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The Orbit PowerPoint Presentation

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Description : Orbit: a pyramid-shaped bony recess in the anterior part of the skull, lined by periosteum called the periorbital fascia.

Tags : medical,Orbit,Lacrimal caruncle,eye,Eyelids,eye problem,extraocular muscles,rectus muscles

Published on : Jun 01, 2023 | Views : 1036 | Downloads : 2

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The Orbit Professor Ali A Razooki BDS, PhD 2020
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Orbit: a pyramid-shaped bony recess in the anterior part of the skull, lined by periosteum called the periorbital fascia
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Eyelids and lacrimal apparatus Each orbit is closed by the upper and lower eyelids bearing eyelashes on their anterior edge. The palpebral fissures are the gaps between the lids when the eyes are open. The lacrimal papilla is a small prominence located near the medial end of each eyelid with a small opening on its summit called the punctum, this is the opening of the lacrimal canaliculus through which tears drain from the eye. Lacrimal caruncle is a pinkish fold of skin at the medial angle or medial canthus of the eye.
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① Lacrimal caruncle ② Superior and inferior lacrimal canaliculi ③ Lacrimal sac ④ Superior and inferior puncta ⑤ Nasolacrimal duct ⑥ Nasolacrimal canal ⑦ Inferior nasal concha ⑧ Lacrimal gland, palpebral part ⑨ Lacrimal gland, orbital part
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① Levator palpebrae superioris ② Supraorbital a. and n. ③ Supratrochlear n. ④ Trochlea ⑤ Infratrochlear n. ⑥ Doral nasal a. and v. ⑦ Lacrimal sac ⑧ Angular a. and v. ⑨ Infraorbital n. and a. ⑩ Lacrimal gland ⑪ Orbital septum
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Eyelids The eyelids are movable flaps which protect the eye. The upper is the larger and more mobile with its own elevator muscle, the levator palpebrae superioris. The orbital septum is a connective tissue sheet attached to the margins of the bony orbit. It is thickened above and below the palpebral fissure into crescentic layers of strong fibrous tissue, forming the superior and inferior tarsal plates which are shaped to fit the curvature of the eyeball.
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Levator palpebrae superioris muscle attaches to the larger upper tarsal plate. The ends of the two plates are attached medially to the lacrimal bone by the medial palpebral ligament and laterally to the zygomatic bone by the lateral palpebral ligament . The orbicularis oculi muscle lies between the skin and tarsal plates.
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The lacrimal apparatus and circulationof tears The lacrimal glands are similar to serous salivary glandular tissue. Each gland consists of a large orbital and a smaller palpebral part. Tears pass through the lacrimal canaliculi into the lacrimal sac contained within the lacrimal groove in the medial wall of the orbit.
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Contents of the orbit • The eyeball and optic nerve; • The extraocular muscles which move the eyeball and upper eyelid; • The vessels and nerves that supply these structures; or pass through the orbit to reach structures
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Extraocular muscles The extraocular muscles comprise six muscles in each orbit that move the eyeball and elevate the upper eyelids.
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⑨ Inferior oblique ⑩ Inferior orbital septum ⑪ Superior orbital septum ⑫ Periorbital fat ① Levator palpebrae superioris ② Ophthalmic a. ③ Superior rectus ④ Optic n. (CN II) with dural sheath ⑤ Inferior rectus ⑥ Central retinal a. ⑦ Sclera ⑧ Infraorbital n. (CN V2)
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① Supratrochlear n. ② Levator palpebrae superioris ③ Lacrimal gland ④ Lacrimal a. and n. (CN V1) ⑤ Superior rectus ⑥ Abducent n. (CN VI) ⑦ Superior ophthalmic v. ⑧ Frontal n. (CN V1) ⑨ Trochlear n. (CN IV) ⑩ Nasociliary n. (CN V1) ⑪ Supraorbital a. ⑫ Supraorbital n. ⑬ Posterior ethmoidal a. and n. ⑭ Supratrochlear a. ⑮ Anterior ethmoidal a. and n. ⑯ Infratrochlear n.
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Levator palpebrae superioris It attaches to the bone of the roof of the orbit close to its apex posteriorly and runs forwards beneath the orbital roof and broadens out to attach to the tarsal plate, skin, and conjunctiva of the upper eyelid. Most of the fibers of the muscle are striated and innervated by the superior branch of the oculomotor nerve . contains some smooth muscle supplied by sympathetic nerves from the superior cervical ganglion
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The 4 rectus muscles The four rectus muscles arise from a common tendinous ring attached to the bone around the opening of the optic canal and the medial end of the superior orbital fissure. The recti pass forwards from this ring as a cone of muscles surrounding the optic nerve; they attach to the fibrous sclera covering the eyeball anterior to the coronal equator which divides the eyeball into anterior and posterior halves.
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Superior rectus lies beneath levator palpebrae superioris and attaches to the upper surface of the eyeball. elevates the eyeball and pulls it medially because of the lateral inclination of the muscle. Inferior rectus has an equivalent attachment on the inferior surface of the eyeball and acts to depress the eyeball and draw it medially. Medial rectus passes along the medial wall of the orbit into the medial surface of the eyeball; it turns the eye medially. Lateral rectus is similarly arranged on the lateral side of the eyeball and moves it laterally Superior rectus Superior oblique Medial rectus Inferior oblique Inferior rectus Lateral rectus
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Superior rectus is innervated by the superior branch of the oculomotor nerve Inferior and medial recti by the inferior branch of the oculomotor nerve. Lateral rectus is supplied by the abducens nerve. ① Inferior oblique ② Tendon of superior oblique ③ Superior rectus ④ Lateral rectus ⑤ Levator palpebrae superioris (cut) ⑥ Medial rectus ⑦ Inferior rectus ⑧ Superior oblique ⑨ Trochlea
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The 2 oblique muscles The superior oblique muscle arises from the bone above and medial to the tendinous ring. It passes forwards above the medial rectus close to the junction of the medial wall and roof of the orbit, becoming tendinous towards the front of the orbit. The tendon passes through the trochlear , a loop of fibrous tissue attached to the roof of the orbit immediately behind the superomedial angle of the orbital margin. The muscle pulls the posterior part of the eyeball upwards and medially, thus turning its front face downwards and laterally. It is supplied by the trochlear nerve.
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① Levator palpebrae superioris (cut) ② Medial rectus ③ Superior oblique ④ Superior rectus ⑤ Lateral rectus (cut) ⑥ Inferior oblique ⑦ Inferior rectus ⑧ Abducent n. (CN VI) ⑨ Trochlear n. (CN IV) ⑩ Oculomotor n. (CN III) ⑫ Common tendinous ring ⑪ Optic n. (CN II)
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The inferior oblique muscle is a narrow muscle which arises from the floor of the orbit lateral to the lacrimal groove. It passes laterally and posteriorly beneath the eyeball and inferior rectus to attach to the lateral surface of the eyeball behind the coronal equator. It elevates the eyeball and draws it laterally. It is supplied by the inferior branch of the oculomotor nerve.
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Nerves of the orbit The optic nerve ; • The oculomotor, trochlear , and abducens nerves to the extraocular muscles; • The branches of the ophthalmic division of the trigeminal nerve which are sensory to structures within the orbit and to a wide area outside the orbit; • The ciliary ganglion and associated branches which are concerned with the autonomic innervation of the eyeball; • The branches of the maxillary division of the trigeminal nerve which pass through the orbit without supplying its contents.
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① CN III, superior branch ② Frontal n. (CN V1) ③ Lacrimal n. (CN V1) ④ Supraorbital n. (CN V1) ⑤ Infratrochlear n. (CN V1) ⑥ Long ciliary nn. ⑦ Nasociliary n. (CN V1) ⑧ Short ciliary nn. (from ciliary ganglion) ⑨ Ciliary ganglion ⑩ Parasympathetic (motor) roots of ciliary ganglion (from CN III) ⑪ Sensory root of ciliary ganglion (to nasociliary n.) ⑫ Sympathetic root of ciliary ganglion (from superior cervical ganglion) ⑬ CN III, inferior branch
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The ciliary ganglion This is a small parasympathetic ganglion lying lateral to the optic nerve . A branch from the inferior branch of the oculomotor carries preganglionic parasympathetic axons and synapses in the ganglion. Post-ganglionic neurons innervate sphincter pupillae and ciliary muscles . The sphincter muscles constrict the pupil The ciliary muscles increase the lens curvature to focus the eye.
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Sympathetic post-ganglionic vasoconstrictor nerves from the internal carotid sympathetic plexus pass through the ganglion to innervate blood vessels in the eyeball. As already mentioned, sympathetic nerves to dilator pupillae reach the eyeball in the long ciliary branches of the nasociliary nerve. A branch of the nasociliary nerve also passes through the ganglion without synapsing to supply the cornea and iris. The dozen or so short ciliary nerves exit the ciliary ganglion and enter the back of the eyeball. They carry the parasympathetic, sympathetic, and sensory nerves from the ganglion into their various targets within the eyeball.
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Orbital blood vessels The ophthalmic artery branches from the internal carotid artery The artery has branches that follow the lacrimal and nasociliary nerves to the same targets, muscular branches to the extraocular muscles, ciliary arteries to the eyeball, and the central artery of the retina which runs within the optic nerve to the retina.
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① Dorsal nasal a. ② Supraorbital a. ③ Lacrimal a. ④ Ophthalmic a. ⑤ Internal carotid a. ⑥ Posterior ethmoidal a. ⑦ Anterior ethmoidal a. ⑧ Supratrochlear a.
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Venous blood leaves the orbit and its contents in the superior and inferior ophthalmic veins . Both pass through the superior orbital fissure to drain into the cavernous sinus. The superior veins communicate with the facial veins and the inferior vein frequently connects with the pterygoid plexus through the inferior orbital fissure. These connections are, like venous connections mentioned in previous chapters, potential routes for spread of infection. Lymph drains from the orbit to the parotid nodes and thence to the deep cervical group.
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① Dorsal nasal v. ② Supraorbital v. ③ Supratrochlear v. ④ Angular v. ⑤ Facial v. ⑥ Infraorbital v. ⑦ Inferior ophthalmic v. ⑧ Ophthalmic v. ⑨ Cavernous sinus ⑩ Superior ophthalmic v.
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