The Eyeball

Question 1

outer layers and associated structures

Answer 1

1. Lacrimal gland
2. Extrinsic skeletal muscles (6)
3. Conjunctiva: outer mucous membrane; vascularized
4. Sclera: white, supportive dense irregular connective tissue
5. Cornea: transparent, convex, anterior circle of sclera serves for preliminary focus(refraction)

Question 2

Middle layer

Answer 2

1. choroid: vascular, darkly pigmented contains ciliary vessels supplying O2 to sclera
2. Ciliary body: anterior portion of choroid; a serrated ring of smooth (ciliary) muscles.
3. Lens: avascular, made of epithelium and protein fibers; pliable, changes shape via action of ciliary muscles
4. Iris:
   - attached to ciliary body
   - contains circular and radial smooth muscle
   - creates opening called the “pupil”
   - may be pigmented with melanin

Question 3

Inner layer:

Answer 3

1. Retina:
   - photoreceptive layer of rods (night vision) and cones (day vision)
   - maintained by branches of central artery
   - macula lutea: center of retina, not crossed by vessels
   - central fovea: inside macula; highest cone cell density.
   - optic disc: at optic nerve; area devoid of rods and cones
2. optic nerve: protected by meninges

Question 4

Fluids in the eye:

Answer 4

A). Aqueous humor (fills anterior segment):

• produced by ciliary processes of the ciliary body
• serves to maintain shape of cornea
• “canal of Schlemm”: drains aqueous humor into anterior ciliary veins leaving eye

B). vitreous humor (fills posterior segment):

• glassy, gel material with phagocytic cells
• supports retina, removes cellular debris