hello anatomy colleagues this is dr alsup and in this video we will be discussing the thyroid and
parathyroid glands so we will start with a little bit regarding function realizing that we will
spend considerably more time with these glands and the endocrine content then we're going to discuss
the location because we will be seeing these and the prolific vascular supply these glands have
the thyroid and parathyroid glands are endocrine glands in fact the thyroid gland is actually
the largest endocrine gland in the body you can kind of see it right here on this image
endocrine organs or glands will secrete a chemical signal called a hormone sometimes they'll release
multiple types of hormones into extracellular fluid often to make its way to the bloodstream
endocrine glands are also ductless which is one of the things that separates them
from their friend's exocrine glands now i don't want to go into too much detail
in terms of the hormones that these glands release as that would be less gross anatomy but will
certainly be discussed in detail in upcoming blocks by other experts however it's a nice
opportunity to at least introduce these names and so you can start getting familiar with the terms
so the thyroid gland will release thyroid hormone which will help control rates of
tissue metabolism so this will be needed in adequate amounts for protein synthesis
additionally it will release calcitonin if blood levels get too high so in essence it will lead
to a decrease in blood calcium levels parathyroid hormone which will be released by the parathyroid
glands will kind of do the opposite of calcitonin leading to increases in blood calcium levels
and is hugely important in terms of regulation of blood calcium levels and as i mentioned don't
get too bogged down in terms of the functions of these specific hormones quite yet i mainly
wanted to just mention them or introduce them so you could at least hear them and it will sound
familiar once you explore these details later on okay but where i really want us to focus on
or focus our attentions on are kind of the more gross anatomy aspects and one
of these is the basic location of the thyroid and parathyroid glands as well as its vascular supply
the thyroid gland which is this large butterfly shaped gland has two lobes a middle isthmus
right here this will typically be located between around the c5 vertebrae cervical vertebrae 5 and
t1 or thoracic vertebrae one and as you can see in this image it is anterior to the larynx as well as
the trachea and deep to the infrahyoid muscles as we discussed when we discuss those muscles
now what is neat is that the parathyroid glands are typically located on the posterior thyroid
gland so we're looking at a posterior view here and you can see these little bitty
little parathyroid glands on the posterior part of the thyroid gland sometimes it looks like it's
a part of the thyroid gland but certainly they are functionally different and they don't have to
be located here either they can be found anywhere in this general area but this is the most typical
place and there are typically four parathyroid glands two sets of superior ones two sets or i
mean two superior ones and two inferior ones but there certainly can be more or less there's all
types of variability with the parathyroid glands but this is kind of the most typical location
all endocrine glands have a very robust vascular supply both types of glands will be supplied by
the superior and the inferior thyroid arteries although the parathyroid glands typically gain
most of their supply from the inferior thyroid arteries the superior thyroid artery is a branch
of the external carotid which you can see sorry the external carotid is going to be up here
this is the common carotid so you can kind of see it coming off the external carotid to supply
the superior portion of the gland the inferior thyroid artery is a branch of the subclavian
artery which is more down towards the root of the neck region and i want you to note here so
you can see the inferior thyroid artery note this close relationship as this circle would indicate
between the inferior thyroid artery and the recurrent laryngeal nerve which is
this in yellow if any type of surgery needs to be done on this area around the thyroid gland such as
the thyroidectomy and the inferior thyroid artery needs to be ligated or tied off for the surgery
a surgeon needs to be mindful of this close relationship and not injure this nerve
if damaged um if the recurrent original nervous damages could lead to hoarseness in the voice
or of the patient or more severely it could lead to paralysis of most of the intrinsic laryngeal
muscles on one side so this is a close anatomical relationship something you hear often there are
typically three sets of veins that drain these glands the superior thyroid vein will run close
to the inferior or excuse me to the superior thyroid artery which you can see here the middle
thyroid vein would be more in the middle but it's important to note that these may or may not
be present there's a lot of variability with the middle thyroid vein and the inferior thyroid veins
are typically the largest you can kind of see them around this area here they're kind of independent
and you will often see them more in the midline region so you can kind of see it kind of running
superficial to the trachea here so that's a that's a interesting and close relationship there
one last big picture clinical note the thyroid gland can increase in size some and sometimes it
can increase considerably and these this increase of the thyroid gland size is called a goiter
this can be caused by a multitude of factors which we're going to let some of your upcoming clinical
lectures discuss such as iodine deficiency or hyper hypothyroidism but on a more anatomical
note think about what could happen if the thyroid gland increases in size substantially what's kind
of missing in these rather simplistic images all of that neurovasculature that we saw over here
so if if you had an increase in size of the thyroid gland it could compress some of that
neurovasculature you can also see that it could uh feasibly compress parts of the
larynx or the trachea but it's usually more that neurovasculature that's going to be a deep that
would be most most commonly compressed in certain increases in size of the thyroid gland excellent
so much fun to touch on the first two glands we will be seeing for this year and we will obviously
have quite a few more to touch on throughout the year here is your summary slide with big picture
takeaway concepts thank you for your time and attention here and have a great rest of your day