Palpebral Aperture Flashcards
Define the term insertion
The point of attachment of a tendon or ligament onto the skeleton or other part of the body
What is the palpebral aperture?
the opening between the upper and lower eyelids when the eye is open. ie the exposed part of the eye when the eyelids are separated
4 functions of eyelids
- shield from monor injuries
- remove foreign objects (blinking)
- control light entry (can improve distance vision)
- contributes and maintains tear film
Functions of tarsal portions and tarsal plates
- provide structural support and shape to eyelids
- muscle attachment ( muller’s muscles)
- attachment of eyelashes
- conjunctiva attachment
- facilitate the function and movement of eyelids
What are tarsal plates
Dense, fibrous structures primarily composed of collagen fibres, found within the upper and lower eyelids of mammals. Serve as supportive frameworks for eyes.
Upper and lower tarsal portion measurements
Upper 29mm x 10mm
Lower 29mm x 5mm
Describe the postions of the lower and upper eyelids in relation to the cornea
Edge of lower eyelid close to edge of cornea
Edge of upper eyelid overlaps cornea
What is the orbital septum and septum portion of eyelids
Septal portion refers to the area of the eyelids that extends from outside tarsal portions to rim of orbit
The orbital septum is a thin fibrous membrane that extends from the margin of eyelids to the periosteum (connective tissue) of orbit
What are palpebral furrows
External skin folds formed where tarsal and septal join
Also known as lid creases
What is the canthus and the two types
Canthus is the corner where the upper and lower eyelids meet
1. Medial canthus- nasal
2. Lateral canthus- temporal
What are epicanthal folds
Skin fold of the upper eyelid that covers the inner corner if the eye
Commonly observed in individuals of east asian descent however is present in foetus of all races
What are tarsal plates made of
Tough collagenous connective tissue
What is the function of tarsal (Meibomian) glands
Produce meibum, an oily substance that lubricates eyelids, prevents tear evaporation,
What condition is a result of dysfunction of tarsal glands
Meibomian gland dysfunction
Evaporative dry eye
Describe how muscles work to widen the palpebral fissure
Upper eyelid is pulled up by levator and Muller’s muscles
Lower eyelid is pulled down by a single inferior tarsal muscle
What conditions are a result of dysfunction of lid muscles esp levator
Ptosis (dropping of upper eyelid)
Lid droop
Describe how the palpebral aperture closes
Orbicularis oculi muscles have circular and radial fibres.
When orbicularis oculi muscles contract, circular fibers tighten, pulling eyelids together from the sides, while radial fibers pull the eyelids downwards
What is the function of canthal tendons
Connect eyelids to the eye orbit
Describe the differences in lid closure for muscles in pretarsal and orbital portions
Pretarsal- reflex/spontaneous lid closure eg foreign object sensation
Orbital- voluntary eyelid closure eg squinting
What is entropion?
Eye condition where eyelid (usually lower), turns inwards causing eyelashes and skin of eyelid to rub against surface if eye leafing to irritation and redness
Caused by chronic overreaction of pre-septal orbicularis
What is the plica semilunaris
Small, crescent shaped fold of conjunctiva located at inner corner of eye, adjacent to medial canthus
What is the lacrimal caruncle?
Small fleshy triangular structure located at the inner of the ye adjacent of medial canthus containing glands and fine hairs
