4) Orbit and Eye.pdf

M.B.Ch.B. M.Sc. Ph.D. Anatomy 20/2/2024 1 1  Learning Objectives 1.Describe the anatomical boundaries of the Orbit. 2.Enumerate the structures contained in the orbit. 3.Illustrate the anatomical structure of the eyelids and their clinical...

M.B.Ch.B. M.Sc. Ph.D. Anatomy 20/2/2024 1 1  Learning Objectives 1.Describe the anatomical boundaries of the Orbit. 2.Enumerate the structures contained in the orbit. 3.Illustrate the anatomical structure of the eyelids and their clinical problems. 4.Describe the lacrimal apparatus. 5.List the extraocular and intraocular muscles. 6.Define the anatomical details of the eyeball and their clinical correlations. 20/2/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 2  The Orbit The orbits are bilateral structures in the upper half of the face below the anterior cranial fossa and anterior to the middle cranial fossa. It contains the eyeball, the optic nerve, the extraocular muscles, the lacrimal apparatus, adipose tissue, fascia, and the nerves and vessels that supply these structures. 20/2/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 3  Bony Orbit Pyramidal space. Roof: frontal and sphenoid. Medial wall: maxilla, lacrimal, ethmoid and sphenoid. Floor: maxilla, zygomatic and palatine. Lateral wall: zygomatic and greater wing of sphenoid. Apex: optic canal. 20/2/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 4  Eyelids Protective fibromuscular structures. Palpebral fissure separates between the two eyelids. Consist of thin skin and subcutaneous tissue overlying muscle layer, and lined by conjunctiva. Orbicularis occuli closes the eye and supplied by facial nerve: a) Palpebral part. b) Orbital part. c) Lacrimal part. Palpebral ligaments.  Orbital Septum An extension of periosteum into both the upper and lower eyelids from the margin of the orbit. Tarsus and levator palpebrae superioris. Tarsal glands, sebaceous glands and sweat glands. Blood Vessels: 1. The supratrochlear, supra-orbital, lacrimal, and dorsal nasal arteries from the ophthalmic artery. 2. The angular artery from the facial artery. 3. The transverse facial artery from the superficial temporal artery.  Innervation of Eyelids Innervation: both sensory and motor. Sensory: 1. Supra-orbital, supratrochlear, infratrochlear, and lacrimal branches of the ophthalmic nerve. 2. Infra-orbital branch of the maxillary nerve. Motor: 1. Facial nerve: palpebral part of O.Occuli. 2. Occulomotor nerve: lev. palpeb. Sup. 3. Sympathetic fibers: tarsal muscles.  Clinical Application Stye: Blockage and inflammation of sweat or sebaceous gland and is on the edge of the eyelid. Chalazion: Blockage and inflammation of tarsal gland and is on the inner surface of the eyelid.  Lacrimal Apparatus It is made up of the lacrimal gland and its ducts, the lacrimal canaliculi, the lacrimal sac, and the nasolacrimal duct. It is involved in the production, movement, and drainage of fluid from the surface of the eyeball.  Lacrimal Apparatus The lacrimal gland is anterior in the superolateral region of the orbit and is divided into two parts by the levator palpebrae superioris: 1. Orbital part is in a depression, the lacrimal fossa, in the frontal bone. 2. Palpebral part is inferior to levator palpebrae superioris in the superolateral part of the eyelid. Fluid is continually being secreted by the lacrimal gland and moved across the surface of the eyeball as the eyelids blink.  Lacrimal Apparatus The fluid accumulates medially into puncta and drained to the lacrimal canaliculi toward lacrimal sac. When the orbicularis oculi muscle contracts during 'blinking', the small lacrimal part of the muscle compresses the lacrimal sac forcing fluid into the nasolacrimal duct which drains into the inferior meatus of the nasal cavity. When the muscle relaxes, the lacrimal sac expands drawing fluid into it through the canaliculi from the conjunctival sac.  Innervation Sensory: lacrimal branch of ophthalmic nerve. Secretomotor (parasympathetic): facial nerve through nerve of pterygoid canal. Sympathetic: superior cervical ganglion through plexus around internal carotid artery.  Muscles of the Orbit There are two groups of muscles within the orbit: 1. Extrinsic Muscles of eyeball (extra- ocular muscles) involved in movements of the eyeball or raising upper eyelids. 2. Intrinsic Muscles within the eyeball, which control the shape of the lens and size of the pupil.  Extrinsic Muscles Include the levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, and inferior oblique. They move the eyeball in three dimensions  Muscle Innervation Action Levator palpebrae superioris Oculomotor nerve Elevation of upper eyelid Oculomotor nerve Elevation, adduction, medial rotation of Superior rectus eyeball Oculomotor nerve Depression, adduction, lateral rotation Inferior rectus of eyeball Oculomotor nerve Medial rectus Adduction of eyeball Lateral rectus Abducent nerve Abduction of eyeball Depression, abduction, medial rotation Superior oblique Trochlear nerve of eyeball Oculomotor nerve Elevation, abduction, lateral rotation of Inferior oblique eyeball  Blood vessels The arterial supply of the orbit, including the eyeball is the Ophthalmic Artery which is a branch of internal carotid artery. The ophthalmic artery passes into the orbit through the optic canal with the optic nerve. Branches: 1. Lacrimal artery 2. Central retinal artery 3. Posterior ciliary arteries 4. Muscular arteries 5. Supraorbital artery 6. Ethmoidal arteries 7. Medial palpebral artery 8. Dorsal nasal artery 9. Supratrochlear artery  Blood vessels There are two venous channels in the orbit, the superior and inferior ophthalmic veins. The superior ophthalmic vein begins by union of supraorbital and angular veins. Leaving posteriorly through sup. Orbital fissure to enter the cavernous sinus. The inferior ophthalmic vein is smaller and leaves the orbit posteriorly by: i. joining with the superior ophthalmic vein ii. passing through the superior orbital fissure on its own to join the cavernous sinus iii. passing through the inferior orbital fissure to join with the pterygoid plexus of veins in the infratemporal fossa.  Innervation Numerous nerves pass into the orbit and innervate structures within its bony walls. They include: 1. Optic nerve 2. Oculomotor nerve 3. Trochlear nerve 4. Abducent nerve 5. Autonomic nerves. Other nerves such as the ophthalmic nerve [V1] innervate orbital structures and then travel out of the orbit to innervate other regions.  Optic nerve The optic nerve is not a true cranial nerve, but rather an extension of the brain carrying afferent fibers from the retina of the eyeball to the visual centers of the brain. It is surrounded by the cranial meninges, including the subarachnoid space, which extend as far forward as the eyeball. The optic nerve leaves the orbit through the optic canal.  Oculomotor nerve It leaves the anterior surface of the brainstem between the midbrain and the pons. It passes forward in the lateral wall of the cavernous sinus. Just before entering the orbit the oculomotor nerve divides into superior and inferior branches.  Trochlear nerve The trochlear nerve arises from the posterior surface of the midbrain, and passes around the midbrain to enter the edge of the tentorium cerebelli. In the orbit the trochlear nerve ascends and turns medially, crossing above the levator palpebrae superioris muscle to enter the upper border of the superior oblique muscle.  Abducent nerve It arises from the brainstem between the pons and medulla. It enters the dura covering the clivus and continues in a dural canal until it reaches the cavernous sinus. Once in the orbit it passes out laterally to supply the lateral rectus muscle.  Ophthalmic nerve The ophthalmic nerve [V1] is the smallest and most superior of the three divisions of the trigeminal nerve. This purely sensory nerve receives input from structures in the orbit and from additional branches on the face and scalp. Just before it enters the orbit it divides into three branches- the nasociliary, lacrimal, and frontal nerves. These branches enter the orbit through the superior orbital fissure with the frontal and lacrimal nerves outside the common tendinous ring, and the nasociliary nerve within the common tendinous ring  Ciliary Ganglion It is a parasympathetic ganglion of the occulomotor nerve. It is a very small ganglion, in the posterior part of the orbit immediately lateral to the optic nerve and between the optic nerve and the lateral rectus muscle. Parasympathetic root : oculomotor Sensory root: short ciliary nerves Sympathetic root: from superior cervical ganglion through plexus around internal carotid artery. It reaches the eyeball and supplies dilator pupillae muscle.  Eyeball The globe-shaped eyeball occupies the anterior part of the orbit. Posterior to the cornea and in order from front to back are the anterior chamber, the iris and pupil, the posterior chamber, the lens, the postremal (vitreous) chamber, and the retina. 20/2/2024 Email :[email protected] Website :http://Alkafeel.edu.iq 25  Anterior and Posterior Chambers The anterior chamber is the area directly posterior to the cornea and anterior to the colored part of the eye (iris). The central opening in the iris is the pupil. Posterior to the iris and anterior to the lens is the smaller posterior chamber. They are filled with a fluid (aqueous humor), which is secreted into the posterior chamber, flows into the anterior chamber through the pupil. The aqueous humor supplies nutrients to the avascular cornea and lens and maintains the intraocular pressure.  Lens and Vitreous humor The lens separates the anterior one-fifth of the eyeball from the posterior four-fifths. It is a transparent, biconvex elastic disc attached circumferentially to muscles associated with the outer wall of the eyeball. This lateral attachment provides the lens with the ability to change its refractive ability to maintain visual acuity. The posterior four-fifths of the eyeball, from the lens to the retina, is occupied by the postremal (vitreous) chamber. This segment is filled with a transparent, gelatinous substance-the vitreous body (vitreous humor). This substance, unlike aqueous humor, cannot be replaced.  Walls of the eyeball They consist of three layers: 1. Outer fibrous layer consists of the Sclera posteriorly and the cornea anteriorly; 2. Middle vascular layer consists of the Choroid posteriorly and is continuous with the ciliary body and iris anteriorly 3. Inner layer consists of the optic part of the Retina posteriorly and the nonvisual retina that covers the internal surface of the ciliary body and iris anteriorly  Fibrous layer Sclera: It is an opaque layer of dense connective tissue that can be seen anteriorly through its conjunctival covering as the 'white of the eye'. It is pierced by numerous vessels and nerves, including the optic nerve posteriorly, and provides attachment for the various muscles involved in eyeball movements. Cornea: Continuous with the sclera anteriorly is the transparent cornea. It covers the anterior one-sixth of the surface of the eyeball and, being transparent, allows light to enter the eyeball.  Vascular layer Choroid: It is a thin, highly vascular, pigmented layer consisting of smaller vessels adjacent to the retina and larger vessels more peripherally. It is firmly attached to the retina internally and loosely attached to the sclera externally. Ciliary Body: Triangular-shaped structure, between the choroid and the iris, forms a complete ring around the eyeball. Its components include the ciliary muscle and the ciliary processes. Iris: Circular structure, projecting outward from the ciliary body, is the colored part of the eye with a central opening (the pupil). Controlling the size of the pupil are smooth muscle fibers within the iris.  Inner layer The RETINA consists of two parts: 1. Optic part: posteriorly and laterally, sensitive to light. 2. Non visual part: anteriorly, which covers the internal surface of the ciliary body and the iris. The junction between these parts is an irregular line (the ora serrata). Optic part: consists of two parts: 1. Pigmented layer is firmly attached to the choroid and continues anteriorly over the internal surface of the ciliary body and iris; 2. Neural layer, which can be further subdivided into its various neural components, is only attached to the pigmented layer around the optic nerve and at the ora serrata.  Special Points of Retina Optic Disc: where the optic nerve leaves the retina in which there is no light sensitivity so called the blind spot. Macula lutea: Lateral to the optic disc a small area with a hint of yellowish coloration, with its central depression the fovea centralis. It is the thinnest area of the retina and has higher light sensitivity.  Clinical Applications Cataract: Glaucoma: (Opacity of the lens) (Increased intra occular pressure) 1. Gray’s Anatomy for Students. 2. Clinical Anatomy by Regions. Richard S. Snell. 3. Clinically Oriented Anatomy. Keith L. Moore. Email :[email protected] Website :http://Alkafeel.edu.iq