When refering to evidence in academic writing, you should always try to reference the primary (original) source. That is usually the journal article where the information was first stated. In most cases Physiopedia articles are a secondary source and so should not be used as references. Physiopedia articles are best used to find the original sources of information (see the references list at the bottom of the article).
If you believe that this Physiopedia article is the primary source for the information you are refering to, you can use the button below to access a related citation statement.
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][3].
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. [4]
Anatomy
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. [5]
Relations
Anteriorly: the body of the sternum, and adjoining costal cartilages; left lung, and pleura (apex)
Location and Structure: The apex is formed by the left ventricle, and it points downward, forward, and to the left.
Anatomical Position: The apex is typically located at the level of the 5th left intercostal space, about 9 cm (3.5 inches) from the midline of the body. This position is just medial to the midclavicular line.
Clinical Relevance: The apex of the heart is clinically significant because it can be palpated during a physical examination. This palpation is commonly referred to as the point of maximal impulse (PMI), which can help assess the size and position of the heart, as well as its function.
Anatomical Composition: The base of the heart is primarily formed by the left atrium (about two-thirds), while the right atrium contributes about one-third. This part of the heart is located opposite to the apex, facing posteriorly.
Orientation: The base of the heart is directed backward and to the right, contrasting with the apex's downward, forward, and leftward direction.
Key Features of the Base:
Opposite to the Apex: As you mentioned, the base lies directly opposite to the apex, at the opposite end of the heart.The passage you provided describes the anatomical structure of the base (or posterior surface) of the heart. Here's a breakdown of the key details:
Base of the Heart: This refers to the portion of the heart that faces backwards (posterior) and is opposite the apex (the tip of the heart). The base is formed primarily by the atria (the upper chambers of the heart).
Left Atrium: The left atrium contributes the majority (about two-thirds) of the base of the heart. This chamber receives oxygenated blood from the lungs via the pulmonary veins.
Right Atrium: The right atrium contributes the remaining one-third of the base. This chamber receives deoxygenated blood from the body through the superior and inferior vena cavae.
Orientation: The base of the heart is directed backwards and to the right, meaning it faces away from the front of the body and towards the right side. This anatomical description is essential for understanding the positioning and relationship of the heart's chambers to other structures in the thoracic cavity.
Relation to Vertebral Column:
In a recumbent (lying down) position, the base of the heart is positioned in front of the middle thoracic vertebrae (T5–T8).
When in an erect posture, the base descends by one vertebra, typically positioned in front of T6–T9.
Separation from Vertebral Column: The base is separated from the vertebral column by several structures:
Oblique pericardial sinus: A recess in the pericardium that allows space for the heart's movement.
Esophagus: The muscular tube connecting the throat to the stomach, which lies behind the heart.
Aorta: The large artery that carries blood from the left ventricle to the rest of the body.
Clinical Relevance:
Great Blood Vessels: The base of the heart is where the major blood vessels are attached, including the superior vena cava, ascending aorta, and pulmonary trunk. This makes the base significant in cardiovascular assessments.
1. Sternocostal (Anterior) Surface
Main contributors: The right atrium and right ventricle primarily form this surface. These two chambers are separated by the anterior atrioventricular groove.
Additional contributors: The left auricle and left ventricle also contribute to the sternocostal surface, but to a lesser extent.
Separation between ventricles: The right ventricle is separated from the left ventricle by the anterior interventricular groove.
Important notes:
The left atrium is not visible from the front because it is hidden by the ascending aorta and pulmonary trunk.
The cardiac notch of the left lung leaves an area of superficial cardiac dullness on the sternocostal surface.
2. Diaphragmatic (Inferior) Surface
Flat and rests on: This surface is flat and lies on the central tendon of the diaphragm, providing support.
Main contributors: It is formed by the left and right ventricles.
The left ventricle forms about two-thirds of the diaphragmatic surface.
The right ventricle forms the remaining one-third.
Separation between ventricles: The posterior interventricular groove separates the left and right ventricles on the diaphragmatic surface.
3. Left Surface
Main contributor: This surface is primarily formed by the left ventricle.
Additional contributors: It is also partially formed by the left atrium and left auricle.
Direction: The left surface is oriented upwards, backwards, and to the left, making it the most lateral surface of the heart.
1. Right Border
Formation: The right border is primarily formed by the right atrium.
Extension: It extends from the right side of the opening of the superior vena cava (SVC) to the right side of the opening of the inferior vena cava (IVC).
Function: This border separates the base of the heart from the sternocostal surface.
2. Left Border
Formation: The left border is formed mainly by the left ventricle and partly by the left auricle.
Curvature: It is curved and oblique, extending from the left auricle to the apex of the heart.
Function: The left border separates the sternocostal surface from the left surface of the heart.
3. Inferior Border
Formation: The inferior border is mainly formed by the right ventricle, with a small contribution from the right atrium.
Extension: It extends from the opening of the IVC to the apex of the heart.
Function: This border separates the sternocostal surface from the diaphragmatic surface.
Notch: Near the apex, the inferior border features a notch called the incisura apicis cordis, which is a slight indentation.
4. Upper Border
Formation: The upper border is formed by both the right and left atria, but it is mainly formed by the left atrium.
Obscured view: This border is obscured from view on the sternocostal surface because it is covered by the ascending aorta and the pulmonary trunk.
Surface marking: On the surface of the body, the upper border can be marked by a line:
From a point on the lower border of the 2nd left costal cartilage (1.5 inches from the median plane).
To a point on the upper border of the 3rd right costal cartilage (1 inch away from the median plane).
Layers of the Heart Walls
The heart wall consists of three layers enclosed in the pericardium[1][7][8]:
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.
The rest of the heart is composed mainly of the subepicardial and subendocardial layers.
Structure and Function
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:
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.[6]
Heart Valves
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.[9] The outflow of each chamber is guarded by a heart valve:
Atrioventricular valves between the atria and ventricles
tricuspid valve (R side of the heart)
mitral valve/bicuspid valve (left side of the heart)
Semilunar valves which are located in the outflow tracts of the ventricles
Overview of the coronary arteries and cardiac veins - anterior and posterior views
The heart is supplied by two coronary arteries:
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.[9]
Image: Overview of the coronary arteries and cardiac veins - anterior and posterior views[10]
Brachiocephalic nodes, in front of brachiocephalic veins
Tracheobronchial nodes, located at the distal end of the trachea[11].[8]
Nerve Supply
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.[12]
Heart Conduction System
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.
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.)
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 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.[13]
Relevance to Physiotherapy
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 diet is a pattern of food you eat over days, weeks and months.
This 10 minute video is a good summary of the heart.[15]
References
↑ 1.01.1Kenny, WL,Wilmore, JH, Costill, DL. Cardiovascular System and its Control. In Physiology of Sport and Exercise, 5rdedn. Human Kinetics, 2011. 140-150.
↑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.
↑ 8.08.1Drake, RL, Vogl, W, Mitchell, AW, Gray, H. Gray's anatomy for Students 2nd ed.
Philadelphia : Churchill Livingstone/Elsevier, 2010.
↑ 9.09.1Rehman 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)
