Conjunctiva Summary PDF

CONJUNCTIVA SUMMARY Sunday, October 22, 2023 1:42 PM CONJUNCTIVA Thin, transparent, and highly vascularized Mucous membrane (full of goblet cells) Goblet cells: type of epithelial cell that secretes mucous ○ Mucous consists of: ▪ Mucin, water, epithelial cel...

CONJUNCTIVA SUMMARY Sunday, October 22, 2023 1:42 PM CONJUNCTIVA Thin, transparent, and highly vascularized Mucous membrane (full of goblet cells) Goblet cells: type of epithelial cell that secretes mucous ○ Mucous consists of: ▪ Mucin, water, epithelial cells, dead leukocytes, and inorganic salts Provides lubrication and protection of the ocular surface ○ Protection: particulates and pathogens become trapped in mucus, preventing their entry into deeper tissue 3 Regions of the Conjunctiva (all together form the conjunctival sac) Palpebral Conjunctiva: lines the underside of the eyelids ○ Subdivided into 3 regions ▪ Marginal Conjunctiva: □ Present at the eyelid margin □ Forms the mucocutaneous junction □ Contains the lid wiper region ▪ Tarsal Conjunctiva: □ Firmly attached to the tarsal plate, providing a smooth tarsal surface in the area of the tarsal plate ▪ Orbital Conjunctiva: □ Present from the edge of the tarsal plate to the forniceal conjunctiva □ Loose connective tissue that allows for free movement of the globe Forniceal Conjunctiva (Conjunctival Fornix): ○ Cul-De-Sac connecting palpebral and bulbar conjunctiva ○ Deepest laterally, extending posterior to the equator of the globe ○ Not present medially due to the plica and caruncle of the bulbar conjunctiva Bulbar Conjunctiva: ○ Lines the anterior globe, covering Tenon's capsule/sclera and EOM insertions ▪ Merges with Tenon's capsule and anterior sclera within 3 mm of cornea before the layers become continuous with the cornea ○ 2 specialized areas medially ▪ Plica Semilunaris: Crescent shaped fold of the bulbar conjunctiva □ Allows full lateral movement of the eye without tissue stretching □ Makes up the floor of the lacrimal lake (tear reservoir) □ Contains high concentration of goblet cells ▪ Caruncle: mound of bulbar conjunctiva/skin that overlies the medial edge of the plica □ Conjunctival elements: non-keratinized epithelial cells, goblet cells, accessory lacrimal glands (of Krause and Wolfring) □ Skin elements: hair follicles, sebaceous glands, and sweat glands □ Function is poorly understood, but it's known that the hairs trap oil, mucus, and debris 2 layers of the Conjunctiva (surface layer and deeper layer) Epithelial layer (Epithelium): functions as a barrier to the outside environment to prevent microbes from entering the globe ○ Composed of non-keratinized epithelial cells, goblet cells, melanocytes, Langerhans cells, and lymphocytes ▪ Non-keratinized epithelial cells (non-keratinized in order for it to retain water) □ Most abundant cell in this layer □ Mostly stratified columnar cells (that are in layers) Stratified squamous cells are present at the mucocutaneous junction and limbus □ Microvilli are present at the apex of non-keratinized surface cells Microvilli: helps bind mucin to the conjunctival surface □ Glycocalyx: secreted from the apex of the non-keratinized surface cells Consists of transmembrane mucins (glycoproteins) MUC1, MUC4, and MUC16 Functions as a barrier to pathogens and injury Helps bind mucin to/spread the tear film on the conjunctival surface ▪ Goblet cells: type of epithelial cell that secretes gel-forming mucins (glycoprotein) □ MUC5AC □ Component of the tear film □ Interspersed among other epithelial cells □ Concentrated in the nasal and inferior nasal region of the conjunctiva ▪ Melanocytes □ Produce melanin (pigment) which functions to filter UV radiation ▪ Langerhans cells □ Type of WBC that helps protect the eye against pathogens ▪ Lymphocytes □ Type of WBC that helps protect the eye against pathogens Stromal Layer (Substantia Propria) ○ Composed of Loose connective tissue ○ Divided into 2 layers: ▪ Outer Lymphoid layer □ Contains lymphocytes and plasma cells Both are types of WBC's and protect the eye against pathogens ▪ Deep Fibrous Layer Anterior Segment Page 1  ○ Divided into 2 layers: ▪ Outer Lymphoid layer □ Contains lymphocytes and plasma cells Both are types of WBC's and protect the eye against pathogens ▪ Deep Fibrous Layer □ Contains accessory lacrimal glands (of Krause and Wolfring) Produce the aqueous component of tear film Glands of Krause: located at the forniceal conjunctiva Glands of Wolfring: located in the palpebral conjunctiva □ Rich in blood vessels, lymphatic vessels, and nerves Function of the Conjunctiva Plays a role in the immunological defense system of the ocular surface ○ Particulates and pathogens become trapped in mucus, preventing their entry into deeper tissues ○ Epithelial and stromal layers contain white blood cells ○ The glycocalyx provides a barrier against pathogens Ensures smooth movement of the eyelids over the globe ○ Goblet cells produce mucus with a major component being mucin (a component of the tear film) Sensory Innervation of the Conjunctiva (all CN V) Palpebral Conjunctiva: ○ V1 (Ophthalmic nerve) ▪ Nasociliary nerve □ Infratrochlear nerve (U+L conj) ▪ Frontal nerve □ Supraorbital nerve (U conj) □ Supratrochlear (U conj) ▪ Lacrimal nerve (U conj) ○ V2 (Maxillary nerve) ▪ Infraorbital nerve (lower conj) Forniceal Conjunctiva: (same as palpebral conj.) ○ V1 (Ophthalmic nerve) ▪ Nasociliary nerve □ Infratrochlear nerve (upper and lower conj) ▪ Frontal nerve □ Supraorbital nerve (upper conj) □ Supratrochlear (upper conj) ▪ Lacrimal nerve (upper conj) ○ V2 (Maxillary nerve) ▪ Infraorbital nerve (lower conj) Bulbar Conjunctiva ○ V1 (Ophthalmic nerve) ▪ Nasociliary nerve □ Long ciliary nerve (all of bulbar conj) Blood Supply to the Conjunctiva Palpebral Conjunctiva: ○ Supply from the palpebral arcades ▪ Ophthalmic artery branches into the lacrimal and medial palpebral arteries □ Lacrimal: enters the UL and LL as the lateral palpebral arteries (2 superior and inferior) Anastomoses with the medial palpebral arteries to form the palpebral arcades ◊ Supplies the palpebral and forniceal conjunctiva Forniceal Conjunctiva: ○ Supply from the palpebral arcades ▪ Ophthalmic artery branches into the lacrimal and medial palpebral arteries □ Lacrimal: Pierce the orbital septum to enter the UL and LL as the lateral palpebral arteries (2 superior and inferior) Anastomoses with the medial palpebral arteries to form the palpebral arcades ◊ Supplies the palpebral and forniceal conjunctiva □ Medial Palpebral Arteries: pierce the orbital septum to enter the UL and LL Anastomoses with the lateral palpebral arteries (from lacrimal branch) to form the palpebral arcades (marginal and peripheral) ◊ Peripheral palpebral arcade (AKA peripheral arterial arcade)  Anterior to Mullers muscle (tarsal plate)  Supplies the UL and LL near the peripheral edge of the tarsal plate  Supplies the forniceal conjunctiva and cornea when eyelids are protracted Bulbar Conjunctiva: ○ Supply from the anterior and posterior conjunctival arteries Anterior Segment Page 2  peripheral edge of the tarsal plate  Supplies the forniceal conjunctiva and cornea when eyelids are protracted Bulbar Conjunctiva: ○ Supply from the anterior and posterior conjunctival arteries ○ Ophthalmic artery branches into the medial palpebral arteries and muscular arteries □ Medial Palpebral Arteries: pierce the orbital septum to enter the UL and LL Palpebral arteries loop posteriorly to enter the bulbar conjunctiva and form the posterior conjunctival arteries Supply the bulbar conjunctiva Anastomose with the anterior conjunctival arteries □ Muscular Arteries (usually 2, lateral and medial or superior and inferior) Lateral (or superior) branch supplies LR, SR, SO, levator muscles Medial (or inferior) branch supplies MR, IR, IO muscles Vessels supplying the rectus muscles continue anteriorly as the anterior ciliary arteries (~7) Give off branches to enter the bulbar conjunctiva and form the anterior conjunctival arteries ◊ Supply the bulbar conjunctiva ◊ Anastomose with the posterior conjunctival arteries (at the end) ◊ Continue anteriorly to form limbal vessels  Supply the limbus and peripheral cornea Blood Drainage from the Conjunctiva Conjunctival veins drain into the superior and inferior ophthalmic veins Conjunctiva -> conjunctival veins -> anterior ciliary veins -> muscular veins -> superior and inferior ophthalmic vein ○ Superior ophthalmic vein -> cavernous sinus -> superior and inferior petrosal sinuses -> right internal jugular vein ○ Inferior ophthalmic vein -> cavernous sinus and pterygoid plexus □ Pterygoid plexus -> maxillary vein -> retromandibular vein -> right internal jugular vein □ Cavernous sinus -> superior and inferior petrosal sinuses -> right internal jugular vein Anterior Segment Page 3