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 (a 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

Withdraw blood and place in tube

1 2 Centrifuge

Plasma(55% of whole blood)

Formed elements

Buffy coat:leukocyctes and platelets(<1% of whole blood)

Erythrocytes(45% of whole blood)

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 (RBCs)• 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.) Heme groups are embedded in the hemoglobin protein,

Production of Erythrocytes• Hematopoiesis – blood cell formation– Occurs in the red bone marrow

• Axial skeleton and girdles• Epiphyses of the humerus and femur

• 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

Erythrocyte Disorders

Leukocytes (WBCs)

– Protect the body from infectious microorganisms

– Can leave capillaries – Move through tissue spaces – Many are phagocytic- that engulfs and absorbs 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

• 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: Neutrophils

• 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: Eosinophils

• 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)

Granulocytes: Basophils

• 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

Agranulocytes: Lymphocytes

• 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.

Monocytes

• Platelets are fragments of megakaryocytes• Platelets function in the clotting

mechanism by forming a temporary plug that helps seal breaks in blood vessels.

Platelets

Platelet

• 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

Human 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

ABO Blood Groups

• The universal donor has Type O negative blood type.

• The universal plasma donor has Type AB positive blood type.

Group A – has only the A antigen on red blood cells (and B antibody in the plasma) Group B – has only the B antigen on red blood cells (and A antibody in the plasma) Group AB – has both A and B antigens on red blood cells (but neither A nor B antibody in the plasma) Group O – has neither A nor B antigens on red blood cells (but both A and B antibody are in the plasma)

• 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

Transfusion Reactions

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 positive — the most common Rh factor. If your blood lacks the protein, you're Rh negative.

• Rh factor doesn't affect your health, it can affect pregnancy. your body might produce Rh antibodies after exposure to the baby's red blood cells.

• Typically, the antibodies aren't a problem during the first pregnancy.

• with a subsequent pregnancy with an Rh positive baby. In this case, your existing Rh antibodies might cross the placenta and fight the baby's red blood cells.

• This could lead to life-threatening anemia