hi let's talk about the root of the neck in this video we'll discuss the root of the neck
we'll explain how various structures such as neurovasculature muscles and bones are
associated with the root of the neck and discuss some of the classic anatomical relationships among
these structures to one another so the root of the neck is a transitional area between
the neck to the superior the thorax to the inferior and the upper limbs to the lateral
it refers to a number of structures that are sitting upon the first ribs
so there's a very clear inferior boundary to the root of the neck but the superior and
lateral boundaries are a little more nebulous they blend well with these other regions
so the structures as they relate we have most anteriorly the subclavian veins
behind the subclavian veins we have the anterior scalene muscles
which you recall are very important for delimiting the subclavian artery
just posterior to the anterior scalene muscles we have the subclavian artery so it goes
vein anterior scalene subclavian artery in that same plane as the subclavian artery we're going
to have a variety of nervous structures so for instance writing down the root of the neck on
the anterior scalene is going to be the phrenic nerve medial to this will be the vagus nerve
and kind of posterior to that anterior scalene muscle we're going to have some roots and trunks
of a nervous plexus called the brachial plexus which serves the upper limbs so this will emerge
posterior to the anterior scalene but anterior to the combination of middle and posterior scalenes
these scalene muscles get their name because they resemble scalene triangles these are strap-like
muscles which attach the transverse processes of cervical vertebrae to either rib one or rib two
the anterior scalene muscle inserts to the scalene tubercle of rib one behind the neurovasculature
here the middle scalene inserts also on rib 1 whereas the posterior scalene inserts on rib 2.
these muscles if they flex unilaterally will laterally bend the c-spine or the neck
when acting on both sides they'll flex the neck or the c-spine they'll move it forward
and with the the head and neck fixed they can actually serve as accessory muscles of respiration
because they can elevate the first two ribs ever so slightly
these muscles are innervated by branches from the vpr of cervical spinal nerves and they're supplied
by blood by the ascending cervical artery which as you recall is a branch of the thyrocervical trunk
now this is a photograph of the first rib so here we can see there's a portion of what would be
the superior thoracic aperture and this would be attaching via cartilage to the manubrium
of the sternum we can see a tubercle here which is a raised area of bone and that gets raised because
the anterior scalene muscle pulls on that bone and by exerting force on the bone osteoblasts deposit
bone tissue and a tubercle is formed just anterior we can see the groove for the subclavian vein
and posterior the groove for the subclavian artery so vein is anterior then muscle then artery
is posterior this is going to be significant because in placing any sort of venous catheter
without the vein being anterior such a placement would be impossible the second rib is where the
posterior scalene muscle attaches and the middle scalene muscle attaches to this ridge here
now let's do a very quick high level review of the neurovasculature in this area so
internal jugular veins draining the brain and neck of blood subclavian veins draining the upper limbs
brain neck thorax of blood where these meet is the venous angle
and they combine to form the brachiocephalic veins the right is shorter and more vertically oriented
the left is longer and more obliquely oriented these come together to form the superior vena cava
which delivers blood from the region superior to the diaphragm into the right atrium of the heart
now the nerves so the vagus nerves are descending down through the
carotid sheath they're originating at the jugular foramina and they're quite medial with respect to
the other contents at the root of the neck and they're coming down anterior to the arteries
the vagus nerves have a variety of functions they have a strong somatic
output both sensory and motor as you recall they are the motor to the pharyngeal plexus
and they are both somatic sensory and motor to the larynx they also have quite a large
parasympathetic outflow so they are supplying the larynx with parasympathetics the cardiac
plexus with parasympathetics the pulmonary plexuses the esophageal plexuses as well as
plexuses that serve the foregut and mid-gut of the gastrointestinal tract so they they do quite a bit
the other major nervous feature here at the root of the neck is the phrenic nerve the
phrenic nerve has a very close relationship with the anterior scalene it rides down the
anterior scalene just anterior to it and then goes below or deep to the subclavian vein
the phrenic nerve is a somatic nerve which supplies the diaphragm
as well as portions of the pericardium it originates in the cervical plexus which is
superior to the brachial plexus the cervical plexus has contributions from ventral primary
rami of c1 through c4 and the branches of this phrenic nerve rc345 so it also incorporates a
portion of the brachial plexus you could remember this the mnemonic is c345 keeps
the diaphragm alive because if denervated half of the diaphragm will then go flaccid
the arteries the arteries are some of the most posterior elements in the root of the neck
uh these are originating from the arch of the aorta recall we have the brachiocephalic trunk
then the left common carotid then the left subclavian artery that brachiocephalic trunk gives
rise to the right subclavian and right common carotid artery and those subclavian arteries are
riding behind behind the anterior scalene muscle the common carotid arteries ascend the neck in the
in the carotid sheath they're going to terminate as the internal and external carotid arteries
internal carotid artery serves predominantly the cranial cavity but exits the cranial cavity
through the orbit as the ophthalmic artery
to supply the superficial superior area around the eye as well as the brow
the external carotid artery is going to serve the neck the face and the superficial head with blood
then finally in this region we have the return of lymph to the venous supply now at the level of
the capillary bed more filtrate is produced than is reabsorbed by the capillaries of the
cardiovascular system so in comes the lymphatic system specialized capillary beds absorb this
excess filtrate and it conducts a fluid now called lymph through a series of channels
these channels tend to coalesce into trunks which are regionally named and these trunks will feed
into ducts which then feed into the vicinity of the venous angle so in terms of the head and neck
in this region there are three trunks that you'll want to know about there is a jugular trunk the
jugular trunk is draining a lymph from the head and the neck and it is descending within the
carotid sheath it is in close association with the internal jugular vein there's a subclavian trunk
which is in close association with the subclavian vein and then there is a bronchomediastinal trunk
which is lateral to the mediastinum which is conducting lymph back from the bronchi and lungs
superiorly so these trunks coalesce and on the right side they feed into the right lymphatic
duct which feeds into the vicinity of the right venous angle but they may feed into the vicinity
independently of the right lymphatic duct that right lymphatic duct when we look at its drainage
drains all of the right upper limb everything of the right thorax and the right head in the neck
all other parts of the body are drained on the left side by the thoracic duct that thoracic duct
is going to originate inferior to the diaphragm as the cisterna kylie and then it ascends the thorax
on the right side it crosses over left to right at about the level of the sternal angle and then it
continues superiorly and it is going to insert in the vicinity of the left venous angle and it is
going to collect the jugular trunk the subclavian trunk in the bronchomediastinal trunk on the left
side as well so there's a thoracic duct which drains everything inferior to the diaphragm
and the left thorax head neck and upper limb and then there's a right lymphatic duct that drains
everything on the right side of the thorax the right side of the head and neck and the upper limb
so we've discussed very many of the key anatomical relationships of the root of the
neck and vascular pathways arterial venous and lymphatic as well as some of the nerve
pathways vagus and phrenic in particular this is your summary slide thank you for your time