Eyelid Anatomy and Function PDF

Eyelids Lacrimal glands and tears 1 Lacrimal glands and tears 2 Cornea 1 Cornea 2 Anterior Posterior Superior Inferior  Medial Latteral Nasal Temporal  Insertion - the point of attachment of a tendon or ligament onto the skeleton or other part of the body The eyelids and the palpeb...

Eyelids Lacrimal glands and tears 1 Lacrimal glands and tears 2 Cornea 1 Cornea 2 Anterior Posterior Superior Inferior  Medial Latteral Nasal Temporal  Insertion - the point of attachment of a tendon or ligament onto the skeleton or other part of the body The eyelids and the palpebral fissure  Eyelids or Palpebrae Covered by skin externally Coverer by conjunctiva internally The palpebral fissure Gap or aperture between the eyelids eyelid function Shield from minor injuries remove foreign objects (blinking) control light entry (improve distance vision depth of field) contribute to and sustain tear film eyelid structure upper and lower tarsal portions made rigid by tarsal plates fibrous conecvtive tissue upper tarsal portion measures 29mm x 10mm lower 29mm x 5mm eyelid structure edge of lower eyelid close to edge of cornea edge of upper eyelid overlaps cornea eyelid structure septal (orbital) portions: outside tarsal portions to rim of orbit eyelid structure superior and inferior palpebral furrows palpebral furrows are external folds in skin marking tarsal and septal join much individual variation eyelid structure lateral canthus medial = nasal lateral = temporal medial canthus eyelid structure epicanthal fold – fold of skin in young occidentals and young and old Asians - present in the foetus (all races)  Tarsal portion contains Tarsal plates. Extend along the lid margins across the width of the lids – contains many glands Septal portion Orbital/Septal portion: skin, orbicularis orbital septum - muscle, orbital septum, preaponeurotic fat pad, levator aponeurosis insertion, Mullers flexible connective muscle, conjunctiva tissue that retains orbital fat tarsal plates made of tough collagenous connective tissue Tarsal portion: skin, orbicularis muscle, tarsal plate, conjunctiva tarsal (meibomian) glands long thin glands embedded inside tarsal plates collecting ducts empty to inner edge of eyelids secretion has high lipid content tarsal (meibomian) glands oily secretion lines lids and prevents movement of aqueous tears onto lid skin also lipid layer on tear film limits aqueous evaporation tarsal (meibomian) glands excretory ducts every 1mm (approx.) more glands in upper plate eyelid movement to widen palpebral fissure upper tarsal plate pulled up by i) levator muscle and ii) superior tarsal muscle (Müller’s muscle) lower tarsal plate pulled down by a single inferior tarsal muscle eyelid movement levator muscle linked to broad flat tendon called levator aponeurosis attached to front of tarsal plate upper edge of levator muscle attached to sphenoid bone inside orbit  superior tarsal muscle (Müller’s) runs behind levator aponeurosis and inserts directly into upper edge of superior tarsal plate upper end joins origin of levator aponeurosis eyelid movement eyelid movement inferior tarsal muscle inserts directly into lower edge of inferior tarsal plate has ill-defined origin in connective tissue near inferior oblique and rectus muscles (Müller’s) eyelid movement problems with lid muscles (levator especially) can cause ptosis, or lid droop Before After eyelid movement palpebral fissure closed by orbicularis oculi muscles NB not be confused with orbicularis oris muscles of the face that enter lids anterior to other lid muscles and run in arcs eyelid movement eyelid movement orbicularis muscles insert into medial palpebral ligament and lateral palpebral ligament  also known as medial and lateral canthal tendons eyelid movement eyelid movement contraction of muscle fibre bundles make orbicularis work like sphincter because of insertions closed palpebral fissure is horizontal slit pretarsal portion involved in reflex or spontaneous lid closure, orbital portion for voluntary lid closure - squinting entropion chronic overreaction of preseptal orbicularis results in entropion eye lashes scratch the cornea Transparent mucous membrane: conjunctiva lines inner eyelids bulbar palpebral - part of a continuous sheet limbal (bulbar) epithelium -continuous with corneal epithelium conjunctiva Folds of conjuntiva in the medial canthus plica semilunaris – vestigial “third eyelid” lacrimal caruncle – contains accessory lacrimal and sebaceous glands conjunctiva Epithelium contains: epithelial cells bulbar Langerhans cells that provide an immune response lymphocytes conjunctiva Substantia propria (stroma) contains: many types of immunocompetent cells bulbar connective tissue vascular network nerve supply conjunctiva Glands: bulbar goblet cells that secrete mucus into the tear film about 50 accessory lacrimal glands Function: conjunctiva Production of the mucus component of tear film bulbar Immunological defence protects ocular surface from infection CONJUNCTIVITIS Conjunctival neoplasm Viral conjunctivitis Toxic conjunctivitis Chlamydial conjunctivitis Bacterial conjunctivitis Mild allergic reaction Pterygium Vernal keratoconjunctivitis