eye

• eye

  labels

  A) pupil

  B) iris

  C) cornea

  D) suspensory ligament

  E) sclera

  F) choroid

  G) retina

  H) optic nerve

  I) vitreous humor

  J) aqueous humor

  K) lens

  
• cornea and sclera are dense connective tissue
• fibrous tunic is made of

  cornea and sclera
• cornea structure

  • transparent
  • helps focus light
  • needs oxygen from atmosphere
• sclera structure

  • collagen fibres and fibroblasts
  • rigid
  • for protection
  • random arrangement of collagen fibres
  • destructive interference
• cornea function

  • refraction of 2/3 of light onto the retina
• lens function

  • refract 1/3 of light
• cornea structure 


  is transparent for vision, so no blood cells, ordered arrangement of collagen fibres, constructive interference
• cornea gets oxygen from the atmosphere
• constructive interference makes the cornea

  transparent
• destructive interference makes the sclera

  opaque
• sclera collagen fibres have different diameters
• cornea collagen fibres all have the same diameter and a crystalline arrangement
• iris function 


  regulate amount of light entering your eye
• amount of light entering the eye is controlled by the autonomic nervous system
• choroid is highly vascular, giving nutrients and O2
• vascular tunic is made of

  choroid, ciliary body and the iris
• ciliary body makes the 


  aqueous humor
• constriction of the pupil by

  circular muscles of the iris contracting
• constriction of pupil is involved with the parasympathetic nervous system
• dilation of the pupil by

  radial muscles of the iris contracting
• dilation of the pupil is controlled by the sympathetic nervous system
• anterior cavity


  anterior chamber and posterior chamber make up the anterior cavity in front of lens
• aqueous humor

  • replaced every 90 minutes, removed through schlemm canal
  • ciliary process make it
  • nourishment for cornea and lens
  • pressurised
• vitreous chamber

  • between lens and retina
  • water, collagen and hyaluronic acid
• pressure in the eye

  16 mm Hg
• glaucoma is caused by pressure pushing against the

  optic nerve
• crystallins in the lens give

  refractive power
• accommodation is the process of 


  looking from distance to close up (and vice versa) and being able to see clearly
• accommodation occurs through changing shape of the lens
• shape of lens is altered by suspensory ligaments (zonular fibres) attached to ciliary process
• lens become more round to focus on close objects
• lens become flatter to focus on distant objects
• the light refracted is focussed on fovea
• to flatten the lens

  ciliary muscle relaxes, suspensory ligaments are taut
• to round lens 


  ciliary muscles contract, suspensory ligaments tension is released, more curved because it is elastic
• ability to accommodate declines with age because 


  lens get stiffer, staying in more flattened shape
• loss of ability to accommodate is called

  presbyopia
• cones function 


  colour vision
• rods function 


  black and white vision