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© Endeavour College of Natural Health endeavour.edu.au
BIOH122Human Biological Science 2
Session 3
Cardiovascular System –
The Heart
Bioscience Department
© Endeavour College of Natural Health endeavour.edu.au 2
Session Plan
o Anatomy of the Heart• Heart Location
• Heart Orientation
• Surface Projection of the Heart
• Pericardium
• Layers of Heart Wall
• Muscle Bundles of the Myocardium
• Chambers and Sulci of the Heart
• Myocardial Thickness and Function
o Heart Valves and Circulation of the Blood• Atrioventricular Valves
• Semilunar Valves
• Blood Circulation
o Histology of Cardiac Muscle Tissue
o The Conduction System
© Endeavour College of Natural Health endeavour.edu.au 3
Anatomy of the Heart
© Endeavour College of Natural Health endeavour.edu.au 4
Cardiovascular system
o The cardiovascular system: consists of the blood, heart,
and blood vessels, Supply blood to whole body tissues
and maintain homeostasis
o The heart is the pump that circulates the blood through
an estimated 97,000 kilometers of blood vessels.
o Heart pumps over 10 million liters per year.
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Location of the Heart
o Location: The heart is situated between the lungs in the thoracic
cavity with about two-thirds of its mass to the left of the midline .
The heart lies between two rigid structures: The vertebral column and the sternum.
External cardiac compression on the chest forces blood out of the heart and into the circulation.
© Endeavour College of Natural Health endeavour.edu.au 6
Heart Orientation
o Apex - directed anteriorly, inferiorly and to the left
o Base - directed posteriorly, superiorly and to the right
o Anterior surface - deep to the sternum and ribs
o Inferior surface - rests on the diaphragm
o Right border - faces right lung
o Left border (pulmonary border) - faces left lung
© Endeavour College of Natural Health endeavour.edu.au 7
Heart Orientation
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 8
Surface Projection of the Heart
© Endeavour College of Natural Health endeavour.edu.au 9
Pericardium
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 10
Pericardiumo Fibrous pericardium
• dense irregular connective tissue
• protects and anchors the heart, prevents overstretching
o Serous pericardium
• thin delicate membrane
• contains
– parietal layer - outer layer
– visceral layer - inner layer
o Pericardial cavity: Space filled with pericardial fluid between the parietal
and visceral pericardium. Reduces friction between the two membranes.
– An inflammation of the pericardium is known as pericarditis. Associated
bleeding / fluid into the pericardial cavity and compresses the heart;
potentially lethal.
© Endeavour College of Natural Health endeavour.edu.au 11
Layers of the Heart Wall
o Three layers: epicardium, myocardium, and
endocardium.
• The epicardium
• The myocardium composed of cardiac muscle, and
• The endocardium primarily endothelium
o Myocarditis is an inflammation of the myocardium.
o Endocarditis in an inflammation of the endocardium. It
usually involves the heart valves.
© Endeavour College of Natural Health endeavour.edu.au 12
Layers of Heart Wall
o Epicardium
• visceral layer of
serous pericardium
o Myocardium
• cardiac muscle layer
is the bulk of the heart
o Endocardium
• chamber lining and
valves
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 13
Muscle Bundles of the Myocardium
o Cardiac muscle fibers swirl diagonally around the heart in interlacing bundles
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 14
Chambers of the Heart
o Four chambers:
• 2 upper atria (left and right)
• 2 lower ventricles (left and right)
© Endeavour College of Natural Health endeavour.edu.au 15
Chambers of the Heart
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 16
Right Atrium
Right Atrium:
o Receives blood from 3 sources
• superior vena cava, inferior vena cava and coronary
sinus
o Interatrial septum partitions the atria
o Fossa ovalis is a remnant of the foetal foramen ovale
o Tricuspid valve
• blood flows through into right ventricle
• has three cusps composed of dense Connective
Tissue covered by endocardium
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Right Ventricle
Right Ventricle:
o Forms most of anterior surface of heart
o Papillary muscles are cone shaped trabeculae carneae
(raised bundles of cardiac muscle)
o Chordae tendineae: cords between valve cusps and
papillary muscles
o Interventricular septum: partitions the ventricles
o Pulmonary semilunar valve: blood flows into pulmonary
trunk (and then pulmonary arteries)
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Left Atrium
Left Atrium:
o Forms most of the base of the heart
o Receives blood from lungs - 4 pulmonary veins (2 right +
2 left)
o Bicuspid valve: blood passes through into left ventricle
• has two cusps
• to remember names of this valve, try the mnemonic
LAMB
– Left Atrioventricular, Mitral, or Bicuspid valve
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Left Ventricle
Left Ventricle:
o Forms the apex of heart
o Chordae tendineae anchor bicuspid valve to papillary
muscles (also has trabeculae carneae like right ventricle)
o Aortic semilunar valve:
• blood passes through valve into the ascending aorta
• just above valve are the openings to the coronary
arteries
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Sulci of the Heart
o Sulci - grooves on surface of heart containing coronary
blood vessels and fat
• coronary sulcus
– encircles heart and marks the boundary between
the atria and the ventricles
• anterior interventricular sulcus
– marks the boundary between the ventricles
anteriorly
• posterior interventricular sulcus
– marks the boundary between the ventricles
posteriorly
© Endeavour College of Natural Health endeavour.edu.au 21
Chambers and Sulci
Anterior View Posterior View
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 22
Myocardial Thickness and Function
o The thickness of the myocardium of the four chambers
varies according to the function of each chamber.
• The atria walls are thin because they only deliver
blood to the ventricles
• The ventricle walls are thicker pumping blood further.
• The right ventricle walls are thinner than the left
because they pump blood into the lungs, which are
nearby and offer very little resistance to blood flow.
– The left ventricle walls are thicker because they pump blood
through the body where the resistance to blood flow is
greater.
© Endeavour College of Natural Health endeavour.edu.au 23
Myocardial Thickness and Function
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 24
Heart Valves
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Heart Valves and Circulation of Blood
o Heart Valves: open and close in response to pressure
changes as the heart contracts and relaxes.
o Fibrous Skeleton of Heart: Dense Connective Tissue
rings surround the valves of the heart, fuse and merge
with the interventricular septum
• Support structure for heart valves
• Insertion point for cardiac muscle bundles
• Electrical insulator between atria and ventricles
– prevents direct propagation of Action Potential to
ventricles
© Endeavour College of Natural Health endeavour.edu.au 26
Fibrous Skeleton of Heart
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 27
Atrioventricular Valves Open
o Atrioventricular (A-V) Valves open and allow blood to flow from atria into ventricles when ventricular pressure is lower than atrial pressure
• occurs when ventricles are relaxed, chordae tendineae are slack and papillary muscles are relaxed
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 28
Atrioventricular Valves Close
o A-V valves close preventing backflow of blood into atria
• occurs when ventricles contract, pushing valve cusps closed, chordae tendinae are pulled taut and papillary muscles contract to pull cords and prevent cusps from everting
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 29
(c) Tricuspid valve open
Cusp of
tricuspid
valve
Chordae
tendineae
Papillary
muscle
© Endeavour College of Natural Health endeavour.edu.au 30
Semilunar Valves Open
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
(e) Superior view with atria removed: pulmonary and aortic valves open, bicuspid and tricuspid valves closed
Pulmonary valve (open)
POSTERIOR
Aortic valve
(open)
Tricuspid valve
(closed)
o Semilunar (SL) valves open with ventricular contraction
• allow blood to flow into pulmonary trunk and aorta
Bicuspid valve
(closed)
© Endeavour College of Natural Health endeavour.edu.au 31
Semilunar Valves Close
o SL valves close with ventricular relaxation
• prevents blood from returning to ventricles, blood fills valve cusps, tightly closing the SL valves
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 32
Semilunar cusp of
aortic valve
(g) Superior view of aortic valve
© Endeavour College of Natural Health endeavour.edu.au 33
Heart Valve Disorders
o Stenosis is a narrowing of a heart valve which restricts
blood flow.
o Insufficiency or incompetence is a failure of a valve to
close completely. Causes regurgitation / back flow
o Stenosed valves may be repaired by balloon
valvuloplasty, surgical repair, or valve replacement.
© Endeavour College of Natural Health endeavour.edu.au 34
Blood Circulation
o Circulation of the
blood: divided into
two closed circuits
• Systemic circulation
(includes coronary
circulation)
• Pulmonary circulation
Blood flow
Blue = deoxygenated
Red = oxygenated
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 35
Blood Circulation
o Systemic circulation
• left side of heart pumps blood through body
• left ventricle pumps oxygenated blood into aorta
• aorta branches into many arteries that travel to
organs
• arteries branch into many arterioles in tissues
• arterioles branch into thin-walled capillaries for
exchange of gases and nutrients
• deoxygenated blood begins its return in venules
• venules merge into veins and return to right atrium
© Endeavour College of Natural Health endeavour.edu.au 36
Blood Circulation
o Pulmonary circulation
• right side of heart pumps deoxygenated blood to
lungs
• right ventricle pumps blood to pulmonary trunk
• pulmonary trunk branches into pulmonary arteries
• pulmonary arteries carry blood to lungs for exchange
of gases
• oxygenated blood returns to heart in pulmonary veins
to left atria
© Endeavour College of Natural Health endeavour.edu.au 37
Coronary Circulation
o Coronary Circulation:
• The flow of blood through the many vessels that flow
through the myocardium of the heart is called the
coronary (cardiac) circulation
• It delivers oxygenated blood and nutrients to and
removes carbon dioxide and wastes from the
myocardium.
• Many anastomoses provide alternate routes if one
artery becomes occluded.
© Endeavour College of Natural Health endeavour.edu.au 38
Coronary Arteries
Coronary Arteries:
o Branches off aorta above aortic semilunar valve
o Left coronary artery
• supplies left atrium and left ventricle
o Right coronary artery
• supplies right atria
• supplies both ventricles
© Endeavour College of Natural Health endeavour.edu.au 39
Coronary Arteries
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 40
Coronary Veins
Coronary Veins:
o Collects wastes from cardiac muscle
o Drains into a large sinus on posterior surface of heart called the coronary sinus
o Coronary sinus empties into right atrium
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Myocardial Ischemia and Infarction
o Myocardial Ischemia: Reduced blood flow through
coronary arteries may cause ischemia. Ischemia causes
hypoxia and may weaken the myocardial cells. Ischemia
is often manifested through angina pectoris.
o Myocardial infarction: A complete obstruction of flow in a
coronary artery may cause myocardial infarction (heart
attack).
• Tissue distal to the obstruction dies and is replaced by scar
tissue.
• Treatment may involve injection of thrombolytic agents, coronary
angioplasty, or coronary artery bypass grafts.
© Endeavour College of Natural Health endeavour.edu.au 42
Histology of Cardiac Muscle Tissue
© Endeavour College of Natural Health endeavour.edu.au 43
https://www.youtube.com/watch?v=rUDqP
hzKzZM
Cardiac muscle fibers:
Shorter in length
Larger in diameter
compared to skeletal muscle fibers.
They also exhibit branching.
Fibers within the networks are connected
by intercalated discs, which consist of
desmosomes and gap junctions.
Gap junctions important for electrical
connectivity
© Endeavour College of Natural Health endeavour.edu.au 44
Cardiac Muscle Histology
o Branching, intercalated discs with gap junctions, involuntary,
striated, single central nucleus per cell
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
© Endeavour College of Natural Health endeavour.edu.au 45
Cardiac Myofibril
Tortora, GJ & Derrickson, B 2012. Principles of Anatomy and Physiology, 13th edn, John Wiley &
Sons, New York.
Have actin and myosin
Arranged in
Lines
Zones
Bands
Z discs
Have less sarcoplasmic
reticulum and require
Ca2+ from extracellular
fluid for contraction.
© Endeavour College of Natural Health endeavour.edu.au 46
Conduction System of Heart
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Conduction System of Heart
o The conduction system in the heart is unique with
autorhythmic cells derived from cardiac muscle.
• Autorhythmic cells are cardiac muscle cells that are self-
excitable. They repeatedly generate spontaneous action
potentials that then trigger heart muscle contractions.
• These cells act as a pacemaker to set the rhythm for the entire
heart.
• They form the conduction system, the route for propagating
action potentials through the heart muscle
o This co-ordinates contraction of heart muscle.
© Endeavour College of Natural Health endeavour.edu.au 48
Conduction System of Heart
o Components of Conduction system:
• Sinoatrial (SA) node (pacemaker),
• Atrioventricular (AV) node,
• Atrioventricular bundle (bundle of His),
• Right and left bundle branches,
• The conduction myofibers (Purkinje fibers)
o Signals from the autonomic nervous system and
hormones, such as adrenaline can modify the heartbeat
(in terms of rate and strength of contraction)
© Endeavour College of Natural Health endeavour.edu.au 49
Conduction System of Heart
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Conduction System of Heart
o SA node
• cluster of cells in wall of right atria
• begins heart activity that spreads to both atria
• sets the rhythm for contraction of the heart—the
natural pacemaker.
• excitation spreads to AV node
o AV node
• in atrial septum, transmits signal to bundle of His
© Endeavour College of Natural Health endeavour.edu.au 51
Conduction System of Heart
o Bundle of His
• the connection between atria and ventricles
• divides into the left and right bundle branches
o Purkinje fibers
• large diameter fibers that conduct signals quickly
© Endeavour College of Natural Health endeavour.edu.au 52
Rhythm of Conduction System
o SA node fires spontaneously 90-100 times per minute
o AV node fires at 40-50 times per minute
o If both nodes are suppressed then the fibers in the
ventricles by themselves fire only 20-40 times per minute
o Artificial pacemaker needed if pace is too slow
o Extra beats forming at other sites are called ectopic
pacemakers
• caffeine and nicotine increase activity
© Endeavour College of Natural Health endeavour.edu.au 53
Timing of Atrial and
Ventricular Excitation
o SA node sets the pace since it is the fastest
o Spreads through both atria and down to AV node
o 100 msec delay at AV node. This allows atria to fully
contract so ventricles are full before ventricles contract
o Excitation spreads through both ventricles
simultaneously
© Endeavour College of Natural Health endeavour.edu.au 54
Abnormal Conduction
o Sick sinus syndrome: An abnormally functioning SA node
that initiates irregular heart beats.
o When abnormal pacing of the heart develops, heart
rhythm can be restored by implanting an artificial
pacemaker, a device that sends out small, regular
currents to stimulate myocardial contraction.
© Endeavour College of Natural Health endeavour.edu.au 55
Readings and Resources
o Tortora, GJ & Derrickson, B 2014. Principles of Anatomy and Physiology, 14th edn, Wiley.
o Harris, P, Nagy, S & Vardaxis, N 2010, Mosby’s Dictionary of Medicine, Nursing and Health Professions, 2nd edn, Mosby Elsevier.
o Guyton, AC & Hall, JE 2011, Textbook of Medical Physiology, 12th edn, Saunders Elsevier.
o Marieb, EN & Hoehn, K 2010, Human Anatomy and Physiology, 8th edn, Benjamin Cummings Pearson.
o Moore, KL, Dalley, AF & Agur, AMR 2010, Clinically Orientated Anatomy, 6th edn, Lippincott, Williams & Wilkins.
© Endeavour College of Natural Health endeavour.edu.au 56
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