hi let's talk about the lacrimal apparatus also known as the lacrimal system this is the pathway
by which tears are secreted drawn across the eye and drained and so our story starts here with
the lacrimal gland the lacrimal gland secretes into the conjunctival sac the conjunctival sac
if you recall consists of palpebral conjunctiva and bulbar conjunctiva it's the space between
these features and this lacrimal fluid or tears are drawn across the anterior aspect of the eye
medially so we're looking that's a medial and that is a lateral portion and we can see that
the lacrimal gland sits in the superior lateral portion of the orbit these tears as they are drawn
medially across the eye some are absorbed by the conjunctiva some evaporate from the surface of
the eye but most accumulate in an area over the medial canthus and that accumulation of
Tears is known as the lacrimal lake deep to that accumulation of Tears we can see
an elevation of tissue this elevation of tissue contains both sebaceous and interestingly enough
some sudoriferous glands and it's known as the lacrimal her uncle so in the mornings when you
wake up if you ever wipe the the medial can't buy of your eyes and you notice that there is
an accumulation of a substance perhaps you call it sleep or I boogers are gunk or whatever those
are secretions from the glands of the lacrimal Karanka anyways embedded in the in the eyelids
so the superior and inferior eyelids going out are going to be canaliculi and these little canals are
going to drain tears even deeper so sitting in feeding into these canals our lacrimal papillae
these are elevations in these papillae hosts the lacrimal Punta so the lacrimal Buchta are what
feed into the lacrimal canaliculi or canals and we'll be able to see that better in just a moment
but I wanted to show you all a living donor here so we can see the accumulation of Tears here so
that that's the lacrimal lake and the border of the the lacrimal lake so there's a membrane here
called the leaky semilunaris this is a message of our third eyelid and what it is is just an
infolding of the bulbar conjunctiva that allows for a more free range of motion of of the eye in
some animals some species of primates reptiles such as birds and some some lizards as well
as sharks this this membrane is a nictitating membrane that can cover nearly the entirety of
the eye and moisten it and protect it while still maintaining some transparency so that the organism
can see through it and humans were left with just this little vestige of it and we can allows us to
move the eye and it also helps to maintain the lack of a lake so here deep these tears or the
lacrimal lake is the core uncle so we can see that collection of of glandular materials and
we can also see at least on the inferior palpebrae here this would be the inferior lacrimal papilla
we can't see the superior one but it's probably about in this area just on the on the conjunctival
side of the superior pal cuber there and so that that inferior pillow hosts the inferior lacrimal
punctum so those are feeding into the kennel oculi which very typically come together and then are
going to drain into the lacrimal sac so here we have more of that dissected away and we can see
the inferior colliculus there the superior there and these are coming together in a common trunk
which is most often the case but they can drain independently into the lacrimal sac you can see
that lacrimal sac here sitting in the lacrimal fossa of the lacrimal bone and so this sac is
going to be contiguous with the nasolacrimal duct and it nasolacrimal duct is going to conduct the
tears down into the the nasal cavity so is to help moisten the the nasal mucosa as well and
so that this lacrimal tears don't spill down the surface of our face which is very efficient
there's also a part of orbicularis oculi known as the lacrimal part that overlies this sac and what
happens when this muscle contracts the sac is squeezed so it exerts pressure on the sac and
then it relieves so it's like a squeeze bulb so when you squeeze it it can push the tears
in but then when that muscle releases it it causes a suction effect to drain the tears
from the lacrimal lake into the lacrimal punctum on the papillae so that is how tears move from the
lacrimal gland through the lacrimal system into the nasal cavity thank you very much for your time