The Heart
The cardiovascular system
Dr Tomasz Cecot
Principal Lecturer
tscecot@hku.hk
Learning outcomes
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Trace the pathway of blood through the heart
Name the heart valves and describe their location, function
and mechanism of operation
Name the major branches and describe the distribution of
coronary vessels
Name the components of the heart conduction pathway
Describe the structural properties of the heart muscle
Name coverings of the heart
Briefly explain main heart diseases
Main function
To pump blood
How is the heart designed to perform this function?
Chambers
The heart has four chambers
Right ATRIUM
Left ATRIUM
Left VENTRICLE
Right VENTRICLE
Septa
The internal partitions that divide the heart
INTERATRIAL septum
separates the atria
INTERVENTRICULAR
septum
separates the ventricles
Chambers
Left ATRIUM
Right ATRIUM
Left VENTRICLE
Right VENTRICLE
Anterior view
Grooves
Anterior
interventricular
sulcus
Coronary sulcus
Anterior view
Venae cave
Superior vena cava
Right ATRIUM
Inferior vena cava
Direction of blood flow
Deoxygenated blood
Pulmonary arteries
Pulmonary artery
Right lung
Pulmonary artery
Left lung
Pulmonary trunk
Right Ventricle
Direction of blood flow
Deoxygenated blood
Pulmonary veins
Pulmonary veins
Pulmonary veins
Left lung
Right lung
Left Atrium
Direction of blood flow
Oxygenated blood
Aorta
Aorta
Left Ventricle
Direction of blood flow
Oxygenated blood
Chambers
Left ATRIUM
Right ATRIUM
Left VENTRICLE
Right VENTRICLE
Posterior view
Grooves
Coronary sulcus
Posterior interventricular sulcus
Posterior view
Great vessels
Think about the direction of blood flow on this diagram. Mark it using arrows.
Pulmonary trunk
Pulmonary arteries
Superior vena cava
Inferior vena cava
Posterior view
Great vessels
Think about the direction of blood flow on this diagram. Mark it using arrows.
Aorta
Pulmonary veins
Pulmonary veins
Posterior view
Circuits
The right side of the heart pumps
blood through the pulmonary circuit
The left side of the heart pumps blood
via the systemic circuit to all body
tissues and back to the right side of
the heart.
Valves
Right atrioventricular valve
Tricuspid valve
Left atrioventricular valve
Bicuspid valve
Mitral valve
Valves
Pulmonary valve
Aortic valve
Mechanism of action
Cusp
Cusp
Chordae tendinae
Papillary muscles
Papillary muscles
Direction of blood flow
Mechanism of action
Cardiac muslce
Striation: actin and myosin
Intercalated disc
Nucleus
centrally located
Artist’s impression
interbranching cells
Properties of Cardiac Muscle
Structural Properties
(Anatomical / Histological Features)
• Striated muscle fibres
• Branched muscle fibres
• Single central nucleus (occasionally
binucleate)
• Sarcomeres present
• Intercalated discs
• Desmosomes
• Gap junctions
• Abundant mitochondria
• Rich blood supply
• Elastic connective tissue support
Functional Properties
(Physiological Characteristics)
•Involuntary
•Functional syncytium
•Aerobic metabolism
•Limited regenerative capacity
•Highly fatigue resistant
•Excitable
•Conductive
•Contractile
•Rhythmic (autorhythmic) cells present
Functional syncytium
Limited regenerative capacity
Aerobic metabolism and fatigue resistance
Conducting system of the heart
Sinoatrial/SA node
Atrioventricular/AV node
Atrioventricular bundle/bundle of His
Purkinje fibres
Direction of impulse propagation
Autorhythmic fibres
Specialised cardiac muscle fibres that can spontaneously depolarise to generate action potentials
Lumen of the heart
Endocardium
Autorhythmic fibres
• repeatedly generate action potentials
Myocardium
Layers of the heart wall
The thickness varies according to the chamber function
Lumen of the heart
Epicardium
mesothelium + connective tissue
Endocardium
endothelium + connective tissue
Pericardial cavity
Atrial wall
Coronary circulation: arteries
Provides circulation to the myocardium via ‘end arteries’
Left coronary artery
in coronary sulcus
Aorta
Circumflex branch
first part in coronary sulcus
Right coronary artery
in coronary sulcus
Anterior interventricular artery
in anterior interventricular sulcus
Posterior interventricular artery
Direction of blood flow
in posterior interventricular sulcus
Anterior view
Coronary circulation: veins
Great cardiac vein
in anterior interventricular and coronary sulcus
Middle cardiac vein
in posterior interventricular sulcus
Small cardiac vein
last part in coronary sulcus
Coronary sinus
in coronary sulcus
Right atrium
Direction of blood flow
Posterior view
Pericardium
Outer fibrous membrane
Inner serous membrane
Pericardial cavity
Pericardial cavity filled with lubricating fluid that reduces the friction between the two layers of the
serous pericardium
= Epicardium
Location of the heart
About the size of a clenched fist located obliquely within the thorax
• 2/3 to the left of the midline
• Shape as a cone lying on its side:
• Apex
• Base
Mediatstinum
Myocardial infarction
Heart attack is the irreversible death (necrosis) of heart muscle caused by prolonged lack of oxygen
supply (ischemia) following acute obstruction of a coronary artery.
Key Features
• Usually caused by rupture of an atherosclerotic
plaque
• Results in acute coronary artery occlusion
• Myocardial cells begin to die after prolonged
ischaemia
• Necrotic myocardium is replaced by scar tissue
area of tissue that has died
(undergone necrosis)
Atherosclerotic
plaque
Plaque rupture
Thrombus
formation
Coronary artery
occlusion
Reduced
oxygen delivery
Myocardial
ischaemia
Myocardial
infarction
Arrythmia
Abnormal heart rhythm caused by a disturbance in the generation or conduction of electrical impulses
within the heart.
Types of Arrhythmias:
• Tachycardia: Heart rate > 100 bpm
• Bradycardia: Heart rate < 60 bpm
• Irregular rhythm: Abnormal timing of heartbeats
(e.g. atrial fibrillation)
A pacemaker is an implanted electronic device that generates electrical impulses to maintain an adequate
heart rate when the heart's conduction system fails.
Summary
• The heart consists of four chambers: the two atria and the two
ventricles.
• There are four valves of the heart
• The heart wall itself can be divided into three distinct layers: the
endocardium, myocardium, and epicardium
• The cardiac conduction system is a collection of nodes and
specialised conduction cells that initiate and co-ordinate
contraction of the heart muscle
• The pericardial sac is made up of two main layers: fibrous
pericardium and serous pericardium
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