Intercalated discs are microscopic identifying features of cardiac muscle. Cardiac muscle consists of individual heart muscle cells (cardiomyocytes) connected by intercalated discs to work as a single functional organ or syncytium. By contrast, skeletal muscle consists of multinucleated muscle fibers and exhibit no intercalated discs. Intercalated discs support synchronised contraction of cardiac tissue. They occur at the Z line of the sarcomere and can be visualized easily when observing a longitudinal section of the tissue.
Three types of adhering junctions make up an intercalated disc — fascia adherens, macula adherens and gap junctions.
Cardiac muscle (heart muscle) is a type of involuntary striated muscle found in the walls and histological foundation of the heart, specifically the myocardium. Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle. These three types of muscle all form in a process known as myogenesis. The cells that constitute cardiac muscle, called cardiomyocytes or myocardiocytes, contain only one, unique nucleus. Coordinated contractions of cardiac muscle cells in the heart propel blood out of the atria and ventricles to the blood vessels of the left/body/systemic and right/lungs/pulmonary circulatory systems. This complex of actions makes up the systole of the heart.
Cardiac muscle cells, like all tissues in the body, rely on an ample blood supply to deliver oxygen and nutrients and to remove waste products such as carbon dioxide. The coronary arteries fulfill this function.
Muscle is a soft tissue found in most animals. Muscle cells contain protein filaments that slide past one another, producing a contraction that changes both the length and the shape of the cell. Muscles function to produce force and motion. They are primarily responsible for maintaining and changing posture, locomotion, as well as movement of internal organs, such as the contraction of the heart and the movement of food through the digestive system via peristalsis.
Muscle tissues are derived from the mesodermal layer of embryonic germ cells in a process known as myogenesis. There are three types of muscle, skeletal, cardiac, and smooth. Their actions can be classified as being either voluntary or involuntary. Cardiac and smooth muscles contract without conscious thought and are termed involuntary.
The heart is a hollow muscular organ that pumps blood throughout the blood vessels to various parts of the body by repeated, rhythmic contractions. It is found in all animals with a circulatory system, which includes the vertebrates.
The adjective cardiac means "related to the heart" and comes from the Greek καρδιά, kardia, for "heart". Cardiology is the medical speciality that deals with cardiac diseases and abnormalities.
The atrial syncytium is a network of cardiac muscle cells (syncytium) connected by intercalated discs that lends to the coordinated contraction of the atria. Ventricular syncytium refers to the same network in the ventricle. The ventral and atrial syncytia are connected by cardiac conduction system fibers.
Electrical resistance through intercalated discs is very low, thus allowing free diffusion of ions. The ease of ion movement along cardiac muscle fibers axes is such that action potentials are able to travel from one cardiac muscle cell to the next, facing only slight resistance. Each syncyntium obeys the all or none law.
A T-tubule (or transverse tubule) is a deep invagination of the sarcolemma, which is the plasma membrane, only found in skeletal and cardiac muscle cells. These invaginations allow depolarization of the membrane to quickly penetrate to the interior of the cell.
Each muscle fibre is surrounded by a sarcolemma (the muscle fiber's plasma membrane). Transverse tubules are invaginations of the sarcolemma. Though the invaginations are normally perpendicular to the length of the fiber, many T-tubules can lie axial to the long-axis of the fiber, both wrapping around and running alongside myofilament bundles. The size and arrangement of T-tubules vary depending on muscle type and species. T-tubules are thought to be rich in a number of proteins, including a large number of L-type calcium channels.
Anatomy (from the Greek ἀνατέμνω – anatemnō, "I cut up, cut open" from ἀνά – ana, "on, upon", and τέμνω – temnō, "I cut") is the study of the body plan of animals. In some of its facets, anatomy is closely related to embryology, comparative anatomy and comparative embryology, through common roots in evolution. Human anatomy is important in medicine.
The discipline of anatomy is subdivided into gross (or macroscopic) anatomy and microscopic anatomy. Gross anatomy is the study of structures that can, when suitably presented or dissected, be seen by unaided vision with the naked eye. Microscopic anatomy is the study of structures on a microscopic scale, including histology (the study of tissues) and cytology (the study of cells).
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, evolution, distribution, and taxonomy. Modern biology is a vast and eclectic field, composed of many branches and subdisciplines. However, despite the broad scope of biology, there are certain general and unifying concepts within it which govern all study and research, consolidating it into single, coherent field. Biology generally recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the synthesis and creation of new species. It is also understood today that all organisms survive by consuming and transforming energy and by regulating their internal environment to maintain a stable and vital condition.
Subdisciplines of biology are defined by the scale at which organisms are studied, the kinds of organisms studied, and the methods used to study them: biochemistry examines the rudimentary chemistry of life; molecular biology studies the complex interactions among biological molecules; botany studies the biology of plants; cellular biology examines the basic building block of all life, the cell; physiology examines the physical and chemical functions of tissues, organs, and organ systems of an organism; evolutionary biology examines the processes that produced the diversity of life; and ecology examines how organisms interact in their environment.
The muscular system is an organ system consisting of skeletal, smooth and cardiac muscles. It permits movement of the body, maintains posture, and circulates blood throughout the body. The muscular system in vertebrates is controlled through the nervous system, although some muscles (such as the cardiac muscle) can be completely autonomous.
There are three distinct types of muscles: skeletal muscles, cardiac or heart muscles, and smooth (non-striated) muscles. Muscles provide strength, balance, posture, movement and heat for the body to keep warm.