Anatomy of the Human Heart: Difference between revisions

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== Introduction  ==
== Introduction  ==
[[File:Heart 2.jpg|350x350px|right|frameless]]The heart is a muscular organ that serves to collect deoxygenated [[Blood Physiology|blood]] from all parts of the body, carries it to the [[Lung Anatomy|lung]]<nowiki/>s to be oxygenated and release carbon dioxide. Then, it transports the oxygenated [[blood]] from the lungs and distributes it to all the body parts<ref name=":2">Kenny, WL,Wilmore, JH, Costill, DL. Cardiovascular System and its Control.  In Physiology of Sport and Exercise, 5rdedn. Human Kinetics, 2011. 140-150.</ref>.
[[File:The Heart surface view.jpg|right|frameless|499x499px]]
The heart is a muscular organ that serves to collect deoxygenated [[Blood Physiology|blood]] from all parts of the body, carries it to the [[Lung Anatomy|lung]]<nowiki/>s to be oxygenated and release carbon dioxide. Then, it transports the oxygenated [[blood]] from the lungs and distributes it to all the body parts<ref name=":2">Kenny, WL,Wilmore, JH, Costill, DL. Cardiovascular System and its Control.  In Physiology of Sport and Exercise, 5rdedn. Human Kinetics, 2011. 140-150.</ref>
* The heart pumps around 7,200 litres of blood in a day throughout the body<ref>[https://www.inovaheart.org/upload/docs/Healthcare%20Services/Heart%20and%20Vascular/fast-facts-about-the-heart.pdf Inovqheart Heart Available from: https://www.inovaheart.org/upload/docs/Healthcare%20Services/Heart%20and%20Vascular/fast-facts-about-the-heart.pdf]</ref>.
* The heart pumps around 7,200 litres of blood in a day throughout the body<ref>[https://www.inovaheart.org/upload/docs/Healthcare%20Services/Heart%20and%20Vascular/fast-facts-about-the-heart.pdf Inovqheart Heart Available from: https://www.inovaheart.org/upload/docs/Healthcare%20Services/Heart%20and%20Vascular/fast-facts-about-the-heart.pdf]</ref>.
* The heart is situated at the centre of the chest and points slightly towards the left.
* The heart is situated at the centre of the chest and points slightly towards the left.
* On average, the heart beats about 100,000 times a day, i.e., around 3 billion beats in a lifetime.
* On average, the heart beats about 100,000 times a day, i.e., around 3 billion beats in a lifetime.
* The average male heart weights around 280 to 340 grams (10 to 12 ounces). In females, it weights around 230 to 280 grams (8 to 10 ounces). Infants heart - about a thirtieth of total body weight<ref>Balaban, NE, Bobick, J, Cardiovascular system.The Handy Anatomy Answer Book. Detroit:Visible Ink Press, 2008. P197.</ref>
* An adult heart beats about 60 to 80 times per minute, and newborn babies heart beats faster than an adult which is about 70 to 190 beats per minute.
* An adult heart beats about 60 to 80 times per minute, and newborn babies heart beats faster than an adult which is about 70 to 190 beats per minute.
It is important to note that, the blood pumped by the heart also circulates many other important substances<ref name=":2" /><ref name=":3">Malouf, JF, Edwards, WD, Tajil, AJ, Seward, JB. Functional anatomy of the heart. In: Fuster, F, Alexander, RW, O’Rourke, RA editors. Hurst’s: The Heart. 10th edn. McGraw-Hill Inc., 2001. p19–62. </ref> such as:
 
# Nutrients from digestion are collected from the small intestine and pumped through the circulatory system to be delivered to all cells of the body.
# [[Hormones]] are produced from one type of tissues and distributed to all cells of the body. The [[Cardiovascular System|circulatory]] system carries waste materials (salts, nitrogenous wastes, and excess water) from cells to the [[kidney]]<nowiki/>s, where they are extracted and passed to the bladder.
# The pumping of interstitial fluid from the blood into the extracellular space is an important function of the heart. Excess interstitial fluid is then returned to the [[Cardiovascular System|circulatory system]] via the [[Lymphatic System|lymphatic system.]]


== Anatomy  ==
== Anatomy  ==
[[File:Chest auscultation.jpg|right|frameless]]
[[File:Heart location.jpg|right|frameless]]
The heart has a somewhat conical form and is enclosed by the pericardium. It is positioned posteriorly to the body of the sternum with one-third situated on the right and two-thirds on the left of the midline.  The heart measures 12 x 8.5 x 6 cm and weighs ~310 g (males) and ~255 g (females)
The heart is a conical hollow muscular organ situated in the middle mediastinum and is enclosed within the pericardium. It is positioned posteriorly to the body of the sternum with one-third situated on the right and two-thirds on the left of the midline.  The heart measures 12 x 8.5 x 6 cm and weighs ~310 g (males) and ~255 g (females). It pumps blood to various parts of the body to meet their nutritive requirements. The Greek name for the heart is cardia from which we have the adjective cardia. <ref>Chaurasia BD. [https://www.pdfdrive.com/bd-chaurasia-books.html Human Anatomy Regional and Applied Dissection and Clinical. Vol 1]. CBS Publishers and Distributors Pvt Ltd, 2010
 
</ref>


Relations
Relations
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* Inferiorly: diaphragm
* Inferiorly: diaphragm
* Laterally: lungs, pleura<ref name=":6">Radiopedia Heart Available: https://radiopaedia.org/articles/heart?lang=gb (accessed 17.6.2021)</ref>
* Laterally: lungs, pleura<ref name=":6">Radiopedia Heart Available: https://radiopaedia.org/articles/heart?lang=gb (accessed 17.6.2021)</ref>
*
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===  Layers of the Heart Walls  ===
===  Layers of the Heart Walls  ===
The heart wall consists of three layers enclosed in the pericardium<ref name=":2" /><ref name=":3" /><ref name=":5">Drake, RL, Vogl, W, Mitchell, AW, Gray, H. Gray's anatomy for Students 2nd ed. 
[[File:Heart layers.jpg|right|frameless|399x399px]]
The heart wall consists of three layers enclosed in the pericardium<ref name=":2" /><ref name=":3">Malouf, JF, Edwards, WD, Tajil, AJ, Seward, JB. Functional anatomy of the heart. In: Fuster, F, Alexander, RW, O’Rourke, RA editors. Hurst’s: The Heart. 10th edn. McGraw-Hill Inc., 2001. p19–62. </ref><ref name=":5">Drake, RL, Vogl, W, Mitchell, AW, Gray, H. Gray's anatomy for Students 2nd ed. 
Philadelphia : Churchill Livingstone/Elsevier, 2010.
Philadelphia : Churchill Livingstone/Elsevier, 2010.
</ref>:
</ref>:
[[File:Heart layers.jpg|450x450px|right|frameless]]
# Epicardium - the outer layer of the wall of the heart and is formed by the visceral layer of the serous pericardium.
# '''Epicardium''' - the outer layer of the wall of the heart and is formed by the visceral layer of the serous pericardium.
# Myocardium - the muscular middle layer of the wall of the heart and has excitable tissue and the conducting system.  
'''2. Myocardium''' - the muscular middle layer of the wall of the heart and has excitable tissue and the conducting system. It is composed of three discernable layers of muscle that are seen predominantly in the left ventricle and inter-ventricular septum alone. It includes:  
# Endocardium .<ref name=":6" />
* A subepicardial layer
* A middle concentric layer
* A middle concentric layer
* A subendocardial layer.
* A subendocardial layer.
The rest of the heart is composed mainly of the subepicardial and subendocardial layers.   
The rest of the heart is composed mainly of the subepicardial and subendocardial layers.   
'''3. Endocardium''' - the innermost layer of the heart is formed of the endothelium and subendothelial connective tissue


=== Structure and Function  ===
=== Structure and Function  ===
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* right ventricle
* right ventricle
* left ventricle<ref name=":6" />.  
* left ventricle<ref name=":6" />.  
The right atrium receives deoxygenated blood from the entire body except for the lungs (the systemic circulation) via the superior and inferior vena cavae. Also, deoxygenated blood from the heart muscle itself drains into the right atrium via the coronary sinus. The right atrium, therefore, acts as a reservoir to collect deoxygenated blood. From here, blood flows through the tricuspid valve to fill the right ventricle, which is the main pumping chamber of the right heart.


The right ventricle pumps blood through the right ventricular outflow tract, across the pulmonic valve, and into the pulmonary artery that distributes it to the lungs for oxygenation. In the lungs, the blood oxygenates as it passes through the capillaries, where it is close enough to the oxygen in the alveoli of the lungs. This oxygenated blood is collected by the four pulmonary veins, two from each lung. All four of these veins open into the left atrium that acts as a collection chamber for oxygenated blood. As with the right atrium, the left atrium passes the blood onto its ventricle both by passive flow and active pumping. Oxygenated blood thus fills the left ventricle, passing through the mitral valve. The left ventricle is the main pumping chamber of the left heart, then pumps, sending freshly oxygenated blood to the systemic circulation through the aortic valve. The cycle is then repeated all over again in the next heartbeat.


All four valves of the heart mentioned below have a singular purpose: allowing forward flow of blood but preventing backward flow.<ref name=":0">Rehman I, Rehman A. Anatomy, Thorax, Heart. [Updated 2020 Dec 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan Available:https://www.ncbi.nlm.nih.gov/books/NBK470256/ (accessed 17.6.2021)</ref>
It is best to remember the four chambers and four valves in order of the series that blood travels through the heart:
=== Heart Valves  ===
The heart has the Four valves.


'''Pulmonary Valve''' - The opening into the pulmonary trunk is closed by the pulmonary valve, which consists of three semilunar cusps with free edges projecting upward into the lumen of the pulmonary trunk thus prevents the backflow of blood as it is pumped from the right ventricle to the pulmonary artery. The cusps are named the left, right and anterior semilunar cusps, relative to their fetal position. Each cusp forms a pocket-like sinus; a dilation in the wall of the initial portion of the pulmonary trunk.<ref name=":5" />
* Venous blood returning from the body drains into the right atrium via the [[Vena Cava|SVC, IVC]] and coronary sinus
[[File:Heart Valves.jpg|450x450px|right|frameless]]
* The right atrium pumps blood through the tricuspid valve into the right ventricle
'''Tricuspid Valve''' - The right atrioventricular opening is closed during ventricular contraction by the tricuspid valve (right atrioventricular valve) thus prevents the backflow of blood as it is pumped from the right atrium to the right ventricle. It’s named tricuspid valve because it made up of three cusps or leaflets.  The naming of the three cusps, the anterior, septal, and posterior cusps, is based on their position in relation to the right ventricle. 
* The right ventricle pumps blood through the pulmonary semilunar valve into the pulmonary trunk to be oxygenated in the lungs
* Blood returning from the lungs drains into the left atrium via the four pulmonary veins
* The left atrium pumps blood through the bicuspid (mitral) valve into the left ventricle
* The left ventricle pumps blood through the aortic semilunar valve into the ascending [[aorta]] to supply the body.<ref name=":6" />


'''Aortic Valve''' - The opening from the left ventricle into the aorta is closed by the aortic valve thus prevents the backflow of blood as it is pumped from the left ventricle to the aorta. It consists of three semilunar cusps with the free edge of each projecting upward into the lumen of the ascending aorta. Between the semilunar cusps and the wall of the ascending aorta are pocket-like sinuses-the right, left, and posterior aortic sinuses. The right and left coronary arteries emanates from the right and left aortic sinuses; Thus, the posterior aortic sinus and cusp are sometimes called noncoronary sinus and cusp.
=== Heart Valves  ===
[[File:Heart Valves.jpg|right|frameless|399x399px]]
The valves of the heart maintain unidirectional flow of the blood and prevent its regurgitation in the opposite direction. There are two pairs of valves in the heart, a pair of atrioventricular valves and a pair of semilunar valves. Apart, it has four valves. All four valves of the heart have a singular purpose: allowing forward flow of blood but preventing backward flow.<ref name=":0">Rehman I, Rehman A. Anatomy, Thorax, Heart. [Updated 2020 Dec 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan Available:https://www.ncbi.nlm.nih.gov/books/NBK470256/ (accessed 17.6.2021)</ref> The outflow of each chamber is guarded by a heart valve:


'''Mitral Valve''' - The left atrioventricular orifice opens into the posterior right side of the superior part of the left ventricle. It is closed during ventricular contraction by the mitral valve (left atrioventricular valve), which is also referred to as the bicuspid valve as it has two cusps; the anterior and posterior cusps.  It prevents the backflow of blood as it is pumped from the left atrium to the left ventricle and are continuous with each other at the commissures.<ref name=":5" /><ref name=":4">Moore, KL, Dalley, AF. Clinically oriented anatomy. 6<sup>th</sup> ed. Philadelphia: Lippincott Williams & Wilkins. 2009</ref> 
Atrioventricular valves between the atria and ventricles


== Conducting System of Heart ==
# tricuspid valve (R side of the heart)
The Conducting system is made up of myocardium. It is specialized for initiation and conduction of the cardiac muscle. Our heart beats as a result of the generation and conduction of electrical impulses. If we talk about cardiac conduction rate, it is the rate at which the heart conducts electrical impulses. These impulses cause the heart to contract and then relax. There are 6 conducting systems of heart namely,
# mitral valve/bicuspid valve (left side of the heart)


# Sinu-artrial node or SA node
Semilunar valves which are located in the outflow tracts of the ventricles
# Atrio-ventricular node or AV node
# Atrio-ventricular bundle or AV bundle or bundle of His
# The right branch of AV bundle
# The left branch of AV bundle
# The purkinje fibers


* Pacemaker impulse generation-The first step of cardiac conduction is impulse generation. SA node is also known as “pacemaker” of the heart. It is located in the upper wall of the right atrium. It usually generates impulse at the rate of about 70/min and initiates the heart beat. It generates nerve impulses that travel throughout the heart wall. This causes both atria to contract.
# aortic valve (L side heart)
* AV Node impulse conduction-The atrio-ventricular (AV) node lies on the right side of the partition that divides the atria, near the bottom of the right atrium. It is capable of generating impulse at a rate of about 60/min.  When the impulses from the SA node reach the AV node, they are delayed for about a tenth of a second. This delay allows atria to contract and empty their contents into the ventricles prior to ventricle contraction.
# pulmonary valve (R side heart)<ref name=":6" />
* AV Bundle impulse conduction-The impulses are then sent down the atrio-ventricular bundle. This bundle of fibers branches off into two bundles (right and left). At the upper part of ventricular septum the impulses are carried down the center of the heart to the left and right ventricles.
See also [[Cardiac Valve Defects]]
* Purkinje fibers impulse conduction'''-'''The Right and Left atrio-ventricular bundles start to divide further into Purkinje fibers. When the impulses reach these fibers they trigger the muscle fibers in the ventricles to contract. The right ventricle sends blood to the lungs via the pulmonary artery. The left ventricle pumps blood to the aorta.<ref>Chaurasia BD. [https://www.pdfdrive.com/bd-chaurasia-books.html Human Anatomy Regional and Applied Dissection and Clinical. Vol 1]. CBS Publishers and Distributors Pvt Ltd, 2010</ref>


== Blood Supply ==
== Blood Supply ==
[[File:Overview of the coronary arteries and cardiac veins - Kenhub.png|alt=Overview of the coronary arteries and cardiac veins - anterior and posterior views|right|frameless|600x600px|Overview of the coronary arteries and cardiac veins - anterior and posterior views]]
The heart is supplied by two coronary arteries:  
The heart is supplied by two coronary arteries:  


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Coronary arteries and veins course over the surface of the heart. Most coronary veins coalesce into the coronary sinus that runs in the left posterior atrioventricular groove and opens into the right atrium. Other small veins, called thebesian veins, open directly into all four chambers of the heart.<ref name=":0" />
Coronary arteries and veins course over the surface of the heart. Most coronary veins coalesce into the coronary sinus that runs in the left posterior atrioventricular groove and opens into the right atrium. Other small veins, called thebesian veins, open directly into all four chambers of the heart.<ref name=":0" />


== Venous drainage ==
Image: Overview of the coronary arteries and cardiac veins - anterior and posterior views<ref >Overview of the coronary arteries and cardiac veins - anterior and posterior views image - © Kenhub https://www.kenhub.com/en/library/anatomy/heart</ref>
 
See also [[Coronary Artery Disease (CAD)|Coronary Artery Disease]]
 
== Venous drainage and Lymphatics ==
Venous drainage is via the variable coronary veins and the coronary sinus<ref name=":6" />.  
Venous drainage is via the variable coronary veins and the coronary sinus<ref name=":6" />.  


==== Lymphatic Drainage of the Heart====
The [[Lymphatic System|lymphatic vessels]] drain mainly into:
The [[Lymphatic System|lymphatic vessels]] drain mainly into:
# Brachiocephalic nodes, in front of brachiocephalic veins
# Brachiocephalic nodes, in front of brachiocephalic veins
# Tracheobronchial nodes''',''' located at the distal end of the trachea<ref name=":4" />.<ref name=":5" /> 
# Tracheobronchial nodes''',''' located at the distal end of the trachea<ref name=":4">Moore, KL, Dalley, AF. Clinically oriented anatomy. 6<sup>th</sup> ed. Philadelphia: Lippincott Williams & Wilkins. 2009</ref>.<ref name=":5" /> 


== Nerve Supply ==
== Nerve Supply ==
The heart has extrinsic and intrinsic innervation, which allows the heart to continue beating if its nerve supply is disrupted (e.g. in cardiac transplant).
[[File:Course and distribution of the glossopharyngeal, vagus, and accessory nerves..gif|right|frameless|600x600px]]
The main control of the heart resides with the [[Brainstem|medulla oblongata.]]  There is an area called the cardioacceleratory centre, or pressor centre, in the upper part of the medulla oblongata, and an area called the cardioinhibitory centre, or depressor centre, in the lower part.  Together they are called the cardioregulatory centre, since they interact to control heart rate, etc.  


The extrinsic supply is from parasympathetic (from the vagus nerve) and sympathetic nerves from both the superficial and deep cardiac plexuses, which provide post-ganglionic fibres to the sinoatrial (SA) and atrioventricular (AV) nodes, as well as other parts of the cardiac conduction system.  
The nervous supply to the heart is autonomic, consisting of both [[Sympathetic Nervous System|sympathetic]] and [[Parasympathetic System|parasympathetic]] parts.  The sympathetic fibres arise from the pressor centre, while the parasympathetic fibres arise in the depressor centre. See also [[Vagus Nerve|Vagal Tone]]


The cardiac conduction system represents the intrinsic component and is composed of:
* The sympathetic nervous system acts on the sinoatrial node, speeding up the depolarisation rate, and therefore increasing the [[Pulse rate|heart rate]]. 
* The parasympathetic system works in reverse in order to slow the heart rate down. 
* The heart itself has a natural pacemaker, the sinoatrial node, which does not need a nervous supply to function.  If you sever all the nerves to the heart, then it will continue to beat.   In fact, it will beat faster than normal, since there is normally a parasympathetic supply slowing the heart down.<ref>Basic heart Anatomy Nervous Supply Heart Available:  https://www.liverpool.ac.uk/~trh/local_html/heartdisease/nerve_supply_to_the_heart.htm (accessed18.7.2021)</ref>


* sinoatrial (SA) node
== Heart Conduction System ==
* internodal connections
[[File:Heart conduction system .jpeg|right|frameless|708x708px]]
* atrioventricular (AV) node
An electrical conduction system regulates the pumping of the heart and timing of contraction of various chambers.  Heart muscle contracts in response to the electrical stimulus received  system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood. Among the major elements in the cardiac conduction system are the sinus node, atrioventricular node, and the autonomic nervous system.
* bundle of His
# The sinus node is the heart's natural pacemaker. The sinus node is a cluster of cells situated in the upper part of the wall of the right atrium. The electrical impulses are generated there. (The sinus node is also called the sinoatrial node.)
* right and left bundle branches
# The electrical signal generated by the sinus node moves from cell to cell down through the heart until it reaches the atrioventricular node (the AV node), a cluster of cells situated in the center of the heart between the atria and ventricles.
* Purkinje fibres
# The AV node serves as a gate that slows the electrical current before the signal is permitted to pass down through to the ventricles. This delay ensures that the atria have a chance to fully contract before the ventricles are stimulated. After passing the AV node, the electrical current travels to the ventricles along special fibers embedded in the walls of the lower part of the heart.
# The autonomic nervous system (the same part of the nervous system as controls the blood pressure) controls the firing of the sinus node to trigger the start of the cardiac cycle. The autonomic nervous system can transmit a message quickly to the sinus node so it in turn can increase the heart rate to twice normal within only 3 to 5 seconds. This quick response is important during exercise when the heart has to increase its beating speed to keep up with the body's increased demand for oxygen.<ref>Medicine net Conduction system heart Available:https://www.medicinenet.com/heart_conduction_system/definition.htm (accessed 18.7.2021)</ref>


Cardiac myocyte conduction spreads through the heart from myocyte-to-myocyte starting at the SA (pacing) node and then via other parts of the cardiac conduction system in turn as outlined above.
== Relevance to Physiotherapy ==


Each part of the cardiac conduction system has its own intrinsic pacemaker, which means that if a higher pacing centre (e.g. SA node) is damaged and stops functioning a lower pacing centre (e.g AV node) can take over.<ref>Radiopedia Innervation of the heart Available:https://radiopaedia.org/articles/innervation-of-the-heart?lang=gb (accessed 17.6.2021)</ref>
# [[File:Gym ladies.jpeg|right|frameless]]Education- Educating your clients re heart health, both for those with a heart condition and those without.  Inform them of the hearts health importance, because it pumps blood and oxygen to all of your organs. When the heart doesn’t get the care it needs, serious problems can develop in the lining of the arteries, which then lead to plaque formation which leads to Heart Disease. General advice includes
 
* A heart healthy [[Nutrition|diet]] is a pattern of food you eat over days, weeks and months.
* Regular [[Physical Activity|physical activity]] reduces your risk of having a [[Acute Coronary Syndrome|heart attack]] or developing [[Cardiovascular Disease|heart disease]].
* Quitting [[Smoking Cessation and Brief Intervention|smoking]] decreases your risk of heart attack and [[stroke]] almost straight away.
* Understanding and controlling [[Atherosclerosis|cholesterol]] and [[Blood Pressure|blood pressure]] is key to your heart health. <ref>Hear Foundation Heart Health Education Available:https://www.heartfoundation.org.au/heart-health-education/keeping-your-heart-healthy (accessed 18.7.2021)</ref>
 
2. See our many  pages on heart related health issues eg  [[Cardiac Rehabilitation]]; [[Myocardial Infarction]]; [[Atrial Fibrillation]]; [[Acute Coronary Syndrome]]; [[Physical Activity and Cardiovascular Disease]].
 
== Videos ==
This 10 minute video is a good summary of the heart.<ref>Anatomy of the heart video -  © Kenhub https://www.kenhub.com/en/library/anatomy/heart</ref>{{#ev:youtube|0zM6VSlKWmw}}
 
*
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== Relevance to Physiotherapy ==
#[[File:Heart location 2.jpg|right|frameless|268x268px]]The surface markings of the heart and the position of the apex beat can show if the heart has shifted its position in relation to the chest wall or if the heart is enlarged by disease. The position of the margins of the heart can be determined by percussion (Snell, 2000).
# [[Auscultation|Percussion]] defines the density and size of the heart. It is performed at the 3<sup>rd</sup>, 4<sup>th</sup>, and 5<sup>th</sup> [[Intercostal Muscle Strain|intercostal]] spaces from the left anterior axillary line to the right anterior axillary line.
# The pericardial sac is influenced by movements of the heart and great vessel, [[Ribs|sternum]], and [[Diaphragmatic Breathing Exercises|diaphragm]]. The heart moves downwards on deep inspiration since the heart’s position depends on that of the diaphragm.
# The fibrous pericardium protects the heart against sudden overfilling and anchors it within the mediastinum.
# If a coronary artery becomes obstructed, by a blood clot for example, part of the myocardium becomes '''ischemic''', that is, deprived of its blood supply. Prolonged ischemia will create an '''infarct''', an area of necrotic (dead) tissue. This is a myocardial infarction, commonly called a [[Myocardial Infarction|heart attack]] (myocardial infarction).
See also, as relevant to physiotherapy: [[Acute Coronary Syndrome]]; [[Physical Activity and Cardiovascular Disease]]; [[Cardiac Rehabilitation]]; [[Myocardial Infarction]]; [[Atrial Fibrillation]].


== References  ==
== References  ==

Latest revision as of 12:55, 14 March 2023

Original Editor - Uchechukwu Chukwuemeka

Top Contributors - Uchechukwu Chukwuemeka, Lucinda hampton, Kim Jackson, George Prudden, Joao Costa, Sai Kripa, Admin and Adam Vallely Farrell

Introduction[edit | edit source]

The Heart surface view.jpg

The heart is a muscular organ that serves to collect deoxygenated blood from all parts of the body, carries it to the lungs to be oxygenated and release carbon dioxide. Then, it transports the oxygenated blood from the lungs and distributes it to all the body parts[1]

  • The heart pumps around 7,200 litres of blood in a day throughout the body[2].
  • The heart is situated at the centre of the chest and points slightly towards the left.
  • On average, the heart beats about 100,000 times a day, i.e., around 3 billion beats in a lifetime.
  • An adult heart beats about 60 to 80 times per minute, and newborn babies heart beats faster than an adult which is about 70 to 190 beats per minute.


Anatomy[edit | edit source]

Heart location.jpg

The heart is a conical hollow muscular organ situated in the middle mediastinum and is enclosed within the pericardium. It is positioned posteriorly to the body of the sternum with one-third situated on the right and two-thirds on the left of the midline. The heart measures 12 x 8.5 x 6 cm and weighs ~310 g (males) and ~255 g (females). It pumps blood to various parts of the body to meet their nutritive requirements. The Greek name for the heart is cardia from which we have the adjective cardia. [3]

Relations

  • Anteriorly: the body of the sternum, and adjoining costal cartilages; left lung, and pleura (apex)
  • Posteriorly: oesophagus, descending thoracic aorta, azygos, hemiazygos veins,  and thoracic duct
  • Superficially : bifurcation of the main pulmonary trunk
  • Inferiorly: diaphragm
  • Laterally: lungs, pleura[4]

Layers of the Heart Walls[edit | edit source]

Heart layers.jpg

The heart wall consists of three layers enclosed in the pericardium[1][5][6]:

  1. Epicardium - the outer layer of the wall of the heart and is formed by the visceral layer of the serous pericardium.
  2. Myocardium - the muscular middle layer of the wall of the heart and has excitable tissue and the conducting system.
  3. Endocardium .[4]
  • A middle concentric layer
  • A subendocardial layer.

The rest of the heart is composed mainly of the subepicardial and subendocardial layers.

Structure and Function[edit | edit source]

Human-heart-chambers.jpg

The heart is subdivided by septa into right and left halves, and a constriction subdivides each half of the organ into two cavities, the upper cavity being called the atrium, the lower the ventricle. The heart, therefore, consists of four chambers:

  • right atrium
  • left atrium
  • right ventricle
  • left ventricle[4].


It is best to remember the four chambers and four valves in order of the series that blood travels through the heart:

  • Venous blood returning from the body drains into the right atrium via the SVC, IVC and coronary sinus
  • The right atrium pumps blood through the tricuspid valve into the right ventricle
  • The right ventricle pumps blood through the pulmonary semilunar valve into the pulmonary trunk to be oxygenated in the lungs
  • Blood returning from the lungs drains into the left atrium via the four pulmonary veins
  • The left atrium pumps blood through the bicuspid (mitral) valve into the left ventricle
  • The left ventricle pumps blood through the aortic semilunar valve into the ascending aorta to supply the body.[4]

Heart Valves[edit | edit source]

Heart Valves.jpg

The valves of the heart maintain unidirectional flow of the blood and prevent its regurgitation in the opposite direction. There are two pairs of valves in the heart, a pair of atrioventricular valves and a pair of semilunar valves. Apart, it has four valves. All four valves of the heart have a singular purpose: allowing forward flow of blood but preventing backward flow.[7] The outflow of each chamber is guarded by a heart valve:

Atrioventricular valves between the atria and ventricles

  1. tricuspid valve (R side of the heart)
  2. mitral valve/bicuspid valve (left side of the heart)

Semilunar valves which are located in the outflow tracts of the ventricles

  1. aortic valve (L side heart)
  2. pulmonary valve (R side heart)[4]

See also Cardiac Valve Defects

Blood Supply[edit | edit source]

Overview of the coronary arteries and cardiac veins - anterior and posterior views

The heart is supplied by two coronary arteries:

  1. Left main coronary artery carries 80% of the flow to the heart muscle. It is a short artery that divides into two branches
  • Left anterior descending artery that supplies anterior two-thirds of the inter-ventricular septum and adjoining part of the left ventricular anterior wall
  • Circumflex coronary artery that supplies blood to the lateral and posterior portions of the left ventricle.

2. Right coronary artery: branches supply the right ventricle, right atrium, and left ventricle's inferior wall.

Coronary arteries and veins course over the surface of the heart. Most coronary veins coalesce into the coronary sinus that runs in the left posterior atrioventricular groove and opens into the right atrium. Other small veins, called thebesian veins, open directly into all four chambers of the heart.[7]

Image: Overview of the coronary arteries and cardiac veins - anterior and posterior views[8]

See also Coronary Artery Disease

Venous drainage and Lymphatics[edit | edit source]

Venous drainage is via the variable coronary veins and the coronary sinus[4].

The lymphatic vessels drain mainly into:

  1. Brachiocephalic nodes, in front of brachiocephalic veins
  2. Tracheobronchial nodes, located at the distal end of the trachea[9].[6] 

Nerve Supply[edit | edit source]

Course and distribution of the glossopharyngeal, vagus, and accessory nerves..gif

The main control of the heart resides with the medulla oblongata.  There is an area called the cardioacceleratory centre, or pressor centre, in the upper part of the medulla oblongata, and an area called the cardioinhibitory centre, or depressor centre, in the lower part.  Together they are called the cardioregulatory centre, since they interact to control heart rate, etc.

The nervous supply to the heart is autonomic, consisting of both sympathetic and parasympathetic parts.  The sympathetic fibres arise from the pressor centre, while the parasympathetic fibres arise in the depressor centre. See also Vagal Tone

  • The sympathetic nervous system acts on the sinoatrial node, speeding up the depolarisation rate, and therefore increasing the heart rate. 
  • The parasympathetic system works in reverse in order to slow the heart rate down. 
  • The heart itself has a natural pacemaker, the sinoatrial node, which does not need a nervous supply to function.  If you sever all the nerves to the heart, then it will continue to beat.   In fact, it will beat faster than normal, since there is normally a parasympathetic supply slowing the heart down.[10]

Heart Conduction System[edit | edit source]

Heart conduction system .jpeg

An electrical conduction system regulates the pumping of the heart and timing of contraction of various chambers.  Heart muscle contracts in response to the electrical stimulus received system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood. Among the major elements in the cardiac conduction system are the sinus node, atrioventricular node, and the autonomic nervous system.

  1. The sinus node is the heart's natural pacemaker. The sinus node is a cluster of cells situated in the upper part of the wall of the right atrium. The electrical impulses are generated there. (The sinus node is also called the sinoatrial node.)
  2. The electrical signal generated by the sinus node moves from cell to cell down through the heart until it reaches the atrioventricular node (the AV node), a cluster of cells situated in the center of the heart between the atria and ventricles.
  3. The AV node serves as a gate that slows the electrical current before the signal is permitted to pass down through to the ventricles. This delay ensures that the atria have a chance to fully contract before the ventricles are stimulated. After passing the AV node, the electrical current travels to the ventricles along special fibers embedded in the walls of the lower part of the heart.
  4. The autonomic nervous system (the same part of the nervous system as controls the blood pressure) controls the firing of the sinus node to trigger the start of the cardiac cycle. The autonomic nervous system can transmit a message quickly to the sinus node so it in turn can increase the heart rate to twice normal within only 3 to 5 seconds. This quick response is important during exercise when the heart has to increase its beating speed to keep up with the body's increased demand for oxygen.[11]

Relevance to Physiotherapy[edit | edit source]

  1. Gym ladies.jpeg
    Education- Educating your clients re heart health, both for those with a heart condition and those without. Inform them of the hearts health importance, because it pumps blood and oxygen to all of your organs. When the heart doesn’t get the care it needs, serious problems can develop in the lining of the arteries, which then lead to plaque formation which leads to Heart Disease. General advice includes

2. See our many pages on heart related health issues eg Cardiac Rehabilitation; Myocardial Infarction; Atrial Fibrillation; Acute Coronary Syndrome; Physical Activity and Cardiovascular Disease.

Videos[edit | edit source]

This 10 minute video is a good summary of the heart.[13]


References[edit | edit source]

  1. ↑ 1.0 1.1 Kenny, WL,Wilmore, JH, Costill, DL. Cardiovascular System and its Control.  In Physiology of Sport and Exercise, 5rdedn. Human Kinetics, 2011. 140-150.
  2. ↑ Inovqheart Heart Available from: https://www.inovaheart.org/upload/docs/Healthcare%20Services/Heart%20and%20Vascular/fast-facts-about-the-heart.pdf
  3. ↑ Chaurasia BD. Human Anatomy Regional and Applied Dissection and Clinical. Vol 1. CBS Publishers and Distributors Pvt Ltd, 2010
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Radiopedia Heart Available: https://radiopaedia.org/articles/heart?lang=gb (accessed 17.6.2021)
  5. ↑ Malouf, JF, Edwards, WD, Tajil, AJ, Seward, JB. Functional anatomy of the heart. In: Fuster, F, Alexander, RW, O’Rourke, RA editors. Hurst’s: The Heart. 10th edn. McGraw-Hill Inc., 2001. p19–62.
  6. ↑ 6.0 6.1 Drake, RL, Vogl, W, Mitchell, AW, Gray, H. Gray's anatomy for Students 2nd ed.  Philadelphia : Churchill Livingstone/Elsevier, 2010.
  7. ↑ 7.0 7.1 Rehman I, Rehman A. Anatomy, Thorax, Heart. [Updated 2020 Dec 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan Available:https://www.ncbi.nlm.nih.gov/books/NBK470256/ (accessed 17.6.2021)
  8. ↑ Overview of the coronary arteries and cardiac veins - anterior and posterior views image - © Kenhub https://www.kenhub.com/en/library/anatomy/heart
  9. ↑ Moore, KL, Dalley, AF. Clinically oriented anatomy. 6th ed. Philadelphia: Lippincott Williams & Wilkins. 2009
  10. ↑ Basic heart Anatomy Nervous Supply Heart Available: https://www.liverpool.ac.uk/~trh/local_html/heartdisease/nerve_supply_to_the_heart.htm (accessed18.7.2021)
  11. ↑ Medicine net Conduction system heart Available:https://www.medicinenet.com/heart_conduction_system/definition.htm (accessed 18.7.2021)
  12. ↑ Hear Foundation Heart Health Education Available:https://www.heartfoundation.org.au/heart-health-education/keeping-your-heart-healthy (accessed 18.7.2021)
  13. ↑ Anatomy of the heart video - © Kenhub https://www.kenhub.com/en/library/anatomy/heart
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