hi let's talk about the heart and its position within the thoracic cavity
in this video we'll introduce the heart we'll describe where the heart is located we'll also
discuss the organization of the thoracic cavity and the mediastinum within the thoracic cavity
so the heart is the central organ for the cardiovascular system blood moves according
to pressure and the heart is what provides the bulk of the pressure within the cardiovascular
system the engine that drives this pump is the myocardium and that myocardium is rich
with cardiac muscle tissue an individual's heart is roughly the size of their loosely closed fist
typically this is going to weigh 200 to 300 grams depending on the the body type and the heart is
going to occupy the middle mediastinum within the thoracic cavity the heart as an organ is hopefully
ever working you know it is one of the first organs to to functionally come online
it begins its beating about the third week of development and you know completes its mission
upon the the death of its owner perhaps not in the case of an organ transplant but you know for for a
person's lifespan the heart continues to beat so the heart is found within the thoracic cavity and
the thoracic cavity is the space which is bounded laterally by the ribs in the intercostal spaces
superiorly by the root of the neck and the root of the neck as it transitions into the
thoracic cavity is above the level of rib 1. inferiorly by the diaphragm posteriorly by the
vertebral column and anteriorly by the sternum now within the thoracic cavity there are three spaces
laterally we have what are known as the pulmonary cavities and these pulmonary cavities are going to
contain the lungs and the serous membranes which encase them called the pluri medial to the lungs
is a region called the mediastinum so roughly this outline here is the mediastinum
that mediastinum is going to contain the pericardium and within the pericardium
the heart it's going to contain neurovasculature in particular the the great vessels of the heart
it's going to contain uh viscera such as the lower limit sometimes of the thyroid gland that can be
in there the thymus gland various lymph nodes the esophagus the the trachea and the primary bronchi
now when we look at the mediastinum we could further subdivide it
into four spaces the the first division is going to be between the superior mediastinum
and the remainder of the space now keep in mind that laterally the mediastinum is bordered by the
pleural cavities i'm sorry the pulmonary cavities and within them the pluri and the pleural cavities
so at the level of the sternal angle
the sternal angle is where the manubrium meets the body of the sternum
if you were to palpate your own sternum you can sometimes feel this convex ridge
that's your sternal angle it's an important landmark that's precisely where rib 2
articulates with the sternum and if we were to draw a plane posteriorly extending to about
the intervertebral disc between the fourth and the fifth thoracic vertebra that plane
would divide the superior mediastinum from the remainder of the mediastinum
now keep in mind that that first rib is the plane for the superior mediastinum so
there's kind of a wedge-shaped superior mediastinum the quote-unquote inferior mediastinum
actually is three separate spaces there's an anterior a middle and a posterior mediastinum
these divisions are all based on the pericardium the pericardium here is outlined in red
and wherever the pericardium is that represents the middle mediastinum anything anterior to the
pericardium is the anterior mediastinum anything posterior to the pericardium is the posterior
mediastinum and you should be able to see here that you know the the diaphragm is a rather
arching structure it doesn't go you know flat across as as a lot of people
presuppose and so that posterior mediastinum has a significant amount of depth compared to
the middle or the anterior mediastinum that that goes down quite far and this leads us
to the assessment question for the video and that is what space within the thorax contains the heart
is it the anterior mediastinum the middle mediastinum the posterior mediastinum the
pulmonary cavity or the superior mediastinum well hopefully you understand that the heart
is surrounded by the pericardium and the pericardium defines where the middle
mediastinum exists so wherever the pericardium is is that middle mediastinum therefore the heart
must be found within the middle mediastinum thank you very much for your time