WEEK 13: Ocular adnexae and tear film Flashcards
Muscles of the orbit
Frontalis Muscle, Corrugator Muscle, Procerus Muscle, orbicularis oculi. All innervated by CN7
Description and function of the frontalis muscle
originates high on the scalp and inserts into connective tissue near the superior orbital rim. The fibers are oriented vertically and raise the eyebrow, causing a look of surprise or attention. Lecture - Raises the eyebrows, wrinkles forehead, moves scalp posteriorly
Description and function of the corrugator muscle
originates on the frontal bone and inserts into skin superior to the medial eyebrow. It is characterized as the muscle of trouble or concentration, and its fibers are oriented obliquely; it moves the brow medially, toward the nose, creating vertical furrows between the brows Lecture - Originates on the frontal bone and inserts into the medial side of eyebrow, creating vertical furrows between brows
Description and function of the procerus muscle
the muscle of menace or aggression, originates on the nasal bone and inserts into the medial side of the frontalis. It pulls the medial portion of the eyebrow inferiorly and produces horizontal furrows over the bridge of the nose. lecture - Originates on nasal bone and inserts into medial side of frontalis. It pulls the medial portion of the eyebrow inferiorly and produces horizontal furrows over the bridge of the nose
Description and function of the orbicularis oculi
lowers the entire brow. lecture - Sphincter muscle arranged in concentric bands around the upper and lower lids. Main function is to close lids and lowers the entire eyebrow. Also assists in tear drainage. has two portions - palpebral portion and orbital portion
List the function of the eyelids
- Cover the globe for protection (e.g. during sleep to restore cornea and conjunctiva; blink reflex and cilia protecting eye from foreign bodies) 2. Deliver Oxygen supply during sleep (through the palpebral conjunctiva, and through atmosphere as a result of an imperfect palpebral aperture seal) 3. Contain the structures that produce the tear film and mediate its stability (meibomian glands, some of the accessory lacrimal glands) 4. Spread the tear film over the surface of the eye Move the tears toward drainage at the medial canthus on eye lid closure
What is the Palpebral Fissure?
The area between open eyelids
What is a Canthus
location where upper and lower lids meet [plural: canthii]
What is the Plica Semilunaris
Conjunctiva adjacent to the medial canthus, that allows for lateral movement of the eye
What is the Caruncle?
Modified skin containing goblet cells (produce/secrete mucins) and fine hair
What is is the Tarsal portion of lid
Area overlying tarsal plate
What is the Orbital portion of lid
Area extending from tarsal region to eyebrow
Describe functions of the eyelid margin
- Rests against the globe and contains the eyelashes and the pores of the Meibomian Glands - represent unique boundary tissue separating mucous membranes from the keratinized skin epithelium -Orifices of the Meibomian glands are located posterior to the cilia (eyelashes) and the transition from skin to conjunctiva resides just posterior to these openings. - The Gray Line: groove running between cilia and meibomian gland pores divides the lids into anterior and posterior portions - Medial 1/6th: lacrimal portion, lateral 5/6ths ciliary portion: division occurs at the lacrimal papillae (elevation containing the lacrimal punctum
Function of eyelashes
- Provide protection to the eye via stimulation that causes the blink reflex to protect the eye -protect from airborne particles falling from above -prevent transfer of pathogens and allergens to the eye (mechanism not clear) -diversion of airflow: passive dust control system -reduce particle deposition and evaporation Also involved in non-verbal communication (e.g. batting of eyelashes; cosmetics)
What is Madarosis?
Decrease in number or complete loss of lashes. Causes: local (e.g. chronic anterior lid margin disease), following removal (e.g. cryotherapy of lid tumour), generalized skin disease (e.g. generalized alopecia), systemic disease (e.g. systemic lupus erythematosus)
What is Poliosis?
localized patch of grey or white hair due to lack of pigment in the epidermis (e.g. Vogt-KoyanagiHarada syndrome, associated with vitiligo)
What is Trichiasis?
Inward turning of previously normal lashes (e.g. idiopathic; trachoma)
What is Distichiasis?
second row of lashes originating from or slightly behind the MGO (congenital, acquired e.g. ocular cicatricial pemphigoid)
What is External hordeolum
Stye A common acute, purulent infection of a lash follicle and its associated gland of Zeis or Moll Tender, localized, inflamed swelling in the lid margin, pointing anteriorly through the skin
Function of the two portion of the Orbicularis Oculi Muscle - Palpebral portion?
Palpebral portion (pretarsal, preseptal) -Occupies area resting on globe and consists of semi-circle muscle fibres -Contraction helps drain the tears through the canaliculi into the nasolacrimal duct -contraction of pretarsal orbicularis closes the lids and involved in involuntary blink (barrier)
Function of the two portion of the Orbicularis Oculi Muscle - Orbital portion?
Fibres encircle area outside the palpebral portion -The upper fibres of this portion blend with the frontalis and corrugator -Contraction closes the eye tightly and the muscles on the face, forehead. The antagonist to the palpebral portion of the Orbicularis is the levator muscle
Describe the functions of the Superior Palpebral Levator Muscle
-Retractor of the upper eyelid -Innervated by CNIII -It originates from the sphenoid bone above the globe and inserts into the upper eyelids and becomes fan shaped (levator aponeurosis) -Fibres penetrate the orbital septum and extend into upper lid -Posterior fibres insert into the lower tarsal plate Function: contraction of levator causes elevation of the eyelid
Describe function of the Levator aponeurosis
sheath that allows coordination between levator and superior rectus which coordinates eyelid position with eye movements During eyelid closure levator relaxes and orbicularis contracts
What is the Capsulopalpebral fascia?
Sheath of the inferior rectus and suspensory ligament (even enveloping IO) insert into the inferior tarsal plate -coordination between lid position and lower eye movements
What is the Muller’s muscle (superior tarsal muscle)
-originates in the posterior-inferor aspect of the levator muscle and inserts into the superior portion of the tarsal plate -contraction of Muller’s muscles causes an additional 2mm of lid elevation Inferior tarsal muscle: similar structure to superior tarsal muscle - Ptosis: paralysis of levator or muller muscle (alpha-2 adrenergic agonist, causes muller muscle to elevate the upper eyelid 1-3mm) Need to DDx ptosis in one eye from proptosis in the other
What it the conjunctive and what are it subsections?
The conjunctiva consists of a surface epithelium overlying a well vascularized stroma Limbal conjunctiva: where the conjunctiva and cornea meet at the limbus Bulbar conjunctiva: covers the anterior sclera Palpebral conjunctiva: lines the posterior surface of both eyelids Fornix conjunctiva: folded conjunctiva where palpebral and bulbar conjunctiva meet results in a deep pocket behind each lid called the fornix
Purpose of the goblet cells?
Interspersed amongst the epithelial cells here are the unicellular mucous secreting Goblet cells. These cells are apocrine glands producing mucin for the tear film. Distribution of these cells is greater in the fornix than the palpebral or bulbar conjunctiva
What is the type and function of this gland? Meibomian
Type - Sebaceous Function - Secretion of meibum: lipid which is responsible for out layer of tear film
What is the type and function of this gland? Glands of Moll
Type - modified Apocrine - secretion of antimicrobial peptides and protein for protection of lashes and ocular surface
What is the type and function of this gland? Glands of Zeiss
Type - Sebaceous Release sebum to hydrate cilia
What is the type and function of this gland? Accessory lacrimal glands
Type - Merocrine Function: secretion of antibacterial agents, lysozyme, lactoferrin, immunoglobulins
Name and layer and measurements of the tear film
- Outer lipid layer (0.1 nanometers thick) (oil layer) 2. Intermediate Aqueous Layer (7 nanometers thick) (watery layer) 3. Inner Mucous Layer (0.5 nanometer thick) (mucous layer) pH of the tear film is 7.6
Function of the Tear Film
- Optical – optically uniform interface between air and cornea 2. Mechanical – Removal of intrinsic and extrinsic debris from tearfilm 3. Lubricant – Allows for smooth movement of lids over globe 4.Bactericidal – Contains immuno-defense mechanisms to prevent ocular infection 5. Nutritional – Supplies cornea with oxygen, glucose, amino acids, vitamins 6. Waste removal – Removes by-products of metabolism from cornea (CO2)
Function of the Lacrimal Gland?
-Receives Parasympathetic input - Oval mass 20 x 15 mm and 8-9mm thick -Consists of small clusters of secretory cells forming small lobules. The 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 -Additional secretion comes from accessory lacrimal glands (Glands of Krause and Wolfring) -Lacrimal secretion includes: Immunoglobulin A and lactoferrin (bacteriostatic), tear-specific prealbumin, lysozyme (bacteriolytic) - Infants younger than 6 weeks do not produce tears
What the afferent lacrimal gland innervation?
Sensory nerves on cornea • Naso-cillary nerve • V1 branch of trigeminal Nerve CNV • Arrives at trigeminal nucleus Sympathetic innervation of lacrimal gland originate from Superior Cervical Ganglion and travel along side the parasympathetic nerve to the lacrimal gland • Increases tearsecretion
Whats the efferent lacrimal gland innervation?
• Para-sympathetic innervation of lacrimal gland • CNS →Facial nerve exits the pons → • Zygomatic branches of the maxillary nerve travel with the lacrimal nerve to the lacrimal gland
Tear Drainage - What is the puncta?
the opening of the tear duct superior and inferior puncta at medial lid margin
Tear Drainage - Canaliculi
(passageways) small tubes of epithelium and connective tissue running for 10 mm past a small sac called Ampulla
Tear Drainage - Lacrimal Sac
Site where canaliculi merge
Tear Drainage - Nasolacrimal duct -
Normally open: therefore allows tears to flow from the nasolacrimal duct into nasal cavity Pressure differential between the Nasal cavity and nasolacrimal duct closes the duct and prevents entry of the nasal contents (Note: in infants, the membrane at the distal Valve of Hasner may persist, causing epiphora. The valve usually opens spontaneously in the first year of life, probing may be indicated if recurrent infections etc.)
The four steps of drainage during blink
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 and lacrimal sac moving fluid to nasolacrimal duct 4.After blink lacrimal sac and canaliculi expand and pressure decreases drawing fluid in from open puncta
Explain the types of dry eye
Evaporative Dry Eye - usually caused by Meibomian Gland Disease Aqueous Deficiency - Sjogrens Disease or non Sjogrens Disease - Defined as Low Volume, Hyperosmolar tear, ocular surface inflammation. Tear Defiency -> Increase Osmolarity -> inflammation -> LacrimalGland Dysfunction -> tear defiency
Lacriminal Gland Innvervation - afferent pathway?
Sensory nerves on cornea Naso-cillarynerve V1 branch of trigeminal NerveCNV Arrives at trigeminalnucleus
Lacriminal Gland Innvervation - efferent pathway?
•Para-sympathetic innervation of lacrimalgland CNS →Facial nerve exits the pons →•Zygomatic branches of the maxillary nerve travel with the lacrimal nerve to the lacrimal gland
What is this called?
External hordeolum (iea “stye”): A common acute, purulent infection of a lash follicle and its associated gland of Zeisor MollTender,localized,inflamedswellinginthelidmargin,pointinganteriorlythroughtheskin
What is this?
Madarosis: Decrease in number or complete loss of lashes.Causes: local (e.g.chronic anterior lid margin disease), following removal (e.g.cryotherapy of lid tumour), generalized skin disease (e.g.generalized alopecia), systemic disease (e.g.systemic lupus erythematosus)
What is this called?
Poliosis: localized patch of grey or white hair due to lack of pigment in the epidermis (e.g.Vogt-Koyanagi-Harada syndrome, associated with vitiligo)
What is this called?
Trichiasis: Inward turning of previously normal lashes (e.g.idiopathic; trachoma)
What is this called?
Distichiasis: second row of lashes originating from or slightly behind the MGO (congenital, acquired e.g.ocular cicatricial pemphigoid)
Review Blink reflex slide
Review Blink reflex slide
Review Blink reflex slide
Review Blink reflex slide
