10. The extraocular muscles are the six muscles that control movement of the eye and one muscle that controls eyelid elevation (levator palpebrae). The actions of the six muscles responsible for eye movement depend on the position of the eye at the time of muscle contraction.

11. Levator Palpebrae Superioris
Attachments: Originates from the lesser wing of the sphenoid bone, immediately above the optic foramen. It attaches to the superior tarsal plate of the upper eyelid (a thick plate of connective tissue).
Actions: Elevates the upper eyelid.
Innervation: The levator palpebrae superioris is innervated by the oculomotor nerve (CN III). The superior tarsal muscle (located within the LPS) is innervated by the sympathetic nervous system.

13. Recti Muscles
There are four recti muscles; superior rectus, inferior rectus, medial rectus and lateral rectus. 
These muscles characteristically originate from the common tendinous ring. This is a ring of fibrous tissue, which surrounds the optic canal at the back of the orbit. From their origin, the muscles pass anteriorly to attach to the sclera of the eyeball.
Superior Rectus
Attachments: Originates from the superior part of the common tendinous ring, and attaches to the superior and anterior aspect of the sclera.
Actions: Main movement is elevation. Also contributes to adduction and medial rotation of the eyeball.
Innervation: Oculomotor nerve (CN III).

14. Inferior Rectus
Attachments: Originates from the inferior part of the common tendinous ring, and attaches to the inferior and anterior aspect of the sclera.
Actions: Main movement is depression. Also contributes to adduction and lateral rotation of the eyeball.
Innervation: Oculomotor nerve (CN III).
Medial Rectus
Attachments: Originates from the medial part of the common tendinous ring, and attaches to the anterio-medial aspect of the sclera.
Actions: Adducts the eyeball.
Lateral Rectus
Attachments: Originates from the lateral part of the common tendinous ring, and attaches to the anterio-lateral aspect of the sclera.
Actions: Abducts the eyeball.
Innervation: Abducens nerve (CN VI).

17. Oblique Muscles
There are two oblique muscles – the superior and inferior obliques. Unlike the recti group of muscles, they do not originate from the common tendinous ring.
Superior Oblique
Attachments: Originates from the body of the sphenoid bone. Its tendon passes through a trochlear, and then attaches to the sclera of the eye, posterior to the superior rectus.
Actions: Depresses, abducts and medially rotates the eyeball.
Innervation: Trochlear nerve (CN IV).
Inferior Oblique
Attachments: Originates from the anterior aspect of the orbital floor. Attaches to the sclera of the eye, posterior to the lateral rectus
Actions: Elevates, abducts and laterally rotates the eyeball.
Innervation: Oculomotor nerve (CN III).

18. intraocular muscles of the eye
The ciliary muscle is a ring of smooth muscle[2][3] in the eye's middle layer (vascular layer) that controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humour into Schlemm's canal. It changes the shape of the lens within the eye, not the size of the pupil which is carried out by the sphincter pupillae muscle and dilator pupillae.

21. Nerves of the Orbit A. Ophthalmic nerve
Enters the orbit through the superior orbital fissure and divides into three branches:
1. Lacrimal nerve
Enters the orbit through the superior orbital fissure.
Enters the lacrimal gland, giving rise to branches to the lacrimal gland, the conjunctiva, and the skin of the upper eyelid.
2. Frontal nerve
Runs superior to the levator palpebrae superioris.
Divides into the supraorbital nerve , which passes through the supraorbital notch or foramen and supplies the scalp, forehead, frontal sinus, and upper eyelid, and the supratrochlear nerve, which passes through the trochlea and supplies the scalp, forehead, and upper eyelid.

22. 3. Nasociliary nerve
Is the sensory nerve for the eye, enters the orbit through the superior orbital fissure.
Gives rise to the following:
A communicating branch to the ciliary ganglion.
Short ciliary nerves , which carry postganglionic parasympathetic and sympathetic fibers to the ciliary body and iris .
Long ciliary nerves , which transmit postganglionic sympathetic fibers to the dilator pupillae.
The posterior ethmoidal nerve , which passes through the posterior ethmoidal foramen to the sphenoidal and posterior ethmoidal sinuses.
The anterior ethmoidal nerve , which passes through the anterior ethmoidal foramen to supply the anterior ethmoidal air cells. It divides into internal nasal branches , which supply the septum and lateral walls of the nasal cavity, and external nasal branches , which supply the skin of the tip of the nose.
The infratrochlear nerve , which innervates the eyelids, conjunctiva, skin of the nose, and lacrimal sac.

23. B. Optic nerve Consists of the axons of the ganglion cells of the retina and leaves the orbit by passing through the optic canal.
Carries Special Sensory fibers for vision from the retina to the brain and mediates the afferent limb of the pupillary light reflex.
Joins the optic nerve from the corresponding eye to form the optic chiasma.
C. Oculomotor nerve Leaves the cranium through the superior orbital fissure.
Divides into a superior division , which innervates the superior rectus and levator palpebrae superioris muscles, and an inferior division , which innervates the medial rectus, inferior rectus, and inferior oblique muscles.
Its inferior division also carries preganglionic parasympathetic fibers to the ciliary ganglion.

24. D. Trochlear nerve Passes through the lateral wall of the cavernous sinus during its course.
Enters the orbit by passing through the superior orbital fissure and innervates the superior oblique muscle.
E. Abducens nerve Enters the orbit through the superior orbital fissure and supplies the lateral rectus muscle. F. Ciliary ganglion Is a parasympathetic ganglion situated behind the eyeball, between the optic nerve and the lateral rectus muscle 

27. Blood Vessels of the Orbit
A. Ophthalmic artery Is a branch of the internal carotid artery and enters the orbit through the optic canal beneath the optic nerve.
Gives rise to the ocular and orbital vessels , which include the following:
1. Central artery of the retina Is the most important branch of the ophthalmic artery.
Travels in the optic nerve; it divides into superior and inferior branches to the optic disk, Its an end artery that does not anastomose with other arteries, and thus its occlusion results in blindness.
2. Long posterior ciliary arteries Pierce the sclera and supply the ciliary body and the iris.
3. Short posterior ciliary arteries Pierce the sclera and supply the choroid.

28. 4. Lacrimal artery Passes along the superior border of the lateral rectus and supplies the lacrimal gland, conjunctiva, and eyelids.
5. Medial palpebral arteries Contribute to arcades in the upper and lower eyelids.
6. Muscular branches Supply orbital muscles and give off the anterior ciliary arteries, which supply the iris.
7. Supraorbital artery Passes through the supraorbital notch (or foramen) and supplies the forehead and the scalp.
8. Posterior ethmoidal artery Passes through the posterior ethmoidal foramen to the posterior ethmoidal air cells.

29. 9. Anterior ethmoidal artery Passes through the anterior ethmoidal foramen to the anterior and middle ethmoidal air cells, frontal sinus, nasal cavity, and external nose.
10. Supratrochlear artery Passes to the supraorbital margin and supplies the forehead and the scalp.
11. Dorsal nasal artery Supplies the side of the nose and the lacrimal sac.

31. B. Ophthalmic veins 1. Superior ophthalmic vein
Is formed by the union of the supraorbital, supratrochlear, and angular veins.
Receives branches corresponding to most of those of the ophthalmic artery and, in addition, receives the inferior ophthalmic vein before draining into the cavernous sinus.
2. Inferior ophthalmic vein
Begins by the union of small veins in the floor of the orbit.
Communicates with the pterygoid venous plexus and often with the infraorbital vein and terminates directly or indirectly in the cavernous sinus.