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Sense Organs I: The Visual System

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Presentation on theme: "Sense Organs I: The Visual System"— Presentation transcript:

1 Sense Organs I: The Visual System
Lecture 15 Sense Organs I: The Visual System

2 Visual System Eye Accessory structures Optic nerve (II)
Eyebrows, eyelids, eyelashes, lacrimal (tear) glands Optic nerve (II) Sensory information travels along optic nerve to thalamus then to occipital lobe

3 Accessory Structures of Eye
Eyebrows Prevent running perspiration into eyes Shade Eyelids or palpebrae Protect and lubricate Lacrimal caruncle has sebaceous and sweat glands Extrinsic eye muscles (6) Lacrimal apparatus Lacrimal gland (facial nerve VII) Conjunctiva Thin mucous membrane over inner surface of eyelids and anterior side of eyeball Fig

4 Anatomy of the Eye Three coats or tunics
Fig Three coats or tunics Fibrous: Consists of sclera and cornea Vascular: Consists of choroid, ciliary body, iris Neural: Consists of retina

5 Anatomy of the Eye Fibrous tunic: Outer
Sclera: White outer layer, maintains shape, protects internal structures, provides muscle attachment point, continuous with cornea Cornea: No blood vessels, transparent, allows light to enter eye and refracts (bends) light Fig

6 Anatomy of the Eye Vascular tunic: Middle
Iris: Controls light entering pupil; smooth muscle Ciliary muscles: Control lens shape; smooth muscle Choroid: pigmented layer that contains melanin

7 Anatomy of the Eye Retina: Inner Cavities
Contains neurons sensitive to light Macula lutea & Fovea centralis: Area of greatest visual acuity Optic disc: Blind spot Cavities Anterior: Aqueous humor Posterior: Vitreous humor

8 Anatomy of the Eye Lens Held by suspensory ligaments attached to ciliary muscles Transparent, biconvex

9 Focus and Accommodation
Fig Far vision: 20 feet or more from eye Near vision: Closer than 20 feet Accommodation

10 Review Question Damage to the retina due to excessive light entering the eyeball could indicate a problem with the Iris Ciliary body Cornea Conjunctiva Choroid

11 Points to Remember Accessory eye structures protect and lubricate the eye. There are 3 basic layers to the eye: fibrous tunic, vascular tunic and neural tunic. Image formation on retina by bending of light rays through cornea and lens. To view close objects, the lens increases its curvature.

12 Questions?

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