Lacrimal apparatus

1. LACRIMAL
APPARATUS
NISHA.S.S
M.OPTOM

2. LACRIMAL APPARATUS
• The lacrimal apparatus comprises the structures concerned with the
formation of tears( the main lacrimal gland and accessory lacrimal glands)
and its transport.
• The lacrimal passage includes:
• Puncta
• Canaliculi
• Lacrimal sac
• Nasolacrimal duct.

3. LACRIMAL GLANDS
Main lacrimal gland
• The main lacrimal gland is situated in the fossa for lacrimal gland,
formed by the orbital plate of frontal bone, in the anterolateral part of the
roof of orbit.
• The gland is divided into two parts-the superior orbital and the inferior
palpebral- which are continuous with each other posteriorly.

4. The orbital part of lacrimal gland
• It is large, about the size and shape of a small almond. It has two surfaces (superior and
inferior), two borders (anterior and posterior) and two extremities (medial and lateral).
• Superior surface of the orbital part is convex and lies in contact with the periorbita lining the
part of the frontal bone forming the fossa for the lacrimal gland.
• Inferior surface of the orbital part is concave and lies on the levator palpebrae superioris
muscle.
• Anterior border is sharp and seems within and parallel to the orbital margin. It lies in contact
with the septum orbitale.
• Posterior border is round and becomes continuous with the palpebral part of the gland.
• Lateral extremity rests on the lateral rectus muscle.
• Medial extremity is related to the levator palpebrae superioris muscle.

5. Palpebral part of lacrimal gland
• It is small (about one-third the size of orbital part) and consists of only
two or three lobules.
• It is situated upon the course of the ducts of orbital part from which it
is separated by the levator palpebrae superioris muscle, which is
related to it superiorly.
• Inferiorly, the gland lies in relation to the superior fornix.
• The gland is compressed from above downwards and can be seen
through the conjunctiva when the upper lid is everted.
• Posteriorly, it is continuous with the orbital part.

8. Ducts of lacrimal gland
• About 10-12 ducts pass downwards from the main lacrimal gland
to open in the lateral part of the superior fornix.
• One or two ducts also open in the lateral part of the inferior fornix.
• Since all the ducts pass through the palpebral part of the gland,
therefore, excision of the palpebral part alone amounts to excision
of the entire gland as far as the secretory function of the gland is
concerned.

10. HISTOLOGICAL STRUCTURE OF THE LACRIMAL GLAND
• Lacrimal gland is a branched tubuloalveolar (serous acinous) gland. Microscopically, it
consists of glandular tissue, stroma and septa .
• Glandular tissue consists of ducts arranged in lobes and lobules.
• Acini are lined by a single layer of pyramidal cells mounted on a basement membrane. These
cells are surrounded by a layer of flattened myoepithelial cells. The pyramidal cells are of the
serous type with eosinophilic secretory granules and a round nucleus situated towards the
base. These cells secrete the tears, expelled by the contraction of myofibrils.
• Ductules and ducts : The secretion of the acinar units is drained by connecting channels which
to begin with are intralobular, then these become extralobular and lastly open in the ducts. The
ducts are lined by two layers of epithelial cells the inner lining is formed by thick cylindrical
cells and the outer layer is of flattened cells.
• Stroma of the lacrimal gland is formed by mesodermal tissue which contains connective
tissue, elastic tissue which contains connective tissue, elastic tissue, lymphoid tissue, plasma
cells, rich nerve terminals and blood vessels.

12. BLOOD SUPPLY
• Arterial supply: Main lacrimal gland is supplied by lacrimal artery, a
branch of ophthalmic artery. Sometimes a branch of the transverse
facial artery may also supply the gland.
• Lacrimal veins draining the gland join the ophthalmic vein.

13. NERVE SUPPLY
• Main lacrimal gland has three modes of innervations:
1. Sensory nerve supply comes from the lacrimal nerve, a branch of
ophthalmic division of the fifth cranial nerve.
2. Sympathetic nerve supply arises from the superior cervical sympathetic
ganglion as postganglionic fibres which from the carotid plexus of the cervical
sympathetics. From the sympathetic plexus around the internal carotid artery,
some fibres join the deep petrosal nerve, then the nerve of pterygoid gland,
and then ultimately reach the lacrimal gland through the lacrimal nerve .

14. ACCESSORY LACRIMAL GLANDS
These include:
• Glands of Krause
• Glands of Wolfring
• Intraorbital glands
• Glands in the caruncle and plica semilunaris

17. • Glands of Krause: These are microscopic glands lying in the
subconjunctival tissue of the foraices .These are about 40-42 in the upper
fornix and about 6-8 in the lower fornix. Their ducts unite to form a long duct
which opens in the fornix.
• Glands of Wolfring: These are microscopic glands present along the upper
border of superior tarsus (2-5 in number), and lower border of inferior
tarsus (2-3 in number).
• Rudimentary accessory lacrimal glands: These are present in the caruncle,
plica semilunaris and infraorbital region.

18. LACRIMAL PASSAGES

19.  LACRIMAL PASSAGES
1. Lacrimal puncta
• These are two small rounded or oval openings one each on the upper and lower eyelids,
at the junction of ciliary and lacrimal portion of the lid margin .
• The upper upon a slight elevation called lacrimal papilla, which becomes prominent in
old age." and the lower puncta lie about 6 mm and 6.5 mm lateral to the inner canthus,
respectively. Thus when the eyelids are closed, the puncta do not overlap each other,
but the upper punctum lies medical to the lower punctum.
• The upper punctum is directed downwards and backwards, while the lower punctum is
directed upwards and backward..
• The puncta are surrounded by a ring of dense fibrous tissue .With each blink, the puncta
slide in the groove between the plica semilunaris and the eyeball.

21. 2. Lacrimal canaliculi
• The superior and inferior canaliculi join the puncta to the lacrimal sac.
• Each canaliculus is 0.5 mm in diameter and has two parts, vertical (2 mm) and
horizontal (8 mm), which lie at right angles to each other . At the junction of the two
portions, there is slight dilatation called the ampulla.
• The horizontal part of each canaliculus converges towards the medial canthus. The
point of opening into the sac lies at the middle of the lateral surface of the sac about
2.5 mm from its apex.

23. 3. Lacrimal sac
• Location: It lies in the lacrimal fossa located in the anterior part of medial orbital
wall. The lacrimal fossa is formed by lacrimal bone and frontal process of the
maxilla.
• Dimension: The lacrimal sac when distended is about 15 mm in length and 5-6
mm in breadth with a capacity of about 20cm.

24. 4. Nasolacrimal duct (NLD)
It continues downward from the neck of the lacrimal sac to its opening in the
inferior meatus of the nose .
• It is about 18 mm (may vary from 12-24 mm) in length and about 3 mm in
diameter. The upper end of the NLD is its narrowest part. Direction of the NLD
is downwards, backwards and laterally. Externally, its location is represented
by a line joining inner canthus with the ala of nose.
• The opening of the NLD in the inferior meatus is situated at a depth of about
30-40 mm from the anterior nares.

26. Structure of the lacrimal sac and NLD
• Epithelium: The lacrimal sac and NLD are lined by 2 layers of cells. The superficial layer is
of non-ciliated columnar cells and contains goblet cells. The deep layer is of flattened
cells.
• Subepithelial tissue contains lymphocytes.
• Fibroelastic tissue of the lacrimal sac becomes continuous with that of the canaliculi.
• Plexus of vessels is well developed around the NLD, forming an erectile tissue resembling
in structure with that on the inferior concha. Engorgement of these vessels is said to be
sufficient to cause obstruction of the NLD and produce epiphora.

27. VESSELS AND NERVES
Blood supply of the lacrimal passages
• Arterial supply to the lacrimal passage is derived from superior and inferior palpebral arteries
(branches of ophthalmic artery), angular artery, infraorbital artery and nasal branches of
sphenopalatine artery.
• Venous drainage occurs into the angular vein and infraorbital vein from above and into the nasal
vein from below.
Nerve supply
• Sensory nerve supply to the lacrimal sac and NLD comes from the infratrochlear nerve and the
anterior superior alveolar nerves.

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