Blood
Blood Blood serves as a vehicle for distributing body heat and for transporting nutrients, respiratory gases, and other substances throughout the body.
Composition of Blood Blood is the only fluid tissue. It is a complex connective tissue in which living blood cells (formed elements) are suspended in a nonliving fluid matrix (plasma).
Physical Characteristics and Volume Sticky opaque fluid Color depends on the amount of oxygen present (oxygenrich=scarlet; oxygen-poor=dull red)
Phys. Characteristics (cont.) Thick, viscous fluid that has a ph between 7.35 and 7.45 (slightly alkaline) Volume in healthy males is 5 to 6 liters
Plasma @ 90% water Over 100 different substances are dissolved in plasma, including nutrients, metal ions (salts), respiratory gases, hormones, plasma proteins, and various wastes and products of cell metabolism.
Plasma (cont.) Plasma proteins most abundant solute Accounts for 55% of whole blood Most are made by liver, except for antibodies and protein-based hormones.
Plasma (cont.) Functions of plasma proteins include: Osmotic balance ph buffering Blood clotting Defense against pathogens
Formed Elements Consist of erythrocytes, leukocytes, and platelets Account for 45% of whole blood
Formed Elements (cont.) Erythrocytes are red blood cells (RBCs) and function to carry oxygen in blood to all cells of the body Characteristics: Anucleate Sacs of hemoglobin molecules
Lack mitochondria and produce ATP anaerobically Cells shaped like bi-concaved discs (mini-doughnuts) @ 5 million cells per cubic millimeter
Formed Elements (cont.) Leukocytes are white blood cells (WBCs) and function to protect the body from disease. Characteristics: Account for less than 1% of total blood volume Form a protective, movable army that defends body against damage by bacteria, viruses, parasites, and tumor cells.
Diapedesis can move in and out of blood vessels Circulation is means of transport Positive chemotaxis move to damaged area in response to chemical signals Move through tissue spaces by ameboid motion
Leukocytosis total WBC count above 11,000 cells/mm 3 ; usually indicates that a bacterial or viral infection is present. Leukopenia an abnormally low WBC count, commonly caused by certain drugs, such as corticosteriods.
Types of Leukocytes Two categories: Granulocytes granule-containing WBCs Neutrophils phagocytes at sites of acute infection Eosinophils move during allergies and parasitic worm infection Basophils contain histamine which makes blood vessels leaky and attracts WBCs
Types of Leukocytes (cont.) Agranulocytes no cytoplasmic granules Lymphocytes found in lymphatic tissues Monocytes macrophages; fight chronic infections
Platelets Platelets are fragments of multinucleate cells called megakaryocytes. Important in the clotting process that occurs in plasma when blood vessels are ruptured or broken.
Disorders of the Blood Anemia decrease in the oxygencarrying ability of the blood. Results from: Lower-than-normal number of RBCs or Abnormal or deficient hemoglobin content in the RBCs.
Disorders (cont.) Sickle-cell anemia genetic disorder whereby the Hb becomes spiky and sharp, when the RBCs unload O 2 molecules or when the O 2 content of blood is lower than normal. Deformed RBCs rupture easily and dam up in small blood vessels, which interferes with O 2 delivery and causes severe pain. Occurs mainly in black people who live in the malaria belt of Africa and among their descendents Prevents malaria
Disorders (cont.) Polycythemia an excessive or abnormal increase in the number of erythrocytes, which results in increased blood viscosity and impairs circulation. Polycythemia vera results from bone marrow cancer. Secondary polycythemia occurs at high altitudes.
Disorders (cont.) Leukemia bone marrow becomes cancerous, resulting in the production of too many WBCs that are immature and incapable of fighting infection.
Hematopoiesis Blood cell formation that occurs in the red bone marrow or myeloid tissue. Hemocytoblast common stem cell from which all formed elements arise. Forms two types of descendents: Lymphoid stem cell produces lymphocytes Myeloid stem cell produces all other blood cells
Hematopoiesis of RBCs RBCs live 100 to 120 days, and as a result new RBCs are continuously produced by the division of hemocytoblasts in the red bone marrow. Developing RBCs multiply many times and synthesize hemoglobin in large amounts. After Hb amounts accumulate, other organelles in RBCs are ejected and cell collapses inward, resulting in a reticulyte (young RBC).
Hematopoiesis of RBCs (cont.) Reticulyte still contains some rough ER and enters bloodstream to transport O 2 Reticulyte ejects rough ER within 2 days and becomes erythrocyte. Erythropoietin hormone that controls rate of erythrocyte production; controlled by the kidneys.
Hematopoiesis of WBCs Stimulated by hormones called colony stimulating factors (CSFs) and interleukins. Increase leukocyte production and effectiveness.
Hematopoiesis of Platelets Thrombopoietin hormone that increases platelet production.
Hemostasis Stoppage of blood flow; fast and localized. Involves three phases: Vascular spasms Platelet plug formation Coagulation or blood clotting
Process of Hemostasis Platelets adhere to collagen fibers and form a platelet plug fibrin clot with trapped RBCs. Platelets release seratonin which causes vessels to constrict (vascular spasm), and chemicals to attract more platelets. Injured tissues release thromboplastin.
Process of Hemostasis (cont.) PF 3 (coating platelets) and thromboplastin, Ca, and clotting factors form activator to trigger clotting cascade. Prothrombin activator converts prothrombin to thrombin. Thrombin joins fibrinogen into fibrin which forms basis of clot. Clot begins to retract, squeezing out and pulling ruptured edges of blood vessel together.
Disorders of Hemostasis Undesirable clotting: Thrombus clot in a an unbroken blood vessel which can cause blockage. Embolus free floating clot; can pose a problem if it becomes lodged in a blood vessel (ex. Cerebral embolism)
Disorders of Hemostasis (cont.) Causes of undesirable clotting include: Burns Physical blows Accumulation of fatty material Slow flowing blood
Disorders of Hemostasis (cont.) Bleeding Disorders Thrombocytopenia insufficient number of circulating platelets arising from any condition that suppresses myeloid tissue. Hemophilia hereditary disease where blood lacks any of the factors needed for clotting.
Blood Groups and Transfusions Transfusions: Needed in cases of substantial blood loss or to treat severe anemia or thrombocytopenia 15 30% loss leads to pallor and weakness Over 30% loss causes severe shock and can be fatal
Transfusions (cont.) Procedure for collecting blood includes mixing donor blood with an anticoagulant to prevent clotting; blood can be stored @35 days.
Human Blood Groups Plasma membranes of RBCs have antigens that reject foreign blood types and stimulate the immune system to release antibodies or mount a defense. During a transfusion reaction agglutination occurs, whereby the binding of the antibodies causes RBCs to clump.
Human Blood Groups The ABO blood groups are based on which of the antigens (A or B) a person inherits. A+A = A B+B = B A+B = AB Neither = O
Blood Groups (cont.) Type O blood is the universal donor. Type AB blood is the universal recipient.
Blood Groups (cont.) Rh blood groups named because Rhesus monkeys were originally identified with one of the eight Rh antigens (agglutinogen D), and later humans were found to carry it also. Most Americans are Rh+, and they carry the Rh antigen.
Blood Groups (cont.) In pregnant Rh- women carrying Rh+ babies, RhoGam serum is given to prevent her immune system from forming anti- Rh+ antibodies that can pass through the placenta and affect subsequent pregnancies. If RhoGam is not given, hemolytic disease of the newborn can develop whereby the Rh+antibodies produced by the mother cross the placenta and destroy the babies RBCs.