BIOS 255 A&P III MIDTERM EXAM STUDY GUIDE / BIOS255 A&P III MIDTERM EXAM STUDY GUIDE (LATEST 2021) | CHAMBERLAIN COLLEGE OF NURSING

BIOS 255 A&P III MIDTERM EXAM STUDY GUIDE

Chapter 20: The Cardiovascular System: The Heart

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