my of the Heart
Location of the heart
o Rests on the diaphragm near midline of thoracic cavity
o Lies in the mediastinum (anatomical region that extends from the
sternum to the vertebral column, from the 1st rib to the diaphragm
& in between the lungs)
o About 2/3 of the mass of the heart lies to the left of the body’s
midline
o Apex: formed by the tip of the left ventricle & rests on diaphragm
—directed anteriorly, inferiorly and to the left
o Base: opposite of apex & is its posterior aspect—formed by the
atria (upper chambers) and mostly the left atrium
o Anterior surface: deep to sternum and ribs
o Inferior surface: part of heart between apex and right surface &
rests on diaphragm
o Right surface: faces right lung & extends from the inferior surface
to the base
o Left surface: faces left lung and extends from base to apex
Pericardium
o Membrane that surrounds and protects the heart
o Confines heart to its position in the mediastinum, while allowing
sufficient freedom of movement for vigorous and rapid contraction
o Consists of 2 main parts:
Fibrous pericardium: superficial- composed of tough,
inelastic, dense irregular connective tissue
Resembles a bag that rests on and attaches to
diaphragm
, Open end is fused to connective tissues of blood
vessels entering and leaving the heart
Prevents overstretching
Provides protection
Anchors heart in mediastinum
Near the apex of the heart, it is partially fused to the
central tendon of the diaphragm, so movement of the
diaphragm facilitates movement of blood by the heart
Serous pericardium: deep- thinner, more delicate membrane
that forms a double layer around the heart
Parietal layer of serous pericardium: outer layer- fused
to the fibrous pericardium
Visceral layer of serous pericardium: also called the
epicardium; adheres tightly to the surface of the heart
b/w the parietal and visceral layers of the serous
pericardium is a thin film of lubricating serous
fluid known as pericardial fluid, that reduces
friction b/w layers of serous pericardium as the
heart moves
space that contains the few milliliters of
pericardial fluid is the pericardial cavity
Layers of the Heart Wall
o 3 layers
Epicardium
Composed of 2 tissue layers
visceral layer of the serous pericardium: thin,
transparent outer layer; composed of
mesothelium
Adipose & fibroelastic tissue: adipose tissue
predominates & becomes thickest over the
ventricular surfaces where it houses the major
coronary and cardiac vessels of the heart
Smooth, slippery texture to the outermost surface of
the heart
Contains blood vessels, lymphatics, and vessels that
supply the myocardium
, Myocardium
Middle
Responsible for the pumping action of the heart & is
composed of cardiac muscle tissue
Makes up ~95% of the heart wall
Muscle fibers (cells) are wrapped and bundled with
connective tissue sheaths composed of endomysium
and perimysium; organized in bundles that swirl
diagonally around the heart and generate the strong
pumping actions
Endocardium
Innermost, thin layer of endothelium overlying a thin
layer of connective tissue
Provides a smooth lining for the chambers of the heart
and covers the valves of the heart
Smooth endothelial lining minimizes the surface
friction as blood passes through the heart
Continuous with the endothelial lining of the large
blood vessels attached to the heart
Chambers of the Heart
o 4 chambers—2 superior receiving chambers are the atria & 2
inferior pumping chambers are the ventricles
o paired atria receive blood from blood vessels returning blood to the
heart (veins), while ventricles eject the blood from the heart into
blood vessels (arteries)
o Auricle: wrinkled, pouchlike structure on the anterior surface of
each atrium; resembles a dog’s ear
each auricle slightly increases the capacity of an atrium so it
can hold a greater volume of blood
o Sulci: series of grooves on the surface of the heart that contain
coronary blood vessels and a variable amount of fat
Each sulcus marks the external boundary between 2
chambers of the heart
Coronary sulcus: deep; encircles most of the heart and marks
the external boundary between the superior atria and inferior
ventricles
, Anterior Interventricular Sulcus: shallow groove on the
anterior surface of the heart that marks the external
boundary between the right and left ventricles on the
anterior aspect of the heart
Posterior Interventricular Sulcus: continues from anterior
interventricular surface onto and around the posterior
surface of the heart, that marks the external boundary
between the ventricles on the posterior aspect of the heart
o Right Atrium
Forms the right surface of the heart and receives blood from
3 veins:
Superior vena cava
Inferior vena cava
Coronary sinus
**veins always carry blood toward the heart**
2-3 mm in thickness
anterior and posterior walls are very different
inside of posterior wall: smooth
inside of anterior wall: rough due to the presence of
muscular ridges called pectinate muscles, which also
extend into the auricle
interartrial septum: thin partition between the right atrium
and left atrium
fossa ovalis: oval depression of the interatrial septum—
remnant of the foramen ovale (an opening in the septum of
the fetal heart that normally closes soon after birth)
blood passes from the right atrium into right ventricle
through a valve called the tricuspid valve (consists of 3
cusps); aka right atrioventricular valve
valves of heart are composed of dense connective tissue
covered by endocardium
o Right Ventricle
About 4-5 mm in thickness and forms most of the anterior
surface of the heart
Inside contains a series of ridges formed by raised bundles
of cardiac muscle fibers called trabeculae carneae
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