The difference in pressure between the aorta and right atrium accounts for blood flow in the circulation, as blood flows from areas of high pressure to areas of low pressure. The aortic arch contains peripheral baroreceptors pressure sensors and chemoreceptors chemical sensors that relay information concerning blood pressure, blood pH, and carbon dioxide levels to the medulla oblongata of the brain.
This information is processed by the brain and the autonomic nervous system mediates the homeostatic responses that involve feedback in the lungs and kidneys. The aorta extends around the heart and travels downward, diverging into the iliac arteries. The five components of the aorta are:. The pulmonary arteries carry deoxygenated blood from the right ventricle into the alveolar capillaries of the lungs to unload carbon dioxide and take up oxygen.
These are the only arteries that carry deoxygenated blood, and are considered arteries because they carry blood away from the heart. The short, wide vessel branches into the left and right pulmonary arteries that deliver deoxygenated blood to the respective lungs. Blood first passes through the pulmonary valve as it is ejected into the pulmonary arteries.
Pulmonary circuit : Diagram of pulmonary circulation. Oxygen-rich blood is shown in red; oxygen-depleted blood in blue. The pulmonary veins carry oxygenated blood from the lungs to the left atrium of the heart. Despite carrying oxygenated blood, this great vessel is still considered a vein because it carries blood towards the heart.
Four pulmonary veins enter the left atrium. The right pulmonary veins pass behind the right atrium and superior vena cava while the left pass in front of the descending thoracic aorta. The pulmonary arteries and veins are both considered part of pulmonary circulation. Learning Objectives Describe the great vessels that carry blood to and from the heart. Key Points Five great vessels enter and leave the heart: the superior and inferior vena cava, the pulmonary artery, the pulmonary vein, and the aorta.
The superior vena cava and inferior vena cava are veins that return deoxygenated blood from circulation in the body and empty it into the right atrium. The pulmonary artery carries deoxygenated blood from the right ventricle into the lungs for oxygenation. The pulmonary veins carry oxygenated blood from the lungs into the left atrium where it is returned to systemic circulation.
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Health Conditions Discover Plan Connect. Artery vs. Medically reviewed by Gerhard Whitworth, R. These systems of tubes are either: Pulmonary. What are the different types of arteries? What are the different types of veins? Artery and vein diagram. Anatomy of veins and arteries. The cardiovascular system. The takeaway. Read this next. The aorta is the largest of the arteries in systemic circulation.
Blood is pumped from the left ventricle through the aortic valve into the aorta. The aorta is a highly elastic artery and is able to dilate and constrict in response to blood pressure and volume. When the left ventricle contracts to force blood through the aortic valve into the aorta, the aorta expands. This expansion provides potential energy to help maintain blood pressure during diastole, when the aorta passively contracts. Blood pressure is highest in the aorta and diminishes through circulation, reaching its lowest points at the end of venous circulation.
The difference in pressure between the aorta and right atrium accounts for blood flow in the circulation, as blood flows from areas of high pressure to areas of low pressure. The aortic arch contains peripheral baroreceptors pressure sensors and chemoreceptors chemical sensors that relay information concerning blood pressure, blood pH, and carbon dioxide levels to the medulla oblongata of the brain.
This information is processed by the brain and the autonomic nervous system mediates the homeostatic responses that involve feedback in the lungs and kidneys. The aorta extends around the heart and travels downward, diverging into the iliac arteries. The five components of the aorta are:. The pulmonary arteries carry deoxygenated blood from the right ventricle into the alveolar capillaries of the lungs to unload carbon dioxide and take up oxygen.
These are the only arteries that carry deoxygenated blood, and are considered arteries because they carry blood away from the heart. The short, wide vessel branches into the left and right pulmonary arteries that deliver deoxygenated blood to the respective lungs.
Blood first passes through the pulmonary valve as it is ejected into the pulmonary arteries. Pulmonary circuit : Diagram of pulmonary circulation. Oxygen-rich blood is shown in red; oxygen-depleted blood in blue.
The pulmonary veins carry oxygenated blood from the lungs to the left atrium of the heart. Despite carrying oxygenated blood, this great vessel is still considered a vein because it carries blood towards the heart. Four pulmonary veins enter the left atrium. The right pulmonary veins pass behind the right atrium and superior vena cava while the left pass in front of the descending thoracic aorta. The pulmonary arteries and veins are both considered part of pulmonary circulation.
The myocardium cardiac muscle is the thickest section of the heart wall and contains cardiomyocytes, the contractile cells of the heart. The myocardium, or cardiac muscle, is the thickest section of the heart wall and contains cardiomyocytes, the contractile cells of the heart. As a type of muscle tissue, the myocardium is unique among all other muscle tissues in the human body. The structure of cardiac muscle shares some characteristics with skeletal muscle, but has many distinctive features of its own.
Cardiomyocytes are shorter than skeletal myocytes and have fewer nuclei. Each muscle fiber connects to the plasma membrane sarcolemma with distinctive tubules T-tubule. At these T-tubules, the sarcolemma is studded with a large number of calcium channels which allow calcium ion exchange at a rate much faster than that of the neuromuscular junction in skeletal muscle. The flux of calcium ions into the muscle cells causes stimulates an action potential, which causes the cells to contract.
Cardiac muscle, like skeletal muscle, is comprised of sarcomeres, the basic, contractile units of muscle. Sarcomeres are composed of long, fibrous proteins that slide past each other when the muscles contract and relax. Two of the important proteins found in sarcomeres are myosin, which forms the thick filament, and actin, which forms the thin filament. Myosin has a long, fibrous tail and a globular head that binds to actin.
The myosin head also binds to ATP, the source of energy for cellular metabolism, and is required for the cardiomyocytes to sustain themselves and function normally. Together, myosin and actin form myofibril filaments, the elongated, contractile threads found in muscle tissue. Cardiac muscle and skeletal muscle both contain the protein myoglobin, which stores oxygen. Cardiac muscle is adapted to be highly resistant to fatigue.
Cardiomyocytes have a large number of mitochondria, enabling continuous aerobic respiration. Cardiac muscle also has a large blood supply relative to its size, which provides a continuous stream of nutrients and oxygen while providing ample removal of metabolic waste.
Cardiac Muscle : The tissue structure of cardiac muscle contains sarcomeres that are made of myofibrils with intercalated disks, that contain cardiomyocytes and have many mitocondria. The myocardium has variable levels of thickness within the heart. Chambers of the heart with a thicker myocardium are able to pump blood with more pressure and force compared to chambers of the heart with a thinner myocardium. The myocardium is thinnest within the atria, as these chambers primarily fill through passive blood flow.
The right ventricle myocardium is thicker than the atrial myocardium, as this muscle must pump all blood returning to the heart into the lungs for oxygenation. The myocardium is thickest in the left ventricle, as this chamber must create substantial pressure to pump blood into the aorta and throughout systemic circulation.
The thickness of the myocardium may change in some individuals as a compensatory adaptation to disease, either thickening and becoming stiff or becoming thinner and flabby. Cardiac hypertrophy is a common result of hypertension high blood pressure in which the cells of the myocardium enlarge as an adaptive response to pumping against the higher pressure.
Eventually, hypertrophy may become so severe that heart failure occurs when the heart becomes so stiff that it can no longer pump blood. A flabby heart is typically the result of myocardial infections, in which the heart muscle becomes so weak that it cannot efficiently pump blood, which also leads to heart failure. Right Ventricular Hypertrophy : If the heart adapts to become too thick, it will not be able to pump blood as efficiently, and heart failure may occur. The cardiac skeleton, or fibrous skeleton of the heart, is the structure of dense connective tissue that separates the atria from the ventricles.
The fibrous skeleton provides critical support for the heart and separates the flow of electrical impulses through the heart. Fibrous Rings of the Heart : Transverse section of the heart showing the fibrous rings surrounding the valves.
The primary structure of cardiac skeleton consists of four dense bands of tough elastic tissue called fibrous rings that encircle the bases of the heart valves. The fibrous skeleton is composed primarily of collagen, a protein found in every type of connective tissue in the human body. There are four fibrous rings:. The fibrous skeleton provides a great amount of structural and functional support for the valves of the heart by enabling them to stay open and provides a point of attachment for the valves to the wall of the heart.
The fibrous skeleton of the heart acts as an insulator for the flow of electrical current across the heart. It stops the flow of electricity between the different chambers of the heart so that electrical impulses do not flow directly between the atria and ventricles. The sinoatrial SA node lies on the top of the heart, while the AV node is located at the center of the fibrous skeleton, the only path by which electricity can flow through the heart.
This electrical separation is essential for cardiac function, because electrical impulses flow from the top of the heart to the bottom of the heart. The separation allows the AV node and AV bundle to delay the wave of depolarization so that the atria can contract and assist in ventricular filling before the ventricles themselves depolarize and contract.
The fibrous skeleton of the heart also protects against cardiac arrhythmias. Privacy Policy. Skip to main content. Cardiovascular System: The Heart. Search for:. The Heart. Anatomy of the Heart The heart is an organ responsible for pumping blood through the blood vessels using rhythmic contractions of cardiac muscle. Learning Objectives Describe the anatomy of the heart. Key Takeaways Key Points The heart is a four-chambered muscular organ containing an involuntary conduction system that initiates rhythmic contractions to pump blood throughout the body.
The heart has its own blood supply and is controlled by self-regulating nerve bundles called nodes. The SA and AV nodes send impulses through the Purkinje fibers that cause muscle contractions to the heart.
The heart is composed of three layers: the epicardium outer layer which prevents excess expansion or movement of the heart, the myocardium middle layer which initiates contractions driving the cardiac cycle, and the endocardium inner layer that lines the cavities and valves.
The heart contains two upper chambers called atria and two lower chambers called ventricles. The left and right sides of the heart are separated by the septum. Valves prevent the backflow of blood and separate the atria from the ventricle and the ventricle from the pulmonary artery or aorta.
Key Terms heart : A fist-sized muscular organ in the chest that pumps blood through the body using involuntary contractions of cardiac muscle. Innervated by the Purkinje fibers. Pericardium The pericardium is a thick, membranous, fluid-filled sac which encloses, protects, and nourishes the heart. Learning Objectives Distinguish between the fibrous and serous layers of the pericardium.
Key Takeaways Key Points The pericardium is a mesothelium tissue of the thoracic cavity which surrounds the heart. The outer layer, the fibrous pericardium, is comprised of dense connective tissue that protects the heart, anchors it to the surrounding walls, and prevents it from overfilling. The inner layer of the pericardium, the serous pericardium, is further divided into two layers, an outer parietal layer and an inner visceral layer with the pericardial cavity in between the two layers.
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