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Anatomy of lacrimal apparatus and conjunctiva
- 1. LACRIMAL APPARATUS Shahana Nethradhama schoolof optometry
- 2. Introduction Lacrimal apparatus comprisesthe structures concerned with the formation of tears i.e the main lacrimal gland and accessory lacrimal glands and its transport Components of lacrimal apparatus • Lacrimal gland • Lacrimal puncta • Lacrimal cannaliculi • Lacrimal sac • Nasolacrimal duct
- 4. Main lacrimal gland Itconsist of an upper orbital and a lower palpebral part. 1. Orbital part: • Situated in fossa for lacrimal gland • Size of small almond • It has two surfaces superior(contact with the bone) and inferior(lies on LPS)
- 5. 2. Palpebral part: •Consist of one or two lobule • Seperated by LPS muscle • Posteriorly continuous with the orbital part
- 6. Ducts of lacrimalgland • 10-12 ducts open in the lateral part of superior fornix • One or two ducts also open in the lateral part of inferior fornix
- 7. Structure of lacrimalgland • Lacrimal gland is branched tubulo alveolar gland similar in structure to the salivery glands • Microscopically it consist of glandular tissue,stroma,and septa. • Glandular tissue consist of acini and ducts arranged in lobes and lobules seperated from each other by fibrovascular septa. • The stroma of the lacrimal gland is formed by mesodermal tissue which contains connective tissue,elastic tissue, lymphoid tissue,plasma cells,rich nerve terminals and blood vessles.
- 9. Accessory lacrimal gland Samestructure as lacrimal gland Very small in size 1. Gland of Krause • Lie beneath the palpebral conjunctiva between fornix and edge of tarsus • About 42 in upper fornix and 6-8 in the lower fornix
- 10. 2.Gland of wolfring •Present near the upper border of the superior tarsal plate and the lower border of the inferior tarsus Blood supply • Main lacrimal gland is supplied by lacrimal artery branch of ophthalmic artery. Nerve supply • Sensory nerve supply comes from the lacrimal nerve,a branch of ophthalmic division of the fifth cranial nerve • Sympathetic nerve supply comes from the carotid plexus of the cervical sympathetics. • Secretomotor fibres are derived from superior salivery nucleus.
- 11. Lacrimal passages 1. Lacrimalpuncta • Small,round or oval opening on upper and lower lids, about 6 and 6.5 mm respectively , from the inner canthus . • Each punctum is situated upon a slight elevation called lacrimal papillae
- 12. 2. Lacrimal canaliculi: •Superior and inferior canaliculi open into the lacrimal sac • Each canaliculus has 2 part:vertical (1- 2mm)and horizontal (6-8mm) • The two canaliculi usually join together to form a common canaliculi which opens immediately into the outer wall of lacrimal sac. • A fold of mucosa at this point forms the valve of rosenmuller which prevent reflex tears.
- 13. 3. The lacrimalsac: • It lies in the lacrimal fossa formed by the lacrimal bone • It is bounded by anterior and posterior lacrimal crests • When distented lacrimal sac is about 12 – 15 mm in length and 5-6 mm in breadth 4. Nasolacrimal duct: • It extent from the neck of lacrimal sac of the inferior meatus of nose • It is about 15-18 mm long and lies in a bony canal formed by maxilla and the inferior turbinate • Direction of NLD is downwards,backward and laterally.
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- 15. INTRODUCTION • It isa translucent mucous membrane which lines the posterior surface of the eyelids and anterior ascept of eyeball • The normal conjunctiva is pink,smooth, thin ,and transparent. • There are normally large deep blood vessels that run vertically.
- 16. Function of conjunctiva •The conjunctiva helps lubricate the eye by producing mucus and tears ,although a smaller volume of tears than the lacrimal gland • It also prevent the entry of microbes into the eye.
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- 18. Palpebral conjunctiva • Itis richly vascular , extremely thin and strongly bounded to the tarsal plate
- 19. • It linesthe lids and is subdivided into Marginal Tarsal Orbital
- 20. 1. Marginal – •Extends from the lid margin to about 2mm back of the lid upto the sulcus subtarsalis • Actually a transitional zone between skin and conjunctiva proper • Lacrimal puncta open in the marginal zone. 2. Tarsal • Thin,transparent and highly vascular • Firmly adherent to the whole tarsal plate in the upper lid and only to half width of the lower tarsus in the lower lid
- 21. 3. Orbital • Itlies loose between tarsal plate and fornix • Orbital margin of the upper eyelid is loose and lies over the muller’s muscle
- 22. Bulbar conjunctiva • Itis transparent and lies loose over the underlying structures and thus can be moved easily • It is separated from the anterior sclera by episcleral tissue and tenons capsule • The average thickness is 33 microns • It is also known as ocular conjunctiva • It is further of two types Limbal Scleral
- 23. Limbal – • A3mm ridge of bulbar conjunctiva around the cornea is called limbal conjunctiva • Strongly adherent to sclero-corneal junction Scleral- • Covers the eyeball above the anterior sclera and hence known as scleral conjunctiva • Thin transparent and loosely attached to underlying sclera
- 24. Conjunctival fornix • Itis thin transparent , continuous cicular cul de sac • It joins the bulbar conjunctiva with palpebral conjunctiva
- 25. Structure of conjunctiva Conjunctivahas 3 layers 1. Epithelium 2. Adenoid layer 3. Fibrous layer
- 26. Epithelium • 2-5 layered, non keratinized epithelium.Also contains goblet cells • The layer of epithelial cells varies from region to region: o Marginal conjunctiva has 5 layered stratisfied squamous type epithelium. o Tarsal conjunctiva has 2 layered epithelium superficial cylinderical and deep cuboidal cells o Fornix and bulbar conjunctiva have 3 layered epithelium cylinderical,polyhedral,and cuboidal cells.
- 27. Adenoid layer • Alsocalled lymphoid layer • Consist of fine connective tissue reticulum in the meshes of which lie lymphocytes. • It is not present since birth but develops after 3-4 months of life.
- 28. Fibrous layer • Consistof a meshwork of collageous and elasticfibres. • This layer contains vessels of nerves and conjunctiva • It blends with the underlying tenon’s capsule in the region of the bulbar conjunctiva.