Blood

1. Blood Mr. Neuberger

2. The Circulatory System • The Circulatory System consists of the heart, blood vessels, and blood • The study of blood is known as Hematology • The fundamental purpose of the circulatory system is to transport substances from place to place in the blood • Blood is the liquid medium needed, the blood vessels ensure the proper routing of the blood to its destinations, and the heart is the pump that keeps the blood flowing • Three main functions are: Transport, Protection, Regulation

3. Components and General Properties of Blood • Adults generally have 4-6 liters of blood circulating through their body • Much like elastic and collagen, blood is a type of connective tissue • The matrix is the Blood Plasma, a clear, yellow fluid constituting a little over half of the blood volume • Suspended in the blood plasma are the Formed Elements- cells and cell fragments including RBCs, WBCs, and platelets • Formed Element is used to denote that these are membrane-enclosed bodies with a definitive structure visible with a microscope • There are 7 kinds of formed elements: Erythrocytes, platelets, and five kinds of Leukocytes • Erythrocytes are the most common element, constituting 37-52% of the blood volume • Leukocytes and platelets form the buffy layer and constitute 1% of the blood volume • Plasma finishes off the concoction by making up about 47-63% of the blood volume

5. Blood Plasma • Important as the matrix of this liquid connective tissue • Complex mixture of water, proteins, nutrients, electrolytes, nitrogenous wastes, hormones, and gases • Serumis essentially identical to plasma except for the absence of the clotting protein fibrinogen • Protein is the most abundant plasma solute by weight, 6-9g/dL • The three major proteins are the albumins, globulins, and fibrinogen

6. Blood Plasma • Albumin- smallest and most abundant plasma protein, it serves to transport various plasma solutes and buffer the pH of the blood • Contributes to the viscosity and osmolarity of blood • With those two effects it can greatly influence blood volume, pressure, and flow • Globulins– alpha, beta, or gamma subclasses, aid in solute transport, clotting, and immunity • Fibrinogen– soluble precurser of fibrin, protein that forms the framework of a blood clot

7. Erythrocytes • Erythrocytes, or Red Blood Cells (RBCs) have two principle functions • (1) to pick up oxygen from the lungs and deliver it to tissues elsewhere • (2) to pick up carbon dioxide from the tissues and unload it in the lungs • They are the most critical formed element to survival • Lack of oxygen, carried by the RBCs, can rapidly lead to death in major cases of trauma or hemorrhage • Without all these organelles the RBCs can hold more hemoglobin • Their biconcave shape gives them a much greater ratio of surface are to volume, enables oxygen and carbon dioxide to diffuse much quicker

8. The Erythrocyte Life Cycle • The production of RBCs is called Erythropoiesis, it is one aspect of the general process known as Hemopoiesis • The tissues that produce blood cells are called Hemopoietic Tissues • The first hemopoietic tissues of the human embryo for in the yolk sac, they eventually migrate to the bone marrow, liver, spleen, and thymus • Around the time of birth, the liver and spleen stop producing RBCs but the spleen continues to produce lymphocytes for life • The bone marrow produces all seven formed elements of blood from birth until death, lymphocytes are also produced in the lymphatic tissues and organs • Myeloid and Lymphoid Hemopoiesis

9. Form and Function • An erythrocyte is a discoid cell with a thick rim and a thin sunken center • RBCs lose nearly all organelles during their development and thus are remarkably devoid of internal structure • Lacking mitochondria, RBCs rely exclusively on anaerobic fermentation to produce ATP • By not using aerobic respiration, they avoid using the oxygen they carry for themselves • Also lack a nucleus and DNA, they cannot undergo protein synthesis or mitosis

10. Blood Types • There are 4 blood types: Type A, Type B, Type AB, Type O • Connected to each type’s RBC is an Rh-group, it acts as an antigen • Blood plasma contains anitbodies that react against incompatible antigens on foreign RBCs

11. Hemoglobin • The red color of RBCs is due to its Hemoglobin, an iron-containing gas-transport protein normally found only in RBCs • Consists of 4 protein chains called globins • Alpha chains- 141 amino acids long • Beta chains- 146 amino acids long • Contains a heme group that is bound to each protein chain • At the center of the heme component is a ferrous ion (Fe2+) • Binding sight for oxygen • 4 heme groups = ability to carry 4 oxygen molecules • 5% of the carbon dioxide in the body is carried by the hemoglobin, but bound to the globin component, can carry both gases simultaneously • The hemoglobin concentration in the body is 13-18g/dL

12. Leukocytes • Least abundant formed element in the blood • 5,000-10,000 WBCs/ microliter • Protect against infections, microorganisms, and other pathogens • Use the blood and blood vessels as a subway system • They are able to undergo protein synthesis because they must do so in order to carry out their functions

13. Types of Leukocytes • There are 5 types of leukocytes, they are distinguished from each other by size and abundance, the size and shape of their nuclei, the presence or absence of certain cytoplasmic granules, the coarseness and staining properties of their granules, and most importantly their function • All WBCs have Nonspecific (azurophilic) Granules called this because they absorb blue or violet dyes of blood stains. Neutophils, eosinophils, and basophils are called Granulocytes because they have various types of Specific Granules that distinguish each cell from each other, they contain enzymes and other chemicals employed in defense against pathogens • Monocytes and lymphocytes are called Agranulocytes because they lack specific granules

14. Granulocytes • Neutrophils- Most abundant WBC, 60-70% of circulating leukocytes. Primary task of neutrophils is to destroy bacteria • Phagocytize, or digest them, or release a potent mixture of toxic chemicals, hypochlorite or superoxide ion • Form a killings zone around the neutrophil, lethal to invaders but also to the neutrophil, suicide organ of the body • Eosinophils- 2-4% of the WBC count, fluctuate greatly day to night, seasonally, and with the phases of the menstrual cycle • Rises in allergies, parasitic infections, collagen diseases, and diseases of the spleen and central nervous system • Secrete chemicals that break down large infections to smaller ones for easier destruction by other leukocytes

15. Granulocytes • Basophils- rarest of the WBCs, 0.5-1% of the mix. • Release Histamine- a vasodilator that widens the blood vessels, speeds flow of blood to an injured tissue, and makes the blood vessels more permeable so that blood components such as neutrophils and clotting proteins can get into the connective tissues more quickly, and release Heparin- anitcoagulant that inhibits blood clotting and thus promotes the mobility of other WBCs in the area

16. Agranulocytes • Monocytes- largest of the WBCs, 3-8% of the WBC count. • Transform into large tissue cells called Macrophages- highly phagocytic cells that consume up to 25% of their own volume per hour, they destroy dead or dying host and foreign cells, pathogenic chemicals and microorganisms, and other foreign matter • Also chop up or process foreign antigens and display them, or mark them, to other leukocytes for destruction • Lymphocytes- 25-33% of the WBC count. • Involved in specific immunity, body has seen before, three classes: natural killer cells, B cells, T cells

17. Platelets • Not cells but rather fragments of marrow cells called megakaryocytes • When they open from stimulation, they are capable of ameboid movement • Secrete vasoconstrictors- chemiclas that cause spasmodic constriction of broken vessels • Platelet plugs, but also can secrete chemicals that remove broken down or worn out blood clots • Secrete chemicals that attract neutrophils and monocytes • They also can phagocytize and destroy bacteria