hi let's talk about the heart the heart as you may recall is a never working pump that applies
pressure to the blood that sends it through the arteries of the cardiovascular system the heart
is located in the thoracic cavity that's the space that's bounded by the ribs and the diaphragm and
the root of the neck the thoracic cavity is broken up into three smaller sections there
are the paired pleura which contain the lungs and then the central mediastinum that mediastinum can
be divided up a number of ways one is between the superior and the inferior mediastinum the heart
occupying a space in the inferior mediastinum and then the space occupied by the inferior
mediastinum has three subdivisions there's an anterior mediastinum a middle mediastinum and
a posterior mediastinum these three separate spaces are separated or defined by the outer
limits of the pericardium which contains the heart and thus the heart within the pericardium occupies
and defines the middle mediastinum the heart is oriented with in the middle mediastinum with its
apex pointing inferior laterally to the left with its great vessels or at least the majority of its
great vessels entering and exiting the heart from the superior the great vessels include the aorta
pulmonary trunk and the superior and inferior vena cava we can see that there are different borders
and surfaces to the heart so for instance there is a right and a left border and an inferior border
there's a sterno kostol surface that would be just deep to the sternum and ribs as well as portions
of the lung and then if we were to look at this inferiorly there's also a diaphragmatic surface
and the pericardium of the heart is adhered to the diaphragm now looking at this heart it may
not be evident because of the presence of so much pericardial fat but there is a coronary
sulcus that is a groove that's going to separate the atria above from the ventricles below there's
also an interventricular sulcus that is both on the anterior surface so that would be the
anterior interventricular sulcus as well as the diaphragmatic surface which hosts the posterior
interventricular sulcus this interventricular sulcus is a surface landmark that represents
where the interventricular septum or the wall that divides right from left ventricle is the heart is
surrounded by the pericardium the pericardium is a protective bag that creates a safe space
called the pericardial cavity in which the heart may function so there are two parts to
the pericardium the fibrous pericardium is the outermost layer of the heart it's rather rigid
and inflexible and then deep to the fibrous pericardium is the serous pericardium and the
serous pericardium comes in two layers there's the outer parietal layer of the serous pericardium and
the inner visceral layer of the serous pericardium and separating the two is the pericardial cavity
now this can sometimes be a difficult concept for students to grasp how this serous pericardium can
exist and to help you along I'd like to employ a prop from my lunch so this sandwich bag so
this is going to represent the serous pericardium with its two layers both a visceral layer and a
parietal layer the parietal layer will be adhered to the fibrous pericardium and the visceral layer
will be contained within the parietal layer and come into contact with the heart represented
here by my finger and so this empty space of the sandwich bag would be the pericardial cavity in
which the heart may expand and contract expand and contract expand and contract and nothing
save a little bit of pericardial fluid should be within that pericardial cavity in fact when
materials do enter that pericardial cavity and sometimes these materials may be blood lymph
or just exudate that could put pressure on the heart such that the heart can't fully expand and
that's a condition known as cardiac tamponade and that's basically a strangling of the heart
beyond the pericardium we have the actual layers of the heart proper and what's interesting about
this is one of these three layers is a part of the pericardium and that's the epicardium here
which is actually the visceral serous pericardium that is so adhered to the heart surface that it
becomes a part of it just deep to the epicardium is the myocardium the myocardium is the muscular
wall of the heart and then contained within the myocardium is the endocardium which is
going to line the various chambers of the heart so we talked a little bit about the heart where
it lives in the body what it does and the various layers that comprise it thank you