this lecture looked at the basic features of the eye; bones, muscles, and nerves. the orbital cavity is a spherical space that houses the eyeball which is composed of many different bones: frontal, maxilla, zygoma, ethmoid, palatine, sphenoid, lacrimal. the orbital cavity is expressly designed such that the eyes are facing forward and parallel to each other, making the line of sight parallel with the ground. the eye itself only takes up 1/3 of the orbital cavity; the rest of the cavity is filled with muscle, periorbital fat, nerves, and fascia. the fascia that surrounds the eye and suspends it above the floor of the orbital cavity is called the fascia bulbi.
a few more anatomical notes: the corners of the eyes are called the inner and outer canthus. the tarsal plates are dense connective tissue that line the eyelids, and contain tarsal glands which secrete mucus to moisten the eyeballs. the superior and inferior fornices are the space on the insides of the eyelids, which are lined with the conjunctiva, a thin covering which also lines the sclera. the lacrimal apparatus produces tears in the upper lateral edge of the orbital cavity, which migrate across the eye, then drain into through the puncta (skin pores) into the lacrimal canaliculi, which collects into the lacrimal sac, which drains into the nasolacrimal duct, which opens up into the inferior meatus (which is why crying instantaneously produces a runny nose).
eye movements are mediated by 6 muscles. the superior rectus produces a elevation / adduction motion, the inferior rectus produces depression and adduction. the medial rectus adducts and the lateral rectus abducts. the superior oblique, which hooks around the trochlea and approaches the eyeball obliquely, depresses and abducts the eye, while the inferior oblique, which originates from the medial orbital cavity floor, elevates and abducts the eye. the superior, medial, inferior rectus, the levator palpabrae, and inferior oblique are all innervated by the oculomotor nerve (CN III). the superior oblique is innervated by the trochlear nerve (CN IV), and the lateral rectus is innervated by the abducens nerve (CN VI).
questions
anatomical features...
1. what are the bones of the orbital cavity?
2. what are the bones of the orbital cavity designed for?
3. how much of the orbital cavity does the eyeball occupy?
4. what is in the remaining space of the orbital cavity?
5. what is the fascia bulbi?
6. what muscle closes and constricts the eyelids?
7. what is the name for the corners of the eyes?
8. what are the tarsal plates?
9. what are tarsal glands and what do they do?
10. what is the conjunctivum?
11. describe the lacrimal apparatus.
12. where do the tears secreted by the lacrimal glands drain into?
eye movements...
13. what are the muscles that control eye movement?
14. superior oblique hooks around...
15. inferior oblique originates from...
motion of...
16. superior rectus...
17. inferior rectus...
18. medial rectus...
19. lateral rectus...
20. superior oblique...
21. inferior oblique...
nerves...
22. where do the nerves to the eye enter the orbital cavity?
23. what are the motor nerves that innervate the eye muscles?
24. what is the sensory nerve that innervates the eyeball and orbital cavity?
answers
1. frontal, maxilla, zygoma, ethmoid, palatine, sphenoid, lacrimal.
2. to orient the eyes in a forward position (so that vision is parallel to the ground)
3. 1/3
4. muscles, fascia, nerves, periorbital fat.
5. the CT sheath that surrounds the eyeball and suspends it off of the orbital floor.
6. orbicularis oculi.
7. the inner and outer canthus.
8. dense CT that support the eyelids.
9. glands within the tarsal plates that secrete mucus to moisten the eyes.
10. the lining of the superior and inferior fornices and covering of the sclera.
11. lacrimal glands in the upper lateral recesses of the eye secretes tears into the superior fornix.
12. puncta (skin pores), canaliculi and lacrimal sac, nasolacrimal duct, inferior meatus.
13. the four rectuses (superior, inferior, lateral, medial), superior and inferior oblique, and levator palpabrae superioris.
14. trochlea
15. medial orbital floor.
16. elevation and adduction
17. depression and adduction
18. adduction
19. abduction
20. depression and abduction
21. elevation and abduction
22. the superior orbital fissure.
23. oculomotor (CN III) innervates the superior, inferior, medial rectus, inferior oblique, levator palpebrae superioris. trochlear (CN IV) innervates the superior oblique. abducens (CN VI) innervates the lateral rectus.
24. trigeminal (V1)
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