8 Lacrimal System
What is the movement of tears?
From the lateral temporal portion of the eye to the medial canthus driven by a horizontal component of lid movement
Name these anatomical landmarks
1. Anterior cilary vein 2. Plica semilunaris 3. Caruncle 4. Anterior cilary artery 5. Lid margin 6. Mucocutaneous junction 7. Punctum
Name the structures of the tear drainage apparatus
1. Vertical caniculus 2. Ampulla 3. Horizontal caniculus 4. Caruncle 5. Lacrimal sac 6. Lacrimal bone 7. Valve of Krause (Beraud) 8. Nasolacrimal duct 9. Inferior Concha 10. Valve of Hasner 11. Inferior Meatus
What percent of people do not have their canaliculi join and thus have two openings to the lacrimal sac?
10%
Name the structures of the lacrimal gland acinus
1: Secretion duct 2: Basement membrane 3: Microvilli 4: Zonula occludens 5: Nerve fibers 6: Serous cell (dark granules) 7: Mucous cell (light granules) 8: Myoepithelial cell
What percentage of the tears is drained through the lacrimal system?
75-80% of tears are drained through the lacrimal system Roughly 25% evaporate
Where is the palpebral accessory lacrimal gland of Wolfring located? A. Eyelid B. Bulbar conjunctiva C. Upper fornix D. Lower fornix E. Medial canthus
A. Eyelid
Severance of which nerve will have the most dramatic effect on lacrimal secretion? A. Greater petrosal nerve B. Deep petrosal nerve C. Rami oculares D. Lacrimal nerve E. Zygomatic nerve
A. Greater petrosal nerve
Which is true for the lacrimal gland? A. It is housed in a depression in the frontal bone B. The myoepithelial cell in the acinus is innervated C. It reached full development during the eighth month of pregnancy D. Its palpebral lobe is located superior to the orbital lobe E. It is an apocrine gland
A. It is housed in a depression in the frontal bone
Which is true for the innervation of the lacrimal gland? A. Sympathetic innervation has little consequence on tear formation B. Sympathetic terminals are found close to serous cells in acini C. The lacrimal nerve provides a large number of fibers to the lacrimal gland D. Parasympathetic secretomotor fibers are mainly myelinated in the lacrimal gland E. The myoepithelial cells of the acinus receives a parasympathetic innervation
A. Sympathetic innervation has little consequence on tear formation
What neurotransmitters are involved in the parasympathetic innervation of the main acinar cells?
Acetylcholine and VIP
What is the secretory pathway for the lacrimal gland?
Acini > tubes > intermediate ducts > main ducts > superior fornix
Which pathway for the CN VII parasympathetic innervation of the lacrimal gland is correct?
B
The lacrimal gland is: A. Found in a small depression of the zygomatic bone near the orbital margin B. Fully developed only sometime after birth C. Divided into two lobes by the tendon of the superior oblique D. An apocrine type of gland E. Enclosed in a capsule which is pigmented in humans
B. Fully developed only sometime after birth
The greater petrosal nerve contains: A. Sympathetic fibers B. Pre-ganglionic secretomotor parasympathetic fibers C. Post-ganglionic secretomotor parasympathetic fibers D. Motor fibers to facial muscles E. Proprioceptive fibers from muscles of mastication
B. Pre-ganglionic secretomotor parasympathetic fibers
Acini are surrounded by:
Collagen fibers, capillaries, lymphatics, vascular, and nervous supply
Describe the lacrimal sac
Collects tears and is located in the medial wall of the orbit in the fossa for the lacrimal sac
Describe the ampulla
Connects vertical and horizontal portions of the canaliculus. Contracts during blinking to force tears to the lacrimal sac
The sympathetic distribution within the lacrimal gland includes: A. Acini B. Secreting ducts C. Serous cells D. Blood vessels E. The lacrimal gland lacks a sympathetic innervation
D. Blood vessels
Which statement is true regarding the parasympathetic innervation of the lacrimal gland? A. At some point the secretomotor fibers link up with the lacrimal nerve B. The post-ganglionic cell station is the geniculate ganglion C. The secretomotor fibers are found in the rami oculares D. Secretomotor fibers enter the orbit through the inferior orbital fissure E. the anastomosing branch between the zygomatic and lacrimal nerves contain postganglionic secretomotor fibers
D. Secretomotor fibers enter the orbit through the inferior orbital fissure
T/F the sympathetic system for the lacrimal gland is involved in tear secretion
False
T/F the zygomatic nerve and lacrimal nerve are connected by an anastamosing branch in the parasympathetic pathway
False
The lacrimal gland is parasympathetically innervated by the pterygopalatine ganglion using which two nervous pathways?
From the retro-orbital plexus Through the rami lacrimales
Describe the caruncle
Glandular tissue containing sweat glands and covered in fine hairs. Found nasal to the plica semilunaris
List the three factors involved in draining tears in order of importance
Gravity (4x tears drain from the inferior punctum relative to the superior punctum), blinking, capillary attraction
What three factors are involved in draining tears?
Gravity, capillary attraction, and blinking
Where are myoepithelial cells directly innervated?
In the intermediate and main ducts, but not in the myoepithelial cells in the acinus
Lacrimal gland secretions are ____tonic
Isotonic
What are the functions of the lacrimal gland?
It moistens, lubricates, and keeps the ocular surface free of irritants
What are the two levels of tear secretion?
Low order: during normal activities High order: during tearing and crying
Describe the punctum
Medially located opening where tears drain into the lacrimal sac. Superior and Inferior
What is the structure and function of #8 in the image?
Myoepithelial cells which contract during times of high lacrimation to help with secretion
Lacrimal gland secretions are rich in these 3 ions:
Na+ Cl- and K+
When does the lacrimal gland begin developing?
Near the third month; functional two weeks after birth
How is neuronal nitric oxide involved in the the lacrimal system?
Neuronal nitric oxide from cells in the pterygopalatine ganglion has been suggested to modulate tear production
What neurotransmitters are involved in the sympathetic innervation of the main acinar cells?
Norepinephrine and NPY
The lacrimal gland is innervated parasympathetically by____ and sympathetically by ____
Parasympathetic: CN VII - pterygopalatine ganglion Sympathetic: superior cervical ganglion
What does the plica semilunaris contain?
Sebaceous and sweat glands
What fibers do the rami lacrimales carry?
Secretomotor fibers
What type of secretions do the gland of Wolfring produce?
Serous secretions
What kind of gland is the lacrimal gland?
Serous tubuloracemose gland
How does blinking aid the movement of tears to the lacrimal sac?
Shortens the vertical and horizontal canaliculi and compresses the ampulla
Describe the canaliculus
Tear passages. The vertical portion moves from the punctum to the ampulla while the horizontal section moves from the ampulla to the lacrimal sac. The superior and inferior canaliculus join to form the common canaliculus before joining to the lacrimal sac.
What do secretomotor fibers innervate?
The acinus
Where are nerve terminals found in the lacrimal gland?
The acinus, blood vessels, and interstitium
Where is the Accessory lacrimal gland of Krause located?
The conjunctival fornix
Describe the nasolacrimal duct
The continuation of the lacrimal sac to the inferior meatus of the nose
Where is the lacrimal gland located?
The fossa for the lacrimal gland in the frontal bone
Describe the plica semilunaris
The human remnant of the third eyelid found in some animals located in the medial canthus.
What arteries contribute to the arterial supply of the lacrimal gland?
The lacrimal artery and the internal maxillary artery
What does the lacrimal system consist of?
The lacrimal gland, the two accessory lacrimal glands, and the drainage system
What veins contribute to the venous supply of the lacrimal gland?
The lacrimal vein
What divides the lacrimal gland?
The levator muscle divides the lacrimal gland into orbital and palpebral portions
Is NaCl rich fluid produced in the main acinar cells or the tear ducts?
The main acinar cells produce NaCl rich fluid KCl rich fluid is produced in the tear ducts
Which portion of the lacrimal gland is superior?
The orbital portion is larger, located superior to the palpebral portion, and drains into the palpebral portion through 12 ducts opening into the superior fornix
Where do sympathetic fibers for the lacrimal system originate?
The superior cervical ganglion
The retro-orbital plexus and the rami lacrimales exit through which fissures respectively?
The superior orbital fissure The inferior orbital fissure
Where is the Palpebral accessory lacrimal gland of Wolfring located?
The tarsal plate of the eyelid
The Crypts of Henle are likely to be: a. Separate glands b. Outlets for the the glands of Wolfring
b. Outlets for the palpebral accessory lacrimal gland of Wolfring
Lacrimal gland secretions consist of:
nutrients, growth factors, glycoproteins, and immunoglobulins
