hello anatomy colleagues this is dr alsup and in this video we will be discussing the four mid and
hindgut derivatives so we'll first define these terms but then we're really going to focus on how
derivatives of these areas will share common blood supply innervation and then we'll get down
into structures of each one and this will really remembering some of those concepts over time it'll
take away a little bit in terms of the cognitive load so the primitive gut tube is divided by
folding into three main compartments and these compartments are referred to as the foregut the
mid gut and the hindgut you will surely discuss how these fold and a bit more detail in this area
when discussing embryology so i'll leave that to those experts but what we're going to focus on is
what those compartments will develop into as those areas will share a sim similar embryological or
origin so that means they'll also share a common arterial source and parasympathetic excuse me i
can't talk parasympathetic innervation with a little bit of overlap so you may hear something
like the stomach is of the foregut which really means it developed from the embryological foregut
now we have this handy-dandy image for you here that gives a breakdown
of the abdominal structures that are going to be derived from each embryological portion the four
gut which we have the list right here will include non-abdominal structures as well so the pharynx is
going to be derived from the foregut as well but we are going to focus on the abdominal structure
structures and i often like to describe them as the more superior structures such as the stomach
and the liver those are going to be derived from the foregut and it will transition into the midgut
right around the level of the major duodenal papilla which is actually internal within the
duodenum so you can't really see it in this image but you can conceptualize about where that occurs
so this brings up an important part of this discussion in that portions of the duodenum
are four gut derived and the more distal portions are midgut derived so you actually
have an example here and you'll have another one in a moment where that same visceral structure
has two different embryological uh divisions so the midgut will continue from the duodenum
and will include most of the small intestine and the more proximal portions of the large intestine
and will transition into the hindgut about two-thirds of the way
on the transverse colon so this more proximal portion of the transverse colon will be mid-gut
whereas the distal one-third of the transverse colon will be hindgut
derived and the hindgut will include the more distal portions of the small intestine
as mentioned these subdivisions have unique arterial supply sources and while there are
small areas of overlap the basic pattern is pretty set and can help in understanding
basic blood supply to these structures so if you remember which structures are derived from say the
foregut you can quickly correlate that with oh i know that's going to have an arterial supply
from a branch of the celiac trunk so in most basic terms four gut derivatives are supplied
by branches of the celiac trunk which is the first major major anterior branch of the abdominal aorta
mid-gut derivatives are supplied by branches of this sma or the superior mesenteric artery this
will be a focus when we get into the large and small intestines in a moment in another video
and hindgut derivatives are going to be supplied by branches of the ima or the inferior mesenteric
artery so keep note that large intestine will have branches from both the sma as well as from the ima
lastly as parasympathetic innervation is of such importance in the abdominal region it's
important to consider this as well and a real quick and easy way to remember the the basic
pattern of innervation so mid gut and foregut receive parasympathetic innervation from the
cranial source and the good old vagus nerve that we have been talking about all year
however once it gets to the end of the mid gut its role is finished it has traveled a long way but
now the vagus nerve's journey is finally over and the hindgut will be parasympathetically innervated
by the sacral component of the parasympathetic system
those pelvic splanchnic nerves which are derived from spinal cord levels s2 through s4
so recall you you learned this a while back and now we're finally actually getting to talk about
those pelvic splanchnic nerves now those fibers from the pelvic splanchnic nerves will get to this area
via autonomic plexuses which we'll discuss in more detail in upcoming videos so we have come
to the summary slide with a hopefully helpful table that you can use for summarizing this
information please take time to review and get the basics regarding which structures are derived from
which part and please reach out if you have any questions have a great rest of your day