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  ==
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)
[[File:Heart location.jpg|right|frameless]]
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>
[[File:Chest auscultation.jpg|right|frameless|451x451px]]
*
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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  ===
 
[[File:Human-heart-chambers.jpg|right|frameless|399x399px]]
=== Chambers of the Heart ===
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:
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:


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* left atrium
* left atrium
* right ventricle
* right ventricle
* left ventricle
* left ventricle<ref name=":6" />.


The division of the heart into four cavities is indicated on its surface by grooves. The atria are separated from the ventricles by the coronary sulcus (atrioventricular groove); this contains the trunks of the nutrient vessels of the heart and is deficient in front, where it is crossed by the root of the pulmonary artery. The interatrial groove, separating the two atria, is scarcely marked on the posterior surface while anteriorly it is hidden by the pulmonary trunk and ascending aorta.


The ventricles are separated by two grooves, one of which, the anterior longitudinal sulcus, is situated on the sternocostal surface of the heart, close to its left margin, the other posterior longitudinal sulcus, on the diaphragmatic surface near the right margin; these grooves extend from the base of the ventricular portion to a notch, the incisura apicis cordis, on the acute margin of the heart just to the right of the apex.<ref name=":6" />
It is best to remember the four chambers and four valves in order of the series that blood travels through the heart:


==== The Left Atrium====
* Venous blood returning from the body drains into the right atrium via the [[Vena Cava|SVC, IVC]] and coronary sinus
* Receives oxygenated blood from the lungs via the left and right pulmonary veins.
* The right atrium pumps blood through the tricuspid valve into the right ventricle
* The pulmonary veins enter the heart as two pairs of veins inserting posteriorly and laterally into the left atrium. In addition, the smallest (Thebesian) veins drain deoxygenated blood from the atrial myocardium directly into the atrium.
* The right ventricle pumps blood through the pulmonary semilunar valve into the pulmonary trunk to be oxygenated in the lungs
* The left atrium is found midline, posterior to the right atrium and superior to the left ventricle.
* Blood returning from the lungs drains into the left atrium via the four pulmonary veins
* Anteriorly, a left atrial appendage (auricle) extends over the atrioventricular (coronary) sulcus.
* The left atrium pumps blood through the bicuspid (mitral) valve into the left ventricle
* The walls of the atrial appendage are pectinate, and the walls of the left atrium are smooth.
* The left ventricle pumps blood through the aortic semilunar valve into the ascending [[aorta]] to supply the body.<ref name=":6" />
* It discharges into the left ventricle through the mitral valve<ref name=":0">Boulpaep, EL,  Boron WF. Organisation of Cardiovascular System.  Elsevier Saunders, 2005. p423–507
</ref><ref>Shah, S, Gnanasegaran, G, Sundberg-Cohon, J, Buscombe, JR. The Heart: Anatomy, Physiology and Exercise Physiology. 2009. DOI: 10.1007/978-3-540-78674-0_1</ref>
[[File:Human-heart-chambers.jpg|right|frameless|600x600px]]


==== The Right Atrium ====
=== Heart Valves  ===
The interior of the right atrium has three anatomically distinct regions.
[[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:


1. Posterior part -  is a smooth-walled and is termed ''sinus venarum.;'' 
Atrioventricular valves between the atria and ventricles


''2.''  Anterior part - which is lined by horizontal, parallel ridges of muscle bundles that resemble the teeth of a comb, hence the name ''pectinate muscle (pectin'' = "a comb,")  
# tricuspid valve (R side of the heart)
# mitral valve/bicuspid valve (left side of the heart)


3. Atrial septum - receives both the superior and inferior [[Vena Cava|venae cavae]] and the coronary sinus. It also contains the fossa ovalis, the sinoatrial node and the atrioventricular node.
Semilunar valves which are located in the outflow tracts of the ventricles


On the "floor" of the right atrium is the atrioventricular portion of the atrial septum, which has muscular and membranous components. At the anterior and inferior aspect of the atrial septum, the tricuspid valve annulus ''(annulus'' = "ring") is attached to the membranous septum.
# aortic valve (L side heart)
# pulmonary valve (R side heart)<ref name=":6" />
See also [[Cardiac Valve Defects]]


====The Left Ventricle====
== Blood Supply ==
* It pumps blood throughout the body via the [[aorta]].
[[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]]
* Most of the left lateral surface of the heart is formed by the left ventricle, also forming part of the inferior and posterior surface.
The heart is supplied by two coronary arteries:  
* Abundant trabeculae carneae characterize the walls of the left relatively
* LV apex is less trabeculated than the RV apex. 
* In contrast to the right ventricle, the muscular ridges tend to be relatively fine and the myocardium in the wall of the left ventricle is three times thicker; thickest towards the base and thinnest towards the apex. 
* The interventricular septum appears from within the left ventricle to bulge into the right ventricle; this creates a barrel-shaped left ventricle. It is made of an inlet portion comprised of mitral valve apparatus, subaortic outflow portion and a trabeculated apical zone<ref name=":0" /><ref name=":1">Weinhaus, AJ, Roberts, KP. Anatomy of the Human Heart. In: Iaizzo, PA. Hand book of Cardiac Anatomy, physiology and Devices. Humana press Inc.Totowa, New Jersey, 2005, P51-79</ref>.


====The Right Ventricle====
# Left main coronary artery carries 80% of the flow to the heart muscle. It is a short artery that divides into two branches
It pumps blood to the lungs through the pulmonary trunk and [[arteries]].  


It comprised of an
* Left  anterior descending artery that supplies anterior two-thirds of the inter-ventricular septum and adjoining part of the left ventricular anterior wall
# The Inlet - extends from tricuspid annulus to the insertions of the papillary muscles. Abundant, coarse trabeculae carneae ("beams of meat") characterize the walls of the right ventricle. Trabeculae carneae are similar to pectinate muscle of the right atrium (as bundles of myocardium) .
* Circumflex coronary artery that supplies blood to the lateral and posterior portions of the left ventricle.
# Outflow tract - conus arteriosus ("arterial cone") or infundibulum ("funnel"), carries blood out of the ventricle in an anterior-superior direction and is relatively smooth walled. A component of the conus arteriosus forms part of the interventricular septum. This small septum, the infundibular (conal) septum, separates the left and right ventricular outflow tracts and is located just inferior to both semilunar valves<ref name=":0" />.


=== Heart Valves  ===
2. Right coronary artery: branches supply the right ventricle, right atrium, and left ventricle's inferior wall.
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" />
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" />
[[File:Heart Valves.jpg|450x450px|right|frameless]]
'''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. 


'''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.
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>


'''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> 
See also [[Coronary Artery Disease (CAD)|Coronary Artery Disease]]


== Conducting System of Heart ==
== Venous drainage and Lymphatics ==
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,
Venous drainage is via the variable coronary veins and the coronary sinus<ref name=":6" />.  


# '''''Sinu-artrial node or SA node'''''
The [[Lymphatic System|lymphatic vessels]] drain mainly into:
# '''''Atrio-ventricular node or AV node'''''
# Brachiocephalic nodes, in front of brachiocephalic veins
# '''''Atrio-ventricular bundle or AV bundle or bundle of His'''''
# 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" /> 
# '''''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.  
== Nerve Supply ==
* '''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.
[[File:Course and distribution of the glossopharyngeal, vagus, and accessory nerves..gif|right|frameless|600x600px]]
* '''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.
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.  
* '''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 ===
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]]


====Arterial Blood Supply to the Heart====
* The sympathetic nervous system acts on the sinoatrial node, speeding up the depolarisation rate, and therefore increasing the [[Pulse rate|heart rate]]. 
The heart has 2 main arteries that supply it and the are namely
* The parasympathetic system works in reverse in order to slow the heart rate down. 
* [[Coronary Artery|Right coronary artery]] (RCA)
* 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>
* [[Coronary Artery|Left coronary artery]] (LCA)


The RCA supplies:
== Heart Conduction System ==
# The right atrium via the atrial branch
[[File:Heart conduction system .jpeg|right|frameless|708x708px]]
# Most of the right ventricle.
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.
# Part of the left ventricle (the diaphragmatic surface) via the posterior interventricular branch
# 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.)
# Part (usually the posterior third) of the IV septum via the right marginal branch
# 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.
# The SA node (in approximately 60% of people) via the sino-nodal branch
# 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 AV node (in approximately 80% of people) via the atrioventricular branch
# 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>


The LCA supplies:
== Relevance to Physiotherapy ==
# The left atrium via the anterior interventricular branch (left anterior descending artery-LAD)
# Most of the left ventricle via the diagonal, circumflex and left marginal artery  branches 
#[[File:The Heart surface view.jpg|550x550px|right|frameless]]Part of the right ventricle. 
# Most of the IVS (usually its anterior two thirds), including the AV bundle of the conducting system of the heart, through its perforating IV septal branches. 
# The SA node (in approximately 40% of people). 


====Venous Drainage of the Heart====
# [[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
The heart is drained mainly by veins that empty into the coronary sinus and partly by small veins that empty into the right atrium.
# The '''coronary sinus''' is a wide venous channel that runs from left to right in the posterior part of the coronary groove. It receives the great cardiac vein at its left end and the middle cardiac vein and small cardiac veins at its right end. The left '''posterior ventricular vein''' which drains the posterior surface of the left ventricule and '''left marginal vein''' also open into the coronary sinus.
# The g'''reat cardiac vein''' is the main tributary of the coronary sinus and it drains the areas of the heart supplied by the LCA. The '''middle cardiac vein (posterior IV vein)''' accompanies the posterior interventricular branch (usually arising from the RCA) and a '''small cardiac vein''' accompanies the right marginal branch of the RCA. Thus these two veins drain most of the areas commonly supplied by the RCA.
# The '''anterior cardiac veins''' begin over the anterior surface of the right ventricle, cross over the coronary groove, and usually end directly in the right atrium; sometimes they enter the small cardiac vein


==== Lymphatic Drainage of the Heart====
* A heart healthy [[Nutrition|diet]] is a pattern of food you eat over days, weeks and months.
The [[Lymphatic System|lymphatic vessels]] drain mainly into:
* Regular [[Physical Activity|physical activity]] reduces your risk of having a [[Acute Coronary Syndrome|heart attack]] or developing [[Cardiovascular Disease|heart disease]].
# '''Brachiocephalic nodes''', in front of brachiocephalic veins
* Quitting [[Smoking Cessation and Brief Intervention|smoking]] decreases your risk of heart attack and [[stroke]] almost straight away.
# '''Tracheobronchial nodes,''' located at the distal end of the trachea<ref name=":4" />.<ref name=":5" /> 
* 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>


=== Nerve Supply ===
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]].
The nerve supply to the heart is from two sets of nerves originating in the [[Brainstem|medulla]] of the [[Brain Anatomy|brain]].


The nerves are part of the [[Introduction to Neuroanatomy|involuntary (autonomic) nervous system]].   
== Videos ==
* One set, the branches from the [https://www.physio-pedia.com/Cranial_Nerves vagus nerve], keeps the heart beating at a slow, regular rate. 
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}}
* The other set, the cardiac accelerator nerves, speeds up the heart. 
* The heart muscle has a special ability; it contracts automatically, but the nerve supply is needed to provide an effective contraction for blood circulation.
Branches from both the parasympathetic and sympathetic systems contribute to the formation of the '''cardiac plexus'''<ref name=":5" />. Branches from the cardiac plexus affect nodal tissue and other components of the conduction system, coronary blood vessels, and atrial and ventricular musculature.


'''[[Parasympathetic System|Parasympathetic]]  preganglionic fibers''' reach the heart as cardiac branches from the right and left vagus nerves. Stimulation of the parasympathetic system decreases heart rate, reduces force of contraction and constricts the coronary arteries.
*
 
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'''[[Sympathetic Nervous System|Sympathetic]] fibers''' (from the upper four or five segments of the thoracic spinal cord ) reach the heart through the cardiac nerves from the sympathetic trunk. Stimulation of the sympathetic system increases heart rate and increases the force of contraction. From the cardiac plexus small branches, which are mixed nerves containing both sympathetic and parasympathetic fibers, supply the heart.
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'''Visceral afferents fibers''' from the heart, a part of the cardiac plexus pass through the cardiac plexus and return to the central nervous system in the cardiac nerves from the sympathetic trunk and in the vagal cardiac branches.
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The afferents associated with the vagal cardiac nerves return to the vagus nerve [X] and mainly concerned with cardiac reflexes.
The afferents associated with the cardiac nerves from the sympathetic trunks return to either the cervical or the thoracic portions of the sympathetic trunk and conduct pain sensation from the heart, which is detected at the cellular level as tissue-damaging events (i.e. cardiac ischemia).
Within the heart muscle itself, there are special groups of nerve fibers that conduct impulses for contraction. These groups make up the '''[https://www.ncbi.nlm.nih.gov/pubmed/21357845 conduction system of the heart]'''<ref name=":2" /><ref name=":5" /><ref name=":4" />. When the conduction system does not operate properly, the heart muscle contractions are uncoordinated and ineffective. The impulses within the heart muscle are tiny electric currents, which can be picked up and recorded by the [https://www.ncbi.nlm.nih.gov/books/NBK354/ electrocardiogram].
== 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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