Blood Functions Blood maintains: Appropriate body temperature by absorbing and distributing heat to other parts of the body Normal pH in body tissues Adequate fluid volume in the circulatory system

Blood Functions: Protection Blood prevents blood loss by: Activating plasma proteins and platelets Initiating clot formation when a vessel is broken Blood prevents infection by: Synthesizing and utilizing antibodies Activating complement proteins & WBCs to defend the body against foreign invaders

Physical Characteristics of Blood Average volume: 5–6 L for males; 4–5 L for females The pH is 7.35–7.45 Accounts for approximately 8% of body weight

Composition of Blood Blood is the body’s only fluid tissue (connective tissue) 2 major components Liquid = plasma (55%) Formed elements (45%) Erythrocytes, or red blood cells (RBCs) Leukocytes, or white blood cells (WBCs) Platelets – cell fragments

Components of Whole Blood Plasma (55% of whole blood) Buffy coat: leukocyctes and platelets (<1% of whole blood) Formed elements Erythrocytes (45% of whole blood) 1 Withdraw blood and place in tube 2 Centrifuge

Blood Plasma Blood plasma components: Water = 90-92% Proteins = 6-8% Albumins-maintain osmotic pressure of the blood Globulins-used for transport purposes Fibrinogen-a clotting protein Organic nutrients – glucose, carbohydrates, amino acids Electrolytes – sodium, potassium, calcium, chloride, bicarbonate Non-protein nitrogenous substances – lactic acid, urea, creatine Respiratory gases – oxygen and carbon dioxide

Formed Elements Only WBCs are complete cells RBCs have no nuclei or organelles, and platelets are just cell fragments Most F.E. survive in the bloodstream for only a few days Most do not divide but are renewed by cells in bone marrow

Erythrocytes (RedBloodCells) Biconcave disc Folding increases surface area (30% more surface area) Anucleate, no centrioles, no organelles No cell division No mitochondria means they generate ATP anaerobically This prevents consumption of O2 being transported Filled with hemoglobin (Hb) - 97% of cell contents Hb functions in gas transport Most numerous of the formed elements

Erythrocyte Function Erythrocytes are dedicated to respiratory gas transport Hb reversibly binds with oxygen and most oxygen in the blood is bound to Hb Composition of Hb A protein called globin A heme molecule (a metal complex with iron as the central metal atom, that can bind or release molecular oxygen.) Each heme group bears an atom of iron, which can bind to one oxygen molecule

Production of Erythrocytes Hematopoiesis – blood cell formation Occurs in the red bone marrow Axial skeleton and girdles Epiphyses of the humerus and femur Marrow contains immature erythrocytes

Erythrocyte Disorders Anemia – blood has abnormally low oxygen-carrying capacity There are many forms of anemia, each with its own cause. Anemia can be temporary or long term, and it can range from mild to severe. Blood oxygen levels cannot support normal metabolism Signs/symptoms include fatigue, paleness, shortness of breath, and chills

Leukocytes (White Blood Cells) Protect the body from infectious microorganisms Can leave capillaries Move through tissue spaces Many are phagocytic- that engulf and absorb waste material, harmful microorganisms, or other foreign bodies in the bloodstream and tissues. Two major types of leukocytes Granulocytes: Neutrophils, Eosinophils, Basophils Agranulocytes: Monocytes, Lymphyocytes Leukemia - a cancer of WBC

Granulocytes Contain cytoplasmic granules that stain specifically with Wright’s stain Are larger and usually shorter-lived than RBCs Have lobed nuclei Are all phagocytic cells

Granulocytes: Neutrophils Account for 65-75% of total WBC’s Neutrophils have two types of granules that: Contain peroxidases, hydrolytic enzymes, and defensins (antibiotic-like proteins) Neutrophils are our body’s bacteria slayers

Granulocytes: Eosinophils Eosinophils account for 1–4% of WBCs Function: Lead the body’s counterattack against parasitic infections Lessen the severity of allergies by phagocytizing immune complexes (ending allergic reactions)

Granulocytes: Basophils Account for 0.5-1% of all WBCs Have large, purplish-black granules that contain histamine Histamine – inflammatory chemical that acts as a vasodilator and attracts other WBCs (antihistamines counter this effect)

Agranulocytes: Lymphocytes Account for 20-25% or more of WBCs and: Found mostly in lymphoid tissue (some circulate in the blood) Most important cells of the immune system Involved in graph rejection, fighting tumors and viruses There are two types of lymphocytes: T cells and B cells T cells - attack foreign cells directly B cells give rise to plasma cells, which produce antibodies

Monocytes Account for 3–7% of leukocytes They are the largest leukocytes They have purple-staining, U- or kidney-shaped nuclei They leave the circulation, enter tissue, and differentiate into macrophages Increase in # during chronic infections.

Platelets Platelets are fragments of megakaryocytes Platelets function in the clotting mechanism –form a temporary plug that helps seal breaks in blood vessels. Platelet

Human Blood Groups RBC membranes have glycoprotein antigens on their external surfaces These antigens are: Unique to the individual Recognized as foreign if transfused into another individual Promoters of agglutination and are referred to as agglutinogens Presence or absence of these antigens is used to classify blood groups

ABO Blood Groups The ABO blood groups consists of: Two antigens (A and B) on the surface of the RBCs Two antibodies in the plasma (anti-A and anti-B) Agglutinogens (antigens) and their corresponding antibodies cannot be mixed without serious reactions

Group A – has only the A antigen on RBCs (and B antibody in the plasma) Group B – has only the B antigen on RBCs (and A antibody in the plasma) Group AB – has both A and B antigens on RBCs (but neither A nor B antibody in the plasma) Group O – has neither A nor B antigens on RBCs (but both A and B antibody are in the plasma) The universal donor has Type O negative blood. The universal recipient has Type AB positive blood.

Transfusion Reactions Transfusion reactions occur when mismatched blood is infused Donor’s cells are attacked by the recipient’s plasma agglutinins causing: Diminished oxygen-carrying capacity Clumped cells that impede blood flow Ruptured RBCs that release free hemoglobin into the bloodstream Circulating hemoglobin precipitates in the kidneys and causes renal failure

Rhesus (Rh) factor Is an inherited trait that refers to a specific protein found on the surface of RBCs. If your blood has the protein, you're Rh(+)— the most common Rh factor. If your blood lacks the protein, you're Rh(-). Rh factor doesn't affect your health.

Rhesus (Rh) factor cont. When pregnant, blood from the baby can cross into the bloodstream. If you're Rh(-)and your baby is Rh(+) your body will react to the baby's blood as a foreign . Your body will create antibodies against the baby's Rh-positive blood. These antibodies usually don't cause problems during a first pregnancy. The antibodies stay in your body once they have formed. Thus, Rh incompatibility is more likely to cause problems in later pregnancies (if the baby is Rh-positive). The Rh antibodies can cross the placenta and attack the baby's red blood cells. This can lead to hemolytic anemia in the baby, which is a condition in which red blood cells are destroyed faster than the body can replace them. Without enough red blood cells, the baby won't get enough oxygen. This can lead to problems and can be fatal.