Comparativ

Notes

•Eye The eye is the organ of vision, consisting of the eyeball and the optic nerve. It is suspended in the bony orbit by six extrinsic muscles that control its movement. A thick layer of adipose tissue partially surrounds and cushions the eye as it moves within the orbit. The eyelids and lacrimal apparatus protect the eye. •Eyelids Eyelids have two surfaces: an external skin-covered surface and an internal palpebral conjunctiva. Between the dermis and the lamina propria of the conjunctiva lies the tarsal plate, a dense connective tissue surrounded by multilobular tarsal glands. These movable skin folds protect and lubricate the eye surface. The outer surface features stratified squamous epithelium, tactile hairs, sebaceous glands (glands of Zeiss), and sweat glands (glands of Möll). The inner surface is lined with the palpebral conjunctiva, a thin, transparent mucous membrane. The bulbar conjunctiva, continuous with the corneal surface at the limbus, may be stratified columnar or squamous, with goblet cells. •Nictitating membrane (third eyelid) This semi-circular conjunctival fold encloses a cartilage plate—hyaline in ruminants and dogs, elastic in horses, pigs, and cats—an...