Oblique vein of the left atrium
The oblique vein of the left atrium is a small vessel which descends obliquely on the back of the left atrium and ends in the coronary sinus near its left extremity. This article incorporates text in the public domain from page 643 of the 20th edition of Gray's Anatomy
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
Valve of coronary sinus
The valve of the coronary sinus is a semicircular fold of the lining membrane of the right atrium, at the orifice of the coronary sinus. It is situated at the base of the inferior vena cava; the valve may vary in size, or be absent. It may prevent the regurgitation of blood into the sinus during the contraction of the atrium; this valve may be double or it may be cribriform. It is named for German anatomist Adam Christian Thebesius; this article incorporates text in the public domain from page 531 of the 20th edition of Gray's Anatomy
Right atrioventricular orifice
The right atrioventricular orifice is the large oval aperture of communication between the right atrium and ventricle. Situated at the base of the atrium, it measures about 4 cm. in diameter and is surrounded by a fibrous ring, covered by the lining membrane of the heart. It is guarded by the tricuspid valve. Left atrioventricular orifice This article incorporates text in the public domain from page 531 of the 20th edition of Gray's Anatomy
Cardiac muscle is one of three types of vertebrate muscles, with the other two being skeletal and smooth muscles. It is an striated muscle that constitutes the main tissue of the walls of the heart; the myocardium forms a thick middle layer between the outer layer of the heart wall and the inner layer, with blood supplied via the coronary circulation. It is composed of individual heart muscle cells joined together by intercalated discs, encased by collagen fibres and other substances that form the extracellular matrix. Cardiac muscle contracts in a similar manner to skeletal muscle, although with some important differences. An electrical stimulation in the form of an action potential triggers the release of calcium from the cell's internal calcium store, the sarcoplasmic reticulum; the rise in calcium causes the cell's myofilaments to slide past each other in a process called excitation contraction coupling. Diseases of heart muscle are of major importance; these include conditions caused by a restricted blood supply to the muscle including angina pectoris and myocardial infarction, other heart muscle disease known as cardiomyopathies.
Cardiac muscle tissue or myocardium forms the bulk of the heart. The heart wall is a three layered structure with a thick layer of myocardium sandwiched between the inner endocardium and the outer epicardium; the inner endocardium lines the cardiac chambers, covers the cardiac valves, joins with the endothelium that lines the blood vessels that connect to the heart. On the outer aspect of the myocardium is the epicardium which forms part of the pericardium, the sack that surrounds and lubricates the heart. Within the myocardium there cardiomyocytes; the sheets of muscle that wrap around the left ventricle closest to the endocardium are oriented perpendicularly to those closest to the epicardium. When these sheets contract in a coordinated manner they allow the ventricle to squeeze in several direction – longitudinally and with a twisting motion to squeeze the maximum amount of blood out of the heart with each heartbeat. Contracting heart muscle uses a lot of energy, therefore requires a constant flow of blood to provide oxygen and nutrients.
Blood is brought to the myocardium by the coronary arteries. These lie on the outer or epicardial surface of the heart. Blood is drained away by the coronary veins into the right atrium; when looked at microscopically, cardiac muscle can be likened to the wall of a house. Most of the wall is taken up by bricks, which in cardiac muscle are individual cardiac muscle cells or cardiomyocytes; the mortar which surrounds the bricks is known as the extracellular matrix, produced by supporting cells known as fibroblasts. In the same way that the walls of a house contain electrical wires and plumbing, cardiac muscle contains specialised cells for conducting electrical signals and blood vessels to bring nutrients to the muscle cells and take away waste products. Cardiac muscle cells or cardiomyocytes are the contracting cells; each cardiomyocyte needs to contract in coordination with its neighbouring cells to efficiently pump blood from the heart, if this coordination breaks down – despite individual cells contracting – the heart may not pump at all, such as may occur during abnormal heart rhythms such as ventricular fibrillation.
Viewed through a microscope, cardiac muscle cells are rectangular, measuring 100–150μm by 30–40μm. Individual cardiac muscle cells are joined together at their ends by intercalated disks to form long fibres; each cell contains myofibrils, specialised protein fibres that slide past each other. These are organised into the fundamental contractile units of muscle cells; the regular organisation of myofibrils into sarcomeres gives cardiac muscle cells a striped or striated appearance when looked at through a microscope, similar to skeletal muscle. These striations are caused by lighter I bands composed of a protein called actin, darker A bands composed of myosin. Cardiomyocytes contain T-tubules, pouches of membrane that run from the surface to the cell's interior which help to which improve the efficiency of contraction; the majority of these cells contain only one nucleus, unlike skeletal muscle cells which contain many nuclei. Cardiac muscle cells contain many mitochondria which provide the energy needed for the cell in the form of adenosine triphosphate, making them resistant to fatigue.
T-tubules are microscopic tubes. They are continuous with the cell membrane, are composed of the same phospholipid bilayer, are open at the cell surface to the extracellular fluid that surrounds the cell. T-tubules in cardiac muscle are fewer in number. In the centre of the cell they join together, running into and along the cell as a transverse-axial network. Inside the cell they lie close to the sarcoplasmic reticulum. Here, a single tubule pairs with part of the sarcoplasmic reticulum called a terminal cisterna in a combination known as a diad; the functions of T-tubules include transmitting electrical impulses known as action potentials from the cell surface to the cell's core, helping to regulate the concentration of cal
Loyola University Chicago
Loyola University Chicago is a private Catholic research university in Chicago, Illinois. Founded in 1870 by the Jesuits, today Loyola is one of the largest Catholic universities in the United States. Loyola's professional schools have educated generations of local business and civic leaders, distinguished programs in medicine and health sciences are anchored by the nationally recognized Loyola University Medical Center. Comprising eleven colleges and schools, Loyola offers over 80 undergraduate and 140 graduate/professional programs and enrolls 16,000 students. Loyola has six campuses across the Chicago metropolitan area, as well as a campus in Rome and guest programs in Beijing and Ho Chi Minh City; the flagship Lake Shore Campus is on the shores of Lake Michigan in the Rogers Park and Edgewater neighborhoods of Chicago, eight miles north of the Loop. Loyola's athletic teams, nicknamed the Ramblers, compete in NCAA Division I as members of the Missouri Valley Conference. Loyola won the 1963 NCAA men's basketball championship, remains the only school from Illinois to do so.
The Ramblers are two-time NCAA champions in men's volleyball. Among the more than 150,000 Loyola alumni, there are executives of major Chicago-based corporations such as McDonald's and Baxter International, as well as dozens of local and national political leaders including the current Illinois Attorney General and Speaker of the House. Loyola alumni have won Emmy, Grammy and Pulitzer awards, as well as Guggenheim and MacArthur fellowships. Loyola was established as St. Ignatius College on June 30, 1870, by Jesuit educator Fr. Arnold Damen. At that time Chicago was a much smaller, but growing, city just shy of 300,000 people, as a result the original campus was much closer to the city center along Roosevelt Road. In 1909 the school was renamed Loyola University, in 1912 it began to move to the current Lake Shore Campus. To meet the growing needs of Chicago, Loyola established professional schools in law, medicine and nursing; the Chicago College of Dental Surgery became part of the university in 1923, was closed 70 years later.
A downtown campus was founded in 1914, with it the School of Sociology. As the predecessor to the School of Social Work, it enrolled Loyola's first female students, though the school would not become coeducational until 1966. Loyola Academy, a college prep high school, occupied Dumbach Hall on the Lake Shore Campus until it was relocated to north suburban Wilmette in 1957; the current Water Tower Campus opened in 1949. In 1962, Loyola opened a campus in Rome near the site of the 1960 Summer Olympics. In 1969, Loyola established the School of Education and consolidated medical programs at the Loyola University Medical Center, a hospital and health care complex located in Maywood, an immediate suburb of Chicago; the university separated from the Jesuits in 1970, today is under lay control and governed by a board of trustees. Loyola purchased neighboring Mundelein College in 1991. Major capital campaigns since the turn of the century have enhanced Loyola's academic profile and campuses. In 2005 the Loyola University Museum of Art was established on the Water Tower Campus, the Rome campus was renamed in honor of Director Emeritus John P. Felice.
In 2009, the Cuneo Foundation presented the university with the Cuneo Mansion and Gardens, a 100-acre estate with an Italianate mansion and extensive collections of art and furnishings located in suburban Vernon Hills. The $50 million gift is the largest in Loyola history. In 2010, Loyola purchased the Resurrection Retreat Center in Woodstock, which became the school's fifth campus for retreat and ecological study. In 2012, Loyola alumnus Michael R. Quinlan donated $40 million to the business school, renamed in his honor. During this time over 200,000 square-feet of LEED-certified sustainable spaces have been built on the Lake Shore Campus alone, along with significant mixed-use developments on the Water Tower Campus. Today, Loyola ranks among the top 89 universities in the nation, is in the midst of over $800 million in capital construction projects. In 2015, the university established Arrupe College, a uniquely structured two-year college designed to give low-income students access to a Loyola education.
On May 23, 2016, Loyola named Jo Ann Rooney its 24th president. She is the first female president in the history of the university. Loyola's flagship Lake Shore Campus is along the shores of Lake Michigan in the Rogers Park and Edgewater neighborhoods on the north side of Chicago, eight miles north of the Loop. Founded in 1912, it is the primary residential campus for the school, is the home of the College of Arts and Sciences, a variety of graduate programs. A collection of over forty buildings, the campus offers ample green space and lakeshore access, as well as several landmarks: The Madonna della Strada Chapel, a striking Art Deco masterpiece completed in 1939, is the center of Loyola's religious life; the Mundelein Center, a 200-foot tall Art Deco skyscraper completed in 1930, is the home of Loyola's fine and performing arts programs and a National Historical Landmark. The Joseph J. Gentile Arena, which holds 5,500 for basketball and campus events, was expanded to include the Norville Center, a student-athlete academic center and home of Rambler athletics.
One of the largest events held annually in Gentile Arena is Colossus, which features a musical artist and comedian. Artists including Jason Derulo and John Mulaney have performed for Colossus; the Halas Recreation Center was remodeled and incorp
Mammals are vertebrate animals constituting the class Mammalia, characterized by the presence of mammary glands which in females produce milk for feeding their young, a neocortex, fur or hair, three middle ear bones. These characteristics distinguish them from reptiles and birds, from which they diverged in the late Triassic, 201–227 million years ago. There are around 5,450 species of mammals; the largest orders are the rodents and Soricomorpha. The next three are the Primates, the Cetartiodactyla, the Carnivora. In cladistics, which reflect evolution, mammals are classified as endothermic amniotes, they are the only living Synapsida. The early synapsid mammalian ancestors were sphenacodont pelycosaurs, a group that produced the non-mammalian Dimetrodon. At the end of the Carboniferous period around 300 million years ago, this group diverged from the sauropsid line that led to today's reptiles and birds; the line following the stem group Sphenacodontia split off several diverse groups of non-mammalian synapsids—sometimes referred to as mammal-like reptiles—before giving rise to the proto-mammals in the early Mesozoic era.
The modern mammalian orders arose in the Paleogene and Neogene periods of the Cenozoic era, after the extinction of non-avian dinosaurs, have been among the dominant terrestrial animal groups from 66 million years ago to the present. The basic body type is quadruped, most mammals use their four extremities for terrestrial locomotion. Mammals range in size from the 30–40 mm bumblebee bat to the 30-meter blue whale—the largest animal on the planet. Maximum lifespan varies from two years for the shrew to 211 years for the bowhead whale. All modern mammals give birth to live young, except the five species of monotremes, which are egg-laying mammals; the most species-rich group of mammals, the cohort called placentals, have a placenta, which enables the feeding of the fetus during gestation. Most mammals are intelligent, with some possessing large brains, self-awareness, tool use. Mammals can communicate and vocalize in several different ways, including the production of ultrasound, scent-marking, alarm signals and echolocation.
Mammals can organize themselves into fission-fusion societies and hierarchies—but can be solitary and territorial. Most mammals are polygynous. Domestication of many types of mammals by humans played a major role in the Neolithic revolution, resulted in farming replacing hunting and gathering as the primary source of food for humans; this led to a major restructuring of human societies from nomadic to sedentary, with more co-operation among larger and larger groups, the development of the first civilizations. Domesticated mammals provided, continue to provide, power for transport and agriculture, as well as food and leather. Mammals are hunted and raced for sport, are used as model organisms in science. Mammals have been depicted in art since Palaeolithic times, appear in literature, film and religion. Decline in numbers and extinction of many mammals is driven by human poaching and habitat destruction deforestation. Mammal classification has been through several iterations since Carl Linnaeus defined the class.
No classification system is universally accepted. George Gaylord Simpson's "Principles of Classification and a Classification of Mammals" provides systematics of mammal origins and relationships that were universally taught until the end of the 20th century. Since Simpson's classification, the paleontological record has been recalibrated, the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself through the new concept of cladistics. Though field work made Simpson's classification outdated, it remains the closest thing to an official classification of mammals. Most mammals, including the six most species-rich orders, belong to the placental group; the three largest orders in numbers of species are Rodentia: mice, porcupines, beavers and other gnawing mammals. The next three biggest orders, depending on the biological classification scheme used, are the Primates including the apes and lemurs. According to Mammal Species of the World, 5,416 species were identified in 2006.
These were grouped into 153 families and 29 orders. In 2008, the International Union for Conservation of Nature completed a five-year Global Mammal Assessment for its IUCN Red List, which counted 5,488 species. According to a research published in the Journal of Mammalogy in 2018, the number of recognized mammal species is 6,495 species included 96 extinct; the word "mammal" is modern, from the scientific name Mammalia coined by Carl Linnaeus in 1758, derived from the Latin mamma. In an influential 1988 paper, Timothy Rowe defined Mammalia phylogenetically as the crown group of mammals, the clade consisting of the most recent common ancestor of living monotremes and therian m