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DEMO-VI (Eye). Ali Jassim Alhashli Year IV – Unit VIII - CNS. STATION-1. The bony orbit : it is protecting our eyeball and resembling a pyramid: With a base directed : anterolaterally . And an apex directed : posteromedially . Notes:
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DEMO-VI(Eye) Ali JassimAlhashli Year IV – Unit VIII - CNS
STATION-1 • The bony orbit: it is protecting our eyeball and resembling a pyramid: • With a base directed: anterolaterally. • And an apex directed: posteromedially. • Notes: • The medial wall of the pyramid is extending farther anteriorly than the lateral wall. • The orbital axes diverge at 45 degrees while the optical axes are parallel to each other.
STATION-1 • The walls of the orbit are formed by the following bones: • Roof of the orbit: frontal bone (mostly) + lesser wing of sphenoid bone. • Floor of the orbit: maxillary bone + zygomatic bone (meeting at the zygomato-maxillary joint). • Lateral wall of the orbit: frontal bone + zygomatic bone (mostly) + greater wing of sphenoid bone. • Medial wall of the orbit: sphenoid body + ethmoid bone + lacrimal bone + maxillary bone.
STATION-1 • In the image of previous slide: • Supraorbital notch: is for the passage of supraorbital nerve which is branch of ophthalmic division of trigeminal nerve. Notice that this nerve is important to elicit deep pain. • Infraorbital foramen: for the passage of infraorbital nerve which is a branch of maxillary division of trigeminal nerve. • Lesser wing of sphenoid bone contains the optic canal through which the optic nerve (2nd cranial nerve) and ophthalmic artery pass. • Lacrimal bone contains the nasolacrimal duct which is involved in the drainage of tears to the nasopharynx. • Notice that the medial wall of the orbit is very thin. • Structures passing through the superior orbital fissure are: • Opthalmic veins. • Ophthalmic division of trigeminal nerve. • 3rd, 4th and 6th cranial nerves. • Structures passing through the inferior orbital fissure are: • Infraorbital vessels. • Inferior division of ophthalmic vein.
STATION-1 • Medial and lateral palpebral tendons of the eye are extensions of orbicularisocculi muscle (the circular muscle which is surrounding the eye). • Tunica bulbi: it is enclosing the eyeball and allowing its rotation. Check ligaments are extensions from it.
STATION-2 • Lacrimal glands are in the superolateral aspect of the eye. They are composed mainly of 2 parts: • Deep orbital lobe. • Superficial palpebral lobe. • Lacrimal glands are innervated by the facial nerve and the lacrimal nerve which is a branch of the ophthalmic division of trigeminal nerve.
STATION-2 • Nerves of the orbit: • Optic nerve (2nd cranial nerve): entering the orbit from middle cranial fossa through the optic canal (accompanied by ophthalmic artery). • Ophthalmic division of trigeminal nerve will give 3 branches • Lacrimal nerve: enters the orbit through the superior orbital fissure. • Frontal nerve: divides into supratrochlear and supraorbital nerves. • Nasociliary. • Oculomotor nerve (3rd cranial nerve): entering the orbit through superior orbital fissure. • Trochlear nerve (4th cranial nerve): entering the orbit through superior orbital fissure. • Abducens nerve (6th cranial nerve): entering the orbit through the superior orbital fissure.
STATION-2 • Anatomy of the eyelid: • Eyelids are movable folds which cover the eyeball anteriorly. • It is covered externally by skin and internally by a mucous membrane called conjunctiva (notice that conjunctiva does not cover the cornea). • The structures which are strengthening the eyelid superiorly and inferiorly are known as superior and inferior tarsi. • Eye lashes are attached to the margins of the eyelid and they are connected with sebaceous glands. • Tarsal glands: they secrete lipids which lubricate edges of the eyelids and prevent them from sticking when they are closed.
STATION-2 • Ciliary ganglion: parasympathetic ganglion in the posterior part of the orbit between the optic nerve and lateral rectus. • Ophthalmic artery (which is passing through the optic canal) is a branch of internal carotid artery. It will give the following branch: central retinal artery (which is an end artery and any occlusion in it can result in blindness ).
STATION-2 • Superior ophthalmic vein is passing in the superior orbital fissure. • Inferior ophthalmic vein is passing in inferior orbital fissure. • Injury to the suspensory ligament of the eye → eyeball will fall → resulting in diplopia.
STATION-3 • General movements of the eye:
STATION-4 • Sympathetic nervous system is innervating: • Sweat glands → this explains the anhidrosis. • Palpebral fissure → therefore, when injured → it will result in partial ptosis. • Sympathetic nervous system is from T1 – (L2/L3). • Parasympathetic nervous system (craniosacrum): • Cranial part from: 3,7,9 and 10. • Saral part from: S2, S3 and S4. • Sympathetic chain/ trunk: • Upper thoracic part: is responsible for innervating the heart and lungs. • T5- (L1/L2) part: is represented by the splanchnic nerves (greater, lesser, least) which are synapsing in prevertebral ganglions: • Celiac. • Superior mesenteric. • Inferior mesenteric. Note: a part of the greater splanchnic nerve which is not synapsing is the one which is going directly to adrenal medulla.
STATION-4 • Parasympathetic nervous system: • From nuclei of cranial nerves to the following ganglia: • Submandibular: innervating the mandible and submandibular salivary gland. • Otic: innervating parotid cerebri gland. • Pterygopalatine: innervating lacrimal gland. • Ciliary: going to Edenger-Westphal nuclei and innervating ciliary muscle and constrictor papillae. • Parasympathetic nerve fibers from S2-S4 are forming the: pelvic splanchnic nerve (which is innervating the organs of the pelvis). • Innervation of internal muscles of the eye: • Sympathetic nerve fibers: innervating radial muscle of the iris (which causes dilation of the pupil). • Parasympathetic nerve fibers: innervating circular muscle of the iris (which causes constriction of the pupil) and ciliary muscle.
