ANATOMY AND PHYSIOLOGY OF LACRIMAL SYSTEM

Dr. Dev Raj Bharati 1st YEAR RESIDENTNEH,NAMS8th Nov,2009

LACRIMAL SYSTEM SECRETORY APPARATUS:

∙Lacrimal gland & Ducts∙Accessory glands of Krause

and Wolfring

EXCRETORY APPARATUS: ∙Puncta

∙Lacrimal canaliculi ∙ Lacrimal sac ∙ Nasolacrimal duct

DEVELOPMENT:Secretory Apparatus

Lacrimal gland begins to develop between 6-7th wks. of gestation

Forms as a series of ectodermal buds that grow superolaterally from the superior fornix of the conjunctiva into the underlying mesenchyme

Buds branch & canalize to form ducts of glands Gland becomes divided into orbital & palpebral parts with

development of LPS Lacrimal gland do not function fully until 6wks. after birth

which explains why new born infants do not produce tears when crying

DEVELOPMENT: EXCRETORY SYSTEM

By the end of 5th wk., the nasolacrimal groove forms as a furrow between the nasal & maxillary prominence

In the floor of the groove, NLD develops from the linear thickening of ectoderm

Solid cord separates from adjacent ectoderm into mesenchyme forming NLD whose superior end becomes dilated to form the lacrimal sac

Canaliculi are formed from invaginated ectoderm canalization is usually complete around the time of

birth but failure of caudal end to completely canalize results in congenital NLD obstruction

MAIN LACRIMAL GLANDo Position: above and anterolateral to eyeballo Parts:∙Lateral horn of Levator aponeurosis indents the gland into:

Large orbital or superior part Small palpebral or inferior part

Lo- Orbital PartLp- Palpebral PartLA- Levator Aponeurosis

THE ORBITAL PART:

Location: lacrimal fossa at anterolateral area of orbital roof

Almond shaped Superior surface :convex ,lies in the fossa of

frontal bone Inferior surface:concave, lies above aponeurosis of

LPS,more laterally above the upper margin of lateral rectus muscle

CONT…

Anterior Border: Orbital septum

Posterior Border: Orbital fat, rounded & levels with posterior pole of eye

Medial extremity: rests on Levator

Lateral extremity: rests on Lateral rectus

THE PALPEBRAL PART:SIZE: about 1/3rd the size of orbital part, consists

of only 1or 2 lobules

LOCATION: below the aponeurosis of LPS and extend into the upper eyelid, lies mainly on the superior fornix, palpebral conjunctiva & superior palpebral muscles

RELATIONS: Superior surface: related to Aponeurosis of LPS Inferior surface: lateral part of superior fornix of

conjunctiva

LACRIMAL DUCTS:

8 – 12 in no.Empty into the superior cul-de-sac approx.

5mm above the lateral tarsal border after passing posterior to the aponeurosis

Ducts from orbital portion run through & join the ducts of palpebral lobe

ACCESSORY LACRIMAL GLANDS: Gland of Krause POSITION: between the superior fornix and tarsus as a

downward continuation of palpebral part. NUMBER: 42 in upper and 6-8 in lower fornix

Gland of Wolfring: present near upper border of superior tarsal plate & along the lower border of inferior tarsus

FUNCTION:Keep Cornea moist in conditions even if main lacrimal glands become non functional

STRUCTURE

Light Microscope: Lobulated tubulo-acinar gland with short branched tubules

lobules are size of pin head

Lobules are separated from one another by loose connective

tissue

Acini are seen as round or tube shaped masses of columnar cells with central lumen

Smallest intralobular ducts are lined with a layer of columnar or cuboidal cells and have myoepithelial cells at the periphery

Larger intralobular ducts have a two layered epithelial lining

CONT..Electron microscope: The epithelial secretory cells of acini are surrounded by a discontinuous

layer of myoepithelial cells and rest on basal lamina

The secretory cells are truncated-conical in shape,have microvilli on their apical or luminal surface

Narrow extension of acinar lumen can be seen between secretory cells known as canaliculi

CONT.. The secretory cell - basally located nucleus, rough

surface endoplasmic reticulum, golgi complex, mitochondria,free ribosomes, lipid droplets & vacuoles

Secretory granules - In apical & middle regions of cytoplasm round or ovoid either homogenous or finely granular vary in their electron density.

Secretory cells –mostly serous type but also of mucus

type Plasma cells of interstitial space – imp. Source of

immunoglobulins secreted into tears.

ARTERIAL SUPPLY: Lacrimal artery ,a branch of Ophthalmic artery which enters

its posterior border The infraorbital artery ,a branch of maxillary artery Sometimes a branch of transverse facial artery

VENOUS & LYMPHATIC DRAINAGE VENOUS DRAINAGE: into Superior ophthalmic vein via

the lacrimal vein

LYMPHATIC DRAINAGE: joins that of conjunctiva & into preauricular nodes

NERVE SUPPLY

Lacrimal gland receives both autonomic

& sensory nerve fibres

THE AUTONOMIC INNERVATION The parasympathetic secretomotor nerve supply is

derived from superior salivatory nucleus of facial nerve

The pre-ganglionic fibres reach pterygopalatine ganglion through facial nerve & its greater petrosal branch & through nerve of pterygoid canal

The post-ganglionic fibres then join the maxillary nerve, then into its zygomatic branch & zygomaticotemporal nerve.They reach the lacrimal gland within lacrimal nerve

CONT……. The sympathetic postganglionic fibres arise from

superior cervical sympathetic ganglion then travel in plexus of nerves around the internal carotid artery

They join deep petrosal nerve,nerve of pterygoid canal ,maxillary nerve, zygomatic nerve, zygomaticotemporal nerve and finally lacrimal nerve

The sensory fibres reach the lacrimal gland in the lacrimal nerve,a branch of ophthalmic division of trigeminal nerve

Ruskell describes a parasympathetic pathway through orbital branches of pterygopalatine ganglion which joins a retro-orbital plexus whose rami lacrimalis carry postganglionic fibres, both sympathetic & parasympathetic .

Postganglionic sympathetic fibres may reach the gland by several routes: along lacrimal artery, through deep petrosal nerve & through lacrimal nerve.

Has identified Sympathetic fibres in the adventitia of lacrimal artery &lacrimal nerve.

HIGHER NERVOUS CONTROL REFLEX CONTROL OF LACRIMAL SECRETION Excessive production of tears in emotional conditions Parasymapthetic lacrimatory nucleus of facial nerve

receive afferent fibres from hypothalamus through descending autonomic pathway in reticular formation

Excessive tear production in response to Olfactory stimuli Similar pathway connect olfactory system with lacrimatory nucleus

Reflex Lacrimation secondary to cornea or conjunctival irritation sensory nuclei of ophthalmic & maxillary division of trigeminal nerve are connected to lacrimatory nucleus by internuncial neurons

APPLIED ANATOMY

Lacrimal gland: Lacrimal ducts originate in orbital part

of gland then traverses the palpebral part of gland to open into superior fornix of conjunctival sac. So surgical removal of palpebral part destroy the drainage of whole gland

Surgical damage to palpebral part of lacrimal gland may occur during surgery as it lies within the upper lid

APPLIED ANATOMY Obstruction to secretion: openings of ducts

into conjunctival sac may be obstructed by scarring of conjunctiva like erythema multiforme, trachoma,chemical burns, ocular cicatricial pemphigoid (Causes of Dry eye)

Tumors of lacrimal gland: ●Benign(common)--mixed cell tumor

(pleomorphic adenoma),benign lymphoid hyperplasia.

●Malignant(less common)—maligant lymphoma, adenocarcinoma

APPLIED ANATOMY Dacryoadenitis: Inflammation of lacrimal gland Dacryops : cystic swelling in upper fornix due to

retention of secretion following blockade of one of the lacrimal ducts

Mikulicz Syndrome: symmetrical enlargement of lacrimal & salivary glands

LACRIMAL SECRETION The secretion are produced by acinar cells----

passes into the duct----the lining cells of duct modify its composition.

Final lacrimal secretion: Lysozyme IgA B-lysin

FUNCTIONS OF LACRIMAL SECRETION Keep corneal epithelium moist so that the surface epithelial

cells have a medium to live

First and major refractive surface of eye

Lubricate apposed surface of lids and eyeball so that it moves freely beneath the lids

Lysozyme(antibacterial enzyme)IgA(Immunoglobin)

B-lysin(bactericidal protein)

secretes substance which affects ocular surface by regulating epithelial cell turnover

LACRIMAL PUNCTA Entrance to the lacrimal drainage system 0.3 mm in diameter

2 small round or oval orifice situated on the papillae lacrimalis at the medial end of lid margin at the junction of its ciliated and non ciliated part

slightly inverted & lying against the globe

The punctum is in line with openings of tarsal glands

The conjunctiva surrounding the puncta is relatively avascular & thus paler than surrounding area

The upper punctum is slightly medial to lower punctum, they are 6 and 6.5mm medial to medial canthus respectively

CONT….

Puncta are visible only on everting eyelids upper punctum opens inferoposteriorly & lower punctum

opens superoposteriorly

Patency maintainance by surrounding dense tissue continued with adjacent tarsal plate

The fibres of orbicularis oculi press the puncta backward towards the lacus lacrimalis. In old age there will be muscle atropy, so there will be prominence of papilla

APPLIED ANATOMY Pallor of puncta is accentuated on applying

lateral tension to lower lid – aids in finding a stenosed puncta

In the elderly the puncta become more prominent due to the atrophy of orbicularis

LACRIMAL CANALICULI

Length: 10mm Parts: Vertical--2mm Horizontal—8mm Diameter : 0.5 mm

vertical part turns medially at a right angle to become horizontal part

Upper canaliculi runs medially & downward,the lower runs medially and upward, upper is shorter

At the junction of vertical &horizontal portions the canaliculi slightly dilate & form ampulla

CONT…. The canaliculi pierce the periorbita covering the lacrimal

sac then they enter the posterolateral surface of sac about 2.5mm below its apex either separately or united to form a common stem

In 90% of patients,upper & lower canaliculi combine to form a single common canaliculus that enters the lateral wall of sac

A small diverticulum of the sac (the sinus of Maier) is situated at the site of entry.

STRUCTURE The canalicular lining - non keratinised stratified

squamous epithelium, supported by elastic tissue

Very thin wall & elastic

CONT….. Also surrounded by fibres of pars lacrimalis of orbicularis

muscle which invert the punctum inwards the lower lid

The medial third are covered in front by two bands which connect the medial palpebral ligaments to tarsi, while behind is the lacrimal part of orbicularis oculi (horner’s muscle)

common canaliculus bends from posterior to an anterior direction behind the medial canthal tendon at an acute angle before entering sac, thus playing a role in blocking reflux

APPLIED ANATOMY Wall is so thin & elastic that it can be dilated to 3 times

normal diameter which is 0.5mm Lateral traction on the lids easily straightens them to

facilitate probing Should remember the direction & length of canaliculi

while passing probe Coloured fluid injected into a canaliculi can be seen

through the transluscent tissue of lid margins

LACRIMAL SAC Position: lacrimal fossa, formed by lacrimal

bone & frontal process of maxilla near the anterior border of medial orbital wall

Length:12mm,when distended 15 mm long & 5-6mm wide

sac closed above & open below &continuous with nasolacrimal duct below

It is enclosed by periorbita splits at posterior lacrimal crest – encloses the

sac – reunites at the anterior lacrimal crest- thus forms lacrimal fascia

CONT.. RELATIONS:Anteriorly: ●Medial palebral ligament ● Angular veinPosteriorly: ● Lacrimal part of

orbicularis oculi ● Orbital septum ● Check ligament of

medial rectusMedially: ● Upper half of sac –Anterior

ethmoidal air sinus ● Lower half of sac—Anterior

part of middle meatus Laterally: ● Skin, Part of Orbicularis

oculi ● Lacrimal fascia ● Few fibres of inferior oblique

STRUCTURE OF SAC

Wall consists of fibroelastic tissue & is lined by 2 layers of columnar cells, goblet cells are present.

is lined by Pseudostratified columnar epithelium & wall contains elastic & lymphoid tissue

APPLIED ANATOMY Dacryocystitis: An Inflammation of the lacrimal sac Anterior to medial palpebral ligament & lateral to facial

artery, angular vein crosses7- 8mm from the medial canthus. Incision for removal of sac should not be more than 2-3mm medial to medial canthus.

upper part of sac is covered anteriorly by medial palpebral ligament & covered below only by fibres of orbicularis so distension of sac with inflammatory exudate or pus will cause swelling below the lower border of ligament, abscess or fistula will point or open in this region

sudden strain on the ligament may tear the sac

CONT. A sheet of areolar tissue ascends laterally from inferior

edge of medial palpaebral ligament to blend with the Lacrimal facsia covering the fundus of sac,thus even relatively slight blows to the eyes may lead to swelling of the lids on blowing the nose.

NASOLACRIMAL DUCT Continuation of lacrimal sac neck to the

inferior meatus in the nose Length:15-18mm, 3mm in diameter

Direction: downward, backward & laterally at 15-25◦◦ Surface anatomy: a line from medial canthus to first

upper molar tooth

Position: lies in the canal formed by maxilla,lacrimal bone & lacrimal process of inferior concha

The wall of NLD is attached to periosteum lining the canal. Within the wall is a venous plexus which continues above with that of lacrimal sac & below with veins of nasal mucosa

opening of inferior orifice varies Structure: 2 layers of epithelium, superficial

layer composed of columnar cells & deeper cells being flatter

CONTD. It connects the lower end of sac with inferior

meatus of nose opening of inferior orifice varies greatly i.e. rounded or slit like

THE VALVES

Definition: folds of mucous membrane with no valvular function. Types

valve of Rosenmullervalve of Huschkevalve of Bochdalekvalve of Foltzvalve of medial palpebral ligament valve of Beraud or of Krausevalve of taillefervalve of Hansner

CONT…. The duct opens below into ant part outer wall of

inferior meatus of nose,the opening is guarded by a flap of mucus membrane called the valve of Hasner

The most constant is valve of Hasner(plica lacrimalis) at the lower end,a relic of fetal septum.

Well developed plica prevent a sudden blast of air entering the lacrimal sac while blowing the nose.

A fold of mucosa at the junction between common canaliculi & lacrimal sac is Valve of Rosenmuller, which prevent reflux of tear from sac back into the canaliculi,acts as one way valve

ARTERIAL SUPPLY TO LACRIMAL SAC AND NLD Medial palpebral branches of ophthalmic artery

Angular artery from facial

Infraorbital artery from maxillary

Sphenopalatine artery of maxillary

VENOUS , LYMPHATIC DRAINAGE & NERVE SUPPLY OF SAC AND NLDVenous drainageAbove: drains into angular &infraorbital vesselsBelow: into nasal veins

Lymphatics: pass to submandibular & deep cervical nodes

Nerve supply: infratrochlear branch of ophthalmic division of trigeminal nerve

Anterior superior alveolar nerve,a branch of maxillary div of trigeminal nerve

APPLIED ANATOMY Nasolacrimal duct: direction of NLD is

downward,backward and laterally. while passing probe ,it is inserted into punctum of upper lid directed vertically and medially into lacrimal sac then downward at right angle in NLD to inferior meatus. End of the probe should be visible within the nose

The distal portion of the duct bends medially in an irregular J-shape in many neonates but it tends to straighten out with growth

NLD is easily separable from bone in upper part but below it is closely adherent forming mucoperiosteum which facilitates spread of infection

PHYSIOLOGY OF TEAR PUMP Physiology of tear pump: Rosengren-Doane mechanism

70% of tear enter the lower canaliculus by capillarity and 30% enter the upper and some evaporate.

In young 10% & in elderly 20% or more ,tear eliminates by evaporation

Capacity of conjunctival sac :25-30 μl. When this volume exceeds then tearing occurs

ROSENGREN-DOANE MECHANISM

CONT..

Tear is produced by main & accessory lacrimal gland--- During the act of blinking, closure of eyelids occurs from lateral to

medial Brings fluid in the conjunctival sac medially

tear then enter the canaliculi by capillarity

blinking causes contraction of lacrimal part of orbicularis muscles which dilate the sac partly by pulling medial palpebral ligament which is attached anteriorly & partly by contracting orbicularis which is attached posteriorly

this creates negative pressure so that fluid is passed into sac from canaliculi

CONTD….

on opening the eye the muscle relax and the sac collapse & a positive pressure created which forces the tear passes from sac into NLD then into nose as a result of gravity

evaporation of tear in nose occur during inspiration and expiration of air.

TEAR FILM Layers:1)Thin superficial oily layer or lipid layer: 0.9-0.2 μm Produced by tarsal (meibomian)gland, sebaceous

gland(Zeis) & sweat gland(Moll)

2)Intermediate thick aqueous layer: 6.5-7.5 μmSecreted by Main lacrimal gland & accessory gland(Gland

of Krause and Wolfring)

3)Inner thin mucin layer: 0.5 μmSecreted by conjunctival goblet cells, glands of Manz &

Henle

FUNCTIONS Lipid layer: reduces the evaporation of underlying

aqueous layer

aqueous layer: contains lysozyme, immunoglobulin, B-lysin , is defence against invading organism

Mucin layer: allows equal distribution of tear film over the ocular surface

APPLIED ANATOMY Dry eye: Either due to Decreased tear

production or Increased tear evaporation Lacrimation: Excessive lacrimation occurs reflexly

as in photophobia, inflammations of conjunctiva, cornea, ciliary body

Epiphora: overflow of tears from the eye due to obstruction ,stenosis, punctal malposition or functional disorder of lacrimal passages

© devJuphal, Dolpa

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