!Eyes - Eyelids

!!Anatomy
An eyelid is a thin ((Sensory - Eyelid Skin|fold of skin)) that covers and protects the eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The __tarsus__ is a plate of ((Musculoskeletal - Cartilage|cartilage)) inside the eyelid.The ((Sensory - Eyelid Muscles|levator palpebrae)) superioris muscle retracts the eyelid to "open" the eye. This can be either ((Nervous - Motoric Innervation|voluntarily)) or ((Organ Walls - Smooth Muscle Layer|involuntarily)). The human eyelid features a row of __eyelashes__ which serve to heighten the __protection of the eye__ from dust and foreign debris, as well as from perspiration. Its key function is to regularly spread the tears and other secretions on the eye surface to keep it moist, since the ((Sensory - Eyes - Cornea|cornea)) must be continuously moist. They keep the eyes from drying out when asleep. Moreover, the __blink reflex__ protects the eye from foreign bodies.

{img fileId="63" thumb="y" rel="box[g]"}

!!Brain
{img fileId="202" thumb="box"}brain parts

{img fileId="123" thumb="box"}cerebral cortex areas

!!!Relays
1. __Cerebral Cortex __( - | + ) in ((Sensory - Eyelid Skin|epidermis)) and eyelashes, ((Sensory - Eyelid Muscles|muscle innervation))
{img fileId="104" thumb="box"}sensory & motoric areas

2. __Cerebellum__ (+/-) dorsal in ((Sensory - Eyelid Skin|dermis, sebaceous and Meibom glands))
{img fileId="174" thumb="box"}

3. __Cerebral Medulla__ (-/+) "skull area" for ((Sensory - Eyelid Muscles|muscles)) and cartilage
{img fileId="175" thumb="box"}

4. __Midbrain/Brain Stem__ (+/-) posterior central, for ((Sensory - Eyelid Muscles|involuntary muscle innervation))
{img fileId="190" thumb="box"}