Cornea Vol. 1 Flashcards
At what week of gestation does the eye begin to develop?
Week 4
From what embryologic germ layer does the optic vessel arise from?
Neuroectoderm
At what week of gestation does the optic cup form?
Week 5
What does the first wave of mesenchymal cells from the neural crest ectoderm become?
Corneal endothelium
What does the second wave of mesenchymal cells from the neural crest ectoderm become?
Corneal stroma and sclera
From what embryologic tissue layer does the corneal epithelium arise?
Surface ectoderm
At what month of gestation do the eyelids fuse?
Month 2
At what month of gestation does Bowman’s layer and scleral spur form?
Month 4
At what month of gestation do the eyelids begin to open?
Month 5
At birth, how large is the globe in proportion to adult size?
80% of adult size
How thick are the eyelids at the eyelid margin?
0.5 mm
How thick are the eyelids at the oribital rim?
1.0 mm
How often are eyelashes normally replaced?
Every 3 to 5 months
How long does it take for eyelashes to regrow if trimmed?
2 weeks
How long does it takes to eyelashes to grow if epilated?
2 months
What type of glands are the glands of Moll?
Apocrine sweat glands
What type of glands are the glands of Zeis?
Sebaceous glands
What nerve provides sensory innervation to the eyelids?
Supraorbital nerve (CN V1)
What portion of the obicularis oculi is responsible for voluntary eyelid closure?
Orbital and preseptal
What portion of the obicularis oculi musce is responsible for subconscious blinking?
Pretarsal
What is the normal rate of blinking in the average person?
One blink per 3-4 seconds
In what direction do the eyelids move during a blink?
Medially and towards each other
What are the two major sources of blood supply to the eyelid?
Facial artery and ophthalmic artery
What are the two major venous sources of drainage of the eyelids?
Superior temporalveins to the jugular vein and ophthalmic vein to the cavernous sinus
