Anatomy of the Orbit and Periorbital Region PDF

Anatomy of the Orbit and Periorbital region Dr Hemin O Sheriff Assistant Professor Plastic Surgeon Orbital cavity Orbital margin Orbital margin and orbital Cavity The Orbit The orbit is a pyramidal cavity with its base in front and its apex behind. The orbital margin is formed above by the frontal b...

Anatomy of the Orbit and Periorbital region Dr Hemin O Sheriff Assistant Professor Plastic Surgeon Orbital cavity Orbital margin Orbital margin and orbital Cavity The Orbit The orbit is a pyramidal cavity with its base in front and its apex behind. The orbital margin is formed above by the frontal bone, the lateral margin is formed by the processes of the frontal and zygomatic bones, the inferior margin is formed by the zygomatic bone and the maxilla, and the medial margin is formed by the processes of the maxilla and the frontal bone. Ieee Boundaries of the Orbital cavity Roof: Formed by the orbital plate of the frontal bone, which separates the orbital cavity from the anterior cranial fossa and the frontal lobe of the cerebral hemisphere Lateral wall: Formed by the zygomatic bone and the greater wing of the sphenoid. Floor: Formed by the orbital plate of the maxilla, which separates the orbital cavity from the maxillary sinus Medial wall: Formed from before backward by the frontal process of the maxilla, the lacrimal bone, the orbital plate of the ethmoid (which separates the orbital cavity from the ethmoid sinuses), and the body of the sphenoid Openings in the orbital cavity optional 1. Optic canal 2. Superior orbital fissure 3. Inferior orbital fissure 4. Orbital opening largest 5. Supraorbital notch ( foramen) 6. Infraorbital groove and canal 7. Nasolacrimal canal 8. Zygomaticotemporal foramen 9. Zygomaticofacial foramen 10. Anterior and Posterior Ethmoidal foramen s sue Openings Into the Orbital Cavity Orbital opening: Lies anteriorly. About one-sixth of the eye is exposed; the remainder is protected by the walls of the orbit. Supraorbital notch (Foramen): The supraorbital notch is situated on the superior orbital margin.It transmits the supraorbital nerve and blood vessels. III Infraorbital groove and canal: Situated on the floor of the orbit in the orbital plate of the maxilla,they transmit the infraorbital nerve (a continuation of the maxillary f nerve) and blood vessels. e Nasolacrimal canal: Located anteriorly on the medial wall; it communicates with the inferior meatus of the nose.It transmits the nasolacrimal duct. III Inferior orbital fissure: Located posteriorly between the maxilla and the greater wing of the sphenoid ,it communicates with the pterygopalatine fossa. Eii.ie It transmits the maxillary nerve and its zygomatic branch, the inferior ophthalmic vein, and sympathetic nerves. Superior orbital fissure: Located posteriorly between the greater and lesser wings of the sphenoid ; it communicates with the middle cranial fossa. It transmits the lacrimal nerve, the frontal nerve, the trochlear nerve, the oculomotor nerve (upper and lower divisions), the abducent nerve, the nasociliary nerve, and the superior ophthalmic vein. Optic canal: Located posteriorly in the lesser wing of the sphenoid ; it communicates with the middle cranial fossa. It transmits the optic nerve and the ophthalmic artery. e __ _E Optic Nerve The optic nerve enters the orbit from the middle cranial fossa by passing through the optic canal. It is accompanied by the ophthalmic artery, which lies on its lower lateral side. The nerve is surrounded by sheaths of pia mater, arachnoid mater, and dura mater. A rise in pressure of the cerebrospinal fluid within the cranial cavity therefore is transmitted to the back of the eyeball. Lacrimal Nerve The lacrimal nerve arises from the ophthalmic division of the trigeminal nerve.. The lacrimal nerve ends by supplying the skin of the lateral part of the upper e eyelid. Eyeball and Eyelids 3cm apperas gift lower editorstatic EEE Orbicularis oculi ssurpli.dk i Y bone for Medial and lateral palpebral ligament lateral medial a E Eyelids The eyelids protect the eye from injury and excessive light by their closure. The upper eyelid is larger and more mobile than the lower, and they meet each other at the medial and lateral angles. msn.pe The palpebral fissure is the elliptical opening between the eyelids and is the entrance into the conjunctival sac. When the eye is closed, the upper eyelid completely covers the cornea of the eye. When the eye is open and looking straight ahead, the upper lid just covers the upper margin of the cornea. The superficial surface of the eyelids is covered by skin, and the deep surface is covered by a mucous membrane, called the conjunctiva. The eyelashes are short, curved hairs on the free edges of the eyelids. They are arranged in double or triple rows at the mucocutaneous junction. The orbital septum is a fibrous sheet that forms the framework of the eyelids. This is attached to the periosteum at the orbital margins. The orbital septum is thickened at the margins of the lids to form the superior and inferior tarsal plates. The lateral palpebral ligament is a band that connects the lateral ends of the tarsal plates to a bony tubercle just within the orbital margin. The medial palpebral ligament attaches the medial ends of the plates to the crest of the lacrimal bone. The superficial surface of the tarsal plates and the orbital septum are covered by the palpebral fibers of the orbicularis oculi muscle. Is The aponeurosis of insertion of the levator palpebrae superioris muscle pierces the orbital septum to reach the anterior surface of the superior tarsal plate and the skin. A thin smooth muscle band, the superior tarsal muscle, underlies the levator. Glands of eyelid hasand I Glands of eyelid The sebaceous glands (glands of Zeis) open directly into the eyelash follicles. f The ciliary glands (glands of Moll) are modified sweat glands that open separately between adjacent lashes. E The tarsal glands ( Meibomian glands) are long, modified sebaceous glands that pour their oily secretion onto the margin of the lid; their openings lie behind the eyelashes. This oily material prevents the overflow of tears and helps make the closed eyelids airtight. Conjunctiva The conjunctiva is a thin mucous membrane that lines the eyelids and is reflected at the superior and inferior fornices onto the anterior surface of the eyeball. Its epithelium is continuous with that of the cornea. The upper lateral part of the superior fornix is pierced by the ducts of the lacrimal gland. Movements of the eyelid The position of the eyelids at rest depends on the tone of the orbicularis oculi and the levator palpebrae superioris muscles and the position of the eyeball. the Then Extrinsic muscles of the eye (Extraocular) Producing movements of the Eye. There are six voluntary muscles that run from the posterior wall of the orbital cavity to the eyeball. straight 1. Superior rectus: Supplied by Oculomotor nerve 2. Inferior rectus: Supplied by Oculomotor nerve 3. Medial rectus: Supplied by Oculomotor nerve CN 13th 4. Inferior oblique: Supplied by Oculomotor nerve RG 5. Lateral rectus: Supplied by Abducent nerve 16 June 6. Superior Oblique: Supplied by Trochlear nerve SOU ** Levator palpebrae superioris Levator and superior oblique E.fi msde a iii The common tendinous ring, also known as the annulus of Zinn, or annular tendon, is a ring of brous tissue surrounding the optic nerve at its entrance at the apex of the orbit. Insertion of the muscles Lacrimal Apparatus The lacrimal gland consists of a large orbital part and a small palpebral part, which are continuous with each other around the lateral edge of the aponeurosis of the levator palpebrae superioris. F It is situated above the eyeball in the anterior and upper part of the orbit posterior to the orbital septum. The gland opens into the lateral part of the superior fornix of the conjunctiva by 12 ducts. Periolateral 0 The more rounded medial angle is separated from the eyeball by a small space, the lacus lacrimalis, in the center of which is a small, reddish yellow elevation, the caruncula lacrimalis. A reddish semilunar fold, called the plica semilunaris, lies on the lateral side of the caruncle. Lacrimal Ducts The tears circulate across the cornea and accumulate in the lacus lacrimalis. From here, the tears enter the canaliculi lacrimales through the puncta lacrimalis. The canaliculi lacrimales pass medially and open into the lacrimal sac , which lies in the lacrimal groove behind the medial palpebral ligament and is the upper blind end of the nasolacrimal duct. The nasolacrimal duct is about (1.3 cm) long and emerges from the lower end of the lacrimal sac. The duct descends downward, backward, and laterally in a bony canal and opens into the inferior meatus of the nose. The opening is guarded by a fold of mucous membrane known as the lacrimal fold. This prevents air from being forced up the duct into the lacrimal sac on blowing the nose.