Anatomy of Lacrimal System

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ANATOMY & PHYSIOLOGY OF LACRIMAL SYSTEM Dr. Adnan
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ANATOMY & PHYSIOLOGY OF LACRIMAL SYSTEM12/10/12

Lacrimal apparatusSecretory systems:lacrimal gland: reflex secretion accessory lacrimal gland: basic secretion conjunctival goblet cells: mucoprotein meibomian glands : lipid sebaceous gland of the palpebral margin: lipid

Drainage systems :upper,lower pancta

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EmbryologyPrimitive Cord of cells derived from surface ectoderm, sequestered in the naso-maxillary groove, forms the future lacrimal drainage system.

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Punctal

membranes open at full term; however, the membrane of Hasner remains imperforate in up to 70% newborns.

This usually opens within the first

month but may remain imperforate for a longer time.12/10/12

Lacrimal Apparatus It consists of:(a) The Lacrimal gland, which secretes the tears, and

its excretory ducts, which convey the fluid to the surface of the eye;

(b) The Lacrimal canaliculi, the Lacrimal sac, and the Nasolacrimal duct, by which the fluid is conveyed into the cavity of the nose.

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Main lacrimal gland Superolateral , Formed by bones of frontal and

Zygomatic

color: grayish - pink 2 lobes orbital: 20 12 5mm anterolateral to

globe

0.78 g Palpebral: inferior to levator

orbital lobe

1/3 1/2 of

8-12 major lacrimal ducts empty to superior to

cul-de-sac approximately 5mm above the lateral tarsal border. 12/10/12

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The lacrimal gland secretes tears, which contain lysozyme and electrolytes similar to plasma. They look similar to salivary glands, with the typical appearance of serous cells. Tubuloacinar gland

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Accessory lacrimal glandKrause and Wolfring. Location: deep within the sup. fornix

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PunctaPuncta

are openings 0.3 mm in diameter located on the medial aspect of the upper and lower eyelid margins. elevated mound known as the papilla lacrimalis.

Each punctum sits on top of an

The puncta are relatively avascular

in comparison with the surrounding tissue, giving them 12/10/12 pale a

Puncta

are directed posteriorly against the globe; therefore, they are not usually visible unless the eyelid is everted. Punctal ectropion may lead to inadequate tear drainage and resulting epiphora. inferior punctum is approximately 0.5 mm lateral to the superior punctum, with distances to the medial canthus of 6.5 mm and 12/10/12 6.0 mm, respectively. Tears within

The

Congenital atresia, supernumerary or

double puncta, and congenital slits of the puncta all may occur from aberrations in the location of the epithelial cord and its opening to the surface epithelium.Lateral displacement of the puncta

may occur in some congenital syndromes such as blepharophimosis.12/10/12

CanaliculiCanaliculi

have an initial vertical segment, measuring 2 mm, followed by an 8-mm horizontal segment. horizontal segments is approximately 90 degrees, and the canaliculi dilate at the junction to form the ampulla.

The angle between the vertical and

In most individuals, the horizontal

portion of the canaliculi converges to form the common canaliculus. 12/10/12

Canaliculi pierce the lacrimal fascia

before entering the lacrimal sac. At its entrance to the lacrimal sac, the common canaliculus may dilate slightly, forming the sinus of Maier.

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Canaliculi

are lined by nonkeratinized, stratified squamous epithelium and are surrounded by elastic tissue, which permits dilation to 2 or 3 times the normal diameter. canaliculus into the lacrimal sac forms the valve of Rosenmller, which prevents retrograde reflux of fluid from the sac into the canaliculi.12/10/12

The oblique entrance of the common

However, the posterior angulation of

the upper and lower canaliculi followed by anterior angulation of the common canaliculus may also block reflux at the canaliculus-sac junction.An incompetent valve of Rosenmller

is observed clinically as air escaping from the lacrimal puncta when the individual blows his or her nose.12/10/12

Atresia or failure of canalization of

the lacrimal canaliculi may occur in conjunction with punctal atresia.In

many cases, particularly in patients with mesodermal dysplasia, the lacrimal canaliculi and puncta may be absent and a normal tear sac and nasolacrimal duct may be present but not connected to the eyelid surface.12/10/12

Lacrimal sacThe

lacrimal sac sits within the lacrimal fossa, which is bound anteriorly by the frontal process of the maxillary bone (anterior lacrimal crest) and posteriorly by the lacrimal bone (posterior lacrimal crest).

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The lacrimal sac is lined by a double-

layered epithelium (superficial is columnar, and deep is flatter). It can be divided into a fundus superiorly and a body inferiorly.The fundus extends 3-5 mm above

the superior portion of the medial canthal tendon, and the body extends approximately 10 mm below the fundus to the osseous opening of 12/10/12 the nasolacrimal canal.

At the posterior lacrimal crest, the

orbital periosteum splits to envelop the lacrimal sac as a covering known as the lacrimal fascia.The lacrimal fascia is surrounded by

fibers of the orbicularis oculi muscle; the superficial head attaches to the anterior lacrimal crest, and the deep head attaches to the posterior lacrimal crest.12/10/12

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A congenital fistula of the lacrimal

sac, lacrimal anlage duct commoner than diverticulums.Autosomal

is

dominant and may coexist with thalassemia. It undoubtedly is the result of canalization of a strand of epithelial cords. The fistulas often completely excised have to be to 12/10/12 prevent

Lacrimal duct anlage. a congenital lacrimal drainage fistula inferonasal to the medial 12/10/12

Nasolacrimal ductThe nasolacrimal duct consists of a

12-mm superior intraosseous portion and a 5-mm inferior membranous portion.The

intraosseous part travels posterolaterally through the nasolacrimal canal within the maxillary bone. the nasal mucosa, eventually 12/10/12

The membranous part runs within

The

double layer of epithelium similar to that observed in the lacrimal sac. The venous plexus surrounding the lacrimal sac continues inferiorly to surround the nasolacrimal duct.

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Dacryostenosis

is a common condition in which the extreme end of the nasolacrimal duct underneath the inferior turbinate fails to complete its canalization in the newborn period; it produces clinical symptoms in 2% to 4% of newborns

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Blood supplyThe

Main Blood supply: Lacrimal artery

Branches of the transverse facial or

infraorbital arteries.Venous

blood returns superior ophthalmic vein.

via12/10/12

the

InnervationOphthalmic division of CN V, which

supplies sensory innervation to the lacrimal gland along with the eye lid and conjunctiva.

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Applied AnatomyThe upper part of the lacrimal sac is

covered by the medial palpabral ligament.Hence

abscesses within the sac bulge below the medial palpabrel ligament, where it should bi incised for letting out the pus.

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Around the nasolacrimal duct there

is the rich plexus of veins, in the form of an erectile tissue, which may engorge and cause obstruction to the duct.

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The angular vein is in front of the sac

and it should be take care during incising the sac.Between the lacrimal sac and the

fascia coverning the sac there is the collection of venous plexus present hence the incising cause considerable bleeding.12/10/12

Physiology

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The lacrimal gland secretes tears

directly into the superior fornix.The

tears are collected at the lacrimal lake and then drained by the superior and inferior lacrimal papillae. papillae from getting stuck to each other.12/10/12

The lacrimal caruncle prevents the

If there are tears:

Puncta opens at the medial part to the Plica Semilunaris Into the Lacunar Caruncle into the lacrimal canaliculi Into lacrimal ducts Into the lacrimal sac (held by lacrimal bone) Opens to the nasolacrimal duct

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Key physiologic point to understand,

is that the lacrimal outflow system is based on an active, dynamic pumping mechanism.

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With the eyelids open before the

start of a blink, the canaliculi are already filled with tears.The

blink acts to compress the canaliculi and lacrimal sac, thus forcing the contained fluid into the nasolacrimal ducts and nasal passages.12/10/12

Tears flow along the upper and lower

marginal strips and enter the upper and lower canaliculi by capillarity and also possibly by suction.

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The

volume of fluid within the lacrimal outflow system is at its minimum at the point of maximum lid closure during a blink.

As the eyelids begin to open, the

muscular compressive force terminates and the elastic walls of the canaliculi and lacrimal sac attempt to restore their original 12/10/12

Other factors contributing to lacrimal eliminationPhysical forces such as gravity and

capillary attraction of the tears,Reservoir drainage into the lacrimal

sac (so-called Krehbiel flow), Microcilliation in the nasolacrimal

duct andEvaporation of tears from the ocular

surface and absorption of tears by the lacrimal sac mucosa.12/10/12

More than 90% off the lacrimal fluid

is removed by the Excretory system.Less than 10% evaporates between

blinks.

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All

efforts should be made preserve the lacrimal canaliculi.

to

Repeated

instrumentation of the lacrimal system or nasolacrimal duct probings are unlikely to help the underlying pathology and may in and of themselves injure the canaliculi and thus permanently impair lacrimal elimination.

Very little can be done to restore 12/10/12

Experimental

and clinical studies show that tear elimination is equivalent through the upper and lower canalicular systems. consideration to a patient with lacerations of either the upper or lower canaliculus.

Surgeons should thus give equal

Traditional

eyelid

teachings that upper canalicular lacerations are 12/10/12

Thank U.

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