BLOOD

Overview of Blood Circulation  Blood leaves the heart via arteries  Oxygen (O 2 ) and nutrients diffuse across capillary walls and enter tissues  Carbon dioxide (CO 2 ) and wastes move from tissues into the blood  Deoxygenated blood flows in veins to the heart  This blood flows to the lungs, releases CO 2 and picks up O 2  Oxygenated blood returns to heart

Physical Characteristics and Volume  Color: from scarlet to dark red  pH: 7.35–7.45  Temperature: 37  C  Blood accounts for approximately 8% of body weight  Average volume  5–6 L for males  4–5 L for females

Functions of Blood  Substance distribution:  Oxygen from lungs and nutrients from digestive tract  Metabolic wastes from cells to the lungs and kidneys for elimination  Hormones from endocrine glands to target organs  Regulation:  Appropriate body temperature by absorbing and distributing heat  Normal pH in body tissues  Adequate fluid volume

Functions of Blood  Body protection  prevents blood loss by:  Initiating clot formation when a vessel is broken  prevents infection by:  Synthesizing and utilizing antibodies  Activating WBCs to defend the body against foreign invaders

Composition of Blood  What type of tissue is blood?  It is composed of liquid plasma (matrix) and formed elements  Formed elements include:  Erythrocytes, or red blood cells (RBCs)  Leukocytes, or white blood cells (WBCs)  Platelets

Composition of Blood

Blood Plasma  Blood plasma contains over 100 solutes:  Proteins – albumin, globulins, clotting proteins, and others  Lactic acid, urea, creatinine  Organic nutrients – glucose, carbohydrates, amino acids  Electrolytes – sodium, potassium, calcium, chloride, bicarbonate  Respiratory gases – oxygen and carbon dioxide

 Accounts for 46-63% of blood volume  92% of plasma is water Plasma

Formed Elements  Leukocytes (WBC), erythrocytes (RBC), platelets  WBCs are complete cells  RBCs have no nuclei or organelles  platelets are cell fragments

Erythrocytes (RBCs)  Biconcave discs, anucleate, no organelles  Filled with hemoglobin (Hb), a protein that functions in gas transport  The biconcave disc shape  provides a large surface to volume ratio  allows RBCs to stack – facilitate flow through narrow blood vessels  allows the RBCs to bend and flex when entering small capillaries  Normal RBC count: 4-5 million per mm 3.

Erythrocytes (RBCs) Figure 17.3

Erythrocyte Function  RBCs are dedicated to respiratory gas transport  Hb reversibly binds with oxygen and most oxygen in the blood is bound to Hb  Each Hb molecule can transport four molecules of oxygen

Structure of Hemoglobin Figure 17.4

Hematopoiesis  process by which immature precursor cells develop into mature blood cells.  process by which immature precursor cells develop into mature blood cells.  A single type of stem cell gives rise to all the mature blood cells in the body.  A single type of stem cell gives rise to all the mature blood cells in the body.  This stem cell is called the hemocytoblast.  The hematopoietic tissue is the red bone marrow

Copyright © The McGraw-Hill Companies, Inc

Figure 19.6 Stages of RBC Maturation In bone marrow

Production of Erythrocytes: Erythropoiesis Figure 17.5

Regulation of Erythropoiesis  Circulating erythrocytes – the number remains constant and reflects a balance between RBC production and destruction  Too few RBCs leads to tissue hypoxia  Too many RBCs causes undesirable blood viscosity  depends on adequate supplies of iron, amino acids, and B vitamins

Fate and Destruction of Erythrocytes  Life span: 100–120 days  Old RBCs become rigid and fragile  Dying RBCs are engulfed by macrophages  Replaced at a rate of approximately 3 million new blood cells entering the circulation per second.

 Anemia – blood has abnormally low oxygen- carrying capacity  It is a symptom, not a disease in itself  Blood oxygen levels cannot support normal metabolism  Signs/symptoms: fatigue, paleness, shortness of breath, and chills  Hemorrhagic anemia – result of acute or chronic loss of blood  Hemolytic anemia – prematurely ruptured RBCs  Aplastic anemia – destruction or inhibition of red bone marrow Erythrocyte Disorders

 Iron-deficiency anemia may result from:  hemorrhagic anemia  inadequate intake of iron-containing foods  impaired iron absorption  Pernicious anemia results from:  Deficiency of vitamin B 12  Lack of intrinsic factor needed for absorption of B 12  Treatment: injections of B 12 Anemia: Decreased Hemoglobin Content

Sickle-Cell Anemia  results from a defective gene coding for an abnormal Hb called hemoglobin S (HbS)  HbS has a single amino acid substitution  This defect causes RBCs to become sickle-shaped in low oxygen situations

Blood samples are typically collected from the median cubital vein. Clinical Aspects

 The hematocrit (also called packed cell volume, PCV) is a measure of the relative percentage of blood cells (mainly erythrocytes) in a given volume of whole blood.  The hematocrit (also called packed cell volume, PCV) is a measure of the relative percentage of blood cells (mainly erythrocytes) in a given volume of whole blood.  Normal hematocrit for Adult Females:  37-48% (ave. 42%)  Normal hematocrit for Adult Males  42-52% (ave. 47%) Hematocrit Measurement

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

 Humans have naturally occurring RBC antigens  The antigens of the ABO and Rh blood groups cause serious transfusion reactions when they are improperly transfused Blood Groups

ABO Blood Groups Table 17.4

 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

Many people also have Rh factor on the red blood cell's surface. Many people also have Rh factor on the red blood cell's surface. This is also an antigen and those who have it are called Rh+. This is also an antigen and those who have it are called Rh+. Those who haven't are called Rh-. A person with Rh- blood does not have Rh antibodies naturally in the blood plasma (as one can have A or B antibodies, for instance). A person with Rh- blood does not have Rh antibodies naturally in the blood plasma (as one can have A or B antibodies, for instance). RH factor blood grouping system

A person with Rh- blood can develop Rh antibodiesA person with Rh- blood can develop Rh antibodies if he or she receives blood from a person with Rh+ bloodif he or she receives blood from a person with Rh+ blood whose Rh antigens can trigger the production of Rh antibodies.whose Rh antigens can trigger the production of Rh antibodies. A person with Rh+ blood can receive blood from a person with Rh- blood without any problems.A person with Rh+ blood can receive blood from a person with Rh- blood without any problems.

Normal whole blood smearNormal whole blood smear Sickle cell anemiaSickle cell anemia LeukemiaLeukemia Blood Slides Misc Qs Low WBC = leukopeniaLow WBC = leukopenia High WBC = leukocytosisHigh WBC = leukocytosis Low platelets = thrombocytopeniaLow platelets = thrombocytopenia

Hemolytic Disease of the Newborn  Rh + antibodies of a sensitized Rh – mother (w/ Rh + father) cross the placenta and attack and destroy the RBCs of an Rh + baby  Rh – mother becomes sensitized when exposure to Rh + blood causes her body to synthesize Rh + antibodies  The drug RhoGAM can prevent the Rh – mother from becoming sensitized