lacrimal gland

Describe the nasolacrimal canal. What passes through the canal and is this structure the same length as the canal?What is the relationship of the canal to the maxillary bone and maxillary sinus?

1. Nasolacrimal canal is the bony structure that surrounds the nasolacrimal duct. It is a vertical opening with the bones of the scull. The nasolacrimal duct first 12.5 mm is housed by the canal and the remaining 5 mm of the duct extends into the inf meatus. If you drill laterally thru the nasolacrimal canal you will reach the maxillary sinus.

Discuss the role of the eyelids for the distribution of the tears from the ocular surface to the lacrimal lake

1. Upper eyelid moves tears vertically to tear strips. Lower lid moves tears horizontally towards lacrimal lake. Ciliary muscle of Riolan is important for keep the eyelid against the cornea or lid globe congruity. This helps to spread the tears during the blink. List the overview of the drainage of tears from the lacrimal lake to the inferior meatus of the nose.

What separates the lacrimal gland into the orbital and palpebral lobe?

Aponeurosis of the levator

1. What glands produce basal tears or are considered basic secretors? What gland produces reflex tears?

Basal or Basic secretors: Accessory lacrimal glands, meibomian glands and glands of Zeis, goblet Cells Reflex secretor: Main lacrimal gland

1. Describe the anatomy and microanatomy of the nasolacrimal duct. What is the clinical significance of the venous plexus that surrounds the duct?

Downward continuation of sac Microanatomy Same as the Sac Mucous membrane Modified respiratory epithelium Columnar cells with goblet cells Connects sac with inferior meatus When the venous plexus that surrounds the duct becomes engorged from inflammation, it narrows the duct and causes tearing. This can be treated with vasoconstrictors or decongestants

1. Describe the histology of the serous acini of the lacrimal gland. What is the secretion of the acini? What is the function of the myoepithelial cells?

Exocrine gland consists of ducts and acini. Serous acini with low cylindrical cells that are surrounded by myoepithelial cells. The myoepithelial cells have the ability to contract and squeeze the contents of the acinus into the lumen. The secretion of the lacrimal acinus is a serous secretion of water, electrolytes and some proteins.

1. Describe the microanatomy and function of the lacrimal puncta.

Function: collection of tears from lacrimal lake opening into canalicular system Microanatomy (allows for flexibility): Lining - stratified squamous epithelium Internally - connective tissue fine elastic fibrils

1. Discuss the accessory lacrimal glands. What is their function?

Glands of Krause - in fornix of upper and lower eyelid - a lot more in upper eyelid - greatest number of these accessory lacrimal glands (around 26-48 total upper and lower lid) Glands of Wolfring - found at the border of the tarsal plate - lower number (total 4 upper and lower lid - much less

1. Describe the Valve of Hasner (Plica lacrimalis). What is its function?

Guards inferior opening of duct Flap of mucous membrane

1. Describe the blood supply, venous drainage and lymph drainage of the lacrimal gland.

Internal carotid artery -> ophthalmic artery -> lacrimal artery to the gland Lacrimal vein -> ophthalmic vein -> superior ophthalmic vein -> cavernous sinus Lymph drains to the preauricular nodes

1. Thru what structures will the tears pass?

Lacrimal Puncta -> Canaliculi -> Lacrimal Sac -> Lacrimal Duct -> Inferior Meatus of Nose

1. Describe the lacrimal fossa. What structure "sits" in the lacrimal fossa?

Lacrimal fossa is formed by the frontal process of the maxillary bone anteriorly and the lacrimal bone posteriorly. The lacrimal sac "sits" in the lacrimal fossa.

Describe the sensory innervation of the lacrimal gland

Lacrimal gland -> lacrimal nerve -> ophthalmic division of trigeminal (V-1) -> CNS (PAIN)

1. Describe the lacrimal gland parasympathetic innervation (mainly for stimulation of reflex tearing).

Lacrimal nucleus -> nervous intermedius of VII - greater superficial petrosal nerve -> nerve of pterygoid canal -> ptergopalatine ganglion -> zygomatic branch of V-2 -> Lacrimal nerve

1. Describe the anatomy, microanatomy and function of the lacrimal sac.

Membrane lined tube continuous with duct Location: Lacrimal Fossa - which is comprised of the lacrimal bone and the maxillary boneMicroscopic Structure Modified respiratory epithelium Mucous membrane lined tube Columnar cells with goblet cells Internally - connective tissue with fine elastic fibrils Function - Receptacle for tears - drains into the nasolacrimal duct

Which lobe of the gland contains the 12 main ducts that empty onto the conjunctiva?

Palpebral lobe

1. List the 3 major functions of the Nasolacrimal System

Production of Tears Distribution of Tears Drainage of Tears

Clinically what can occur if this lobe is damaged? Palpebral one

Removal of/or damage to palpebral lobe - Prevents emptying of contents of the gland onto conjunctival surface - dry eye

Where is the location of the main lacrimal gland?

Shallow depression within orbital part of Frontal Bone Superior Temporal Orbit

1. Describe the anatomy, microanatomy, dimensions and function of the canaliculi. How is this clinically relevant for the dilation and irrigation procedure?

Shape: 10 mm long 2 mm vertical 8 mm horizontal Microanatomy - allows for flexibility Lining - stratified squamous epithelium Internally - connective tissue with fine elastic fibrils Allows for flexibility for dilation and irrigation procedure

1. Describe the lacrimal gland sympathetic innervation (mainly for vasomotor control of the lacrimal gland vessels).

Superior cervical ganglion -> carotid plexus -> deep petrosal nerve -> nerve of pterygoid canal-> ptergopalatine ganglion -> zygomatic branch of V-2-> lacrimal nerve

1. Describe the histology of the duct cells and what do they secrete?

The duct cells are cuboidal epithelial cells and they secrete water electrolytes and protein and they modify the primary lacrimal acinus fluid.

1. What is found in the stroma of the lacrimal gland?

The stroma is the loose connective tissue that surrounds the glandular tissue that is mostly collagen and some elastic tissue. It contains nerves and blood vessels with cells of the immune system (Plasma cells, lymphocytes, mast cells macrophages).

1. Describe the Valve of Rosenmuller and discuss its function and clinical relevance.

Where canaliculus opens into sac Canaliculus enters at angle - creates a valve Prevents regurgitation Damage from probing procedure An incompetent valve of Rosenmüller is observed clinically as air escaping from the lacrimal puncta when the individual blows his or her nose.

1. Describe the supportive tissues of the lacrimal gland. What can happen if these tissues become damaged?

Whitnall's Ligament Lateral horn of Aponeurosis of Levator Both attach to the orbital wall to give structural support to the gland Keep gland in the superior temporal portion of orbit Damage to supportive tissue can lead to prolapse of the gland

1. Describe the characteristics of the orbital and palpebral lobe of the lacrimal gland. Orbital Lobe

orbital - larger, more superior - bean shaped mass - lies along orbital wall Palpebral Lobe - smaller, more inferior - 1/3 size of orbital lobe - lies between aponeurosis and conjunctiva - firmly attached to conjunctiva