Posterior interventricular artery
In the coronary circulation, the posterior interventricular artery, most called the posterior descending artery, is an artery running in the posterior interventricular sulcus to the apex of the heart where it meets with the anterior interventricular artery or known as Left Anterior Descending artery. It supplies the posterior third of the interventricular septum; the remaining anterior two-thirds is supplied by the anterior interventricular artery, a septal branch of the left anterior descending artery, a branch of left coronary artery. It is a branch of the right coronary artery. Alternately, the PIV can be a branch of the circumflex coronary artery which itself is a branch of the left coronary artery, it can be supplied by an anastomosis of the left and right coronary artery. Variants have been reported; the anatomical position of the artery is not posterior, but inferior. The terminology posterior is based on viewing the heart from the "Valentine" position, not by the heart's actual position in the body.
Anatomy figure: 20:04-04 at Human Anatomy Online, SUNY Downstate Medical Center - "Posterior view of the heart." Image Image at guidant.com
Right coronary artery
In the coronary circulation, the right coronary artery is an artery originating above the right cusp of the aortic valve, at the right aortic sinus in the heart. It travels towards the crux of the heart, it branches into the right marginal artery. Although rare, several anomalous courses of the right coronary artery have been described including origin from the left aortic sinus. At the origin of the RCA is the conus artery. In addition to supplying blood to the right ventricle, the RCA supplies 25% to 35% of the left ventricle. In 85% of patients, the RCA gives off the posterior descending artery. In the other 15% of cases, the PDA is given off by the left circumflex artery; the PDA supplies the inferior wall, ventricular septum, the posteromedial papillary muscle. The RCA supplies the SA nodal artery in 60% of people; the other 40% of the time, the SA nodal artery is supplied by the left circumflex artery. Overview at Cleveland Clinic 00462 at CHORUSthoraxlesson4 at The Anatomy Lesson by Wesley Norman Anatomy figure: 20:03-04 at Human Anatomy Online, SUNY Downstate Medical Center - "Anterior view of the heart."
Figure of the marginal artery of the heart - merck.com
The atrioventricular septum is a septum of the heart between the right atrium and the left ventricle. Although the name "atrioventricular septum" implies any septum between an atrium and a ventricle, in practice the divisions from RA to RV and from LA to LV are mediated by valves, not by septa. There is no communication between the LA and the RV, it has muscular part. When considering only the membranous septum, it is known as the "atrioventricular component of the membranous septum", it is formed by the union of ventral AV cushion. This septum divides the atrioventricular canal. In some cases, defects can be identified with an echocardiogram. Incomplete formation of the endocardial cushions can lead to atrioventricular septal defects, such as an ostium primum defect. Https://web.archive.org/web/20091030081540/http://www.acc.org/membership/community/pediatric/opinion_apr03/Slide11. JPG
The atrium is the upper chamber through which blood enters the heart. There are two atria in the human heart – the left atrium connected to the lungs, the right atrium connected to the venous circulation; the atria receive blood, when the heart muscle contracts they pump blood to the ventricles. All animals with a closed circulatory system have at least one atrium; the atrium used to be called the "auricle", that term is still used to describe this chamber in, for example, the Mollusca, but in humans that name is now used for an appendage of the atrium. Humans have a four-chambered heart consisting of the right atrium, left atrium, right ventricle, left ventricle; the atria are the two upper chambers. The right atrium receives and holds deoxygenated blood from the superior vena cava, inferior vena cava, anterior cardiac veins and smallest cardiac veins and the coronary sinus, which it sends down to the right ventricle which in turn sends it to the pulmonary artery for pulmonary circulation; the left atrium receives the oxygenated blood from the left and right pulmonary veins, which it pumps to the left ventricle for pumping out through the aorta for systemic circulation.
The right atrium and right ventricle are referred to as the right heart and the left atrium and left ventricle are referred to as the left heart. The atria do not have valves at their inlets and as a result, a venous pulsation is normal and can be detected in the jugular vein as the jugular venous pressure. Internally, there are the rough pectinate muscles and crista terminalis of His, which act as a boundary inside the atrium and the smooth walled part of the right atrium, the sinus venarum derived from the sinus venosus; the sinus venarum is the adult remnant of the sinus venous and it surrounds the openings of the venae cavae and the coronary sinus. Attached to the right atrium is the right atrial appendage – a pouch-like extension of the pectinate muscles; the interatrial septum separates the right atrium from the left atrium and this is marked by a depression in the right atrium –the fossa ovalis. The atria are depolarised by calcium. High in the upper part of the left atrium is a muscular ear-shaped pouch – the left atrial appendage.
This appears to "function as a decompression chamber during left ventricular systole and during other periods when left atrial pressure is high". The sinoatrial node is located in posterior aspect of the right atrium, next to the superior vena cava; this is a group of pacemaker cells. The cardiac action potential spreads across both atria causing them to contract, forcing the blood they hold into their corresponding ventricles; the atrioventricular node is another node in the cardiac electrical conduction system. This is located between the ventricles; the left atrium is supplied by the left circumflex coronary artery, its small branches. The oblique vein of the left atrium is responsible for venous drainage. During embryogenesis at about two weeks, a primitive atrium begins to be formed, it begins as one chamber which over the following two weeks becomes divided by the septum primum into the left atrium and the right atrium. The interatrial septum has an opening in the right atrium, the foramen ovale which provides access to the left atrium.
At birth, when the first breath is taken fetal blood flow is reversed to travel through the lungs. The foramen ovale is no longer needed and it closes to leave a depression in the atrial wall. In some cases, the foramen ovale fails to close; this abnormality is present in 25% of the general population. This is known as an atrial septal defect, it is unproblematic, although it can be associated with paradoxical embolization and stroke. Within the fetal right atrium, blood from the inferior vena cava and the superior vena cava flow in separate streams to different locations in the heart, this has been reported to occur through the Coandă effect. In human physiology, the atria facilitate circulation by allowing uninterrupted venous flow to the heart during ventricular systole. By being empty and distensible, atria prevent the interruption of venous flow to the heart that would occur during ventricular systole if the veins ended at the inlet valves of the heart. In normal physiologic states, the output of the heart is pulsatile, the venous inflow to the heart is continuous and non-pulsatile.
But without functioning atria, venous flow becomes pulsatile, the overall circulation rate decreases significantly. Atria have four essential characteristics. There are no atrial inlet valves to interrupt blood flow during atrial systole; the atrial systole contractions are incomplete and thus do not contract to the extent that would block flow from the veins through the atria into the ventricles. During atrial systole, blood not only empties from the atria to the ventricles, but blood continues to flow uninterrupted from the veins right through the atria into the ventricles; the atrial contractions must be gentle enough so that the force of contraction does not exert significant back pressure that would impede venous flow. The "let go" of the atria must be timed so that they relax before the start of ventricular contraction, to be able to accept venous flow without interruption. By preventing the inertia of interrupted venous flow that would otherwise occur at each ventricular systole, atria allow 75% more cardiac output
The cardiac skeleton known as the fibrous skeleton of the heart, is a high density single structure of connective tissue that forms and anchors the valves and influences the forces exerted through them. The cardiac skeleton partitions the atria from the ventricles; the cardiac skeleton consists of four bands of dense connective tissue, as collagen, that encircle the bases of the pulmonary trunk and heart valves. While not a "true" skeleton, it does provide structure and support for the heart, as well as isolating the atria from the ventricles. In youth, this collagen structure is quite flexible. With aging some calcium can accumulate on this skeleton; this accumulation contributes to the delay of the depolarisation wave in geriatric patients that can take place from the AV node and the bundle of His. The right and left fibrous rings of heart surround arterial orifices; the right fibrous ring is known as the anulus fibrosus dexter cordis, the left is known as the anulus fibrosus sinister cordis.
The right fibrous trigone is continuous with the central fibrous body. This is the strongest part of the fibrous cardiac skeleton; the upper chambers and lower are electrically divided by the properties of collagen proteins within the rings. The valve rings, central body and skeleton of the heart consisting of collagen are impermeable to electrical propagation; the only channel allowed through this collagen barrier is represented by a sinus that opens up to the atrioventricular node and exits to the bundle of His. The muscle origins/insertions of many of the cardiomyocytes are anchored to opposite sides of the valve rings; the atrioventricular rings serve for the attachment of the muscular fibers of the atria and ventricles, for the attachment of the bicuspid and tricuspid valves. The left atrioventricular ring is connected, by its right margin, with the aortic arterial ring. Lastly, there is the tendinous band referred to, the posterior surface of the conus arteriosus; the fibrous rings surrounding the arterial orifices serve for the attachment of the great vessels and semilunar valves, they are known as The aortic annulus.
Each ring receives, by its ventricular margin, the attachment of some of the muscular fibers of the ventricles. The attachment of the artery to its fibrous ring is strengthened by the external coat and serous membrane externally, by the endocardium internally. From the margins of the semicircular notches the fibrous structure of the ring is continued into the segments of the valves; the middle coat of the artery in this situation is thin, the vessel is dilated to form the sinuses of the aorta and pulmonary artery. In some animals, the fibrous trigone can undergo increasing mineralization with age, leading to the formation of a significant os cordis, or two, it has been known since Classical times in harts and oxes and was thought to have medicinal properties and mystical properties. It is observed in goats, but in other animals such as otters. Against the opinion of his time, Galen wrote that the os cordis was found in elephants; the claim endured up to the nineteenth century and was still treated as fact in Gray's Anatomy, although it is not the case.
Electrical signals from the sinoatrial node and the autonomic nervous system must find their way from the upper chambers to the lower ones to ensure that the ventricles can drive the flow of blood. The heart functions as a pump delivering an intermittent volume of blood, incrementally delivered to the lungs and brain; the cardiac skeleton ensures that the electrical and autonomic energy generated above is ushered below and cannot return. The cardiac skeleton does this by establishing an electrically impermeable boundary to autonomic electrical influence within the heart. Put, the dense connective tissue within the cardiac skeleton does not conduct electricity and its deposition within the myocardial matrix is not accidental; the anchored and electrically inert collagen framework of the four valves allows normal anatomy to house the atrioventricular node in its center. The AV node is the only electrical conduit from the atria to the ventricles through the cardiac skeleton, why atrial fibrillation can never degrade into ventricular fibrillation.
Throughout life, the cardiac collagen skeleton is remodeled. Where collagen is diminished by age, calcium is deposited, thus allowing imaged mathematical markers which are valuable in measuring systolic volumetrics; the inert characteristics of the collagen structure that blocks electrical influence makes it difficult to attain an accurate signal for imaging without allowing for an applied ratio of collagen to calcium. Boundaries within the heart were first described and magnified by Drs. Charles S. Peskin and David M. McQueen at the Courant Institute of Mathematical Sciences. Chordae tendineae Fibrous ring of intervertebral disk This article incorporates text in the public domain from page 536 of the 20th edition of Gray's Anatomy Description at cwc.net Histology
Left anterior descending artery
The left anterior descending artery is a branch of the left coronary artery. Occlusion of this artery is called the widow-maker infarction due to a high death risk, it passes at first behind the pulmonary artery and comes forward between that vessel and the left atrium to reach the anterior interventricular sulcus, along which it descends to the notch of cardiac apex. Although rare, multiple anomalous courses of the LAD have been described; these include the origin of the artery from the right aortic sinus. In 78% of cases, it reaches the apex of the heart; the LAD gives off two types of branches: diagonals. Septals originate from the LAD at 90 degrees to the surface of the heart and supplying the anterior 2/3rds of the interventricular septum. Diagonals run along the surface of the heart and supply the lateral wall of the left ventricle and the anterolateral papillary muscle; the artery supplies the anterolateral myocardium and interventricular septum. The LAD supplies 45-55% of the left ventricle and is therefore considered the most critical vessel in terms of myocardial blood supply.
The widow maker is an alternative name for the anterior interventricular branch of the left coronary artery. The name widow maker may apply to the left coronary artery or severe occlusions to that artery; this term is used because the left main coronary and/or the left anterior descending supply blood to large areas of the heart. This means that if these arteries are abruptly and occluded it will cause a massive heart attack that will lead to sudden death; the blockage that kills is made up of platelets streaming to the site of a ruptured cholesterol plaque. A small amount of plaque in this area can rupture and cause death. An example of the devastating results of a complete occlusion of the LAD artery was the sudden death of former NBC News Washington Bureau Chief Tim Russert, as well as the near-death of film director Kevin Smith. From the minute a widow maker heart attack hits, survival time ranges from minutes to several hours. Progressing symptoms should signal the need for immediate attention.
Symptoms of initial onset may include nausea, shortness of breath, pain in the head, arms or chest, numbness in fingers of a novel but imprecise sensation which builds with irregular heart beat. Early symptoms may be mistaken for flu or general malaise until they intensify. A widow maker cannot kill but induces cardiac arrest which may do so within 10 to 20 minutes of no circulation. A victim with no pulse or breath is still alive, living off oxygen stored in the blood and may be able to be rescued if treatment is begun promptly within this window; this article incorporates text in the public domain from page 547 of the 20th edition of Gray's Anatomy Anatomy photo:20:09-0102 at the SUNY Downstate Medical Center - "Heart: The Left Coronary Artery and its Branches" Anatomy figure: 20:03-08 at Human Anatomy Online, SUNY Downstate Medical Center - "Anterior view of the heart."
Anatomical terminology is a form of scientific terminology used by anatomists and health professionals such as doctors. Anatomical terminology uses many unique terms and prefixes deriving from Ancient Greek and Latin; these terms can be confusing to those unfamiliar with them, but can be more precise, reducing ambiguity and errors. Since these anatomical terms are not used in everyday conversation, their meanings are less to change, less to be misinterpreted. To illustrate how inexact day-to-day language can be: a scar "above the wrist" could be located on the forearm two or three inches away from the hand or at the base of the hand. By using precise anatomical terminology such ambiguity is eliminated. An international standard for anatomical terminology, Terminologia Anatomica has been created. Anatomical terminology has quite regular morphology, the same prefixes and suffixes are used to add meanings to different roots; the root of a term refers to an organ or tissue. For example, the Latin names of structures such as musculus biceps brachii can be split up and refer to, musculus for muscle, biceps for "two-headed", brachii as in the brachial region of the arm.
The first word describes what is being spoken about, the second describes it, the third points to location. When describing the position of anatomical structures, structures may be described according to the anatomical landmark they are near; these landmarks may include structures, such as the umbilicus or sternum, or anatomical lines, such as the midclavicular line from the centre of the clavicle. The cephalon or cephalic region refers to the head; this area is further differentiated into the cranium, frons, auris, nasus and mentum. The neck area is called cervical region. Examples of structures named according to this include the frontalis muscle, submental lymph nodes, buccal membrane and orbicularis oculi muscle. Sometimes, unique terminology is used to reduce confusion in different parts of the body. For example, different terms are used when it comes to the skull in compliance with its embryonic origin and its tilted position compared to in other animals. Here, Rostral refers to proximity to the front of the nose, is used when describing the skull.
Different terminology is used in the arms, in part to reduce ambiguity as to what the "front", "back", "inner" and "outer" surfaces are. For this reason, the terms below are used: Radial referring to the radius bone, seen laterally in the standard anatomical position. Ulnar referring to the ulna bone, medially positioned when in the standard anatomical position. Other terms are used to describe the movement and actions of the hands and feet, other structures such as the eye. International morphological terminology is used by the colleges of medicine and dentistry and other areas of the health sciences, it facilitates communication and exchanges between scientists from different countries of the world and it is used daily in the fields of research and medical care. The international morphological terminology refers to morphological sciences as a biological sciences' branch. In this field, the form and structure are examined as well as the changes or developments in the organism, it is functional.
It covers the gross anatomy and the microscopic of living beings. It involves the anatomy of the adult, it includes comparative anatomy between different species. The vocabulary is extensive and complex, requires a systematic presentation. Within the international field, a group of experts reviews and discusses the morphological terms of the structures of the human body, forming today's Terminology Committee from the International Federation of Associations of Anatomists, it deals with the anatomical and embryologic terminology. In the Latin American field, there are meetings called Iberian Latin American Symposium Terminology, where a group of experts of the Pan American Association of Anatomy that speak Spanish and Portuguese and studies the international morphological terminology; the current international standard for human anatomical terminology is based on the Terminologia Anatomica. It was developed by the Federative Committee on Anatomical Terminology and the International Federation of Associations of Anatomists and was released in 1998.
It supersedes Nomina Anatomica. Terminologia Anatomica contains terminology for about 7500 human gross anatomical structures. For microanatomy, known as histology, a similar standard exists in Terminologia Histologica, for embryology, the study of development, a standard exists in Terminologia Embryologica; these standards specify accepted names that can be used to refer to histological and embryological structures in journal articles and other areas. As of September 2016, two sections of the Terminologia Anatomica, including central nervous system and peripheral nervous system, were merged to form the Terminologia Neuroanatomica; the Terminologia Anatomica has been perceived with a considerable criticism regarding its content including coverage and spelling mistakes and errors. Anatomical terminology is chosen to highlight the relative location of body structures. For instance, an anatomist might describe one band of tissue as "inferior to" another or a physician might describe a tumor as "superficial to" a deeper body structure.
Anatomical terms used to describe location