L3 Lacrimal Gland Physiology

What are the three main cell types of the lacrimal gland?

acinar cells

ductal cells

myoepithelial cells

Which cells of the lacrimal gland are interdigitated by autonomic nerves?

acini and myoepithelial cells

Which hormone causes contraction of myoepithelial cells of the lacrimal gland?

oxytocin

T/F: lacrimal gland formation occurs at the same time ad eyelid formation

true

Lacrimo-auriculo-dento-digital syndrome (LADD)

congenital alacrima in which there is genesis of the lacrimal gland/ducts due to mutations in the FGF ligand/receptor genes

Familial Dysautonomia

rare genetic condition in which there is no autonomic nerve development and therefore no ability to stimulate lacrimation of the lacrimal gland

apical domain

plasma membrane domain of a polarized epithelial cells which faces an internal lumen or outside environment

basolateral domain

the surface region of a polarized epithelial cell that is in contact with adjacent cells or the extracellular matrix

non-leaky tight junction

intercellular junction that does not allow any paracellular transport

leaky tight junction

allows for some paracellular transport

transcellular tranport

transport that occurs through cells

paracellular transport

transport of substances through the intercellular space between cells

What do mutations in the Claudin 10b gene cause?

alacrima because the paracellular transport of the lacrimal gland is disrupted

What nerves predominate the innervation of the lacrimal gland?

parasympathetic nervers

What is the primary inducer of aqueous secretion?

parasympathetic stimulation

T/F: not all lacrimal cells are associated with a nerve

true, impulse propagation occurs vis gap junctions to neighboring cells

What passes through gap junctions?

small molecules and ions

What do gap junctions in the lacrimal gland allow for?

stimulus in one cell can trigger secretion by neighboring cells

What kind of receptor do parasympathetic target organs have?

muscarinic receptors

What kind of receptors do sympathetic target organs have?

adrenergic receptors

What is the lacrimal gland's sympathetic neurotransmitter?

norepinephrine

What is the lacrimal gland's parasympathetic neurotransmitter?

acetylcholine

What are the effects of antimuscuarinc drugs on lacrimal secretions?

cause decreased lacrimal secretions

What does vasodilation of the blood vessels of the lacrimal drainage system cause?

constriction of the ducts of the lacrimal drainage system and therefore less tear drainage

What does vasoconstriction of the blood vessels of the lacrimal drainage system cause?

dilation of the ducts of the lacrimal drainage system and therefore increased tear drainage

Where do most tear proteins come from?

lacrimal gland

exocytosis of lacrimal gland proteins

secretion of proteins made in the ER of the cell through the apical membrane and into the lumen

transcytosis of lacrimal gland proteins

a protein that is no produced by the lacrimal gland cells is endocytose from the interstitial and then exocytosed from a lacrimal gland cell

ectodomain shedding of lacrimal gland proteins

protease cuts a membrane protein and it is released outside of the cell

How is lactoferrin secreted?

exocytosis

lactoferrin

protein found in tears that is a bacteriostatic because it binds iron and removes its availability to growing bacteria

How is lipocalin secreted?

exocytosis

Which tear protein is responsible for the shear-thinning property of tears?

lipocalin

What are the functions of lipocalin

shear-thinning property

provides stabilization of the tear film

inhibits bacterial growth

decreases surface tension

How is lysozyme secreted?

exocytosis

What is the function of lyzozyme in the tears?

it has a bacteriolytic effect on Gram positive bacteria

How is lacritin secreted?

exocytosis

What is the functions of lacritin in the tears?

induces basal tear secretion

promotes corneal wound-healing

What is the function of IgA in the tears?

binds to pathogens and steric ally inhibits pathogen binding to epithelial cells

How is the IgA receptor secreted from cells?

ectodomain shedded

How is IgA secreted from cells?

transcytosis

Which cells synthesize IgA receptors in the lacrimal gland?

acinar cells

Which cells synthesize IgA?

plasma cells

What type of stimulation causes lacrimal protein secretion?

BOTH parasympathetic and sympathetic innervation

What happens during neural regulation of protein secretion?

1. neurotransmitter binds receptor

2. cytoplasmic activation of second messengers

3. leads to increase in cytoplasmic Ca+

4. Exocytic vesicle fusion with apical membrane

5. Releases protein cargo

What happens during EGF regulation of protein secretion?

1. EGF binds receptor

2. cytoplasmic activation of second messengers

3. leads to increase in cytoplasmic Ca+

4. Exocytic vesicle fusion with apical membrane

5. Releases protein cargo

Sjogren's syndrome

chronic autoimmune disorder of exocrine glands

What is the mechanism of reduced secretion in Sjögren's syndrome?

1. lacrimal/salivary tissue is destroyed inhibiting secretion

2. autoantibodies to lacrimal and salivary gland muscarinic M3 acetylcholine receptors

3. reduced myoepithelial cell function

Is Sjogren's more common in men or women?

women