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Ocular Anatomy and Physiology > Week 13: Ocular Adnexa and Lacrimal System > Flashcards

Week 13: Ocular Adnexa and Lacrimal System Flashcards

1
Q

List the muscles of the forehead

A
  1. Frontalis
  2. Orbicularis oculi
  3. Corrugator
  4. Procerus
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2
Q

Describe the innervation of the muscles of the forehead and muscles surrounding the orbit

A
  • Innervated by the frontal branch of CNVII (facial nerve)
  1. Frontalis
    - Originates on scalp and inserts into superior orbital rim
    - Raises the brows, forehead wrinkles, moves scalp posteriorly
  2. Orbicularis Oculi
    - Sphincter muscle arranged in concentric bands around the upper & lower lids
    - Function: close lids and lowers the entire brow.
    - Assists in tear drainage.
  3. Corrugator
    - Originates on the frontal bone & inserts into the medial side of brow
    - Creating vertical furrows between brows
  4. Procerus
    - Originates on nasal bone & inserts into medial side of frontalis.
    - Creating horizontal furrows over the bridge of the nose
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3
Q

List functions of the eyelids

A
  • Cover the globe for protection
  • Deliver oxygen supply during sleep
  • Spreads tear film over the surface of the eye
  • Move the tears toward drainage at the medial canthus on eye lid closure
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4
Q

Describe the eyelid

A
  • Primary protectors of the tear film, corneal nerves, and conjunctiva
  • Proper lid closure, innervation & blink mechanisms are designed to produce, mix, and spread the tear components across the ocular surface
  • Guides movement of tear film and debris through the nasolacrimal apparatus
  • When the lids fail to do their job, a host of problems will occur (e.g. dry eye/inflammation)
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5
Q

Describe the eyelid margin structure

A
  • Rests against the globe, contains eyelashes and pores of the meibomian glands
  • Orifices of meibomian gland located posterior to cilia
  • Gray line: divides the lids into anterior and posterior portions, runs between cilia & meibomian gland pores

Two zones divided by the punctum:

  1. Lacrimal portion
  2. Ciliary portion
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6
Q

Describe what is in the ciliary portion

A
  • It contains pores of meibomian glands and cilia (eyelashes)
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7
Q

What are the functions of the ciliary portion/eyelashes?

A
  • Protect the eye via stimulation causing blink reflex
  • Protect from airborne particles
  • Prevent transfer of pathogens and allergens to the eye
  • Involved in non-verbal communication
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8
Q

Describe the blink reflex

A
  1. Passes through trigeminal afferent (V1 stimulating eyelashes; cornea)
  2. Brainstem
  3. Facial efferent to orbicularis oculi
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9
Q

List the nerves and branches of the ophthalmic division of CNV and what the branches innervate

A
  1. Frontal (largest branch)
    - Supraorbital: innervates upper eyelid, conjunctiva, scalp
    - Supratrochlear: innervates upper eyelid, conjunctiva, forehead
  2. Lacrimal (smallest branch)
    - Receives branch from zygomatic nerve of CNV2 containing parasympathetic fibres
    - Innervates upper eyelid, conjunctiva, lacrimal gland
    - Contains parasympathetic & sympathetic efferent to lacrimal gland
  3. Nasociliary
    - Anterior ethmoid nerve: innervates mucous membranes of frontal, ethmoid sphenoid sinuses
    - Posterior ethmoid nerve (~ 30% of people): innervates mucous membrane if sphenoid sinuses
    - Infratrochlear nerve: innervates upper eyelid, conjunctiva, bridge of nose
    - Long ciliary nerves (contains sympathetic fibres to dilator pupillae muscle: innervates eye
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10
Q

List the structures of the eyelid

A
  1. Orbicularis oculi muscle
    - Palpebral portion
    - Orbital portion
  2. Superior palpebral levator muscle
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11
Q

Describe Orbicularis Oculi Muscle and its portions

A
  • Innervated by frontal branch of CNVII
  1. Palpebral portion
    - Consists of semi circle muscle fibres and occupies area resting on globe
    - Contraction helps drain the tears through the canaliculi into the nasolacrimal duct
    - Contraction of pretarsal orbicularis closes the lids & involved in involuntary blink
  2. Orbital Portion
    - Upper fibres of this portion blend with the frontalis and corrugator
    - Contraction closes the eye tightly & muscles on face, forehead
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12
Q

Describe Superior Palpebral Levator Muscle

A
  • Function: contraction of levator causes elevation of the eyelid
  • Innervated by CNIII (oculomotor nerve)
  • Originates from the sphenoid bone above the globe
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13
Q

Describe the conjunctiva and list them with a short description

A
  • Consists of a surface epithelium overlying a well vascularized stroma
    1. Limbal conjunctiva: where conjunctiva & cornea meet at the limbus
    2. Bulbar conjunctiva: covers the anterior sclera
    3. Palpebral conjunctiva: lines posterior surface of both eyelids
    4. Fornix conjunctiva: folded conjunctiva where palpebral and bulbar conjunctiva meet
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14
Q

List the type of glands and function for:

  1. Meibomian
  2. Glands of moll
  3. Glands of zeiss
  4. Accessory lacrimal gland
A
  1. Meibomian
    - Sebaceous
    - Secretion. of meibum: lipid which is responsible for outer layer of tear film
  2. Glands of moll
    - Modified apocrine
    - Secretion of antimicrobial peptides and proteins for protection of lashes and ocular surface
  3. Glands of zeiss
    - Sebaceous
    - Release sebum to hydrate cilia
  4. Accessory lacrimal gland
    - Merocrine
    - Secretion of antibacterial agents, lysozyme, lactoferrin, immunoglobulins
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15
Q

List the measurements of the tear film and the layers with its thickness

A
  • Tear Film = 7 µm thick
  • pH tear film = 7.6
  • Composed of 3 layers:
    1. Outer Lipid Layer/oily layer (0.1 µm thick)
    2. Intermediate Aqueous Layer/watery layer (7 µm thick)
    3. Inner Mucous Layer/mucous layer (0.5 µm thick)
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16
Q

What are the functions of tear films

A
  • Optical: uniform interface between air and cornea
  • Mechanical: remove intrinsic and extrinsic debris from tear film
  • Lubricant: allows for smooth movement of lids over globe
  • Waste removal: removes by products of metabolism from cornea
17
Q

Explain the tear supply process

A
  • Receives Parasympathetic input
  • Consists of small clusters of secretory cells forming small lobules
  • Lumen combine to form large ducts that open into the upper lateral fornix
  • Tear fluid is produced at a rate of 1 µL/min = 1.5 mL/day
  • Infants younger than 6 weeks do not produce tears
18
Q

Describe the Lacrimal Gland Innervation (afferent and efferent)

A

Afferent:

  • Sensory nerves on cornea (nasocillary nerve CNV1)
  • Arrives at trigeminal nucleus

Efferent :

  • Parasympathetic innervation of lacrimal gland
  • Sympathetic innervation of lacrimal gland originate from Superior Cervical Ganglion
  • Central Nervous System –> Facial nerve exits the pons –> Zygomatic branches of the maxillary nerve travel with the lacrimal nerve —> lacrimal gland
  • Increases tear secretion
19
Q

Describe the tear drainage during blink

A
  1. Tears move freely into puncta
  2. Puncta close at the start of blink due to orbicularis muscle and puncta contact
  3. Further compression of orbicularis compresses canaliculi & lacrimal sac moving fluid to nasolacrimal duct
  4. After blink lacrimal sac and canaliculi expand and pressure decreases drawing fluid in from open puncta
20
Q

Describe evaporated dry eyes

A
  1. Tear Film instability
  2. Hyperosmolarity
  3. Neurosensory abnormalities
  4. Inflammation and damage
21
Q

Describe Aqueous Deficient Dry Eye

A
  1. Low volume of tears
  2. Hyperosmolar tears
  3. Ocular surface inflammation – initiates a vicious cycle
22
Q

Give examples of Dry Eye Management for:

  1. Dietary Modifications
  2. Local Environment Conditions
  3. Complementary Medicines
  4. Lid Margin and Tears
  5. Anti-Inflammatory Therapy
  6. Surgical Therapies
A
  1. Dietary Modifications = water hydration, essential fatty acids (omega 3)
  2. Local Environment Conditions = chronic topical medications
  3. Complementary Medicines = honey
  4. Lid Margin and Tears = topical antibiotics, IPL therapy
  5. Anti-Inflammatory Therapy = steroid therapy
  6. Surgical Therapies = lid corrections

Ocular Anatomy and Physiology (10 decks)

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