Chapter 21 The Cardiovascular System: The Blood

Functions of Blood Transportation Regulation O2, CO2, metabolic wastes, nutrients, heat & hormones Regulation helps regulate pH through buffers helps regulate body temperature coolant properties of water vasodilatation of surface vessels dump heat helps regulate water content of cells by interactions with dissolved ions and proteins Protection from disease & loss of blood

Components of Blood 55% plasma 45% cells 99% RBCs < 1% WBCs and platelets

Blood Plasma 0ver 90% water 7% plasma proteins albumin maintain blood osmotic pressure globulins (immunoglobulins) antibodies bind to foreign substances called antigens form antigen-antibody complexes fibrinogen for clotting

Formed Elements of Blood Red blood cells ( erythrocytes ) White blood cells ( leukocytes ) granular leukocytes neutrophils eosinophils basophils agranular leukocytes lymphocytes = T cells, B cells, and natural killer cells monocytes Platelets (special cell fragments)

Hematocrit Percentage of blood occupied by cells Anemia Polycythemia not enough RBCs or not enough hemoglobin Polycythemia too many RBCs (over 65%) dehydration, tissue hypoxia, blood doping in athletes

Formation of Blood Cells Most blood cells types need to be continually replaced die within hours, days or weeks process of blood cells formation is hematopoiesis or hemopoiesis occurs only in red marrow of flat bones like sternum, ribs, skull & pelvis and ends of long bones

Red Blood Cells or Erythrocytes Contain oxygen-carrying protein hemoglobin that gives blood its red color 1/3 of cell’s weight is hemoglobin Biconcave disk 8 microns in diameter increased surface area/volume ratio flexible shape for narrow passages no nucleus or other organelles no cell division or mitochondrial ATP formation

RBC Life Cycle RBCs live only 120 days wear out from bending to fit through capillaries no repair possible due to lack of organelles Worn out cells removed by fixed macrophages in spleen & liver Breakdown products are recycled

WBC Anatomy and Types All WBCs (leukocytes) have a nucleus and no hemoglobin Granular or agranular classification based on presence of cytoplasmic granules made visible by staining

WBC Physiology Less numerous than RBCs 1 WBC for every 700 RBC Leukocytosis is a high white blood cell count microbes, strenuous exercise Leukopenia is low white blood cell count radiation, shock or chemotherapy

Complete Blood Count (CBC) Screens for anemia and infection Total RBC, WBC & platelet counts; differential WBC; hematocrit and hemoglobin measurements Normal hemoglobin range 12 to 18g/100mL of blood

Platelet Adhesion Platelets stick to exposed collagen underlying damaged endothelial cells in vessel wall

Blood Clotting Blood drawn from the body thickens into a gel If clotting occurs in an unbroken vessel is called a thrombosis Substances required for clotting are Ca+2, enzymes synthesized by liver cells and substances released by platelets or damaged tissues

Role of Vitamin K in Clotting Normal clotting requires adequate vitamin K Produced by bacteria in large intestine

Intravascular Clotting Thrombosis clot (thrombus) forming in an unbroken blood vessel may dissolve spontaneously or dislodge & travel Embolus clot, air bubble or fat from broken bone in the blood Low dose aspirin blocks synthesis of thromboxane A2 & reduces inappropriate clot formation

Blood Groups and Blood Types RBC surfaces are marked by genetically determined glycoproteins & glycolipids agglutinogens or isoantigens distinguishes at least 24 different blood groups ABO, Rh, and others

ABO Blood Groups Based on 2 antigens called A and B found on the surface of RBCs display only antigen A -- blood type A display only antigen B -- blood type B display both antigens A & B -- blood type AB display neither antigen -- blood type O Plasma contains antibodies or agglutinins to the A or B antigens not found in your blood anti-A antibody reacts with antigen A anti-B antibody reacts with antigen B

Universal Donors and Recipients People with type AB blood called “universal recipients” since have no antibodies in plasma People with type O blood cell called “universal donors” since have no antigens on their cells theoretically can be given to anyone

Anemia = Not Enough RBCs Symptoms oxygen-carrying capacity of blood is reduced fatigue, cold intolerance & paleness Types of anemia iron-deficiency =lack of absorption or loss of iron pernicious = lack of intrinsic factor for B12 absorption hemorrhagic = loss of RBCs due to bleeding (ulcer) hemolytic = defects in cell membranes cause rupture thalassemia = hereditary deficiency of hemoglobin aplastic = destruction of bone marrow (radiation/toxins)

Sickle-cell Anemia (SCA) Genetic defect in hemoglobin molecule at low very O2 levels, RBC is deformed by changes in hemoglobin molecule within the RBC Found among populations in malaria belt Mediterranean Europe, sub-Saharan Africa & Asia Person with only one sickle cell gene increased resistance to malaria

Hemophilia Inherited deficiency of clotting factors bleeding spontaneously or after minor trauma subcutaneous & intramuscular hemorrhaging nosebleeds, blood in urine, articular bleeding & pain Treatment is transfusions of fresh plasma or concentrates of the missing clotting factor

Leukemia Acute leukemia Chronic leukemia uncontrolled production of immature leukocytes crowding out of normal red bone marrow cells by production of immature WBC prevents production of RBC & platelets Chronic leukemia accumulation of mature WBC in bloodstream because they do not die