Facial Muscles and Eyelid Function Quiz

Facial Muscles Involved in Eye Movement

• Facial muscles innervated by cranial nerve VII (CN VII)
  • Frontalis: raises eyebrows
  • Corrugator: moves eyebrows medially and downward
  • Procerus: moves eyebrows downward and medially
  • Orbicularis oculi: lowers eyebrows

Eyelid Functions

• Protect the eye
• Move tears down the medial canthus
• Spread tear film with blinking
• Produce tear film components

Eyelid Muscles and Actions

• Identify cranial nerves innervating eyelid muscles
• Distinguish voluntary and involuntary muscle actions (smooth vs. striated)
• Identify accessory muscles originating from primary eyelid muscles
• Describe conditions arising from muscle dysfunction

Orbicularis Oculi

• Lowering/Closing:
  • Palpebral: light, gentle eye closure (reflex blink)
    • Muscle of Riolan: maintains lids close to globe; may secrete meibum
    • Muscle of Horner: moves tears through drainage system
  • Orbital: forceful eye closure (forceful blink)
• Innervated by CN VII
• Dysfunction: CN VII palsy impairs all facial muscles regulated by CN VII (including those for eyebrow and eyelid movement), causing inability to move or drain tears.

Superior Palpebral Levator

• Opening: OPENS eyelids.
• Innervated by CN III superior division
• Associated structures:
  • Whitnall ligament: supports the upper lid
  • Lockwood ligament: supports the lower globe
• Dysfunction: CN III palsy causes ptosis (drooping eyelid) alongside potential extraocular muscle (EOM) issues (eye turning down and out).

Superior Tarsal Plate of Muller

• Smooth muscle for involuntary movements
• Additional lid elevation
• Ptosis if dysfunctional

Eyelid Gland Function/Location

• Exocrine Glands:
  • Holocrine: Meibomian glands, Glands of Zeis — secrete complete cells.
  • Apocrine: Glands of Moll — secrete part of cytoplasm.
  • Merocrine: Lacrimal glands — acellular.
• Location: dispersed throughout the eyelid, including meibomian glands in the tarsal plate, Glands of Zeis/Moll near eyelashes, and accessory lacrimal glands.
• Function: lubrication, immune defense, and secretion of aqueous tear film components (i.e., sebum).

Conjunctiva

• Transition: tissue transition from eyelid skin to palpebral conjunctiva (smooth membrane lining the eyelid).
• Palpebral: lines the eyelids (2 layers stratified non-keratinized epithelium and underlying stroma). Contains goblet cells (involved in tear film production)
  • Bulbar: lines the white part of the eye (sclera)
• Structure & Function:
  • Goblet cells secrete mucin for tear film.
  • Deficiency of vitamin A may cause loss of goblet cells.
  • Stimulated by parasympathetic nervous system, involving nerves and crypts of Henle
• Contains goblet cells for mucin production, supporting tear film function and lubrication

Orbital Anatomy (Septum and Associated Structures)

• Orbital Septum: Protects orbit from infection, with eyelids encompassing structures anterior to it
• Tenon Capsule: Dense connective tissue around the globe, reducing friction.
• Canthus: Point where upper and lower eyelids meet (medial or lateral).
• Plica Semilunaris: Fold of conjunctiva, and it allows eye movement,
• Caruncle: Mass of modified skin
• Lacrimal lake: Reservoir for tear collection
• Lid Margin:
  • Papillae: Contain puncta for drainage
  • Puncta: Openings for tear drainage
  • Meibomian glands: Produce lipid layer of tear film
  • Cilia: Eyelashes
  • Epicanthal folds: vertical folds that conceal medial canthus, potentially

Test your knowledge on the facial muscles involved in eye movement and the intricate functions of the eyelids. This quiz covers the innervation by cranial nerves, muscle actions, and conditions related to muscle dysfunction. Perfect for students studying anatomy and physiology!