lab lesson # 1.docx
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Blood is composed of plasma and formed elements including red blood cells, white blood cells, and platelets. Plasma is mostly water but also contains proteins, nutrients, gases, electrolytes, and waste products. Red blood cells contain hemoglobin and transport oxygen from the lungs to tissues and carbon dioxide from tissues back to the lungs. White blood cells are responsible for the body's defenses against infection and are produced in the bone marrow and lymphoid tissues. The learning objectives cover the composition, function, and production of blood and blood cells.
lab lesson # 1.docx
- 1. Lessom # 1 BLOOD Learning Objectives • Explain the composition of blood • Describe the function of blood • Describe the formation of blood cells . • Explain the regulatory mechanisms in hemopoiesis • Indicate the sites of hemopoiesis in infancy, childhood and adulthood .1 Composition blood Hematology Blood is a circulating tissue composed of fluid plasma and cells. It is composed of different kinds of cells (occasionally called corpuscles); these formed elements of the blood constitute about 45% of whole blood. The other 55% is blood plasma, a fluid that is the blood's liquid medium, appearing yellow in color. The normal pH of human arterial blood is approximately 7.40 (normal range is 7.35-7.45), a weak alkaline solution. Blood is about 7% of the human body weight, so the average adult has a blood volume of about 5 liters, of which 2.7-3 liters is plasma. The combined surface area of all the red cells in the human body would be roughly 2000 times as great as the body's exterior surface. Blood plasma When the formed elements are removed from blood, a straw-colored liquid called plasma is left. Plasma is about 91.5% water and 8.5% solutes, most of which by weight (7%) are proteins.. Some of the proteins in plasma are also found elsewhere in the body, but those confined to blood are called plasma proteins. These proteins play a role in maintaining proper blood osmotic pressure, which is important in total body fluid balance. Most plasma proteins are synthesized by the liver, including the albumins (54% of plasma proteins), globulins (38%), and fibrinogen (7%). Other solutes in plasma include waste products, such as urea, uric acid, creatinine, ammonia, and bilirubin; nutrients; vitamins; regulatory substances such as enzymes and hormones; gasses; and electrolytes. Formed elements The formed elements of the blood are broadly classified as red blood cells (erythrocytes), white blood cells (leucocytes) and platelets (thrombocytes) and their numbers remain remarkably constant for each individual in health. I. Red Blood Cells
- 2. They are the most numerous cells in the blood. In adults, they are formed in the in the marrow of the bones that form the axial skeleton. Mature red cells are nonnucleated and are shaped like flattened, bilaterally indented spheres, a shape often referred to as ”biconcave disc” with a diameter 7.0-8.0µm and thickness of 1.7-2.4µm. In stained smears, only the flattened surfaces are observed; hence the appearance is circular with an area of central pallor corresponding to the indented regions. They are primarily involved in tissue respiration. The red cells contain the pigment hemoglobin which has the ability to combine reversibly with 02. In the lungs, the hemoglobin in the red cell combines with 02 and releases it to the tissues of the body (where oxygen tension is low) during its circulation. Carbondioxide, a waste product of metabolism, is then absorbed from the tissues by the red cells and is transported to the lungs to be exhaled. The red cell normally survives in the blood stream for approximately 120 days after which time it is r e m o v e d b y t h e p h a g o c y t i c c e l l s o f t h e reticuloendothelial system, broken down and some of its constituents re utilized for the formation of new cells. II. White Blood Cells They are a heterogeneous group of nucleated cells that are responsible for the body’s defenses and are transported by the blood to the various tissues where they exert their physiologic role, e.g. phagocytosis. WBCs are present in normal blood in smaller number than the red blood cells (5.0-10.0 × 103/µl in adults). Their production is in the bone marrow and lymphoid tissues (lymph nodes, lymph nodules and spleen). Hematology 5 There are five distinct cell types each with a characteristic morphologic appearance and specific physiologic role. These are: • Polymorphonuclear leucocytes/granulocytes o Neutrophils o Eosinophils o Basophiles • Mononuclear leucocytes oLymphocytes oMonocytes