Orbital cavity
• pair of pyramidal shape bony cavities Anterior base and apex at posteriorly.
• Margins are formed by....
1. Superior - frontal bone
2. Lateral - zygomatic and frontal bones
3. Inferior - zygomatic and maxilary bones
4. Medial - frontal and maxilary bones
• walls are formed by....
1. Roof. - frontal bone ( separate from Anterior cranial fossa. )
2. Lateral - zygomatic and sphenoid ( greater wing) bones
3. Floor - maxilary bone ( separet from maxilary sinus )
4. Medial - frontal, maxilary, ethmoid ( separate from ethmoid sinus ), and sphenoid bones
• contains each eye balles and intra ocular eye muscles, nerves, blood and lymphatic vessels, fat, also lacrimal apparatus.
• Anterior opening of orbits are two thin, fold and movable Eyelids
• opening into the orbital cavity
1. Supraorbital notch ( foramen ) - situated superior orbita margin. Transmit Supraorbital nerve and blood vessels.
2. Infraorbital groove and canal - situated floor of the orbit. Transmit Infraorbital nerve and blood vessels.
3. Nasolacrimal canal - located Anterior on medical wall. Transmit nasolacrimal duct. ( connect with the Inferior meatus of nose )
4. Inferior orbital fissure - located posteriorly between maxilary and greater wing of sphenoid and zygomatic bones. Transmit Inferiorly Ophthalmic vein and sympathetic nerves.
5. Superior orbital fissure - located posteriorly between greater and lesser wing of sphenoid bone. Transmit superior opthalmic vein also lacrimal, abducent and nasociliary nerves. ( connect with middle cranial fossa )
6. Optic canal - located in the posterior wing of the sphenoid. Transmit opthalmic artery and optic nerve.
• orbital fascia - is perosteum of the bone form the walls of the orbit. it is loosely attached to the bones and covering foramina and fissures of outer surface of bones.
Eyelid
• Protect from injuries and excessive light
• upper Eyelids larger and movable than lower one.
• Two Eyelids meat each other at medial and lateral angles.
• at the eye closed upper Eyelids completely close Cornea of the eye.
• the palpebral fissure is elliptical opening between Eyelids and also it entrance into the Conjunctival sac.
• superior surface formed by skin and inferior surface formed by mucous membrane ( also called as Conjunctiva ).
• the Eyelashes are short, curved hair at the free edges of the Eyelids and they are arranged double or triple rows at the mucocutaneous junction.
Glands of Eyelid
1. Sebaceous gland - open directly into the Eyelash follicles.
2. Ciliary glands - are modified sweat glands that are open separately between adjacent lashes.
3. Tarsal glands - are long modified sebaceous gland.
• Position of the Eyelids depending on
1. Orbicularis oculi muscle
2. Levator palpebrae superioris muscle
• Eyelids closed by
1. Contraction of Orbicularis oculi muscle
2. Relaxation of Levator palpebrae superioris muscle
• eyelids opened by
1. Contraction of Levator palpebrae superioris muscle ( also eyeball upward moves)
Lacrima system or gland/tear film
•it situated at large orbital part and small palpebral part.
• posteriorly to the orbital septum of lateral edge of aponeurosis.
• The gland opening to lateral part of the Conjunctiva ( superior fornix ) by 12 ducts.
• nerve innovation by facial nerve - parasympathetic tear secretion.
• The tear circulate across the Cornea and accumulate in the lacus lacrimalis after tear enter canaliculi lacrimalis through punta lacrimalis passe medialy and enter lacrimal sac to nasolacrimal duct after opening inferior meatus of nose.
Tags:
Ocular anatomy