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Blood vessels are not cardiac muscle. Cardiac muscle, or myocardium, is a type of muscle tissue that forms the heart and is found only in the heart. It is one of three types of muscle in the body, the other two being skeletal and smooth muscle. The myocardium is surrounded by a thin outer layer called the epicardium and an inner endocardium. Coronary arteries supply blood to the myocardium, and cardiac veins drain this blood. Blood vessels, on the other hand, are part of the circulatory system, which includes the heart, blood, and blood vessels. The circulatory system is responsible for transporting blood and nutrients throughout the body.
| Characteristics | Values |
|---|---|
| Found in | Heart |
| Type of tissue | Muscle |
| Consists of | Cardiac muscle cells or [cardiomyocytes]; [pacemaker cells] |
| Controlled by | Autonomic nervous system (ANS) |
| Contractions | Rhythmic; involuntary; rapid; [coordinated] |
| Blood supply | Coronary arteries |
| Blood drainage | Cardiac veins |
| Diseases | [Cardiomyopathies]; [ischemic heart disease]; [coronary artery disease] |
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What You'll Learn
- Cardiac muscle cells, or cardiomyocytes, are the contractile cells of the heart
- The coronary arteries supply blood to the heart muscle
- Cardiac muscle tissue is only found in the heart
- Cardiomyopathies are diseases that affect cardiac muscle tissue
- Pacemaker cells are specialised cardiac muscle cells that control heart rate
Cardiac muscle cells, or cardiomyocytes, are the contractile cells of the heart
Cardiac muscle cells are roughly rectangular in shape, measuring approximately 100-150μm by 30-40μm. Each cardiomyocyte contains myofibrils, specialised protein contractile fibres of actin and myosin that slide past each other. These myofibrils are composed of repeating sections of sarcomeres, the fundamental contractile units of the muscle cells. Sarcomeres consist of long proteins that organise into thick and thin filaments, known as myofilaments. The interaction between these thick and thin filaments forms the basis of the sliding filament theory, which explains muscle contraction.
Cardiac muscle cells are joined at their ends by intercalated discs, forming long fibres. These intercalated discs are complex adhering structures that enable the transmission of contractile force from one cardiomyocyte to another. They consist of three types of cell-cell junctions: actin filament anchoring fascia adherens junctions, intermediate filament anchoring desmosomes, and gap junctions. The gap junctions between adjacent cardiomyocytes allow for the propagation of coordinated electrical impulses, resulting in synchronous contraction.
Additionally, specialised modified cardiomyocytes called pacemaker cells set the rhythm of heart contractions. These pacemaker cells are weakly contractile and are connected to neighbouring contractile cells via gap junctions. They are located in the sinoatrial node (primary pacemaker) and the atrioventricular node (secondary pacemaker), generating electrical impulses that control heart rate and determine how fast the heart pumps blood.
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The coronary arteries supply blood to the heart muscle
The heart is a muscular organ that pumps blood around the body. It is made up of three layers: the outer epicardium, the thick middle layer of myocardium, and the inner endocardium. The myocardium is the cardiac muscle that makes up the heart.
Like all other tissues in the body, the heart muscle needs a constant supply of oxygen-rich blood to function. The coronary arteries supply oxygenated blood to the heart muscle. The aorta, the main blood supplier to the body, branches off into two main coronary blood vessels (also called arteries). These two main coronary arteries are the left coronary artery and the right coronary artery. The left coronary artery supplies blood to the left side of the heart, while the right coronary artery supplies blood to the right side of the heart.
The left coronary artery branches into the left anterior descending artery and the circumflex artery. The circumflex artery supplies blood to the left atrium, side, and back of the left ventricle. The left anterior descending artery supplies blood to the front and bottom of the left ventricle and the front of the septum. The right coronary artery supplies blood to the right ventricle, the right atrium, and the SA (sinoatrial) and AV (atrioventricular) nodes, which regulate heart rhythm. The right coronary artery also branches into smaller arteries, including the right posterior descending artery and the acute marginal artery.
The coronary arteries wrap around the outside of the heart, with small branches diving into the heart muscle to bring it blood. These arteries and their branches supply all parts of the heart muscle with blood. The cardiac veins then drain this blood away from the heart muscle into the right atrium.
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Cardiac muscle tissue is only found in the heart
The human body contains three kinds of muscle tissue: skeletal, smooth, and cardiac. Cardiac muscle tissue, or myocardium, is a specialized, organized type of tissue that exists only in the heart. It is responsible for keeping the heart pumping and blood circulating around the body.
Cardiac muscle is made up of cardiac muscle cells, or cardiomyocytes, which are tubular structures composed of chains of myofibrils. These myofibrils consist of repeating sections of sarcomeres, which are the fundamental contractile units of the muscle cells. The individual cardiac muscle cells are joined at their ends by intercalated discs to form long fibers. Each cell contains mitochondria, which are often referred to as the powerhouses of the cells.
Cardiac muscle cells are the contracting cells that allow the heart to pump. They contract and release involuntarily, keeping the heart pumping blood around the body. These contractions require a constant supply of oxygen and nutrients to meet the energy demands of the cardiac muscle. Blood supply is delivered to the myocardium by coronary arteries, which are the first branches of the aortic root.
The heart also contains specialized types of cardiac tissue containing "pacemaker" cells. These contract and expand in response to electrical impulses from the nervous system. Pacemaker cells generate electrical impulses, or action potentials, that tell cardiac muscle cells to contract and relax. The pacemaker cells control heart rate and determine how fast the heart pumps blood.
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Cardiomyopathies are diseases that affect cardiac muscle tissue
Cardiac muscle tissue, or myocardium, is a type of muscle tissue that forms the heart. It is one of three types of muscle in the body, the other two being skeletal and smooth muscle. The myocardium is surrounded by a thin outer layer called the epicardium (or visceral pericardium) and an inner endocardium. The heart wall is a three-layered structure with a thick layer of myocardium sandwiched between the inner endocardium and the outer epicardium.
There are several types of cardiomyopathy, including dilated cardiomyopathy, restrictive cardiomyopathy, and hypertrophic cardiomyopathy. Dilated cardiomyopathy is the most frequent form, where the cavity of the heart is enlarged and stretched, compromising its ability to pump normally and relax appropriately. This can be caused by various factors, including chronic heavy alcohol use, nutritional deficiencies, infections, and illicit drugs. Restrictive cardiomyopathy occurs when the walls of the ventricles become stiff, preventing the ventricles from filling with blood properly. This can be caused by the collection of amyloid proteins, forming deposits in the walls of the left ventricle. Hypertrophic cardiomyopathy is a genetic condition where the muscle of the left ventricle thickens, blocking blood flow to the rest of the body and potentially affecting the heart's mitral valve.
Cardiomyopathies can affect people of any sex, race, or age, and the symptoms can vary. Some people may experience shortness of breath, fatigue, dizziness, swelling in the legs or ankles, or chest pain. Diagnosis and treatment of cardiomyopathies involve tests such as echocardiography and genetic testing, along with medications, procedures, healthy lifestyle changes, and stress management.
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Pacemaker cells are specialised cardiac muscle cells that control heart rate
The human heart is made up of cardiac muscle tissue, or myocardium, which is one of three types of muscle tissue in the body, the other two being skeletal and smooth muscle. The myocardium forms the thick middle layer of the heart, sandwiched between the inner endocardium and the outer epicardium.
Cardiac muscle cells, or cardiomyocytes, are the contracting cells that allow the heart to pump. They are the individual cells that make up the cardiac muscle and are responsible for its contractile function. The primary function of cardiomyocytes is to contract, which generates the pressure needed to pump blood through the circulatory system.
Pacemaker cells are a type of cardiomyocyte with specialised functions. They are located in the sinoatrial node (SA node), the primary pacemaker, which is positioned on the wall of the right atrium near the entrance of the superior vena cava. The SA node controls the rate of contraction for the entire heart muscle because its cells have the quickest rate of spontaneous depolarization, thus initiating action potentials the fastest. The action potential generated by the SA node passes down the electrical conduction system of the heart, depolarising other potential pacemaker cells such as those in the atrioventricular node (AV node), which acts as the secondary pacemaker.
Pacemaker cells carry the impulses that are responsible for the beating of the heart. They are distributed throughout the heart and are responsible for several functions. These specialised myocardial cells have an intrinsic ability to depolarise rhythmically and initiate an action potential. They produce electrical impulses, known as cardiac action potentials, which control the rate of contraction of the cardiac muscle, or heart rate. Pacemaker cells contract and expand in response to electrical impulses from the nervous system. They generate electrical impulses, or action potentials, that tell cardiac muscle cells to contract and relax.
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Frequently asked questions
Blood vessels are part of the circulatory system, which delivers oxygen and nutrients to the body's tissues via the arteries and carries waste products away via the veins.
Cardiac muscle is one of three major muscle types and is found only in the heart. It is highly coordinated and contracts involuntarily to pump blood into the vessels of the circulatory system.
No. Blood vessels are not cardiac muscle. Cardiac muscle is only found in the heart and is responsible for pumping blood into the vessels of the circulatory system. Blood vessels are part of the circulatory system, which delivers oxygen and nutrients to the body's tissues and carries waste products away.
