anatomy And Physiology of lacrimal secretions

Diagnosis, Management, and Surgery by Adam J. Cohen, Michael Mercandetti & Brian G. Brazzo.  The dry eye , a practical approach by Sudi Patel & Kenny J Blades.  Jack J Kanski’s clinical ophthalmology  Clinical Anatomy of the Eye by Richard S. Snell & Michael A. Lemp.
3.  It is concerned with the tear formation & transport.  Lacrimal passage includes : Lacrimal gland Conjunctival sac Lacrimal puncta Lacrimal canaliculi Lacrimal sac Nasolacrimal duct
4.  The following components of the lacrimal apparatus are discussed :  Embryology  Osteology  Secretory system  Excretory system  Physiology
5.  Ectodermal origin  Solid epithelial buds(first 2 months)  Supero

1. Presented by
Dr Rohit Rao

2. Wolff'sAnatomy of the Eye and Orbit.
Adler'sPhysiology of the Eye .
The Lacrimal System
Diagnosis, Management, and Surgery by Adam J.
Cohen, Michael Mercandetti & Brian G. Brazzo.
The dry eye , a practical approach by SudiPatel
& Kenny J Blades.
Jack J Kanski’sclinical ophthalmology
Clinical Anatomy of the Eye by Richard S. Snell
& Michael A. Lemp.

4. It is concerned with the tear formation &
transport.
Lacrimal passage includes :
Lacrimal
gland
Conjunctival
sac
Lacrimal
puncta
Lacrimal
canaliculi
Lacrimal
sac
Nasolacrimal
duct

6. The following components of the lacrimal
apparatus are discussed :
Embryology
Osteology
Secretory system
Excretory system
Physiology

7. Ectodermal origin
Solid epithelial buds(first 2 months)
Superolateral conjunctival fornix.

8. Lacrimal sac and nasolacrimal duct : ectoderm
of the naso-optic furrow or nasolacrimal furrow
The ectoderm of the furrow buries and forms a
solid cord .
Canalization : begins at 4 months and may
continue after birth.

10. The lacrimal sac fossa is a depression in the
inferomedial orbital rim,
Maxillary and lacrimal bones.
Bordered by the anterior lacrimal crest
(maxillary bone) & posterior lacrimal crest
(lacrimal bone).
The fossa is approximately 16-mm high, 4-to 9-
mm wide, and 2-mm deep.

12. The medial orbital wall : Frontal process of
maxilla, lacrimal , ethmoid , lesser wing of
sphenoid bone.
The frontoethmoidal suture is important in
lacrimal surgery
It marks the roof of the ethmoid sinus. Bony
dissection superior to this suture may expose
the dura of the cranial cavity.

13. The nasolacrimal canal originates at base of
lacrimal fossa.
Formed by the maxillary bone laterally and the
lacrimal and inferior turbinate bones medially.
The width of superior opening is 4–6 mm.
The duct courses posteriorly and laterally in
the bone for 12 mm to drain into the inferior
meatus of the nasal cavity.

14. It includes lacrimal gland, accessory glands
Lacrimal gland is above & anterolateral to globe.
Secretes tears into superior fornix.
Tears moisten & lubricates the : cornea
, conjunctiva.
It contributes 43D of 50D of refractive power of
eye .

15. It consists of
Large Orbital Part
Smaller Palpebral Part
Lateral expansion of levator separates the parts

16. Paired almond-shapedglands.
It is present in a fossa on the anterolateral area
of orbit
It has 2 surfaces, 2 borders, 2 extremities
Superior surface
Frontal bone
Inferior surface
Levator palpebrae superioris & lateral rectus

17. Anterior border
Septum orbitale
Posterior border
Contact with orbital fat , level with posterior
pole.
Lateral extremity
Rest on lateral rectus
Medial extremity
On levator

18. 1/3
rd
size of orbital part
Superior fornix , seen on lid eversion.
It is situated upon the course of ducts
Related to levator superiorly, inferiorly to
superior fornix
Posteriorly it continues with orbital part.

19. Are small, compound, branched, tubular glands
Located in the middle of lid (Wolfring glands)
or superior & inferior fornices (Krause glands).
Ectopic portions of lacrimal gland tissue.

20. It is with connective tissue coat and excretory
duct.
The excretory duct splits & form intralobular
ducts, connected to secretory glandular
epithelia.
Secretory epithelia have elongated tubules.
True acini are absent.

23. Tubuloacinar with short, branched tubules
Acini are pyramidal secretory cells with apex
towards a central lumen .
Myoepithelial cells., contractile & aid the
secretion

24. In acinus, secretory cells are joined by
junctional complexes
Apical microvilli extend into the lumen
Nucleus and rough endoplasmic reticulum are
basal in the cells.
Abundant secretory granules, at apex .

26. The ducts have two or three cell layers and
microvilli at luminal surface.
Plasma cells of the interstitial space are an
important source of immunoglobulins secrete
IgA(and fewer lgG, lgM, IgE)

28. Artery supply : Lacrimal artery , branch of
ophthalmic artery.
Venous drainages : Ophthalmic Vein.
Lymphatic drainage : Joins that of conjunctiva &
drain into the preauricular lymph nodes.

29. Sensory nerve supply : lacrimal nerve
, branch of ophthalmic division of Vth nerve
Sympathetic nerve supply : carotid plexus
Secretomotor fibers : superior salivary
nucleus

32. A small, round or oval orifice on the
elevation, the papilla lacrimalis.
At medial end of lid margin at the junction of its
ciliated and non-ciliated parts.
Upper punctum medial to lower, from the
medial canthus being 6 and 6.5 mm.
The upper punctum opens inferoposteriorly, the
lower superoposteriorly.

34. First vertical and then horizontal
Vertical part is 2 mm & turns medially at right-angle
to become horizontal 8 mm
At angle -dilatation or ampulla.
The canaliculi pierce the fascia (i.e. the periorbita
covering the lacrimal sac) separately,
Uniting to enter lacrimal sac.
Stratified squamous epithelium supported by
elastic tissue.

35. Lacrimal fossa, formed by lacrimal bone and
frontal process of maxilla .
The sac, closed above and open below, is
continuous with the nasolacrimal duct.
The sac is enclosed by a periorbita, splits &form
the lacrimal fascia .

36. Relations
Medial : periorbita and bone, arc of ethmoid
sinuses.
Lateral : skin, orbicularis oculi, and lacrimal
fascia.
Anterior: medial palpebral ligament and
angular vein.
Posterior : lacrimal fascia and muscle

37. The nasolacrimal duct, continuation of lacrimal
sac to the inferior meatus.
15 mm.
It lies in a canal formed by the maxilla, lacrimal
bone and lacrimal process of inferior concha.
It descends posterolaterally, a surface indication
a line from medial canthus to first upper molar.

38. The valves
They are folds of mucous
membrane with no
valvular function.
The most constant is the
'valve' of Hasner at the
lower end.
It prevents sudden blast of
air (when blowing the
nose) from entenng the
lacrimal sac.

39. Structure
Double-layered Epithelium
The superficial layer composed of columnar
cells, the deeper cells being flatter.
The membranous wall of the sac is of
fibroelastic tissue, the elastic element being
continued around the canaliculi.

40. Around the nasolacrimal duct is plexus of
vessels, forming erectile tissue like that on the
inferior concha.
Engorgement of these vessel obstruct the duct.
The course of the lacrimal sac and duct can be
demonstrated by dacryocystography

41. Vessels
Artery supply : palpebral branches of the
ophthalmic, angular and infraorbital arteries and nasal
branch of the sphenopalatine.
Venous drainages : Angular and infraorbital vessels
above, below into the nasal veins
Lymphatic drainage: submandibular and deep cervical
nodes.
Nerves
Infratrochlear and anterior superior alveolar nerves.

42. The tear film overlays corneal and conjunctival
epithelia.
Tears produced by the ocular surface epithelia
and adnexa.
Thickness of up to 40 µm,
Volume of tears covering the ocular surface
range from 2.74 ±2.0µL to 7 µL

43. For mucous and aqueous layers, secretion is
regulated by neural reflexes.
For the lipid layer, the blink itself regulates
release of pre-secreted meibomian gland .
Tear secretion is balanced by drainage and
evaporation.
Drainage is regulated by neural reflexes ,causing
vasodilation and vasoconstriction of blood sinus.
Evaporation depends blink rate and
temperature, humidity, and wind speed.

44. To protect the cornea from drying;
To maintain the refractive power of the cornea;
To defend against eye infection;
To allow gas to move between the air and the
avascular cornea;
To support corneal dehydration (assisted by the
tear film hyperosmolality).

45. Consists of four layers
Glycocalyx
Mucous layer
Aqueous layer.
Lipid layers

47. Structure
The glycocalyx is a network of polysaccharides that project
from cellular surfaces.
Mucins are classified into secreted and membrane-spanning
mucin.
Secreted mucins are either gel-forming or small soluble
Function
The membrane-spanning mucins function to hydrate the
ocular surface and serve as a barrier to pathogens.
Membrane-spanning mucins appear to be altered in dry eye

48. Structure
The mucous layer backbone is the gel-forming
mucin , synthesized and secreted by conjunctival
goblet cells.
Function
To resistance of the eye to infection by providing
protection against microorganisms.
Mucins serve as wetting agents that keep the apical
epithelia hydrated.

49. Lacrimal gland produce aqueous layer.
Other ocular surface epithelia also contribute to the
aqueous layer, eg. conjunctiva, accessory lacrimal
glands
7µm thick.
Without the lubrication , the shearing forces
produced on blinking will cause accumulative
ocular surface damage.

50. Composed of water, with many solutes, including
dissolved mucins, electrolyte sand proteins.
The osmotic pressure : concentrations of
sodium, potassium and chloride ions.
The tear film’s osmotic pressure is important in
the control of cornea–tear film water flux.
Bicarbonate and carbonate : pH
buffering, maintaining the pH at 7.3–7.6 when the
eyes open & 6.8 eyes closed.

51. Aqueous layer function
Aqueous deficiency dry eye.
Protection from bacterial infection
Reflex secretion washes away noxious
substances.
Protects against changes in pH.

52. Meibomian glands, modified sebaceous glands, that
line the upper and lower eyelids.
Meibomian gland lipids are stored in vesicles.
The secretory product contains a complex mixture
of lipids and proteins and is termed meibum.
Meibum is released on to the ocular surface in small
amounts with each blink.
0.1m in thickness

53. Function
Hydrophobic barrier to prevent tear overflow.
The meibomforms a water-tight seal of the
apposed lid margins during sleep.
Reduce tear evaporation .
Lipids enhance the stability of the tear
film and provide a smooth optical.

55. Conjunctival fornices, preocular tear film, and
marginal tear strips.
Marginal tear strips are wedge shaped tear
menisci, borders of upper and lower lids.
Apposed lacrimal puncta dip into marginal
strip of tears
Anterior limit of the marginal strip is the
mucocutaneousjunction of the lid,

57. Tears are lost from the conjunctiva sac by
absorption, evaporation, and nasolacrimal
system.
This is related to the size of the palpebral
aperture, the blink rate, ambient temperature
and humidity.

58. Tears flow
the upper and lower marginal strips →upper and
lower canaliculi (capillarity+suction)
Eyes close
Pretarsalorbicularis oculi compresses the
ampullae+ shortens and compresses
canaliculi+punctamedially.
Lacrimal part of the orbicularis oculi, contracts →
compresses the sac,(positive pressure) tears →
nasolacrimal duct →nose.
Eyes open
Muscles relax →canaliculi and sac expand(negative
pressure)+capillarity= tears into sac.