Blood Anatomy Ch. 10

Components of Blood Complex connective tissue Formed elements: living blood cells Plasma: nonliving fluid matrix Proteins that assist in clotting process Most of the formed elements are erythrocytes (red blood cells or RBCs) which function in oxygen transport Other formed elements include leukocytes (white blood cells or WBCs) that protect the body and platelets which are cell fragments that help stop bleeding The percentage of RBCs in blood makes up the hematocrit (45%) Plasma (55%) WBCs and platelets (buffy coat) (< 1%)

Physical Characteristics and Volume of Blood Blood is a sticky opaque fluid with a metallic taste The amount of oxygen determines the color of blood Thicker, heavier, and more viscous than water Slightly alkaline (basic): pH of 7.4 Temperature is always slightly higher than the body Makes up 8% of body weight 5 to 6 liters are found in adults

Plasma 90% water Liquid part of blood Contains many different dissolved substances: Nutrients, electrolytes, respiratory gases, hormones, proteins, and wastes & products of cell metabolism Proteins are the most abundant solutes 3 most abundant proteins: Albumins: carriers, blood buffers, assists with osmotic pressure Fibrinogen: clotting Globulins: antibodies The composition of plasma is kept relatively constant by the liver (proteins), lungs CO2 and O2), and kidneys (pH) Plasma helps to distribute heat

Erythrocytes Red blood cells Carry O2 in blood to all cells of the body Lack nuclei Contain hemoglobin which is an iron bearing protein that transports the majority of O2 Do not take up any of the O2 they transfer because they make ATP using anaerobic processes. Biconcave shape Large surface area

Erythrocytes Cont. Most abundant formed elements Although the number of RBCs is important, it is the amount of hemoglobin in blood that determines oxygen transport The more hemoglobin molecules in RBCs the more oxygen they can carry A single RBC contains 250 million hemoglobin molecule. Each hemoglobin has 4 molecules of O2. So each RBC can carry 1 billion molecules of O2. Hemoglobin content is slightly higher in men than women.

Leukocytes White blood cells Important for defense against disease Less than 1% of total blood volume The only complete cells in blood (nuclei & organelles) WBCs are able to slip into and out of blood (diapedesis) Function in inflammatory and immune responses Respond to cell damage and infection by responding to chemicals from damaged cells (chemotaxis) Move through tissue space by a process called amoeboid motion which is movement along cytoplasmic extensions.

Leukocytes Cont. WBC production increases in response to need Leukocytosis: high WBC count in response to infection Leukopenia: low WBC count typically caused certain drugs Classified into 2 major groups – granulocytes and agranulocytes – depending on granules in the cytoplasm.

Granulocytes Neutrophils (purple) Eosinophils (red) Basophils (blue) Multilobed nucleus Most numerous WBCs Phagocytes of acute infections of bacteria and fungi Eosinophils (red) Nucleus looks like old telephone receiver Number increases during infections of parasitic worms Basophils (blue) Rarest WBCs Contain histamines which are inflammatory chemicals that make blood vessels leaky and attract other WBCs to the site of infection

Agranulocytes Lymphocytes Monocytes Large nucleus, most of the volume of the cell Found in lymphatic tissue Role in immune response 2nd most numerous Monocytes U or kidney shaped nucleus Largest Macrophages which are important in fighting chronic infections

Most to least abundant WBCs Neutrophils Lymphocytes Monocytes Eosinophils Basophils

Platelets Fragments of large cells called megakaryocytes No nuclei Scattered throughout blood Needed for clotting when blood vessels are broken

Hematopoiesis Blood cell formation Occurs in red bone marrow of flat bones Blood cells are produced in different numbers in response to changing body needs Daily blood cell production: 200 billion red blood cells 10 billion white blood cells 400 billion platelets All formed elements come from the same type of stem cell called hemocytoblasts Once a cell is committed to a specific blood pathway it cannot change Hemocytoblasts become 1 of 2 types of cells Lymphoid stem cells (lymphocytes) Myeloid stem cells (all other elements)

Formation of Red Blood Cells RBCs are anucleate which means they do not have a nucleus and therefore do not grow or divide The lifespan of a RBC is about 4 months At the end of the lifespan, cells are broken down by the spleen or liver. Any parts of hemoglobin that can be reused are kept in the blood and any waste is removed. Iron – stored in the liver or reused Globin – broken down to amino acids Heme – converted to bile in the liver RBCs synthesize large amounts of hemoglobin as they develop.

This early stage of the cell is called a reticulocyte. Life cycle of an RBC: hemocytoblast -> erythroblast -> reticulocyte (15 days) When enough hemoglobin is formed the nucleus and organelles are ejected and the cell collapses in the center This early stage of the cell is called a reticulocyte. A reticulocyte becomes a mature erythrocyte in about 1 to 2 days. The rate of RBC production is controlled by a hormone produced in the kidney called erythropoietin. The target of this hormone is the red bone marrow. Levels of oxygen in the body determine RBC production.

Formation of White Blood Cells and Platelets Production of WBCs is stimulated by proteins (colony stimulating factors & interleukins) The hormones are released in response to chemical signals in the environment The hormone thrombopoietin accelerates production of platelets by stimulating production of megakaryocytes.

Hemostasis Stoppage of Bleeding Involves 3 major phases Vascular spasms Platelet plug formation Coagulation (blood clotting)

Platelet plug formation Vascular spasms Blood vessels go into spasms (vasoconstriction) The blood vessels narrow at the point of the break decreasing blood loss Platelet plug formation Platelets become sticky and cling to the damaged site Platelets release chemicals that enhance spasms and attract more platelets A mass of platelets is called a platelet plug

Coagulation The injured tissue releases substances that lead to the formation of the enzyme thrombin Thrombin is responsible for causing proteins called fibrinogen to become long fibers called fibrin Fibrin forms a meshwork that traps RBCs and forms the basis of the clot Within the hour the clot begins to retract and pull the ruptured edges of the blood vessel closer together

Normally blood clots within 3 to 6 minutes. Once clotting has started other factors are rapidly inactivated in other parts of the blood vessel to prevent widespread clotting.

Blood Groups and Transfusions The body can compensate for a loss of blood volume only up to a certain limit. Losses of 15 to 30% leads to pale coloring of the skin and weakness Loss over 30% causes severe shock A usual blood bank collection procedure involves collecting blood from a donor and mixing it with an anticoagulant. Treated blood can be stored for about 35 days

Blood Groups The plasma membranes of RBCs have genetically determined proteins called antigens. An antigen is a substance that the body recognizes as foreign. Antigens stimulate the immune system to release antibodies. Our bodies tolerate our own “self” antigens. RBC antigens will be recognized as foreign if they are transfused into a person with different RBC antigens. Antibodies found in plasma attach to the surface of the foreign RBCs. The causes the foreign RBCs to clump.

The process of clumping is called agglutination. Agglutination leads to clogging of small vessels throughout the body. In less severe cases fever, chills, nausea, and vomiting may occur. In more severe cases rupturing of blood cells, lack of oxygen to cells, kidney failure, or death may occur. There are over 30 RBC antigens The antigens of the ABO and Rh blood groups cause the most vigorous transfusion reactions.

ABO Blood Groups Based on 2 antigens: Type A or Type B Type O blood: absence of both A and B antigens Type AB blood: presence of both A and B antigens Type A blood: presence of A antigens only Type B blood: presence of B antigens only

How we get our blood types Type O Receive type O from both parents Type O is recessive to all other blood types Type AB Receive type A from one parent and type B from the other Type A and B are codominant Type A Receive type A from both parents or receive type A from one parent and type O from the other. Type A is dominant to type O Type B Receive type B from both parents or receive type B from one parent and type O from the other. Type B is dominant to type O

Antibodies Antibodies form during infancy against foreign antigens Type O blood: both anti-A and anti-B antibodies formed Type AB blood: no antibodies formed Type A blood: anti-B antibodies formed Type B blood: anti-A antibodies formed

Because type O blood can be given to any person needing transfusion this blood type has been called the universal donor. People that have type O blood can only receive type O blood however because they produce antibodies for type A and B. Because type AB blood can accept all other blood types in transfusion this blood type has been called the universal recipient. This is because no antibodies are produced. The most common blood types are O+ and A+ The least common blood types are B- and AB-

Rh Blood Groups (+ and -) Named for one of the antigens (D) that was identified in the Rhesus monkey. Most Americans are Rh+ meaning their RBCs carry the Rh antigen. Rh antibodies are not automatically formed and present in the blood of Rh- people. If an Rh- person receives Rh+ blood the immune system will begin producing antibodies. Hemolysis or RBC rupture normally doesn’t occur with the first transfusion. It is the 2nd and those thereafter when rupture can occur.

An important Rh problem occurs in pregnant Rh- women carrying Rh+ babies. The first pregnancy usually has no problems. After the first pregnancy the mother will form Rh+ antibodies. If her 2nd baby is Rh+ her antibodies will destroy the RBCs of the 2nd baby. The baby will be anemic, hypoxic, and cyanotic. Brain damage and death may result. The can be prevented by the mother being treated with RhoGAM.

Blood Typing Blood is tested by mixing it with 2 types of immune serum: Anti-A and Anti-B. If clumping occurs when mixed with a serum then that blood type is present.