Lacrimal apparatus Flashcards
(118 cards)
1
Q
What are the components of the lacrimal apparatus?
A
The lacrimal gland, lacrimal lake, lacrimal canaliculi, lacrimal sac, nasolacrimal duct
The nasolacrimal duct carries tears into the nasal cavity.
2
Q
What are the two parts of the lacrimal gland?
A
Orbital part, palpebral part
The palpebral part is about one-third the size of the orbital part.
3
Q
Where is the lacrimal gland located?
A
In the lacrimal fossa on the anterior and lateral part of the roof of the orbit
It lies just within the margin of the orbit.
4
Q
What shape is the larger orbital part of the lacrimal gland?
A
Almond-shaped
The superior surface of the orbital part is convex and related to bone.
5
Q
What is the function of the lacrimal gland?
A
Secretes tears
Tears are essential for keeping the eye moist and for protection.
6
Q
What is the relationship of the inferior surface of the lacrimal gland?
A
Lies above the aponeurosis of the levator palpebrae superioris
It also lies above the upper margin of the lateral rectus muscle.
7
Q
How many ducts from the orbital part of the lacrimal gland?
A
About 12 ducts
These ducts pass from the orbital part through the palpebral part to open into the superior conjunctival fornix. More ducts arise from palpabral part
8
Q
What type of structure is the lacrimal gland?
A
Lobulated tubulo-acinar structure
The lobules are separated from one another by loose connective tissue.
9
Q
What is the size comparison between the orbital part and the palpebral part of the lacrimal gland?
A
The palpebral part is about one-third the size of the orbital part
This indicates a significant difference in their respective sizes.
10
Q
Where are accessory lacrimal glands found and what is their significance?
A
Scattered around the conjunctival sac. Keep the cornea moist if the main gland is nonfunctional
11
Q
Fill in the blank: The lacrimal gland has no definite _______.
A
capsule
The periorbita is believed to split and enclose the gland.
12
Q
True or False: The lacrimal gland is enclosed by a definite capsule.
A
False
The gland is believed to be enclosed by the split of the periorbita.
13
Q
What type of cells line the acini of the lacrimal gland? What shape are they in cross section?
A
Columnar cells - “truncated-conical” shape
The acini appear as round or tube-shaped masses with central lumens.
14
Q
What is seen on apical/luminal surface of secretory columnar cells of acini of lacrimal gland?
A
Microvilli
15
Q
How are sectretory acinar calls (lacirmal gland) attached together?
A
Junctional complexes + scattered desomosomes on lateral cell membranes
16
Q
What is the primary function of the lacrimal gland?
A
To produce tears and keep the eye moist.
17
Q
Where is the nucleus found in the secretory acinar cells (columnar) of the lacrimal gland?
A
Basally
18
Q
Which organelles are the secretory cells of the lacrimal gland acini rich in?
Extra q: what type of vaculoles, what shape and what binds them?
A
1) rough endoplasmic reticulum
2) Golgi apparatus
3) mitochondria
4) free ribosomes
5) lipid droplets
6) vacuoles - serous and mucous (ovoid in shape and membrane bound)
19
Q
Where in the secretory acinar cells of the lacrimal gland are sectretory granules mostly found?
A
middle and apical regions
20
Q
What type of cell surrounds the secretory epithelial cells of the acini? IS this continuous
A
Discontinuous layer of myoepithelial cells that sit on basemement membrane
21
Q
Structure of small vs large intra-lobular ducts of lacrimal gland
A
Small = lined by single layer of columar cells, myoepithelium at periphery
Large = two-layered epithelial lining
22
Q
What is the anterior border of the lacrimal gland related to?
A
Related to the orbital septum
The posterior border is in contact with orbital fat.
23
Q
Which nucleus provides parasymphatic secretorymotor innervation to the lacrimal gland?
A
Lacrimatory nucleus of facial nerve.
24
Q
What is the main blood supply of the lacrimal gland?
Which other vessel sometimes supplies it?
A
Lacrimal artery (branch of ophthalmic artery)
Sometimes infraorbital artery (branch of maxillary artery, from external carotid)
25
What is the venous drainage of the lacrimal gland?
ophthalmic vein
26
Describe the lymphatic drainage of the lacrimal gland
Joins conjunctival lymphatic drainage --> superficial parotid lymph nodes
27
Two types of nerve supply to lacrimal gland
autonomic (sympathetic + parasympathetic) and sensory
28
Describe the **pre-ganglionic** parasympathetic secretorymotor supply of the lacrimal gland
Lacrimatory nucleus facial nerve --> nervus intermedius --> great petrosal branch of nervus intermesius --> nerve of the pterygoid canal --> pterygopalatine ganglion (aka spehnopalatine ganglion)
29
Describe the **post-ganglionic** parasympathetic secretorymotor supply of the lacrimal gland
From pterygoplatine nucleus, parasympathetic fibres join the **maxillary nerve,** pass into its **zygomatic branch ** (V2) and **zygomaticotemporal nerve** (V2) , then reach the lacrimal gland via the **lacrimal nerve**
30
Where do the first order paraympathitic nerves supplying the lacrimal gland synapse?
Pterygopalatine ganglion (aka sphenopalaltine ganglion)
31
True or False: The larger intralobular ducts of the lacrimal gland have a single-layered epithelial lining.
False.
32
Fill in the blank: The lacrimal nerve is a branch of the _______. It is responsible for....
a) Ophthalmic division of trigeminal nerve (V2).
b) Providing sensation to lacrimal gland
33
What are canaliculi?
Narrow extensions of the acinar lumen between adjacent secretory cells
34
What characterizes the secretory granules in secretory cells?
They are round or ovoid and membrane-bound
35
Where is the parasympathetic secretomotor nerve supply for the lacrimal gland derived from?
The lacrimatory nucleus of the facial nerve
36
From where do the sympathetic postganglionic fibers arise?
Superior cervical sympathetic ganglion
37
What is the pathway of sympathetic fibers to the lacrimal gland?
Travel in the plexus around the internal carotid artery --> deep petrosal nerve --> **nerve of the pterygoid canal --> maxillary nerve --> zygomatic nerve --> zygomaticotemporal nerve --> lacrimal nerve**
| Bold = common pathway
## Footnote
Controls tear production AND blood flow to gland (obvs :p)
38
Draw the sympathetic and parasympathetic nerve supply to the lacrimal gland
39
Which nerve carries sensory fibers to the lacrimal gland?
Lacrimal nerve, a branch of the ophthalmic division of the trigeminal nerve
40
What is believed to provide afferent fibers to the parasympathetic lacrimatory nucleus?
Hypothalamus through descending autonomic pathways in the reticular formation
| Explains emotional tears
41
Describe the pathway that stimulates tears seconary to irritation of cornea/conjunctiva
Afferent stimuli along ophthalmic and maxillary division of trigeminal nerve --> internuncial neurons --> lacrimatory nucleus --> parasympathetic pathway
42
What components are found in the final watery secretion (tears)?
* Lysozyme (antibacterial enzyme)
* IgA (immunoglobulin)
* Beta-lysin (bactericidal protein)
| Acini produce tears, cells in ducts modify composition
43
What is the main function of tears?
Keep the corneal epithelium moist + Lubricate the front of the eyeball to allow movement
44
Which glands also contribute to lubrication of the eye?
Meibomian glands
45
Fill in the blank: The lacrimal gland secretes substances that affect the ocular surface by regulating _______.
epithelial cell turnover
46
True or False: Hormones, particularly androgens, suppress lacrimal secretion.
False
47
What is the punctum lacrimale?
A small round or oval orifice at the summit of the papilla lacrimalis
## Footnote
Located at the medial end of the lid margin, in line with the openings of the tarsal glands
48
Where is the punctum lacrimale located in relation to the tarsal glands?
In line with the openings of the tarsal glands
## Footnote
The conjunctiva surrounding the punctum appears pale red due to being somewhat avascular
49
How does the upper punctum differ from the lower punctum in orientation?
The upper punctum looks downward and backward; the lower punctum looks upward and backward
## Footnote
The upper punctum is slightly medial to that of the lower lid
50
What is the length of each lacrimal canaliculus?
About 10 mm long
## Footnote
Each canaliculus consists of a vertical and a horizontal portion
51
Describe the path of the lacrimal canaliculi.
They begin at the puncta, pass vertically from the lid margin, then turn sharply medially
## Footnote
The upper canaliculus runs medially and downward; the lower one runs medially and upward
52
What forms at the junction of the vertical and horizontal portions of the canaliculi?
An ampulla
## Footnote
The canaliculi are slightly dilated at this junction
53
Where do the canaliculi enter the lacrimal sac?
At the lateral surface of the sac about 2.5 mm below its apex
## Footnote
They may be separate or united to form a common stem at the point of entrance
54
What is the sinus of Maier?
A small diverticulum of the lacrimal sac
## Footnote
Situated at the site of entry of the canaliculi into the sac
55
What anatomical structure do the canaliculi lie behind?
The medial palpebral ligament
## Footnote
They are surrounded by fibers of the pars lacrimalis of the orbicularis oculi muscle
56
What type of epithelium lines the walls of the canaliculi?
Stratified squamous epithelium
## Footnote
The walls are thin and elastic
57
True or False: During blinking, the canaliculi are pulled laterally and lengthened.
False
## Footnote
The canaliculi are pulled medially, shortened, and compressed by the lacrimal part of the orbicularis oculi
58
Fill in the blank: The pumping action during blinking assists in the _______ of the lacrimal sac.
dilatation
## Footnote
This action is caused by the lacrimal part of the orbicularis oculi
59
What is the length of the lacrimal sac?
About 12 mm long
60
Where is the lacrimal sac located?
In the lacrimal fossa - lacrimal bone and the frontal process of the maxilla
61
What does the lacrimal sac receive on its lateral side?
The openings of the lacrimal canaliculi
62
What encloses the lacrimal sac? What is it formed by?
What lies between it and the lacrimal sac?
The lacrimal fascia - formed by perirobita (ie periostium of orbital bones)
Venous plexus lies between lacrimal sac and lacrimal fascia
63
What is the relationship of the lacrimal fascia to the lacrimal bone and maxilla?
Attached behind to the posterior lacrimal crest of the lacrimal bone and in front to the anterior lacrimal crest of the maxilla
64
What type of cells form the lacrimal sac?
Fibroelastic tissue wall lined by two layers of columnar cells + some goblet cells
65
What is the length of the nasolacrimal duct?
About 18 mm long
66
Where does the nasolacrimal duct connect?
The lower end of the lacrimal sac with the inferior meatus of the nose
67
What is the direction of the nasolacrimal duct?
Downward, backward, and lateral
68
What forms the bony nasolacrimal canal?
The maxilla, the lacrimal bone, and the inferior nasal concha
| nasolacrimal duct passes throigh here
69
What is the relationship between the nasolacrimal duct and the periosteum?
The wall of the duct is closely attached to the periosteum lining the canal
70
What type of epithelium lines the nasolacrimal duct?
Two layers of columnar epithelium, some of which are ciliated
71
What guards the opening of the nasolacrimal duct?
A flap of mucous membrane called the plica lacrimalis
72
What is the function of the plica lacrimalis?
Prevents air from entering the lacrimal sac when blowing the nose
73
True or False: The nasolacrimal duct opens below into the anterior part of the inferior meatus of the nose.
True
74
Where is the nasolacrimal duct narrowest?
In the middle
75
What is related medially to the upper half of the lacrimal sac?
The anterior ethmoidal sinuses
76
What is related medially to the lower half of the lacrimal sac?
The anterior part of the middle meatus of the nose
77
What vein crosses the anterior surface of the medial palpebral ligament?
Where does it cross it?
The angular vein
8mm medial to the medial canthus => important anterior relation to lacrimal sac
78
What forms the angular vein?
What does the angular vein later become?
The union of the supratrochlear and supraorbital veins
Later becomes facial vein
79
What are the sources of arterial supply to the lacrimal sac and the nasolacrimal duct?
Branches of:
- the medial palpebral (of the ophthalmic)
- facial
- infraorbital (from the maxillary)
- sphenopalatine arteries (of the maxillary)
## Footnote
These arteries provide the necessary blood supply to the lacrimal structures.
80
Which nerves supply the lacrimal sac and nasolacrimal duct?
- Infratrochlear branch of V1
- Anterior superior alveolar nerve of V2
## Footnote
These nerves are responsible for sensory innervation to the lacrimal apparatus.
81
Where does normal tear formation occur?
Accessory lacrimal glands scattered throughout the conjunctival sac.
## Footnote
These glands secrete tears continuously to maintain moisture.
82
What triggers excessive tear production, such as during crying?
Reflex nervous stimulation of the main lacrimal gland.
## Footnote
This stimulation can be a response to emotional or physical stimuli.
83
What happens to the tears produced under normal conditions?
They just exceed that lost by evaporation and the remainder passes down the nasolacrimal duct.
## Footnote
This balance is crucial for maintaining tear volume.
84
Where does tear fluid accumulate in the conjunctival sac?
In the conjunctival fornices and the lacus lacrimalis.
## Footnote
These areas are important for tear distribution and drainage.
85
How does the superior marginal strip of tear fluid behave?
It overlaps the cornea for about 1 mm as a straight line.
## Footnote
This strip is influenced by eye movements and eyelid positioning.
86
How does the inferior marginal strip of tear fluid behave?
It rises up over the cornea for about 1 mm due to surface tension.
## Footnote
This strip also plays a role in tear distribution.
87
What is the capacity of the conjunctival sac?
About 25 to 30 mL.
## Footnote
Understanding this capacity is important for diagnosing conditions related to tear production.
88
What occurs when the volume of tears secreted exceeds the conjunctival sac's capacity?
Clinical tearing results.
## Footnote
This can be a sign of underlying issues with tear production or drainage.
89
What are the main sources of tear production?
Lacrimal gland and accessory lacrimal glands
## Footnote
These glands produce the fluid that enters the conjunctival sac.
90
How does tear fluid travel across the conjunctival sac?
Capillarity and blinking movements of the eyelids
## Footnote
These physical influences help move the tear fluid across the sac.
91
What prevents tears from pouring over the cornea under normal conditions?
The physical structure of the eye and blinking
## Footnote
Tears are wiped across the cornea to prevent desiccation.
92
What role do the tarsal glands play in tear drainage?
They produce an oily secretion that prevents overflow of tears
## Footnote
This secretion helps maintain the tear film and prevents excessive tear flow.
93
What happens to tears during exaggerated tear production, such as crying?
Tears flow across the cornea and escape down the cheek
## Footnote
This interferes with the cornea's function as an efficient lens.
94
What occurs to the conjunctival sac during sleep?
The conjunctival sac is closed
## Footnote
The lid margins are in apposition, preventing tear loss.
95
How are tears drained from the lacus lacrimalis?
Through the canaliculi
## Footnote
The puncta of the canaliculi maintain contact with the lacus lacrimalis.
96
What mechanism aids the entry of tear fluid into the canaliculi when eye is closed?
Capillarity
## Footnote
The tone of the orbicularis oculi helps maintain the position for drainage.
97
What is referred to as the pumping action of the orbicularis oculi?
The contraction of the lacrimal part that compresses the canaliculi
*Orbicularis oculi = attached to medial palpebral ligament, which is attached to lacrimal sac by fascia => contraction lacrimal part of orbicularis oculi --> shortening and compression of canaliculi + DILATION of lacrimal sac => tears sucked into tear sac.*
## Footnote
This action causes dilatation of the lacrimal sac, sucking tears into it.
98
How do tears pass down the nasolacrimal duct?
Gravity and evaporation of fluid
## Footnote
Air movement during breathing also assists in this process.
99
What are the three layers of the precorneal tear film?
1) Oily layer 2) Watery layer 3) Mucin layer
## Footnote
Each layer has distinct properties and functions in maintaining eye health.
100
What is the thickness range of the three layers of the tear film?
- oily layer 0.9 to 0.2 microns
- watery layer 6.5-7.5 microns
- mucin layer 0.5 microns
## Footnote
This layer is primarily produced by the tarsal glands.
101
What is the primary function of the watery layer of the tear film?
Defense against invading organisms
**It contains lysozyme, immunoglobulin, and beta-lysin.**
102
What does the mucin layer do in the tear film?
Wets the microvilli of the corneal epithelium
## Footnote
This layer is secreted by conjunctival goblet cells.
103
What happens if the palpebral part of the lacrimal gland is surgically removed?
Destroys the drainage of the whole gland
| because 12 ducts of orbital portion pass through palpebral portion
## Footnote
The palpebral part is crucial for tear drainage.
104
What conditions can obstruct the openings of the lacrimal ducts?
Scarring from erythema multiforme, ocular cicatricial pemphigoid, trachoma, and chemical burns
## Footnote
These conditions can lead to blockage of tear drainage.
105
What type of tumors are most commonly associated with the lacrimal gland?
Benign tumors
## Footnote
Examples include mixed cell tumors and benign lymphoid hyperplasia. Malignant = lymphoma + adenocarcinoma, erode lacrimal fossa --> PAIN
106
What symptoms are associated with malignant tumors of the lacrimal gland?
Early erosion of the lacrimal fossa and severe pain
## Footnote
Malignant tumors are less common but more aggressive.
107
What causes dry eyes related to the lacrimal gland?
Deficiency of the watery component of tears or mucin component
## Footnote
Conditions include disease of the main and accessory lacrimal glands and goblet cell dysfunction.
108
How can the outflow of tears in dry eyes be restricted?
By reducing the size of the punctum lacrimale
## Footnote
Techniques include using plugs, cautery, or laser.
109
Where is the lacrimal sac located?
In the lacrimal fossa in the anterior part of the medial wall of the orbit
## Footnote
The sac is covered by the medial palpebral ligament.
110
What occurs if the lacrimal sac is distended with inflammatory exudate?
Causes visible swelling below the lower border of the medial palpebral ligament
## Footnote
This can indicate an abscess or fistula in the region.
111
What must be avoided when making an incision close to the medial canthus of the eye?
The angular vein
## Footnote
The angular vein is the upper part of the facial vein and is formed by the union of the supratrochlear and supraorbital veins.
112
Where is the angular vein located in relation to the medial canthus?
About 8 mm medial to the medial canthus
## Footnote
It descends across the anterior surface of the medial palpebral ligament lateral to the facial artery.
113
What may need to be divided to fully expose the lacrimal sac?
The medial palpebral ligament
## Footnote
This division may be necessary to avoid complications during surgery.
114
What is a potential complication when approaching the lacrimal sac?
Bleeding from the venous plexus around the lacrimal sac
## Footnote
This bleeding may be troublesome during surgical procedures.
115
How can the lacrimal sac be approached besides the anterior incision?
Via endoscopy through the nasal cavity
## Footnote
This method provides an alternative route for accessing the sac.
116
What is the orientation of the nasolacrimal duct when passing a probe?
Downward, backward, and laterally
## Footnote
The duct is approximately 18 mm long.
117
Where does the nasolacrimal duct open?
Into the anterior part of the inferior meatus of the nose
## Footnote
This opening is crucial for drainage.
118
What is the correct technique for inserting a probe into the nasolacrimal duct?
Insert into the punctum of the upper lid, direct vertically, then medially into the lacrimal sac, and turn downward at right angles
## Footnote
The end of the probe should be visible within the nose after correct insertion.
