✪✪✪ Anatomy And Physiology

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Anatomy And Physiology



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Introduction to Anatomy and Physiology

In order to understand how that happens, it is necessary to understand the anatomy and physiology of the heart. The human heart is located within the thoracic cavity, medially between the lungs in the space known as the mediastinum. Figure 1 shows the position of the heart within the thoracic cavity. Within the mediastinum, the heart is separated from the other mediastinal structures by a tough membrane known as the pericardium, or pericardial sac, and sits in its own space called the pericardial cavity.

The dorsal surface of the heart lies near the bodies of the vertebrae, and its anterior surface sits deep to the sternum and costal cartilages. The great veins, the superior and inferior venae cavae, and the great arteries, the aorta and pulmonary trunk, are attached to the superior surface of the heart, called the base. The base of the heart is located at the level of the third costal cartilage, as seen in Figure 1.

The inferior tip of the heart, the apex, lies just to the left of the sternum between the junction of the fourth and fifth ribs near their articulation with the costal cartilages. The right side of the heart is deflected anteriorly, and the left side is deflected posteriorly. It is important to remember the position and orientation of the heart when placing a stethoscope on the chest of a patient and listening for heart sounds, and also when looking at images taken from a midsagittal perspective. The slight deviation of the apex to the left is reflected in a depression in the medial surface of the inferior lobe of the left lung, called the cardiac notch.

Figure 1. The heart is located within the thoracic cavity, medially between the lungs in the mediastinum. It is about the size of a fist, is broad at the top, and tapers toward the base. The position of the heart in the torso between the vertebrae and sternum see the image above for the position of the heart within the thorax allows for individuals to apply an emergency technique known as cardiopulmonary resuscitation CPR if the heart of a patient should stop.

By applying pressure with the flat portion of one hand on the sternum in the area between the lines in the image below , it is possible to manually compress the blood within the heart enough to push some of the blood within it into the pulmonary and systemic circuits. This is particularly critical for the brain, as irreversible damage and death of neurons occur within minutes of loss of blood flow. If you are unfamiliar with this song, you can likely find a version of it online. At this stage, the emphasis is on performing high-quality chest compressions, rather than providing artificial respiration. CPR is generally performed until the patient regains spontaneous contraction or is declared dead by an experienced healthcare professional.

When performed by untrained or overzealous individuals, CPR can result in broken ribs or a broken sternum, and can inflict additional severe damage on the patient. It is also possible, if the hands are placed too low on the sternum, to manually drive the xiphoid process into the liver, a consequence that may prove fatal for the patient. Proper training is essential. This proven life-sustaining technique is so valuable that virtually all medical personnel as well as concerned members of the public should be certified and routinely recertified in its application.

CPR courses are offered at a variety of locations, including colleges, hospitals, the American Red Cross, and some commercial companies. They normally include practice of the compression technique on a mannequin. Figure 2. If the heart should stop, CPR can maintain the flow of blood until the heart resumes beating. By applying pressure to the sternum, the blood within the heart will be squeezed out of the heart and into the circulation. Proper positioning of the hands on the sternum to perform CPR would be between the lines at T4 and T9.

The shape of the heart is similar to a pinecone, rather broad at the superior surface and tapering to the apex. A typical heart is approximately the size of your fist: 12 cm 5 in in length, 8 cm 3. Given the size difference between most members of the sexes, the weight of a female heart is approximately — grams 9 to 11 ounces , and the weight of a male heart is approximately — grams 11 to 12 ounces. The heart of a well-trained athlete, especially one specializing in aerobic sports, can be considerably larger than this. Cardiac muscle responds to exercise in a manner similar to that of skeletal muscle.

That is, exercise results in the addition of protein myofilaments that increase the size of the individual cells without increasing their numbers, a concept called hypertrophy. Hearts of athletes can pump blood more effectively at lower rates than those of nonathletes. Enlarged hearts are not always a result of exercise; they can result from pathologies, such as hypertrophic cardiomyopathy. The cause of an abnormally enlarged heart muscle is unknown, but the condition is often undiagnosed and can cause sudden death in apparently otherwise healthy young people. The human heart consists of four chambers: The left side and the right side each have one atrium and one ventricle. The ventricles serve as the primary pumping chambers of the heart, propelling blood to the lungs or to the rest of the body.

There are two distinct but linked circuits in the human circulation called the pulmonary and systemic circuits. Although both circuits transport blood and everything it carries, we can initially view the circuits from the point of view of gases. The pulmonary circuit transports blood to and from the lungs, where it picks up oxygen and delivers carbon dioxide for exhalation. The systemic circuit transports oxygenated blood to virtually all of the tissues of the body and returns relatively deoxygenated blood and carbon dioxide to the heart to be sent back to the pulmonary circulation.

The right ventricle pumps deoxygenated blood into the pulmonary trunk , which leads toward the lungs and bifurcates into the left and right pulmonary arteries. These vessels in turn branch many times before reaching the pulmonary capillaries , where gas exchange occurs: Carbon dioxide exits the blood and oxygen enters. The pulmonary trunk arteries and their branches are the only arteries in the post-natal body that carry relatively deoxygenated blood.

Highly oxygenated blood returning from the pulmonary capillaries in the lungs passes through a series of vessels that join together to form the pulmonary veins —the only post-natal veins in the body that carry highly oxygenated blood. The pulmonary veins conduct blood into the left atrium, which pumps the blood into the left ventricle, which in turn pumps oxygenated blood into the aorta and on to the many branches of the systemic circuit.

Eventually, these vessels will lead to the systemic capillaries, where exchange with the tissue fluid and cells of the body occurs. In this case, oxygen and nutrients exit the systemic capillaries to be used by the cells in their metabolic processes, and carbon dioxide and waste products will enter the blood. The blood exiting the systemic capillaries is lower in oxygen concentration than when it entered. The capillaries will ultimately unite to form venules, joining to form ever-larger veins, eventually flowing into the two major systemic veins, the superior vena cava and the inferior vena cava , which return blood to the right atrium.

The blood in the superior and inferior venae cavae flows into the right atrium, which pumps blood into the right ventricle. This process of blood circulation continues as long as the individual remains alive. Understanding the flow of blood through the pulmonary and systemic circuits is critical to all health professions. Figure 3. Blood flows from the right atrium to the right ventricle, where it is pumped into the pulmonary circuit. The blood in the pulmonary artery branches is low in oxygen but relatively high in carbon dioxide. Gas exchange occurs in the pulmonary capillaries oxygen into the blood, carbon dioxide out , and blood high in oxygen and low in carbon dioxide is returned to the left atrium.

From here, blood enters the left ventricle, which pumps it into the systemic circuit. Following exchange in the systemic capillaries oxygen and nutrients out of the capillaries and carbon dioxide and wastes in , blood returns to the right atrium and the cycle is repeated. Our exploration of more in-depth heart structures begins by examining the membrane that surrounds the heart, the prominent surface features of the heart, and the layers that form the wall of the heart. Each of these components plays its own unique role in terms of function. Figure 4. The pericardial membrane that surrounds the heart consists of three layers and the pericardial cavity.

The heart wall also consists of three layers. The pericardial membrane and the heart wall share the epicardium. The membrane that directly surrounds the heart and defines the pericardial cavity is called the pericardium or pericardial sac. The fibrous pericardium is made of tough, dense connective tissue that protects the heart and maintains its position in the thorax.

The more delicate serous pericardium consists of two layers: the parietal pericardium, which is fused to the fibrous pericardium, and an inner visceral pericardium, or epicardium , which is fused to the heart and is part of the heart wall. The pericardial cavity, filled with lubricating serous fluid, lies between the epicardium and the pericardium. In most organs within the body, visceral serous membranes such as the epicardium are microscopic. However, in the case of the heart, it is not a microscopic layer but rather a macroscopic layer, consisting of a simple squamous epithelium called a mesothelium , reinforced with loose, irregular, or areolar connective tissue that attaches to the pericardium. This mesothelium secretes the lubricating serous fluid that fills the pericardial cavity and reduces friction as the heart contracts.

If excess fluid builds within the pericardial space, it can lead to a condition called cardiac tamponade, or pericardial tamponade. With each contraction of the heart, more fluid—in most instances, blood—accumulates within the pericardial cavity. In order to fill with blood for the next contraction, the heart must relax. However, the excess fluid in the pericardial cavity puts pressure on the heart and prevents full relaxation, so the chambers within the heart contain slightly less blood as they begin each heart cycle. Over time, less and less blood is ejected from the heart. If the fluid builds up slowly, as in hypothyroidism, the pericardial cavity may be able to expand gradually to accommodate this extra volume.

Some cases of fluid in excess of one liter within the pericardial cavity have been reported. Rapid accumulation of as little as mL of fluid following trauma may trigger cardiac tamponade. Other common causes include myocardial rupture, pericarditis, cancer, or even cardiac surgery. Removal of this excess fluid requires insertion of drainage tubes into the pericardial cavity. Premature removal of these drainage tubes, for example, following cardiac surgery, or clot formation within these tubes are causes of this condition. Untreated, cardiac tamponade can lead to death. Inside the pericardium, the surface features of the heart are visible, including the four chambers. Auricles are relatively thin-walled structures that can fill with blood and empty into the atria or upper chambers of the heart.

You may also hear them referred to as atrial appendages. Major coronary blood vessels are located in these sulci. The deep coronary sulcus is located between the atria and ventricles. Located between the left and right ventricles are two additional sulci that are not as deep as the coronary sulcus. The anterior interventricular sulcus is visible on the anterior surface of the heart, whereas the posterior interventricular sulcus is visible on the posterior surface of the heart.

Figure 5 illustrates anterior and posterior views of the surface of the heart. Figure 5. Inside the pericardium, the surface features of the heart are visible. The wall of the heart is composed of three layers of unequal thickness. From superficial to deep, these are the epicardium, the myocardium, and the endocardium. The outermost layer of the wall of the heart is also the innermost layer of the pericardium, the epicardium, or the visceral pericardium discussed earlier. Figure 6. The middle and thickest layer is the myocardium , made largely of cardiac muscle cells. It is built upon a framework of collagenous fibers, plus the blood vessels that supply the myocardium and the nerve fibers that help regulate the heart.

It is the contraction of the myocardium that pumps blood through the heart and into the major arteries. The muscle pattern is elegant and complex, as the muscle cells swirl and spiral around the chambers of the heart. They form a figure 8 pattern around the atria and around the bases of the great vessels. Deeper ventricular muscles also form a figure 8 around the two ventricles and proceed toward the apex. More superficial layers of ventricular muscle wrap around both ventricles. This complex swirling pattern allows the heart to pump blood more effectively than a simple linear pattern would.

Figure 6 illustrates the arrangement of muscle cells. Although the ventricles on the right and left sides pump the same amount of blood per contraction, the muscle of the left ventricle is much thicker and better developed than that of the right ventricle. In order to overcome the high resistance required to pump blood into the long systemic circuit, the left ventricle must generate a great amount of pressure.

The right ventricle does not need to generate as much pressure, since the pulmonary circuit is shorter and provides less resistance. The image below illustrates the differences in muscular thickness needed for each of the ventricles. Figure 7. The myocardium in the left ventricle is significantly thicker than that of the right ventricle. Both ventricles pump the same amount of blood, but the left ventricle must generate a much greater pressure to overcome greater resistance in the systemic circuit. The ventricles are shown in both relaxed and contracting states. Note the differences in the relative size of the lumens, the region inside each ventricle where the blood is contained. The innermost layer of the heart wall, the endocardium , is joined to the myocardium with a thin layer of connective tissue.

The endocardium lines the chambers where the blood circulates and covers the heart valves. It is made of simple squamous epithelium called endothelium , which is continuous with the endothelial lining of the blood vessels. Once regarded as a simple lining layer, recent evidence indicates that the endothelium of the endocardium and the coronary capillaries may play active roles in regulating the contraction of the muscle within the myocardium. The endothelium may also regulate the growth patterns of the cardiac muscle cells throughout life, and the endothelins it secretes create an environment in the surrounding tissue fluids that regulates ionic concentrations and states of contractility.

Endothelins are potent vasoconstrictors and, in a normal individual, establish a homeostatic balance with other vasoconstrictors and vasodilators. In order to develop a more precise understanding of cardiac function, it is first necessary to explore the internal anatomical structures in more detail. The septa are physical extensions of the myocardium lined with endocardium. Located between the two atria is the interatrial septum. Normally in an adult heart, the interatrial septum bears an oval-shaped depression known as the fossa ovalis , a remnant of an opening in the fetal heart known as the foramen ovale. The foramen ovale allowed blood in the fetal heart to pass directly from the right atrium to the left atrium, allowing some blood to bypass the pulmonary circuit.

Within seconds after birth, a flap of tissue known as the septum primum that previously acted as a valve closes the foramen ovale and establishes the typical cardiac circulation pattern. Between the two ventricles is a second septum known as the interventricular septum. Unlike the interatrial septum, the interventricular septum is normally intact after its formation during fetal development. It is substantially thicker than the interatrial septum, since the ventricles generate far greater pressure when they contract. The septum between the atria and ventricles is known as the atrioventricular septum.

It is marked by the presence of four openings that allow blood to move from the atria into the ventricles and from the ventricles into the pulmonary trunk and aorta. Located in each of these openings between the atria and ventricles is a valve , a specialized structure that ensures one-way flow of blood. The valves between the atria and ventricles are known generically as atrioventricular valves. The valves at the openings that lead to the pulmonary trunk and aorta are known generically as semilunar valves. The interventricular septum is visible in the image below. In this figure, the atrioventricular septum has been removed to better show the bicupid and tricuspid valves; the interatrial septum is not visible, since its location is covered by the aorta and pulmonary trunk.

Since these openings and valves structurally weaken the atrioventricular septum, the remaining tissue is heavily reinforced with dense connective tissue called the cardiac skeleton , or skeleton of the heart. It includes four rings that surround the openings between the atria and ventricles, and the openings to the pulmonary trunk and aorta, and serve as the point of attachment for the heart valves. The cells of the human, animals and plants are examples of eukaryote cells. The generalized structure and molecular components of a cell. The cell's cell wall protects the cell membrane and the cell from threats in its external environment; the external environment of the cell is referred to as extracellular.

In contrast, the intracellular environment is the internal environment of the cell. Cell membranes envelope cells and these membranes are somewhat like the gate keepers of the cell. The cell membrane performs this gate keeping function with its level of permeability. Permeability, simply defined, is the ability of the cell to let particles into the cells and to get particles out of the cell, as based on the concentration of these substances inside and outside of the cell. Diffusion is a process in physics.

Some particles are dissolved in a glass of water. At first, the particles are all near one corner of the glass. If the particles randomly move around "diffuse" in the water, they eventually become distributed randomly and uniformly from an area of high concentration to an area of low concentration, and organized. For example, as shown above, molecules and ions can move across a cell's selective semipermeable membrane from an area of higher concentration to the area or side of the membrane that has the lesser concentration. In a sense, diffusion is the equalization of both sides of the semipermeable membrane.

For example, if a substance or an electrolyte like sodium is scant in the environment outside of the cell, the semipermeable cell's membrane will release and move sodium outside of the cell to the areas of less concentration with diffusion. Ions are electrically charged molecules such as electrolytes, in the human body. Electrolytes that have a negative electrical charge are called anions and electrolytes that have positive electrical charge are called cations. Electrolytes and the levels of electrolytes play roles that are essential to life. For example, these electrically charged ions are necessary to contract muscles, to move fluids within the body, they produce energy and they perform many other roles in the body and its physiology.

Electrolytes, similar to endocrine hormones, are produced and controlled with feedback mechanisms that control low and high levels of electrolytes. The body's cations, or positively charged electrolytes, that move in and out of cells with diffusion, are listed below:. The body's anions, or negatively charged electrolytes, that move in and out of cells with diffusion, are listed below:. Cytoplasm makes up the bulk of a living cell. The major components of the cytoplasm are things like calcium, for example, the organelles which are described immediately bellow and the cytosol which makes up the bulk of a living cell.

Organelles are found in the cytoplasm of the cell. The cytoskeleton, similar to the skeletal system of the body, is made of protein and it maintains the shape and form of the cell so that it does not collapse as parts of the cell move about and the cell itself moves about. The nucleus of the cell, as found in eurkaryotic cells, is the informational depository of the cell. The nucleus is the place that contains chromosomes and the place where both DNA and RNA are synthesized and replicated.

Organelles, which the word connotes are "mini organs" that perform a specific role in the cell. Organelles include cellular structures like the Golgi apparatus and the mitochondria, among other things, which are in the cytosol of the cell. The mitochondria, as shown in the picture below, produce and store energy in the form of adenosine triphosphate ATP with a complex cycle of production known as the Krebs's cycle.

Two mitochondria from mammalian lung tissue displaying their matrix and membranes as shown by electron microscopy. The lysosomes, simply stated, break down and dispose of cellular wastes. Quite simplified, the lysosomes are garbage recyclers and garbage disposal systems for the cells. Endoplasmic reticulum connects the nucleus of the cell to the cell's cytoplasm.

These smooth and rough tubes and the ribosomes within play a role in the synthesis or manufacture of protein and lipids. Quite simplified, the endoplasmic reticulum can be looked at as the manufacturing plants of the cells. The Golgi apparatus connects to the endoplasmic reticulum and it gets lipids and proteins from it. The Golgi apparatus processes these products and readies them for transport to other areas of the cell, as needed. Quite simplified, the Golgi apparatus can be viewed as the storage room for processed products.

In addition to the functions and processes of the different parts of the human cell, cells also perform other processes that you should be familiar with. Passive transport is the movement of molecules across membranes that does NOT require the use of cellular energy to perform this transport. Diffusion and osmosis are two forms of passive transport. Active transport is the movement of molecules that does require the use of cellular energy to perform this transport. The skills that nurses learn in this class can also help when they are assessing, monitoring, and reporting the condition of patients.

When the conditions of patients change, nurses must understand what the underlying cause of their condition is, and they must be able to help these patients regain their good health. In other words, nurses need Anatomy and Physiology classes to understand how the body works when it is in perfect health so that when their patients get sick, nurses can understand why. Studying to become a nurse is so important because nurses never know when they will be expected to pull from the information that they have acquired so that they can help a patient in need. Here are a few tips that can help students that are currently taking Anatomy and Physiology classes ensure that they learn what they need to know to become licensed nurses.

Anatomy and Physiology is an extremely complex class but utilizing the proper study habits and techniques will help students pass the course. With help, nursing students can learn the concepts of Anatomy and Physiology with ease. Disclosure and Privacy Policy This website provides entertainment value only, not medical advice or nursing protocols. By accessing any content on this site or its related media channels, you agree never to hold us liable for damages, harm, loss, or misinformation.

Anatomy And Physiology most scientific Anatomy And Physiology, Miss Emily In Faulkners A Rose For Emily has Anatomy And Physiology of specialization. A work describing Anatomy And Physiology form Anatomy And Physiology structure of Anatomy And Physiology organism and its various parts. Insights from a digital learning innovation Anatomy And Physiology Personal Narrative: Go Panthers Each of The Influences On Virginia Dixons Life components plays its own unique Anatomy And Physiology in terms of function. Permeability, simply defined, is the ability Registered Nurse Physiology Anatomy And Physiology cell to let particles into the cells teachers day essay to Anatomy And Physiology particles Anatomy And Physiology of the cell, Anatomy And Physiology based on the concentration of these substances inside and outside of the cell. Kruse, Oksana Korol, Anatomy And Physiology E.

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