Transcript 07-orbit(1)
ORBIT It is a pyramidal cavity with its apex above and its base behind. CONTENTS (1) Eye ball. (2) Extraocular muscles. (3) Bulbar fascia. (4) Nerves. (5) Vessels. (6) Orbital fat. ORBITAL FASCIA It is the periosteum covering the bones of the walls of the orbit. It is continuous through the foramina and fissures with the periosteum on the outer surface of the bones. ORBITAL FASCIA In case of : Superior orbital fissure. Optic canal. Anterior ethmoidal canal, it is continuous with the endosteal layer of the dura. ORBITAL FASCIA The inferior orbital fissure is bridged by the muscle of Muller (orbitalis) muscle. EXTRAOCULAR MUSCLES A. Levator palpebrae superioris. B. Four recti (superior, inferior, medial and lateral). C. Two oblique (superior and inferior). LEVATOR PALPEBRAE SUPERIORIS Origin : Undersurface of the lesser wing of the sphenoid above the optic canal. LEVATOR PALPEBRAE SUPERIORIS The muscle ends anteriorly in a wide aponeurosis. This aponeurosis splits into two lamellae : Superior and Inferior. LEVATOR PALPEBRAE SUPERIORIS Insertion : Suprior lamella : To the superior tarsal plate and the skin of the upper eyelid. Inferior lamella : Contains (Muller’s muscle) It is inserted into the superior tarsal plate. LEVATOR PALPEBRAE SUPERIORIS Nerve supply : Oculomotor nerve (superior division). Muller’ muscle : superior cervical sympathetic ganglion. LEVATOR PALPEBRAE SUPERIORIS Action : Elevation of the upper eye lid. Sympathetic stimulation causes further elevation of the eye lid. PTOSIS It is Dropping of the upper eye lid. It is due to division of the oculomotor nerve or the cervical sympathetic ganglion (Horner’s syndrome). THE RECTI Origin : From the common tendinous ring (it is thickened periosteum which surrounds the optic canal and bridges over the medial end of the superior orbital fissure). THE RECTI The muscles are attached to the ring in positions implied by their names. The lateral rectus arises by two heads. THE RECTI Insertion : The muscles pass forwards to the sclera to be inserted (6mm) behind the cornea (in front the equator of the eyeball). THE RECTI Nerve supply : 1. Oculomotor nerve : to Superior, Inferior and Medial recti. 2. Abducent nerve: to Lateral rectus. THE RECTI Action : The medial rectus rotates the cornea medially. The lateral rectus rotates the cornea laterally. THE RECTI Action : Superior and Inferior recti elevate and depress the cornea respectively (in the transverse axis). THE RECTI The superior and inferior recti are inserted medial to the vertical axis of the eye ball. So they can rotate the cornea medially. SUPERIOR OBLIQUE Origin : Body of the sphenoid above the common tendinous ring. It hooks around a fibrocartilaginous pulley (trochlea) on the superomedial border of the front of the orbit. SUPERIOR OBLIQUE Insertion : Into the sclera beneath the superior rectus and behind the coronal equator of the eye ball. Nerve supply : Trochlear nerve. INFERIOR OBLIQUE Origin : Anteromedial floor of the orbit. Insertion : Posterolateral part of the sclera behind the equator. Nerve supply : oculomotor nerve (inferior division). ACTION Superior oblique: Rotates the cornea downwards. Inferior oblique: Rotates the cornea upwards. Both muscles rotate the cornea laterally. ACTION The line of pull of both muscles pass medial to the vertical axis and behind the equator. FASCIAL SHEATH OF THE EYEBALL It separates the eye ball from the orbital fat and forms a socket for its free movement. It surrounds the eyeball from the optic nerve to the corneoscleral junction. FASCIAL SHEATH OF THE EYEBALL It is pierced by the tendons of the orbital muscles. It is reflected onto each of them as a tubular sheath. FASCIAL SHEATH OF THE EYEBALL Thickening of the fascia is attached to the lacrimal and zygomatic bones. It forms the medial and lateral check ligaments. Inferiorly, it forms the suspensory ligament which connects the check ligaments. The eyeball is suspended from the medial and lateral walls of the orbit. LACRIMAL APPARATUS It is composed of the structures producing lacrimal fluid and controlling its passage to the nasal cavity. They are : Lacrimal gland and its ducts. Conjunctival sac. Lacrimal sac. Naso lacrimal duct. LACRIMAL GLAND It is a serous gland almond in shape in the supero lateral angle of the orbit behind the upper lid. It consists of a large orbital part and a small palpebral part. LACRIMAL GLAND The two parts are continuous at the lateral margin of the aponeurosis of levator palpebrae superioris. The gland has (6- 12) ducts that open into the lateral part of the superior fornix. LACRIMAL GLAND Nerve supply: Facial nerve (through greater petrosal and nerve of pterygoid canal ) to the pterygopalatine ganglion. The post ganglionic fibers pass to the gland through the zygomatic branch of zygomatico temporal or through the lacrimal nerve. LACRIMAL CANALICULUS Tears accumulate in the lacus lacrimalis before it enters the lacrimal punctuae . LACRIMAL CANALICULUS They are two. Each about (10) mm long. They pass from the lacrimal punctum in each eye lid to the lacrimal sac. LACRIMAL SAC It is a thin fibrous sac on the medial side of the orbit in the lacrimal fossa. It receives both canaliculi and drains to the nasolacrimal duct. NASO LACRIMAL DUCT It descends in the medial wall of the orbit. It opens into the inferior meatus of the nose. Its opening is guarded by a flap of mucous membrane which prevents air passing up the duct when the nose is blown. LACRIMAL APPARATUS The lacrimal fluid constantly washes the front of the eye ball and its conjunctival covering . It is drained by plinking when the increased intra conjunctival pressure produced by the closed eye lids forces the fluid into the lacrimal puncta. CONCLUSION OF ACTION (1) R. Superior rectus + L. inferior oblique. (2) Superior rectus + inferior oblique (both eyes). (3) R. Inferior oblique + L. Superior rectus. CONCLUSION OF ACTION (4) R. Lateral rectus + L. Medial rectus. (5) Fixed primary position. (6) R. Medial rectus + L. Lateral rectus. CONCLUSION OF ACTION (7) R. Inferior rectus + L. Superior oblique. (8) Inferior recti + Superior oblique of both eyes. (9) R. Superior oblique + L. Inferior rectus.