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Blood Circulation

• Blood leaves the heart via arteries, branching into capillaries for tissue oxygen and nutrient delivery.
• Oxygen and nutrients diffuse from capillary walls into tissues.
• Carbon dioxide and metabolic wastes move from tissues into the blood.
• Oxygen-deficient blood flows from capillaries to veins, returning to the heart.
• Blood releases carbon dioxide and picks up oxygen in the lungs.
• Oxygen-rich blood returns to the heart.

Composition of Blood

• Blood is the body's only fluid tissue.
• Blood consists of liquid plasma and formed elements.
• Formed elements include erythrocytes (red blood cells), leukocytes (white blood cells), and platelets.
• Plasma accounts for 55% of whole blood.
• Erythrocytes account for 45% of whole blood.
• Leukocytes and platelets make up less than 1% of whole blood and form a buffy coat between the plasma and erythrocytes after centrifugation.

Physical Characteristics and Volume of Blood

• Blood is a sticky, opaque fluid with a metallic taste.
• Blood color varies from scarlet to dark red.
• Blood's pH is between 7.35 and 7.45.
• Blood temperature is 37°C.
• Blood accounts for approximately 8% of body weight.
• The average blood volume is 5-6 L for males and 4-5 L for females.

Functions of Blood

• Blood has several functions related to substance distribution, regulation of blood levels, and body protection.

Distribution

• Blood transports oxygen from the lungs and nutrients from the digestive tract.
• Blood transports metabolic wastes from cells to the lungs and kidneys for elimination.
• Blood transports hormones from endocrine glands to target organs.

Regulation

• Blood maintains appropriate body temperature by absorbing and distributing heat.
• Blood maintains normal tissue pH using buffer systems.
• Blood maintains adequate fluid volume in the circulatory system.

Protection

• Blood prevents blood loss by activating plasma proteins and platelets and initiating clot formation when a vessel is broken.
• Blood prevents infection by synthesizing and utilizing antibodies, activating complement proteins, and activating WBCs to defend against foreign invaders.

Blood Plasma

• Blood plasma contains over 100 solutes.
• Solutes in blood plasma include proteins (albumin, globulins, clotting proteins), lactic acid, urea, creatinine, organic nutrients (glucose, carbohydrates, amino acids), electrolytes (sodium, potassium, calcium, chloride, bicarbonate), and respiratory gases (oxygen and carbon dioxide).

Formed Elements

• Erythrocytes, leukocytes, and platelets constitute the formed elements of blood.
• Only WBCs are complete cells.
• RBCs lack nuclei and organelles.
• Platelets are cell fragments.
• Most formed elements survive only a few days in the bloodstream.
• Most blood cells cannot divide but are renewed by cells in bone marrow.

Erythrocytes (RBCs)

• Erythrocytes or RBCs, are biconcave discs without a nucleus.
• The diameter across is 7.5 μm
• The depth is 2.5 μm
• RBCs are essentially bags of hemoglobin (Hb).
• Hemoglobin is a protein that functions in gas transport.

Hemoglobin (Hb)

• Oxyhemoglobin is hemoglobin bound to oxygen and occurs when oxygen loading takes place in the lungs.
• Deoxyhemoglobin results after oxygen diffuses into tissues.
• Carbaminohemoglobin is hemoglobin bound to carbon dioxide.
• Carbon dioxide loading takes place in the tissues.

Erythrocyte Disorders

• Anemia is when blood has an abnormally low oxygen-carrying capacity.
• Anemia is a symptom rather than a disease itself.
• Blood oxygen levels cannot support normal metabolism with anemia.
• Signs and symptoms of anemia include fatigue, paleness, shortness of breath, and chills.

Leukocytes

• Leukocytes (WBCs) are the only blood components with complete cells.
• WBCs are less numerous than RBCs.
• WBCs make up 1% of the total blood volume.
• WBCs can leave capillaries via diapedesis and move through tissue spaces.
• Leukocytosis occurs when the WBC count exceeds 11,000/mm3. It is a normal response to bacterial or viral invasion.

Percentages of Leukocytes

• Neutrophils make up 50-70% of leukocytes.
• Lymphocytes make up 25-45% of leukocytes.
• Monocytes make up 3-8% of leukocytes.
• Eosinophils make up 2-4% of leukocytes.
• Basophils make up 0.5-1% of leukocytes.

Summary of Formed Elements

• Erythrocytes (Red blood cells) transport oxygen and carbon dioxide.
• Red blood cells are biconcave, anucleate discs that are salmon colored and between 7-8 μm and 4-6 million cells/ μl of blood.
• Development is about 15 days, and the lifespan is approximately 100-120 days.
• Neutrophils are spherical, nucleated cells that defend immunity.
• Neutrophils are multilobed and range in size from 10-12 μm, the cytoplasm is granuled with 3000-7000 cells/ μl of blood.
• Development is about 14 days, and only lasts for a few hours.
• Eosinophils kill parasitic worms, destroy antigen-antibody complexes, and inactivate some inflammatory chemicals of allergy
• Eosinophils range in size from 10-14 μm, are bilobed, and have red cytoplasm with 100-400 cells/ μl of blood, and last approximately 5 days.
• Basophils release histamine and other mediators of inflammation and contain heparin, an anticoagulant.
• Basophils range from 10-14 μm, have a lobe and are purple with 20-50 cells/ μl of blood with a few hour lifespan.
• Lymphocytes mount an immune response by direct cell attack or via antibodies.
• Lymphocytes range in size from 5-17 μm and are spherical or indented with 1500-3000 cells/ μl of blood with different lifespan.
• Monocytes have spherical, nucleated cells and undergo Phagocytosis and develop into macrophages.
• Monocytes range in size from 14-24 μm and are U or kidney shaped with 100-700 cells/ μl of blood with a few months lifespan.
• Platelets seal tears in blood vessels and aid instrumentally in blood clotting.
• Platelets are fragments that contain granules, stain deep purple, and range from 2-4 μm with 150,000-400,000 cells/ μl with approximately 5-10 day average lifespan.

Leukemia

• Leukemia refers to cancerous conditions involving WBCs.
• Immature WBCs are found in the bloodstream in all leukemias.
• Bone marrow becomes totally occupied with cancerous leukocytes.
• WBCs produced, though numerous, are not functional.
• Death is caused by internal hemorrhage and overwhelming infections.
• Treatments include irradiation, antileukemic drugs, and bone marrow transplants.

Platelets

• Platelets are fragments of megakaryocytes that aid in blood clotting.
• Platelets function in the clotting mechanism by forming a temporary plug that helps seal breaks in blood vessels.

Hemostasis

• Hemostasis is a series of reactions for stopping bleeding.
• During hemostasis, the following phases occur in rapid sequence: vascular spasms (immediate vasoconstriction in response to injury), platelet plug formation, and coagulation (blood clotting).

Clotting Time

• Clotting time will be prolonged if the volume of blood per tube or the diameter of the tube is increased, or if the temperature decreased.
• Normal clotting time ranges between 5-15 minutes.

Bleeding Time

• During cold weather, construction of time is shorter due capillary construction, and reverse case in hot weather.
• Prolonged bleeding time may result from decreased numbers of thrombocytes or impaired blood vessels.
• Prolonged bleeding may be a result of low platelet counts or impaired vessel contraction.

Blood Transfusions

• Whole blood transfusions are used when blood loss is substantial.
• Packed red cells (cells with plasma removed) are used to treat anemia.

Human Blood Groups

• RBC membranes have glycoprotein antigens on their external surfaces.
• These antigens are unique to an individual and recognized as foreign when transfused into another individual.
• Antigens promote agglutination and are referred to as agglutinogens.
• The presence or absence of antigens classifies blood groups.
• Humans have 30 varieties of naturally occurring RBC antigens.
• Antigens of the ABO and Rh blood groups cause vigorous transfusion reactions when improperly transfused.

ABO Blood Groups

• The ABO blood groups consist of two antigens (A and B) on the surface of the RBCs and two antibodies in the plasma (anti-A and anti-B).
• ABO blood groups can have various types of antigens and preformed antibodies.
• Agglutinogens and their corresponding antibodies cannot be mixed without serious hemolytic reactions.

Rh Blood Groups

• Eight different Rh agglutinogens exist; three (C, D, and E) are common.
• The presence of Rh agglutinogens on RBCs indicated as Rh+.
• Anti-Rh antibodies are not spontaneously formed in Rh- individuals.
• If an Rh- individual receives Rh+ blood, anti-Rh antibodies form.
• A second exposure to Rh+ blood will result in a typical transfusion reaction.

Hemolytic Disease of the Newborn

• Hemolytic disease of the newborn occurs when Rh+ antibodies of a sensitized Rh- mother cross the placenta and attack and destroy the RBCs of an Rh+ baby.
• An Rh- mother becomes sensitized when exposure to Rh+ blood causes her body to synthesize Rh+ antibodies.
• RhoGAM can prevent the Rh- mother from becoming sensitized.
• Treatment of hemolytic disease of the newborn involves pre-birth transfusions and exchange transfusions after birth.

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, and ruptured RBCs that release free hemoglobin into the bloodstream.
• Circulating hemoglobin precipitates in the kidneys and causes renal failure.

The Immune System

• The body's defense against disease-causing organisms, malfunctioning cells, and foreign particles is known as the immune system.

The First Line of Defense

• The dead, outer layer of skin known as the epidermis forms a shield against invaders and secretes chemicals that kill potential invaders.
• 40-50 thousand skin cells are shed every day.
• Foreign particles and bacteria get caught in mucus in the respiratory symptom.
• Hair-like structures called cilia sweep the mucus into the throat.
• Saliva contains chemicals that break down bacteria.
• Swallowed bacterium are broken down by strong acids in the stomach.
• The stomach contains a special mucus coating because the strong acids can eat through the stomach.

The Second Line of Defense

• When invaders get within the body, the white blood cells begin their attack.
• WBCs normally circulate throughout the blood, but will enter the body's tissues if invaders are detected.
• Phagocytes are WBCs responsible for eating foreign particles by engulfing them.
• After being engulfed, phagocytes release enzymes that break down foreign particles in organelles called lysosomes.
• Virus-infected body cells release interferon when an invasion occurs.
• Interferon interferes with the ability of viruses to attack other body cells.
• Injured body cells release chemical called histamines which begin the inflammatory response.
• T-cells are often called natural killer cells and recognize infected human cells and cancer cells.
• Signs of the inflammation are: capillaries dilate, pyrogens released, reach hypothalamus, and increasing temperature, pain receptors are activated and WBCs flock to infected area like sharks to blood
• Phagocytes and T Cells make up the cell-mediated immunity.

Two Divisions of the Immune System

• The efforts of the WBCs known as phagocytes and T-cells is called the cell-mediated immune system.
• Other part of the immune system is antibody-mediated immunity which is controlled by antibodies that are considered the third line of defense.

Antibodies

• Most infections are fought off without antibodies
• Antibodies are triggered to be released for infections that are not easily fought off.
• Antibodies latch onto, damage, clump, and slow foreign particles
• Each antibody binds only to one specific binding site, known as an antigen

Antibody Production

• WBCs engulf the invading particles and show them T-cells.
• T-Cells identify the foreign body and find specific B-cells to help.
• B-Cells then produce antibodies in order to stop further infection.

Immunity

• It takes time for the body to identify and neutralize the new invaders.
• Immunity develops when the invader is identified and the person is not longer ill.

Active Immunity

• Antibodies produces from exposure to the actual antigen or planned exposure.
• Planned exposure vaccine is a killed or weakened antigens.

How Long Does Active Immunity Last

• Duration depends on the antigen and each antigen requires different number of vaccinations.
• Boosters work to remind the body on certain vaccine.
• Some antigens become lifetime immunities.

Passive Immunity

• The body does not produce the antibodies.
• Immunities are typically passed down from mother.

Immune Disorders - Allergies

• The immune system mistakenly recognizes harmless particles
• This can lead to sneezing, runny nose, and watery eyes
• Anti-histamines help with allergies

Acquired Immune Deficiency Syndrome (AIDS)

• Caused by the human Immunodeficiency Virus and was discovery in 1983
• The infections target and kill T-Cells
• The immune response does not launch because it doesn't affect the body.

AIDS - The Modern Plague

• HIV virus cripples the immune system
• With the shut of the immune system other diseases become life threatening.
• Can stay in the body for several months to upwards of 10 years before any signs of infections.