L4 - Vision

• What percentage of the body's sensory receptors are in the eye?

  70%
• Why is vision considered our dominant sense?

  It involves nearly half of the cerebral cortex
• What is the primary muscle responsible for elevating the upper eyelid?

  Levator palpebrae superioris muscle
• What is the function of the orbicularis oculi muscle?

  It closes the eyelids
• What is the visible part of the eye called?

  Anterior eye
• What is the structure of the eyeball?

  It is a hollow sphere with three layers
• What are the accessory structures of the eye?

  Eyebrows, eyelids, conjunctiva, lacrimal apparatus
• What is the function of eyebrows?

  They shade eyes and block perspiration
• How do eyelids protect the eye?

  They prevent physical danger and drying out
• What triggers blinking in the eye?

  Activation of orbicularis oculi and levator palpebrae muscles
• What is the conjunctiva?

  A transparent mucous membrane
• Where does the conjunctiva cover?

  Inner surface of eyelids and anterior surface of the eye
• What is the function of the lacrimal gland?

  It secretes a dilute saline solution (tears)
• What is the pathway of tears?

  Lacrimal gland → lacrimal ducts → eye → lacrimal puncta → lacrimal sac → nasolacrimal duct → nasal cavity
• What does lacrimal fluid contain?

  Mucus, antibodies, and lysozyme
• How many extrinsic eye muscles control eyeball movement?

  Six
• Which cranial nerves innervate the extrinsic eye muscles?

  Oculomotor (III), abducens (VI), trochlear (IV)
• What are the functions of the extrinsic eye muscles?

  Maintain eyeball shape, hold it in orbit, precise eye movement
• What are the three layers (tunics) of the eyeball wall?

  Fibrous layer, vascular layer, retina
• What is the function of the fibrous layer of the eyeball?

  Maintains shape and protects inner surface
• What is the role of the choroid in the vascular layer?

  It absorbs excess light and nourishes eye layers
• What does the ciliary body do?

  Regulates lens shape and secretes aqueous humor
• What is the iris?

  The colored part of the eye
• How does the iris control pupil size?

  Through circular and radial smooth muscle contraction
• What happens to the pupil in bright light?

  It constricts as sphincter pupillae muscles contract
• What happens to the pupil in dim light?

  It dilates as dilator pupillae muscles contract
• What are the two layers of the retina?

  Pigmented layer and neural layer
• What is the function of the pigmented layer of the retina?

  Absorbs excess light to reduce scattering
• What is the role of the photoreceptor layer in the retina?

  It detects light and converts it into neural signals
• What are the two types of photoreceptors?

  Rods and cones
• What is the function of rods?

  They are sensitive to dim light and peripheral vision
• What is the function of cones?

  They provide bright light and high-resolution color vision
• Where is the fovea centralis located?

  At the center of the macula lutea
• What is the significance of the fovea centralis?

  It has the highest density of cones for detailed color vision
• What is the optic disc?

  Where the optic nerve exits the eye
• What is a cataract?

  Clouding of the lens due to protein changes
• What is the function of the aqueous humor?

  Provides oxygen and nutrients to lens and cornea
• What happens in glaucoma?

  Blocked drainage of aqueous humor increases pressure
• What is the anterior cavity of the eye filled with?

  Aqueous humor
• What is the role of suspensory ligaments?

  They hold the lens in position and transmit tension