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Chapter 20

Nursing HAP201 Chapter Notes - Chapter 20: Anterior Interventricular Sulcus, Posterior Interventricular Sulcus, Chordae Tendineae


Department
Nursing
Course Code
Nursing HAP201
Professor
Judith Card
Chapter
20

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HAP201 Week Four Chapter 20: The Cardiovascular System The Heart
LO 20.1: Demonstrate the location of the heart with reference to surface landmarks
The heart rests on the diaphragm, near the midline of the thoracic cavity
The heart lies in the mediastinum, an anatomic region that extends from the sternum to the vertebral column, from the first
rib to the diaphragm, and between the lungs.
The pointed apex is formed by the tip of the left ventricle (a lower chamber of the heart) and rests on the diaphragm. It is
directed anteriorly, inferiorly, and to the left.
The base of the heart is opposite to the apex and is its posterior aspect. It is formed by the atria (upper chambers) of the heart,
mostly the left atrium
The heart has several distinct surfaces. The anterior surface is deep to the sternum and ribs. The inferior surface is the part
of the heart between the apex and right surface and rests mostly on the diaphragm. The right surface faces the right lung and
extends from the inferior surface of the base. The left surface faces the left lung and extends from the base to the apex
LO 20.2: Identify the location, general structure and function of the following:
PERICARDIUM
This is the membrane the surrounds and protects the heart.
It confines the heart to the its position in the mediastinum, while allowing sufficient freedom of movement for vigorous and
rapid contraction.
It consists of two main parts:
o Fibrous pericardium: superficial and composed of tough, inelastic, dense irregular connective tissue. Its open end
is fused to the connective tissues of the blood vessels entering and leaving the heart. It prevents overstretching of the
heart, provides protection, and anchors the heart in the mediastinum. The fibrous pericardium near the apex of the
heart is partially fused to the central tendon of the diaphragm, thus movement of the diaphragm (e.g. deep
breathing), facilitates the movement of blood by the heart
o Serous pericardium: this is a deeper, thinner, and more delicate membrane the forms a double layer around the
heart. The outer parietal layer of the serous pericardium is fused to the fibrous pericardium. The inner visceral
layer of the serous pericardium, also called the epicardium, is one of the layers of the heart wall and adheres
tightly to the surface of the heart. Between these two layers is a thin film of lubricating serous fluid. It is secreted by
pericardial cells and is called pericardial fluid. It reduces friction between the two layers as the heart moves. The
space that contains the pericardial fluid is the pericardial cavity
LAYERS OF THE HEART WALL
There are three layers of the heart wall
o Epicardium: composed of two tissue layers. The outermost is the visceral layer of the serous pericardium. This
layer is composed of mesothelium. Beneath the mesothelium is a layer of fibroelastic tissue and adipose tissue. The
adipose tissue predominates and becomes thickest over the ventricular surfaces, where it houses the major coronary
and cardiac vessels of the heart. The epicardium contains blood vessels, lymphatics, and vessels that supply the
myocardium
o Myocardium: the middle layer responsible for the pumping action of the heart. It is composed of cardiac muscle
tissue. The muscle fibres (cells) are wrapped and bundled with connective tissue sheaths composed of endomysium
and perimysium. The cardiac muscle fibres are organized in bundles that swirl diagonally around the heart and
generate the strong pumping actions of the heart. The cardiac muscle is involuntary like smooth muscle
o Endocardium: this is the innermost layer. It is a thin layer of endothelium overlying a thin layer of connective
tissue. It provides a smooth lining of the chambers of the heart and covers the valves of the heart. The lining
minimizes friction as blood passes through the heart. The endocardium is continuous with the endothelial lining of
the large blood vessels attached to the heart
CHAMBERS OF THE HEART
The heart has four chambers
The two superior receiving chambers are the atria and the two inferior pumping chambers are the ventricles
The paired atria receive blood from veins that return blood to the heart. The ventricles eject the blood from the heart into
arteries.
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On the anterior surface of each atrium is an auricle. Each auricle slightly increases the capacity of an atrium so that it can
hold a greater volume of blood.
The heart’s surface also contains grooves called sulci that contain coronary blood vessels and a variable amount of fat. Each
sulcus marks the external boundary between two chambers of the heart.
o Coronary sulcus: this is deep and encircles most of the heart and marks the external boundary between the superior
atria and inferior ventricles.
o Anterior interventricular sulcus: this is a 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.
o Posterior interventricular sulcus: this marks the external boundary between the ventricles on the posterior aspect
of the heart
Right Atrium
o This forms the surface of the heart and receives blood from three veins: superior vena cava, inferior vena cava,
and coronary sinus.
o The anterior and posterior walls of the right atrium are very different.
The inside of the posterior wall is smooth; the inside of the anterior wall is rough due to muscular ridges
called pectinate muscles.
o Between the right and left atrium is a thin partition called the interatrial septum. A prominent feature of this
septum is the fossa ovalis, an oval depression and the remnant of the foramen ovale, an opening in the interatrial
septum of the fetal heart that closes after birth.
o Blood passes from the right atrium into the right ventricle through the tricuspid valve, as it consists of three cusps.
It is also called the right atrioventricular valve.
o The valves of the heart are composed of dense connective tissue covered by endocardium
Right Ventricle
o This forms most of the anterior surface of the heart.
o The inside contains bundles of cardiac muscle fibres called trabeculae carneae. Some of these bundles convey part
of the heart’s conduction system
o The cusps of the tricuspid valve are connected to tendon-like cords, the chordae tendineae. These are connected to
the papillary muscles.
o Internally, the interventricular septum separates the right ventricle from the left ventricle
o Blood passes from the right ventricle through the pulmonary valve (pulmonary semilunar valve) into a large artery
called the pulmonary trunk, which divides the right and left pulmonary arteries and carries blood to the lungs.
Left Atrium
o This forms the most of the base of the heart
o It receives blood from the lungs through four pulmonary veins.
o The inside of the left atrium has a smooth posterior wall. Because pectinate muscles are confined to the auricle of
the left atrium, the anterior wall of the left atrium is also smooth.
o Blood passes from the left atrium into the left ventricle through the bicuspid (mitral) valve (has two cusps). It is also
called the left atrioventricular valve
Left Ventricle
o This is the thickest chamber and it also contains trabeculae carneae and chordae tendineae that anchor the cusps of the
bicuspid valve to papillary muscles.
o Blood passes from the left ventricle through the aortic valve (aortic semilunar valve) into the ascending aorta.
o Some of the blood in the aorta flows into the coronary arteries, which branch from the ascending aorta and carry
blood to the heart wall.
o The remainder of the blood passes into the arch of the aorta and descending aorta (thoracic aorta and abdominal
aorta).
o Branches of the arch of the aorta and descending aorta carry blood through the body.
MYOCADRDIAL THICKNESS AND FUNCTION
The thickness of the myocardium of the four chambers varies according to each chamber’s function
The thin-walled atria deliver blood under less pressure into the adjacent ventricles
Because the ventricles pump blood under higher pressure over greater distances, their walls are thicker.
The right and left ventricles act as two separate pumps that simultaneously eject equal volumes of blood, but the right side has
a much smaller workload
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