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part of the swallowing process. Well let us look
at the trachea. Trachea has got a number of
components as I said they lie, we can feel them
in our neck region, we have 16 to 20 of them,
the rings of cartilage, horseshoe shaped cartilage
and they joined at the ends of these horseshoes
by some connective tissue and also by the
trachealis muscle. The trachea has a mucosa
again of respiratory tract epithelium. It
has a submucosa to support that epithelium
and also has, as I mentioned before, rings of hyalin
cartilage and on the outside the adventitia,
which is going to blend with surrounding structures.
The trachealis muscle can alter the dimensions
of the trachea and therefore, the amount
of air flowing to the lungs and the tissue
adjacent to the trachealis muscle then blends
with the esophagus. The esophagus lies just
behind the trachea. Now those are cartilage rings
and they are separated from each other by
connective tissue and also elastic tissue
because the trachea alters its dimensions.
01:21
It can lengthen and contract during the
process of air passing through it, down to
the lungs, or out from the lungs. So there's
elastic tissue in between these cartilage
rings as well as the normal supporting connective
tissue. Let us have a look at the epithelium
of the trachea and components of the trachea
in a little bit more detail. There's the
elastic fibres sitting in the lamina propria.
The elastic fibres are running in a longitudinal
direction to the epithelium and these elastic
fibres also give the lamina propria and the
supporting tissues and the epithelium the
ability to expand and lengthen and shorten
along with trachea during the same thing that
I've described a moment ago. The epithelium sits
on a very prominent basement membrane and that
basement membrane will support the epithelium
and then just underneath the lamina propria,
you find some submucosal glands. These are
both mucous and serous and again they keep the
surface of the epithelium moist. And again
you maintain the mucous content on the epithelium
to create that raft I mentioned earlier that
can carry debris that is stuck to that epithelial
surface, stuck to the mucous that can be carried
up to where it can be swallowed or coughed
and gotten rid off from the body because that
epithelium is still ciliated and those cilia
beat and move that mucous raft along.
03:06
The elastic fibres you see on the left-hand image
actually divide. They are the division between
the lamina propria, the very loose connective tissue
supporting the epithelium just underneath
the basement membrane and then below that
there is the division between that lamina
propria and the underlying submucosa. When you
go down from the trachea towards the lung,