Visual Anatomy & Physiology (Part II)

503 Pages·81.751 MB·English

by  Martini F.H., Ober W.C., Nath J.L., Bartholomew E.F., Pettl K.

The Heart and
19
Cardiovascular Function
L e A R n i n G o U tco M e S
Section 1 • Structure of the Heart
These Learning
Outcomes
19.1 Describe the heart’s location, shape, and borders.
correspond
19.2 Describe the structure of the pericardium and explain its functions, identify the layers of
by number to
the heart wall, and describe the structures and functions of cardiac muscle.
this chapter’s
19.3 Describe the location and general features of the heart.
modules and
19.4 Describe the cardiac chambers and the heart’s external anatomy.
indicate what
19.5 Describe the major vessels supplying the heart, and cite their locations.
you should be
19.6 Trace blood flow through the heart, identifying the major blood vessels, chambers, and
able to do after
heart valves.
completing
19.7 Describe the relationship between the AV and semilunar valves during a heartbeat.
the chapter.
19.8 CLINICAL MODULE Define arteriosclerosis, and explain its significance to health.
Section 2 • Cardiac Cycle
19.9 Explain the complete round of cardiac systole and diastole.
19.10 Explain the events of the cardiac cycle, and relate the heart sounds to specific events.
19.11 Describe the components and functions of the conducting system of the heart.
19.12 Describe an action potential in cardiac muscle, and explain the role of calcium ions.
19.13 Describe the factors affecting the heart rate.
19.14 Describe the variables that influence stroke volume.
19.15 Explain how stroke volume and cardiac output are coordinated.
19.16 CLINICAL MODULE Identify the electrical events shown on an electrocardiogram.
Section 3 • Coordination of Cardiac Output and Blood Flow
19.17 Explain the effects of pressure, resistance, and venous return on cardiac output.
19.18 Describe the factors that influence total peripheral resistance.
19.19 Describe the factors that determine blood flow.
19.20 Describe the movement of fluids between capillaries and
interstitial spaces.
19.21 Explain central regulation, autoregulation, and baroreceptor
reflexes in response to changes in blood pressure and blood
composition.
19.22 Explain the hormonal regulation of blood pressure and blood
volume.
19.23 Describe the role of chemoreceptor reflexes in adjusting
cardiovascular activity.
19.24 Explain how the cardiovascular system responds to the
Learning Outcomes demands of exercise.
are repeated at the 19.25 CLINICAL MODULE Explain the body’s response to
bottom of each blood loss.
module.
684
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Module 19.1
SECTION 1 • Structure of the Heart
The heart has a superior base, an
inferior apex, and four borders
The base of the heart is at its
superior border, where the
great veins and arteries are
1 The heart is located near the attached. The base sits
anterior chest wall, directly posterior to the sternum at
the level of the third costal
posterior to the sternum. A mid-
sagittal section through the trunk 1 1 cartilage, centered about 1.2
cm (0.5 in.) to the left side.
does not divide the heart into
equal halves. Note that (1) the 2 2
center of the base lies slightly to
the left of the midline, (2) a line 3 3 Ribs
drawn between the center of
the base and the apex points 4 4 The inferior, pointed tip of the
further to the left, and (3) the heart is the free apex (Ā-peks).
5 5
entire heart is rotated to the A typical adult heart measures
left around this line, so that the 6 6 approximately 12.5 cm (5 in.)
right atrium and right ventricle from the base to the apex,
dominate an anterior view of 7 7 which reaches the fifth
the heart ( 2 ). 8 intercostal space approxi-
8 mately 7.5 cm (3 in.) to the left
9 9 of the midline.
10 10
2 This anterior view illustrates the Superior border
borders of the heart. The base forms
the superior border. The right border of
the heart is formed by the right atrium. The
left border is formed by the left ventricle
and a small portion of the left atrium. The
left border extends to the apex, where it
meets the inferior
border. The inferior
Right
border is formed
atrium
mainly by the inferior
wall of the right Right border Right
ventricle. ventricle
Left border
Module 19.1 Review
Inferior border
This section examines the anatomy a. The anterior view of the heart is
dominated by which structures?
of the heart. We will then consider
the regulation of cardiac function b. The great veins and arteries are attached
to which aspect of the heart?
(Section 2) before considering how
cardiac and vasomotor activities c. Is the apex located on the superior or
inferior aspect of the heart?
are coordinated.
19.1 Describe the heart’s location, shape, and borders. 685
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Module 19.2
The heart wall contains concentric
3 This light micrograph shows the
histological characteristics that
layers of cardiac muscle tissue The Pericardium
distinguish cardiac muscle tissue from
skeletal muscle tissue: (1) small cell size,
The pericardium is the serous
Each cardiac muscle cell is
membrane that lines the (2) a single, centrally located nucleus,
connected to several
1 This is a view of a section taken from the wall pericardial cavity and covers the (3) branching interconnections others at specialized sites
heart (Module 4.14, p. 160). between cells, and (4) specialized
of the heart and the surrounding pericardium. known as intercalated
The heart wall contains three layers: epicardium, intercellular connections. (in-TER-ka-lā-ted) discs.
Parietal Pericardium
myocardium, and endocardium.
The parietal pericardium is the
portion of the serous membrane
that lines the outer wall of the
pericardial cavity. The parietal Cardiac muscle tissue LM × 575
pericardium is reinforced by a
dense fibrous layer; together 4 Cardiac muscle cells are found only in the heart. Like skeletal
Connective Pericardial cavity they form the pericardial sac muscle fibers, cardiac muscle cells contain organized
tissues (contains serous fluid) that surrounds the heart. myofibrils, and the presence of many aligned sarcomeres gives Cardiac muscle cells are relatively
the cells a striated appearance. They are almost totally small, averaging 10–20 μm in
Dense fibrous layer dependent on aerobic metabolism to obtain the energy they diameter and 50–100 μm in length.
Areolar tissue need to continue contracting. The sarcoplasm of a cardiac
muscle cell contains many mitochondria and abundant Intercalated
Mesothelium disc (sectioned)
reserves of myoglobin that store oxygen. Because these cells
Myocardium
Epicardium are metabolically very active and have a high demand for
The myocardium, or muscular oxygen and nutrients, cardiac tissues are richly supplied
The epicardium, or visceral Nucleus
wall of the heart, forms both atria with capillaries.
pericardium, covers the outer
and ventricles. This middle layer
surface of the heart. This portion
contains cardiac muscle tissue,
of the serous membrane Mitochondria
blood vessels, and nerves. The
consists of an exposed mesothe- 5 At an intercalated disc, the plasma membranes of two
myocardium consists of concen-
lium and an underlying layer of adjacent cardiac muscle cells are extensively intertwined
tric layers of cardiac muscle tissue.
areolar tissue that is attached to and bound together by gap junctions and desmosomes. These
the myocardium. connections help stabilize the positions of adjacent cells. The gap
Endocardium junctions allow ions and small molecules to move from one cell to another. Bundles of
Mesothelium myofibrils
This creates a direct electrical connection between the two muscle cells. An
The inner surfaces of the
Areolar tissue
heart, including those of the Endothelium action potential can travel across an intercalated disc, moving quickly from one
thheea retn vdaolvceasr, dairue mco, vae sriemdp bley Areolar tissue H e art wall cfiarrmdliya ca nmcuhsocrleed c etoll tthoe a mnoetmhebrr. aMney oafti bthriel si ninte trhcea ltawteod i ndtisecrl aonckdi ncagn m “puusclll et ocgeelltsh aerre” Idnistecrcalated
squamous epithelium and with maximum efficiency. Because the cardiac muscle cells are mechanically,
underlying areolar tissue. chemically, and electrically connected to one another, the entire tissue resembles
The squamous epithelial a single, enormous muscle cell. For this reason, cardiac muscle has been called a
lining of the cardiovascular functional syncytium (sin-SISH-ē-um; a fused mass of cells).
system is called an endothe-
lium. The endothelium of Gap junction
the heart is continuous with
the endothelium of the
attached great vessels.
Intercalated Disc
Atrial
Z lines bound to
musculature
2 The atrial myocardium contains opposing cell
membranes
muscle bundles that wrap around
the atria and form figure-eights that Desmosomes
encircle the great vessels. Superficial
ventricular muscles wrap around both
ventricles; deeper muscle layers
spiral around and between the
ventricles toward the apex in Ventricular
musculature
a figure-eight pattern.
686 • Chapter 19: The Heart and Cardiovascular Function
M19_MART8949_02_SE_CH19.indd 686 12/4/13 2:48 PM
3 This light micrograph shows the
histological characteristics that
The Pericardium
distinguish cardiac muscle tissue from
skeletal muscle tissue: (1) small cell size,
The pericardium is the serous
Each cardiac muscle cell is
membrane that lines the (2) a single, centrally located nucleus,
connected to several
1 This is a view of a section taken from the wall pericardial cavity and covers the (3) branching interconnections others at specialized sites
heart (Module 4.14, p. 160). between cells, and (4) specialized
of the heart and the surrounding pericardium. known as intercalated
The heart wall contains three layers: epicardium, intercellular connections. (in-TER-ka-lā-ted) discs.
Parietal Pericardium
myocardium, and endocardium.
The parietal pericardium is the
portion of the serous membrane
that lines the outer wall of the
pericardial cavity. The parietal Cardiac muscle tissue LM × 575
pericardium is reinforced by a
dense fibrous layer; together 4 Cardiac muscle cells are found only in the heart. Like skeletal
Connective Pericardial cavity they form the pericardial sac muscle fibers, cardiac muscle cells contain organized
tissues (contains serous fluid) that surrounds the heart. myofibrils, and the presence of many aligned sarcomeres gives Cardiac muscle cells are relatively
the cells a striated appearance. They are almost totally small, averaging 10–20 μm in
Dense fibrous layer dependent on aerobic metabolism to obtain the energy they diameter and 50–100 μm in length.
Areolar tissue need to continue contracting. The sarcoplasm of a cardiac
muscle cell contains many mitochondria and abundant Intercalated
Mesothelium disc (sectioned)
reserves of myoglobin that store oxygen. Because these cells
Myocardium
Epicardium are metabolically very active and have a high demand for
The myocardium, or muscular oxygen and nutrients, cardiac tissues are richly supplied
The epicardium, or visceral Nucleus
wall of the heart, forms both atria with capillaries.
pericardium, covers the outer
and ventricles. This middle layer
surface of the heart. This portion
contains cardiac muscle tissue,
of the serous membrane Mitochondria
blood vessels, and nerves. The
consists of an exposed mesothe- 5 At an intercalated disc, the plasma membranes of two
myocardium consists of concen-
lium and an underlying layer of adjacent cardiac muscle cells are extensively intertwined
tric layers of cardiac muscle tissue.
areolar tissue that is attached to and bound together by gap junctions and desmosomes. These
the myocardium. connections help stabilize the positions of adjacent cells. The gap
Endocardium junctions allow ions and small molecules to move from one cell to another. Bundles of
Mesothelium myofibrils
This creates a direct electrical connection between the two muscle cells. An
The inner surfaces of the
Areolar tissue
heart, including those of the Endothelium action potential can travel across an intercalated disc, moving quickly from one
thheea retn vdaolvceasr, dairue mco, vae sriemdp bley Areolar tissue H e art wall cfiarrmdliya ca nmcuhsocrleed c etoll tthoe a mnoetmhebrr. aMney oafti bthriel si ninte trhcea ltawteod i ndtisecrl aonckdi ncagn m “puusclll et ocgeelltsh aerre” Idnistecrcalated
squamous epithelium and with maximum efficiency. Because the cardiac muscle cells are mechanically,
underlying areolar tissue. chemically, and electrically connected to one another, the entire tissue resembles
The squamous epithelial a single, enormous muscle cell. For this reason, cardiac muscle has been called a
lining of the cardiovascular functional syncytium (sin-SISH-ē-um; a fused mass of cells).
system is called an endothe-
lium. The endothelium of Gap junction
the heart is continuous with
the endothelium of the
attached great vessels.
Intercalated Disc
Atrial
Z lines bound to
2 The atrial myocardium contains musculature opposing cell Module 19.2 Review
membranes
muscle bundles that wrap around
a. From superficial to deep, name the
the atria and form figure-eights that Desmosomes layers of the heart wall.
encircle the great vessels. Superficial
b. Describe the tissue layers of the
ventricular muscles wrap around both
epicardium.
ventricles; deeper muscle layers
c. Why is it important that cardiac tissue
spiral around and between the
ventricles toward the apex in Ventricular contain many mitochondria and
musculature capillaries?
a figure-eight pattern.
19.2 Describe the structure of the pericardium and explain its functions, identify the
Section 1: Structure of the Heart • 687
layers of the heart wall, and describe the structures and functions of cardiac muscle.
M19_MART8949_02_SE_CH19.indd 687 12/4/13 2:48 PM
Module 19.3
The heart is located in the mediastinum,
and enclosed by the pericardial cavity
1 The position and orientation of the heart
Trachea 4 This is a diagrammatic superior view of a partial dissection
relative to the major vessels and the ribs,
Thyroid gland of the thoracic cavity. The image illustrates the position of the
sternum, and lungs can be seen in this anterior
First rib (cut) pericardial cavity and the physical relationships among the
view. The heart, surrounded by the pericardial
components in the mediastinum.
sac, sits in the anterior portion of the
mediastinum (mē-dē-as-TĪ-num), the Esophagus Posterior
region between the two pleural cavities. Base of heart mediastinum
The mediastinum also contains the great
Aorta (arch
vessels, thymus, esophagus, and trachea. Right lung Left lung
segment removed)
Apex of heart Left pulmonary
Diaphragm artery
Pericardial sac Right pleural cavity
Left pleural
(cut)
cavity
Anterior view of chest cavity Right Left
lung lung
2 To visualize the relationship between the Wrist (corresponds Left
heart, pericardium, and the pericardial to base of heart) Bronchus pulmonary
Inner wall (corresponds of lung vein
cavity, imagine pushing your fist toward the
to epicardium)
center of a large, partially inflated balloon. The
balloon represents the pericardium, and your fist
Air space (corresponds Right Aortic Pulmonary
is the heart. Your wrist, where the balloon folds to pericardial cavity) pulmonary arch trunk
back on itself, corresponds to the base of the
artery
heart, to which the great vessels, the largest Outer wall (corresponds Left atrium
veins and arteries in the body, are attached. to parietal pericardium) Right pulmonary
vein Left ventricle
The air space inside the balloon corresponds
Balloon
to the pericardial cavity. Superior vena cava Pericardial cavity
Epicardium
Right atrium
3 The pericardial sac, or fibrous pericardium,
The pericardial cavity contains 15–50 mL of
surrounds the heart. The pericardial sac
pericardial fluid, secreted by the pericardial Right ventricle Pericardial sac
consists of a dense network of collagen fibers. membranes. This fluid acts as a lubricant that Anterior mediastinum
It attaches to the central tendon of the reduces friction between the opposing surfaces as
diaphragm and sternum, and stabilizes the heart beats. Pathogens can infect the peri-
Base of heart
the position of the heart and associ- cardium, producing the condition pericarditis.
ated vessels within the mediastinum. The inflamed pericardial surfaces rub against one As you can see in this image, the heart does not have a lot
The parietal pericardium lines its another, producing a distinctive scratching sound of empty space around it—the thoracic cavity is very
that can be heard through a stethoscope.
inner surface. crowded. Traumatic injuries that damage the pericar-
dium or chest wall can result in fluid accumulation
within the pericardial cavity, which can restrict the
Parietal Pericardium
movement of the heart. This condition, called cardiac
Cut edge of epicardium Areolar tissue tamponade (tam-po-NĀD; tampon, plug), can also be
Mesothelium caused by acute pericarditis.
Cut edge of parietal
pericardium
Fibrous tissue of
pericardial sac
Fibrous attachment to Apex of heart
central tendon of diaphragm
688 • Chapter 19: The Heart and Cardiovascular Function
M19_MART8949_02_SE_CH19.indd 688 12/4/13 2:48 PM
1 The position and orientation of the heart
Trachea 4 This is a diagrammatic superior view of a partial dissection
relative to the major vessels and the ribs,
Thyroid gland of the thoracic cavity. The image illustrates the position of the
sternum, and lungs can be seen in this anterior
First rib (cut) pericardial cavity and the physical relationships among the
view. The heart, surrounded by the pericardial
components in the mediastinum.
sac, sits in the anterior portion of the
mediastinum (mē-dē-as-TĪ-num), the Esophagus Posterior
region between the two pleural cavities. Base of heart mediastinum
The mediastinum also contains the great
Aorta (arch
vessels, thymus, esophagus, and trachea. Right lung Left lung
segment removed)
Apex of heart Left pulmonary
Diaphragm artery
Pericardial sac Right pleural cavity
Left pleural
(cut)
cavity
Anterior view of chest cavity Right Left
lung lung
2 To visualize the relationship between the Wrist (corresponds Left
heart, pericardium, and the pericardial to base of heart) Bronchus pulmonary
Inner wall (corresponds of lung vein
cavity, imagine pushing your fist toward the
to epicardium)
center of a large, partially inflated balloon. The
balloon represents the pericardium, and your fist
Air space (corresponds Right Aortic Pulmonary
is the heart. Your wrist, where the balloon folds to pericardial cavity) pulmonary arch trunk
back on itself, corresponds to the base of the
artery
heart, to which the great vessels, the largest Outer wall (corresponds Left atrium
veins and arteries in the body, are attached. to parietal pericardium) Right pulmonary
vein Left ventricle
The air space inside the balloon corresponds
Balloon
to the pericardial cavity. Superior vena cava Pericardial cavity
Epicardium
Right atrium
3 The pericardial sac, or fibrous pericardium,
The pericardial cavity contains 15–50 mL of
surrounds the heart. The pericardial sac
pericardial fluid, secreted by the pericardial Right ventricle Pericardial sac
consists of a dense network of collagen fibers. membranes. This fluid acts as a lubricant that Anterior mediastinum
It attaches to the central tendon of the reduces friction between the opposing surfaces as
diaphragm and sternum, and stabilizes the heart beats. Pathogens can infect the peri-
Base of heart
the position of the heart and associ- cardium, producing the condition pericarditis.
ated vessels within the mediastinum. The inflamed pericardial surfaces rub against one As you can see in this image, the heart does not have a lot
The parietal pericardium lines its another, producing a distinctive scratching sound of empty space around it—the thoracic cavity is very
that can be heard through a stethoscope.
inner surface. crowded. Traumatic injuries that damage the pericar-
dium or chest wall can result in fluid accumulation
within the pericardial cavity, which can restrict the
Parietal Pericardium
movement of the heart. This condition, called cardiac
Cut edge of epicardium Areolar tissue tamponade (tam-po-NĀD; tampon, plug), can also be
Mesothelium caused by acute pericarditis.
Module 19.3 Review
Cut edge of parietal
pericardium
a. Define mediastinum.
Fibrous tissue of
pericardial sac b. Describe the heart’s location in the body.
Fibrous attachment to Apex of heart c. Why can cardiac tamponade be a life-
central tendon of diaphragm
threatening condition?
19.3 Describe the location and general features of the heart. Section 1: Structure of the Heart • 689
M19_MART8949_02_SE_CH19.indd 689 12/4/13 2:48 PM
Module 19.4
The boundaries between the 2 This view of the posterior surface of the
heart shows the left atrium and its
chambers of the heart can be connection to the pulmonary veins. It Aortic arch
also shows the right atrium and Left pulmonary artery
identified on its external surface its connection to the coronary Right pulmonary
Left pulmonary veins artery
veins and the venae cavae.
Superior vena cava
1 The four cardiac chambers can easily be identified in
Left
a superficial view of the anterior surface of the heart.
atrium
The two atria have relatively thin muscular walls and are highly
Fat and vessels in
expandable. When not filled with blood, the outer portion of each
the coronary sulcus Right pulmonary veins
atrium deflates and becomes a lumpy, wrinkled flap. Shallow
(superior and inferior)
grooves, or sulci (singular, sulcus), mark the boundaries between
the atria and ventricles and between the left and right ventricles. The coronary sinus carries
blood collected from the
The connective tissue of the epicardium generally contains
myocardium by numerous Right
substantial amounts of fat, especially along the sulci. In fresh coronary veins and conveys Left atrium
or preserved hearts, this fat must be stripped away to expose
the blood to the right atrium. ventricle
the underlying grooves. These sulci also contain the arteries
and veins that carry blood to and from the cardiac muscle.
Inferior vena cava
Right
ventricle
The posterior interventricular
sulcus is a shallow depression
The ligamentum arteriosum
on the posterior surface that
Aortic arch attaches the pulmonary trunk to the
marks the boundary between
aortic arch. It is a fibrous remnant of
the left and right ventricles.
the fetal connection between the
aorta and the pulmonary trunk.
Ascending aorta Posterior surface
Superior vena cava 3 As you see in this anterior view, a
Pulmonary trunk dissected heart from a preserved
cadaver is not conveniently
Left subclavian artery
The auricle (AW-ri-kl; auris, color-coded.
Auricle of left atrium Left common carotid artery
ear) of the atrium is an
Right
expandable pouch. It has Brachiocephalic trunk
atrium
this name because it Fat and vessels in the
reminded early anatomists anterior interventricular Ligamentum arteriosum
of the external ear. sulcus
Right Left pulmonary artery
Ascending aorta
ventricle
Pulmonary trunk
Superior vena cava
Left ventricle
Auricle of left atrium
The coronary sulcus, a
Left coronary artery
deep groove, marks the The anterior interventricular
border between the atria sulcus is a shallow depression Auricle of right atrium Anterior interventricular
and the ventricles. It on the anterior surface that sulcus
Right atrium
contains fat and vessels. marks the boundary between
the left and right ventricles. Right coronary Left
Right
artery ventricle
ventricle
Coronary sulcus
Anterior
Anterior surface Marginal branch interventricular
artery
of right coronary
artery
Cadaver dissection, anterior view
690 • Chapter 19: The Heart and Cardiovascular Function
M19_MART8949_02_SE_CH19.indd 690 12/4/13 2:48 PM
2 This view of the posterior surface of the
heart shows the left atrium and its
connection to the pulmonary veins. It Aortic arch
also shows the right atrium and Left pulmonary artery
its connection to the coronary Right pulmonary
Left pulmonary veins artery
veins and the venae cavae.
Superior vena cava
1 The four cardiac chambers can easily be identified in
Left
a superficial view of the anterior surface of the heart.
atrium
The two atria have relatively thin muscular walls and are highly
Fat and vessels in
expandable. When not filled with blood, the outer portion of each
the coronary sulcus Right pulmonary veins
atrium deflates and becomes a lumpy, wrinkled flap. Shallow
(superior and inferior)
grooves, or sulci (singular, sulcus), mark the boundaries between
the atria and ventricles and between the left and right ventricles. The coronary sinus carries
blood collected from the
The connective tissue of the epicardium generally contains
myocardium by numerous Right
substantial amounts of fat, especially along the sulci. In fresh coronary veins and conveys Left atrium
or preserved hearts, this fat must be stripped away to expose
the blood to the right atrium. ventricle
the underlying grooves. These sulci also contain the arteries
and veins that carry blood to and from the cardiac muscle.
Inferior vena cava
Right
ventricle
The posterior interventricular
sulcus is a shallow depression
The ligamentum arteriosum
on the posterior surface that
Aortic arch attaches the pulmonary trunk to the
marks the boundary between
aortic arch. It is a fibrous remnant of
the left and right ventricles.
the fetal connection between the
aorta and the pulmonary trunk.
Ascending aorta Posterior surface
Superior vena cava 3 As you see in this anterior view, a
Pulmonary trunk dissected heart from a preserved
cadaver is not conveniently
Left subclavian artery
The auricle (AW-ri-kl; auris, color-coded.
Auricle of left atrium Left common carotid artery
ear) of the atrium is an
Right
expandable pouch. It has Brachiocephalic trunk
atrium
this name because it Fat and vessels in the
reminded early anatomists anterior interventricular Ligamentum arteriosum
of the external ear. sulcus
Right Left pulmonary artery
Ascending aorta
ventricle
Pulmonary trunk
Superior vena cava
Left ventricle
Auricle of left atrium
The coronary sulcus, a
Left coronary artery
deep groove, marks the The anterior interventricular
border between the atria sulcus is a shallow depression Auricle of right atrium Anterior interventricular
and the ventricles. It on the anterior surface that sulcus
Right atrium
contains fat and vessels. marks the boundary between
the left and right ventricles. Right coronary Left Module 19.4 Review
Right
artery ventricle
ventricle
a. Name the four cardiac chambers.
Coronary sulcus
Anterior b. Name and describe the shallow
Anterior surface Marginal branch interventricular depressions and grooves found on the
artery
of right coronary heart’s external surface.
artery
c. Which structures collect blood from
the myocardium, and into which heart
Cadaver dissection, anterior view chamber does this blood flow?
19.4 Describe the cardiac chambers and the heart’s external anatomy. Section 1: Structure of the Heart • 691
M19_MART8949_02_SE_CH19.indd 691 12/4/13 2:48 PM
Module 19.5
Coronary Arteries
The heart has an extensive blood supply
Aortic
The heart works continuously, so cardiac muscle cells require reliable
arch
supplies of oxygen and nutrients. Although a great volume of blood
3 This view identifies the
flows through the chambers of the heart, the myocardium needs its own,
major collecting vessels on Left
separate blood supply. The coronary circulation supplies that blood to the
the anterior surface of the heart. atrium
muscle tissue of the heart. During maximum exertion, blood flow to the
myocardium may increase to nine times that of resting levels. The great cardiac vein begins on the
Right anterior surface of the ventricles, along
1 The left and right coronary arteries originate at the base of atrium the interventricular sulcus. This vein
Left Coronary Artery
the ascending aorta, where blood pressure is the highest in Pulmonary drains blood from the region supplied
the systemic circuit. However, myocardial blood flow is not trunk The left coronary by the anterior interventricular
steady: It peaks while the heart muscle is relaxed, and almost Aaorrcthic artery supplies The anterior cardiac veins, Right artery. The great cardiac vein reaches
ceases while it contracts. blood to the left which drain the anterior surface ventricle Left the level of the atria and then curves
ventricle, left atrium, of the right ventricle, empty ventricle around the left side of the heart within
Left and interventricular directly into the right atrium. the coronary sulcus to empty into the
atrium
septum. coronary sinus.
Circumflex artery
Right Anterior view
Right Coronary Artery atrium The large anterior
interventricular (left
The right coronary artery, which follows the coronary sulcus
around the heart, supplies blood to the right atrium, portions Right aanrtteerriyo rru dness caelonndgin g) 4 This view identifies the major
of both ventricles, and portions of the conducting system of ventricle Left collecting vessels on the posterior
the surface within
the heart, which contols and coordinates the heartbeat. ventricle surface of the heart.
the anterior
interventricular
Great
Marginal arteries from the right coronary artery supply sulcus. Left
cardiac vein
the surface of the right ventricle. atrium
Anterior view The coronary sinus is an
expanded vein that opens into
the right atrium near the base Right
2 Branches of the left and right coronary arteries Arterial anastomoses between the of the inferior vena cava. Left atrium The small cardiac vein receives blood
continue onto the posterior surface of the heart. anterior and posterior interventricular ventricle from the posterior surfaces of the right
arteries maintain a fairly continuous atrium and ventricle. It empties into the
The circumflex artery is a branch of the blood flow despite pressure fluctua- coronary sinus along with the middle
left coronary artery that curves to the left tions in the left and right coronary The posterior cardiac cardiac vein.
around the coronary sulcus, eventually arteries. vein drains the area
Right
meeting and fusing with small branches supplied by the ventricle
of the right coronary artery. A marginal circumflex artery. The middle cardiac vein, draining
artery branches from the circumflex the area supplied by the posterior
artery to supply the posterior surface Left Posterior view interventricular artery, empties into
atrium
of the left ventricle. the coronary sinus.
Marginal
artery Each time the left ventricle contracts, it forces blood into the
Right
Left atrium The right coronary artery continues across aorta. The arrival of additional blood at elevated pressures
ventricle the posterior surface of the heart, supply-
stretches the elastic walls of the aorta. When the left
ing the posterior interventricular
ventricle relaxes, pressure decreases, and the walls of the
(posterior descending) artery, which runs
toward the apex within the posterior aorta recoil. This recoil, called elastic rebound, pushes
Right interventricular sulcus. This vessel supplies blood both forward, into the systemic circuit, and backward,
ventricle blood to the interventricular septum and into the coronary arteries. Thus, the combination of blood
Right coronary adjacent portions of the ventricles. pressure and elastic rebound ensures a continuous flow of
artery
blood to meet the demands of active cardiac muscle tissue.
Posterior view
692 • Chapter 19: The Heart and Cardiovascular Function
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