Lacrimal apparatus Flashcards
what are the functions of the lacrimal gland
provide aqueous portion of tear film and lubricate the eye
which way do the tears spread on the eye
lateral to medial
where do the tears go after entering the lid margin and the canaliculi
they drain into the lacrimal sac, then into the naso-lacrimal duct, opening into the inferior meatus of the nasal cavity
where is the lacrimal gland located
superotemporally, just posterior to the supraorbital rim in a fossa of the frontal bone
which lobe of the lacrimal gland is larger?
the orbital lobe (almond shape)
how big is the palepral portion of the lacrimal gland
1/3 the size of the orbital lobe
where is the palpebral portion of the lacrimal gland located
lies underneath the aponeurosis of the levator, inferior to the orbital lobe
which lobe can be seen by gross inspection of the supratemporal fornix of the conjunctiva
the palpebral portion
the acini of the lacrimal gland are composed of what two layers
a basal myoepithelial cell layer (flat) and an inner layer of secretory columnar cells
what do the myoepithelial cells of the acini do
they contract and force secretions from the inner layer of columnar cells into the central lumen
what type of gland is the lacrimal gland
a tubuloacinar exocrine gland
what 5 things are tears composed of
proteins, electrolytes, anti-bacterial enzymes, immoglobulins, and bacterial proteins
what does blinking do to the tear film
it distributes substances, supplies oxygen to cornea, remove foreign bodies and exfoliates cells
what is the tear film comprised of
lipid or oily layer, aqueous layer, and mucus layer
what layer of the tear film is the largest
the aqueous layer
where is the mucous layer secreted
in goblet cells located in the palpebral conjunctiva
what is the purpose of the mucus layer
it is hydrophilic and decreases surface tension, provides a wettable surface for the aqueous layer
what is the arterial supply for the lacrimal gland
the lacrimal branch of the ophthalmic artery
what sensory stimuli innervates the lacrimal gland
lacrimal branch of the ophthalmic division of the trigeminal nerve (CN 5)
what nerves stimulate reflex tearing
ophthalmic division of the trigeminal nerve (afferent pathway or sensory)
where does the lymph drain for the lacrimal gland
into the conjunctival lymphatics and then into the preauricular nodes
what is the gland of Krause
an accessory lacrimal gland located in the deep subconjunctival tissue
what is the gland of Wolfring
an accessory lacrimal gland in the tarsus (inferior to gland of Krause)
what is the small elevation at the junction of the ciliary and lacrimal portions of the lid called
the papilla lacrimalis (lacrimal papilla)
what is located on the submit of the lacrimal papilla
small round aperture the punctum lacrimale
what keeps the punctum lacrimale in tact
a small ring of very dense connective tissue
how many portions are the canaliculi composed of
two: a vertical and horizontal (90 degrees apart)
which portion of the canaliculi is longer; vertical or horizontal
the horizontal is longer
what do the superior and inferior horizontal canaliculi form when they unite
the common canaliculus
how big can the canaliculi increase to
three times their normal diameter (0.5-1.0mm)
where is the lacrimal sac located
in the anterior part of the medial wall of the orbit within the fossa
what part of the lacrimal sac is open
the inferior end is open and continuous with the nasolacrimal duct (apex is closed)
where is the nasolacrimal duct located
it is a downward continuation of the lacrimal sac, between the maxillary sinus and the nasal cavity
what lines the nasolacrimal duct
two layers of columnar epithelium, some have cilia
where does the nasolacrimal duct open
into the inferior meatus of the nasal cavity
what regulates the duct of the nasolacrimal duct
a flap or mucus membrane “valve” of Hasner
what is the arterial supply for the lacrimal sac and nasolacrimal duct
medial superior and inferior palpebral arteries
what sensory nerve innervates the lacrimal sac and nasolacrimal duct
infratrochlear branch of the ophthalmic division of the trigeminal nerve
how does the parasympathetic innervate the lacrimal gland
through a series of nerves, ultimately the facial nerve (CN 7)
where do the parasympathetic preganglion fibers synapse in the lacrimal route
in the pterygopalatine ganglion
what nerves make up the vidian nerve
the GSPN (greater superficial petrosal nerve) and the DPN (deep petrosal nerve)
where do the parasympathetic preganglion fibers originate
in the lacrimatory nucleus of the facial nerve (3) in the pons
what nerves are part of the GSPN- greater superficial petrosal nerve
preganglionic parasympathetic fibers
what nerves are part of the DPN- deep petrosal nerve
postganglionic sympathetic fibers, originating from the superior cervical ganglion
what nerve does the postganglionic parasympathetic fibers hitch a ride with
maxillary nerve, second division of the trigeminal nerve
where do the postganglionic parasympathetic nerves leave the maxillary branch
the zygomatic branch
where does the arterial supply to the lacrimal gland originate from
the lacrimal branch of the ophthalmic artery
how thick is the total tear film
about 7 microns thick
how thick is the oily layer of the tear film
about 0.1-0.5 microns thick
how thick is the aqueous layer of the tear film
about 5 microns thick
how thick is the mucoid layer of the tear film
about 1 micron thick
how much fluid can the conjunctival sac hold at one time
about 6.2 micoliters
what is the rate that tears are produced
1.2 microliters per minute
how quickly do tears evaporate
3 microliters per hour
which nerve causes sensory innervation to the lacrimal gland
the lacrimal nerve (Trigmenial nerve 5)
Does the lacrimal nerve cause the larcimal gland to secrete tears
No it only supplies sensory innervation, the facial nerve 7 causes secretion
