera and cornea The Fibrous Tunic (layer) The Fibrous Tunic (layer) The middle coat of the eyeball Composed of choroid, ciliary body, Ciliary body – thickened ring of tissue and iris – encircles the lens Choroid – vascular, darkly Composed of ciliary muscle pigmented membrane Ciliary processes – posterior surface of the Prevents scattering of light rays within ciliary body the eye Ciliary zonule (suspensory ligament) Attached around entire circumference of the Choroid corresponds to the lens. arachnoid and pia maters The Iris Medial View of the Eye Visible colored part of the eye Attached to the ciliary body Composed of smooth muscle Pupil – the round, central opening Sphincter pupillae muscle (constrictor or circular) Dilator pupillae muscle (dilator or radial) Act to vary the size of the pupil 2
  3. 3. 7/6/2012Posterior View of the Anterior Half of the Eye Pupillary dilation and constriction The Sensory Tunic (layer Microscopic Anatomy of the ) (Retina) Retina Retina – the deepest tunic Composed of two layers Pigmented layer – single layer of melanocytes Neural layer – sheet of nervous tissue Contains three main types of neurons Photoreceptor cells Bipolar cells Ganglion cells Photoreceptors Photoreceptors Two main types Rod cells – more sensitive to light Allow vision in dim light Cone cells – operate best in bright light Enable high-acuity, color vision Considered neurons 3
  4. 4. 7/6/2012Blood Supply of the RetinaRetina receives blood from two sources Outer third of the retina – supplied by capillaries in the choroidInner two-thirds of the retina – suppliedby central artery and vein of the retina Internal Chambers and FluidsInternal Chambers and Fluids Anterior segmentThe lens and ciliary zonules divide the Divided into anterior and posterior eye chambers Anterior chamber – between the cornea and Posterior segment (cavity) iris Filled with vitreous humor Posterior chamber – between the iris and Clear, jelly-like substance lens Transmits light Filled with aqueous humor Supports the posterior surface of the lens Renewed continuously Helps maintain intraocular pressure Formed as a blood filtrate Supplies nutrients to the lens and cornea Internal Chambers and Fluids The Lens 4
  5. 5. 7/6/2012The Eye as an Optical Device Visual Pathways Structures in the eye bend light rays Light rays converge on the retina at a single focal point Most visual information travels to the Light bending structures (refractory cerebral cortex media) Responsible for conscious “seeing” The lens, cornea, and humors Other pathways travel to nuclei in theAccommodation – curvature of the lens is midbrain and diencephalon adjustable Allows for focusing on nearby objects Visual Pathways to the Visual Pathways to the Cerebral Cortex Cerebral Cortex Pathway begins at the retina Optic tracts send axons to: Light activates photoreceptors Lateral geniculate nucleus of the thalamus Photoreceptors signal bipolar cells Synapse with thalamic neurons Bipolar cells signal ganglion cells Fibers of the optic radiation reach the Axons of ganglion cells exit eye as the primary visual cortex optic nerveVisual Pathways to the Brain and Visual Fields Regional Specializations of the Retina Macula lutea – contains mostly cones Fovea centralis – contains only cones Region of highest visual acuity Optic disc – blind spot 5
  6. 6. 7/6/2012 The Ear: Hearing and Equilibrium The ear – receptor organ for hearing and equilibrium it is supplied by 8th cranial The Ear nerve that is vestibulocochlear nerve. Composed of three main regions Outer ear – functions in hearing Middle ear – functions in hearing Inner ear – functions in both hearing and equilibrium The Outer (External) Ear The Outer (External) Ear Composed of: The auricle (pinna) Helps direct sounds External acoustic meatus Lined with skin Contains hairs, sebaceous glands, and ceruminous glands Tympanic membrane Forms the boundary between the external and middle ear The Middle Ear Structures of the Middle Ear The tympanic cavity A small, air-filled spaceLocated within the petrous portion of the temporal bone Medial wall is penetrated by: 1.Oval window 2.Round windowPharyngotympanic tube (auditory or eustachian tube) Links the middle ear and pharynx 6
  7. 7. 7/6/2012 The Middle Ear Ear ossicles – smallest bones in the body Malleus – attaches to the eardrum Incus – between the malleus and stapesStapes – vibrates against the oval window The Inner (Internal) Ear The Inner (Internal) Ear The Inner (Internal) Ear The Inner (Internal) Ear Membranous labyrinth Series of membrane-walled sacs and Membranous labyrinth (continued) ducts Filled with a clear fluid – endolymph Fit within the bony labyrinth Confined to the membranous labyrinth Consists of three main parts Bony labyrinth is filled with perilymph A. Semicircular ducts Continuous with cerebrospinal fluid B. Utricle and saccule C. Cochlear duct 7
  8. 8. 7/6/2012The Membranous Labyrinth The Vestibule The central part of the bony labyrinth Lies medial to the middle ear Utricle and saccule – suspended in perilymph Two egg-shaped parts of the membranous labyrinth House the macula – a spot of sensory epithelium The Vestibule Macula – contains receptor cells Monitor the position of the head when the head is still Contains columnar supporting cells Receptor cells – called hair cells Synapse with the vestibular nerve The Semicircular Canals The Semicircular Canals Lie posterior and lateral to the vestibuleAnterior and posterior semicircular canals Lie in the vertical plane at right angles Lateral semicircular canal Lies in the horizontal plane 8
  9. 9. 7/6/2012 The Semicircular Canals The Cochlea Semicircular duct – snakes through A spiraling chamber in the bony each semicircular canal labyrinthMembranous ampulla – located within bony ampulla Houses a structure called a crista ampullaris Cristae contain receptor cells of rotational accelerationEpithelium contains supporting cells and receptor hair cells The Cochlea The Cochlea The cochlear duct (scala media) – contains receptors for hearing The cochlear duct (scala media) – Lies between two chambers contains receptors for hearing The scala vestibuli Organ of Corti – the receptor The scala tympani epithelium for hearing The vestibular membrane – the roof of the Consists of: cochlear duct Supporting cells The basilar membrane – the floor of the Inner and outer hair cells (receptor cells) cochlear duct Equilibrium and Auditory Pathways References •Tortora, J. G., Derrichson, B. The equilibrium pathway (2006).Principles of Anatomy and Transmits information on the position Physiology. (11th ed). USA: New and movement of the head York. John Willey 7 sons , Inc. Most information goes to lower brain centers (reflex centers) •Ross and Wilson, Anatomy and Physiology (ninth edition) in health The ascending auditory pathway and illness. Transmits information from cochlear receptors to the cerebral cortex 9