ANATOMY - CONJUNCTIVA Flashcards
What are the 3 types of conjunctiva? Subtypes?
Palpebral (inner eyelid) - marginal, tarsal, orbital
Bulbar (anterior eyeball) - scleral, limbal
Forniceal (in between both)
Where is the conjunctiva firmly adherent to? Where is the conjunctiva loosly attached to?
Adherent to lids over tarsal plates (upper > lower)
Loosely attached to fornices and over globe (except limbus)
- What is the sulcus subtarsalis?
- How far is it away from lid margin?
- When is the subtarsalis scarred?
- Groove 2mm away from lid margin
- 2mm - common site for foreign body lodging
- Trachoma - Arlt’s line
What are the different structures in the palpebral conjunctiva?
- Marginal conjunctiva (anterior - posterior lid margin)
- Sulcus Subtarsalis
- Tarsal Conjunctiva (covers tarsal plate)
- Orbital Conjunctiva (between tarsal plate and fornix, over muller’s muscle)
What are the types of epithelium in the conjunctiva?
Marginal - 5 layers of non keratinised stratified squamous epithelium
Tarsal/palpebral - 2 layers of stratified squamous epithelium
Fornix/bulbar - 3 layers of stratified columnar epithelium
Limbal - 10 layers of stratified squamous epithelium
WAY TO REMEMBER: 5 + (2 + 3 ) = 10
What is the main property of forniceal conjunctiva?
Thicker conjunctiva and is loosely present to allow movement of globe
How much tear fluid is present in the conjunctival sac?
7 microlitres, can hold up to 30 microlitres
Where is the bulbar conjunctiva firmly adherent (2 places)
- 3mm zone near limbus
- Insertion of rectus muscles
What happens to the conjunctival epithelium when goes from fornices to the limbus?
Becomes thicker
What is the pathological mechanism of squamous metaplasia of the conjunctiva?
transition of squamous, moist non-keratinised to become dry, keratinised epithelium
The lid margins are covered anteriorly by dry, keratinised epithelium which mergies into moist non keratinised epithelium in the tarsus. In many ocular surface disorders, the change of normal epithelium to become non-secretory and keratinised (squamous metaplasia)
What are the side effects of topical drugs on the conjunctiva?
look at diagram.
What is the function of the goblet cells ? (2) Where are they located (1)
Secrete 2.2ml of mucin
Ensure stability of tear film by decreasing surface tension
Located throughout the conjunctival epithelium and arise from basal layer
What are the layers of the conjunctiva?
- Epithelium
- Adenoid/Lymphoid Layer
- Fibrous Layer
What are the structures within the adenoid/lymphoid layer of conjunctiva? (3)
- Lymphoid tissue (follicles are formed)
- Mast cells (6000 per mm cubed)
- Plasma cells, lymphocytes, neutrophils (CALT - conjunctival associated lymphoid tissue)
At what age does the lymphoid/adenoid layer of the conjunctiva arise?
3-4 months old
What is the structure of the fibrous layer of the conjunctiva?
Connective tissue which attaches to tarsal plate - contributes to papillae
Where are the Popov glands located?
Located within the substance of the caruncle
How many Krause /Wolfring glands are there?
Krause - 20-40 in upper fornix, 6-8 in lower fornix
Wolfring - 2-5 located along superior tarsal border
What are the accessory lacrimal glands? What is their role?
Krause, Wolfring, Popov
- Contribute 10% of lacrimal secretions
- Contribute to basal tear secretion, no contribution to reflex tear secretion
What artery supplies the palpebral conjunctiva? What artery supplies the bulbar conjunctiva?
Palpebral : marginal arcade (marginal) and peripheral arcade (forniceal + orbital + tarsal)
Bulbar:
1. anterior conjunctival artery (branch of anterior ciliary for limbus)
2. posterior conjunctival artery (branch of peripheral arcade)
What vein does the conjunctiva drain into ? What vein does the limbus drain into?
Superior and inferior ophthalmic veins from eyelid plexus
Limbus –> anterior ciliary vein
What is the nerve supply of the conjunctiva?
- Superior Palpebral and forniceal - V1 (lacrimal and frontal branches)
- Inferior palpebral and forniceal - V1 and V2 (lacrimal branches and infraorbital nerve)
- Bulbar : long ciliary nerve (nasociliary nerve - V1)
What is the function of the conjunctiva? (4)
- Tear production (mucin by goblet cells, aqueous by accessory lacrimal glands
- Supply of oxygen directly to cornea when eye is open
- Wash off debris and maintain smooth ocular surface
- Protection of eye by defense mechanisms - secretory IgA, mucin clumping, mast cell outpouring, intact epithelial barrier, lacrimation
Where are the goblet cells most abundant?
Fornices and plica semilunaris
Which nutrients are the most essential for health of conjunctival epithelium and goblet cells?
retinoids and vitamin A
Where do the lymphatics drain laterally and medially?
Laterally : superficial parotid nodes
Medially: submandibular nodes
Epithelial basement membrane of the conjunctiva is composed of which type of collagen?
Type IV
The lateral fornix of the conjunctiva extends how far from the limbus to the equator?
14mm
In primary gaze position, where does the upper lid and lower lid cover in relation to the cornea?
upper lid : covers 1/6th of cornea
lower lid: covers inferior limbus
Where does the lateral canthus lie in relation to the lateral orbital margin?
5-7mm
What types of cells are present in the conjunctival epithelium (4)
- Goblet cells
- Melanocytes
- Dendritic cells (Langerhan’s cells)
- Lymphocytes (CD3 + T cells and B cells)
What type of muscle is found in the plica semilunaris?
Non striated muscle
How often are eyelashes replaced?
Every 100-150 days.
What is the difference between Henle’s crypts and Manz’s glands?
Henle’s crypts are hidden.: Goblet cell accumulation in tarsal conjunctiva
Manz’s glands - Goblet cell accumulation in bulbar conjunctiva nasal to limbus
