1.Define function of the C/CV system, and, in particular the explain the functio
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Question
1.Define function of the C/CV system, and, in particular the explain the functions of blood.
2.Describe the structures and explain the functions of the formed elements.
3.Explain hematopoiesis and how it is regulated.
4.Explain the functions of blood plasma.
5.Explain the genetic basis of blood type.
6.Explain the 3 processes of homeostasis
Explanation / Answer
1. The cardiovascular system is essentially composed of the heart, the arteries and veins, and the blood. All of these work together to form circulation, which keeps the body working in smooth order. The Heart The heart is the center of the cardiovascular system; if it is injured or not working properly, then the rest of the system is going to fail also. The heart pumps the blood out to the body through blood vessels. The heart is composed of four chambers; the right atrium, the right ventricle, the left atrium and the left ventricle. Think of a one-way road. Blood comes into the right atrium through the superior vena cava and the inferior vena cava, where it then passes through the tricuspid valve down to the right ventricle. From the right ventricle, it flows up through the pulmonic valve, where it goes to the lungs. After reaching the lungs and ridding itself of the carbon dioxide, oxygen is then taken in, and the blood transports this oxygen-rich blood back through the pulmonary veins to the left atrium. From the left atrium, it makes its way through the mitral valve to the left ventricle, which releases it through the aortic valve to the aorta, where it then flows back out into the body to deliver the necessary oxygen and nutrients. Arteries Arteries carry the nutrient-rich, oxygenated blood out to the rest of the body. Each and every cell in the body receives this. Nutrients may be derived from the intestines or even excess supplies from elsewhere in the body. There are major arteries, such as the aorta, which branches down into the lower parts of the abdomen and branches off in many different places, supplying blood to the extremities and even the head through the carotid arteries. The coronary arteries keep blood flowing through the heart muscle. Major arteries are larger, but to reach all of the tiny cells in the body, they become smaller, and the tiniest ones are called arterioles. Sponsored Links Easy-Forex® Tradingwww.Easy-Forex.com/Forex-Trading Enter | Learn | Practice | Succeed. What You Set is What You Get! Veins As the blood returns to the heart, it carries with it waste substances, such as carbon dioxide, which is carried from the heart to the lungs where it can be breathed out of the system, and oxygen can be taken back in; other waste products are excreted through the kidneys. Some of the major veins are the venae cavae. The superior vena cava's name gives a hint to where its blood comes from: the upper portion of the body, such as the head and arms. The inferior vena cava brings blood back from the lower part of the body, such as the abdomen and the legs. Blood Blood is the life of a person, and without it, it is impossible to live. Without blood to rid the body of wastes and carry nutrients and oxygen in, the body would become very ill. Blood helps our bodies fight off illness and can even clot itself when there is an open wound. Plasma is the fluid portion of blood. The more solid parts that make up blood are the red blood cells, white blood cells and the platelets. Red blood cells take oxygen out to all the parts of the body. White blood cells help to fight disease or infection. Platelets are the part of the blood that clot when there is any kind of injury. Blood Type Each person has his own particular blood type. The four types are A, B, AB and O. Type O blood can be given to patients having any blood type because it does not have either A or B antigens; therefore it will mesh with the person's blood no matter the type. People with type AB blood can, on the other hand, accept blood from any donor. Our blood type is derived from our genetic history. When the need arises for a blood transfusion, it is imperative that the right blood type be given. 2..Blood is classically considered to be one of the connective tissues, since it has all of the three components which characterize these: fibers, an amorphous matrix, and cells. The fibrous component is latent in normal blood, and is normally expressed only in response to injury. The amorphous matrix is blood plasma, a low viscosity aqueous solution of proteins and some other constituents. In this laboratory exercise we will consider only the cellular and cell-derived components, i.e., the "formed elements" of normal circulating blood. The true cells (as distinct from non-cells) found in circulating blood are in many cases the same cells found in loose CT's, and this is yet another reason for putting blood in this category of basic tissues. Wright's Stain In most of this exercise you'll be using smear preparations made with Wright's stain (named after its developer, James H. Wright, 1871-1928, an American pathologist). A blood smear is made by putting a drop on a slide and spreading it into a thin film, which is fixed and stained simultaneously. Wright's is an alcohol based mixture of rosin and methylene blue whose staining reactions are similar (but not identical to) the common H&E stain used on tissue sections. It's sold commercially under various names, the most familiar being "Diff-Quick." The slide is dipped into the first stain jar, rinsed, and then dipped into the second. Then it's air dried and cover-slipped. Most people develop a mental image of what formed elements of blood "ought" to look like based solely on smears made this way; and specifically, based on smears stained with Wright's solution. Unfortunately, as useful as these smears are, you could hardly find a less congenial environment for the somewhat delicate formed elements. They're held down to the glass of the slide by surface tension, stretched and flattened out like a road-killed possum on Interstate 81. Under these conditions, they tend to look larger than they really are. There are also subtle differences in the colors produced by Wright's stain and the common H&E stain used in sections. Because it's important to be able to identify cells in sections, I've tried to include examples of the various cell types from both situations. You need to become skilled at spotting blood cell types in sections, and to remember that however useful smears are (and they're very useful) the differences in appearance exist. Commonalities of Formed Elements and Cells of CT Most of what we think of as "blood cells" are really cells of connective tissues in general. Most of them use the bloodstream simply as a transport system, residing in it only a few hours, or at most a couple of days. Almost any of the formed elements can normally be found outside the circulatory system, interspersed among the fibers of irregular CT. Some of the circulating cells are immature forms, whose true nature (and final morphology) are demonstrated only after they take up residence in the CT. Erythrocytes & Platelets Begin with slide 1004, a smear of normal canine blood. (If you're a cat person, try slide 1001, normal feline blood, instead.) I've put these two formed elements first because they have some things in common: in mammals they're not true cells, but are derived from true cells. They lack a nucleus and organelles and have limited, specific functions. The most common formed element is the erythrocyte, or "red blood cell" (RBC). Despite the common term, this is not a cell at all, although it's derived from true cells. The RBC is the mature stage of development of a cell line in which the nucleus (present in earlier forms) has been lost. Structurally RBCs are pretty uninteresting: they're merely bags of hemoglobin, the oxygen transport material. They usually take on the shape of a bi-concave disc, and have no internal organelles. Even in the EM they are internally uniform and amorphous. In the image at left there are a few of the millions scattered this slide of a smear. At right, a few hundred are seen in the lumen of a small artery, at slightly lower magnification than in the smear. The morphology of RBCs is pretty much the same in all the common mammalian species; most of the variations in shape can be accounted for as processing artifacts and/or the results of disease. One notable exception is in the camelids (camels, dromedaries, and llamas). These animals have oval RBCs, rather than the round ones found in all other mammals. At one time, though, the precursors of erythrocytes were true nucleated cells. These precursors exist in the bone marrow. As the last step of the developmental process, the nucleus is extruded. At that point the fully-formed erythrocyte is normally released into the blood circulation. Under normal circumstances there shouldn't be any of the nucleated precursors in circulation, but sometimes, if there's a high demand for new erythrocytes (as, for example, when there's continuing blood loss) some not-quite-mature cells will be released with nuclei in them. These will later be expelled while in the circulation. The life span of erythrocytes is limited: about 90-120 days. After that time they develop surface "senescence" markers and get engulfed in the spleen and liver by resident macrophages. The hemoglobin and plasma membranes are broken down and scavenged for re-usable components, and the residue becomes the iron containing pigment hemosiderin. There's one thing that RBCs are handy for (besides carrying oxygen, of course). In most mammals they're about 5.5 to 7.5 microns in diameter, and very uniform in size (as the pictures make clear). They make a handy built-in "size gauge" in tissue sections, since there are always a few around somewhere in a tissue section. It's worth your time to look for "free" erythrocytes such as the ones above, and use them to get a better idea of the size of things in the other parts of the field. Platelets The platelet, like the erythrocyte, isn't a cell at all. Platelets initiate the clotting process. Like the erythrocyte, the platelet was once part of a cell, but in its maturation it loses its true cellularity. In fact, it's nothing but a fragment of a pre-existing precursor cell of the bone marrow a very large megakaryocyte. In the course of its differentiation, the megakaryocyte develops fissures in its cytoplasm, and literally falls apart, the membrane bound cytoplasmic fragments being thenceforth known as platelets. Platelets are little bitty things, only 2 to 4 microns in diameter (about half the size of an RBC), and round to oval in shape. They have a central zone that is slightly basophilic, and a pale, homogeneous periphery. Look for them in the spaces between erythrocytes. The image above shows platelets in a smear: they appear as small fragments with a blue cast to them. They're much smaller than the erythrocytes: maybe 1-3 microns. The scanning electron micrograph at the right is of a group of platelets which have begun to initiate a clot. The stringy material covering them is fibrin, the matured, insoluble fibrillar component of blood. Leukocytes The "white blood cells," or leukocytes, are true cells with nuclei and organelles. Despite the term "white blood cell," these really aren't "blood" cells at all. They generally function (and in some cases mature) only after leaving the blood compartment for the connective tissue space, and hence they're connective tissue cells. The blood is their means of transit. These cells are capable of recognizing specific sites in the walls of blood vessels, and squeezing through these locations (a process called diapedesis) using a amoeboid form of motion. They're subdivided into two major categories. Granulocytes have inclusions in their cytoplasm; agranulocytes don't. The granulocytes also have lobulated or segmented nuclei; the agranulocytes typically do not. The principal granulocytes are neutrophils, eosinophils, and basophils. The agranulocytes are the lymphocytes and the monocytes. 3...Department of Hematology and Medical Oncology, Hospital Clinico Universitario, University of Valencia, Spain; and † Stem Institute, and Division of Hematology, Oncology and Transplantation, Department of Medicine, University of Minnesota, Minneapolis Correspondence: Catherine M. Verfaillie, M.D., Professor of Medicine, Box 806 UMHC, 420 Delaware St., SE, Minneapolis, MN 55455. E-mail: verfa001@tc.umn.edu Normal steady-state hematopoiesis takes place in the bone marrow microenvironment. Soluble factors as well as contact interactions between the hematopoietic cells and the marrow microenvironment dictate the fate of hematopoietic stem cells and progenitors. Over the last decade it has become clear that cell-cell and cell-extracellular matrix interactions through adhesion receptors play a major role in the hematopoietic process. They are required for the residence of stem cells and progenitors in the marrow, as well as for homing of stem and progenitor cells to the marrow in the setting of stem cell transplantation. Furthermore, adhesion receptors play an important role in regulation of cell behavior, either through direct activation of signal pathways important for cell survival, cell growth, and cell fate decision-making processes, or by modulating responses to growth factors. Insights in the abnormalities seen in these interactions in diseases of the hematopoietic system will help to develop better therapeutic strategies based on the pathogenesis of these diseases. 4....Plasma is the liquid portion of the blood. This slightly yellow fluid is made up of 90 percent water, according to the Franklin Institute. Although often thought of as less important than the cells of the blood that carry oxygen and provide immunity, the plasma is equally important. It is responsible for many different functions in the body. Transport Nutrients 5.....Blood is a complex, living tissue that contains many cell types and proteins. A transporter, regulator, and defender, blood courses through the body carrying out many important functions. PROTEINS & BLOOD TYPES Distinct molecules called agglutinogens (a type of antigen) are attached to the surface of red blood cells. There are two different types of agglutinogens, type "A" and type "B". Each type has different properties. The ABO blood type classification system uses the presence or absence of these molecules to categorize blood into four types: Another level of specificity is added to blood type by examining the presence or absence of the Rh protein. Each blood type is either positive "+" (has the Rh protein) or negative "-" (no Rh protein). For example, a person whose blood type is "A positive" (A +), has both type A and Rh proteins on the surface of their red blood cells. BLOOD TYPE IS GENETIC The A and B antigen molecules on the surface of red blood cells are produced by two different enzymes. These two enzymes are encoded by different versions, or alleles, of the same gene: A and B. The A and B alleles code for enzymes that produce the type A and B antigens respectively. A third version of this gene, the O allele, codes for a protein that is not functional and does not produce surface molecules. Two copies of the gene are inherited, one from each parent. The possible combinations of alleles produce blood types in the following way: WHEN BLOOD TYPES MIX Blood plasma is packed with proteins called antibodies. The body produces a wide variety of antibodies that will recognize and attack foreign molecules that may enter from the outside world. A person's plasma does not contain any antibodies that will bind to molecules that are part of his or her own body. When conducting a blood transfusion, it is important to carefully match the donor and recipient blood types. If the donor blood cells have surface molecules that are different from those of the recipient, antibodies in the recipient's blood recognize the donor blood as foreign. This triggers an immune response resulting in blood clotting. If the donor blood cells have surface molecules that are the same as those of the recipient, the recipient's body will not see them as foreign and will not mount an immune response. There are two special blood types when it comes to blood transfusions. People with type O blood are universal donors because there are no molecules on the surface of the red blood cells that can trigger an immune response. People with type AB blood are universal recipients because they do not have any antibodies that will recognize type A or B surface molecules. Note: Blood cells are covered with a variety of surface molecules. For simplicity, only type A and B surface molecules are shown here. One of the most important functions of the plasma is to transport nutrients throughout the body. As food is digested in the stomach and intestines, it is broken down into its components. This includes amino acids (the building blocks of proteins), lipids (fats), sugars (glucose) and fatty acids. These nutrients are distributed to cells throughout the body where they are utilized to maintain healthy functions and growth. Proteases from Abpro Labs Recombinant Human Proteins; Full-length, Active, >95% Pure www.abpro-labs.com/products Sponsored Links Transport Waste In addition to transporting nutrients, the plasma transports waste products, such as uric acid, creatinine and ammonium salts, from the cells of the body to the kidneys. The kidneys filter these wastes out of the plasma and excrete them from the body as urine. Maintain Blood Volume Approximately 7 percent of the plasma is protein, according to the Science Encyclopedia. The protein found in the highest concentration in plasma is albumin, a protein important for tissue repair and growth. This high concentration of albumin is important for maintaining the osmotic pressure of the blood. Albumin is also present in the fluids that surround the cells, known as the interstitial fluid. The concentration of albumin in this fluid is lower than in plasma. Because of this, water is not able to move from the interstitial fluid into the blood. If the plasma did not contain so much albumin, water would move into the blood, increasing blood volume and causing an increase in blood pressure which would make the heart work harder. Balance Electrolytes Plasma carries salts, also called electrolytes, throughout the body. These salts, including sodium, calcium, potassium, magnesium, chloride and bicarbonat,e are important for many bodily functions. Without these salts, muscles would not contract and nerves would not be able to send signals to and from the brain. Defend the Body Plasma carries other proteins besides albumin throughout the body. Immunoglobulins, also known as antibodies, are proteins that fight off foreign substances, such as bacteria, that invade the body. Fibrinogen is a protein necessary to help the platelets (cells in the blood) to form blood clots. By carrying these proteins, the plasma is playing a critical role in defending the body against infection and blood loss 6......Homeostasis" refers to keeping some aspect of the body's functioning at a fixed level: not too high, not too low. A good example is human body temperature (strictly, core temperature, since the skin may get pretty cold in winter, for example). The body has a set point (typically about 98.4 deg Fahrenheit or 36.9 deg Celsius, although it varies with the time of day and, in women, time of the menstrual cycle). The body detects any deviation from this set point, in other words any rise above or fall below this point, and corrects it. Another example is blood sugar level (plasma glucose concentration). There are many others, such as blood levels of calcium and other ions. Many of these levels are regulated using hormones, although temperature correction mostly involves the nervous system (reflex responses).
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