Blood

Circulatory System The circulatory system consists of: Heart Blood Vessels Blood Adults have 4-6 liters of blood. The study of blood is hematology

What are the Functions of Blood? Transportation: Oxygen, nutrients, wastes, carbon dioxide, and hormones Defense: Against invasion by pathogens Regulatory functions: Body temperature, water-salt balance, and body pH

Composition of blood Formed elements: produced in red bone marrow Red blood cells/erythrocytes (RBC) White blood cells/leukocytes (WBC) Platelets Plasma 91% water and 9% salts and organic molecules

Venipuncture by phlebotomist Composition of blood

Fig. 6.2

Formed Elements The formed elements are produced in red bone marrow which is found in almost every bone of a child, but in only certain bones of adults. Flat bones of sternum, hips Ends of long bones Red bone marrow contains pluripotent stem cells, which divide and give rise to all of the various types of blood cells.

Erythrocytes Red blood cells (RBC) Discoid shape No nucleus Biconcave disks No nucleus Lack many organelles

RBC RBC’s are the most abundant formed elements. There are 4 to 6 million red blood cells per mm3 of whole blood. RBC’s have 2 main functions. To pick up oxygen from the lungs and deliver it to tissues of the body. To pick up carbon dioxide from the tissues and unload it in the lungs.

Red blood cells They contain many molecules of hemoglobin. Hemoglobin is a pigment that makes RBC’s red. Oxygen binds to heme on the hemoglobin molecule

How Red Blood Cells Carry Oxygen Red blood cells contain hemoglobin, the respiratory pigment that transports oxygen. Each hemoglobin molecule has four polypeptides that comprise the protein globin and an iron-containing, oxygen-carrying heme portion. Oxyhemoglobin and deoxyhemoglobin are the names for the shapes that hemoglobin can take with or without bound hemoglobin.

How Red Blood Cells Help Transport Carbon Dioxide Hemoglobin directly transports about 25% of carbon dioxide which binds to the terminal amino groups of the globin molecules. The remaining carbon dioxide is transported as the bicarbonate ion in the plasma. The enzyme carbonic anhydrase, contained in red blood cells, catalyzes the reaction of carbon dioxide and water to form carbonic acid. When blood containing bicarbonate ions reaches the lungs, carbon dioxide diffuses out of the blood into the lungs and is exhaled.

RBC life cycle Last about 120 days As a RBC ages, its membrane becomes fragile. Eventually it ruptures as it tries to flex through narrow capillaries. RBC’s are destroyed in the liver and the spleen The spleen= the erythrocyte graveyard RBC’s have a hard time passing through its small channels. Here the old cells become trapped, broken up, and destroyed.

RBC life cycle

RBC life cycle Hemoglobin is released when blood cells are broken down. Iron is recovered and recycled to the bone marrow. Pigments from hemoglobin are excreted as bile pigments. The kidneys release the erythropoietin hormone which stimulates bone marrow stem cells to make more red blood cells.

Disorders of RBC’s Anemia A condition resulting from too few RBC’s or hemoglobin that causes a run-down feeling Sickle-Cell Disease Sickle-cell disease is a hereditary condition in which the hemoglobin molecule is abnormal and the individual has sickle-shaped red blood cells that tend to rupture as they pass through the narrow capillaries.

Disorders of RBC’s Hemolytic disease of the newborn A condition with incompatible blood types that leads to rupturing of blood cells in a baby before and continuing after birth

White Blood Cells

White Blood Cells White blood cells (leukocytes) are large, nucleated, and function in immunity. Some live days and others live months or years. Memory cells last for decades! WBC’s are not as numerous as RBC’s Colony-stimulating factors (CSFs) are proteins that regulate the production of white blood cells.

White Blood Cells Functions of WBC’s Found in the blood as well as tissues Can squeeze through pores in the capillary wall to go and fight infections (diapedesis) Invade tissues when needed Fight infection Important part of the immune system Numbers can double within hours if needed

White Blood Cells The immune system defends the body against pathogens, cancer cells, and foreign proteins. An antigen is a cell or other foreign substance that provokes an immune response. For example: Foreign proteins Viruses Bacteria Abnormal or foreign cells

How do blood cells leave circulation? Diapedesis

WBC types Agranulocytes Granulocytes Lymphocytes Monocytes Neutrophils Eosinophils Basophils

Neutrophils Most numerous WBC Contains a multi-lobed nucleus Fight off bacterial infections Upon infection they move out of circulation into tissues to engulf pathogens

Lymphocyte 2nd most numerous WBC Develops into B and T cells that are important in the immune system B lymphocytes mature into plasma cells that make antibodies T lymphocytes control immune response Important in fighting off viral infections

Monocyte Largest of the WBC’s Count increases in inflammation and viral infections Leave the bloodstream and transform into macrophages Play a role in immune response

Eosinophils Small percentage of WBC’s Many large granules function in parasitic infections and play a role in allergies

Basophils Smallest percentage of WBC’s Release histamine related to allergic reactions Histamine dilates blood vessels and constricts air tubes leading to lungs

Disorders of WBC’s Severe combined immunodeficiency disease (SCID) An inherited disease in which stem cells of WBC’s lack an enzyme that allows them to fight any infection Lymphoma A group of cancers that begin in cells of the immune system. There are two basic categories of lymphomas: Hodgkin lymphoma and non-Hodgkin lymphomas, which includes a large, diverse group of cancers of immune system cells.

Leukemia A group of cancers in which white blood cells proliferate without control

Disorders of WBC’s Infectious mononucleosis- also know as the “kissing disease” occurs when the Epstein-Barr virus (EBV) infects lymphocytes resulting in fatigue, sore throat, and swollen lymph nodes 50% monocytes with at least 10% atypical lymphocytes (large, irregular nuclei),

Platelets

Platelets Small fragments of megakaryocytes Aide in blood clotting Live for about 10 days About 200 million are made per day

Platelets and Blood Clotting When tissues are damaged, platelets stick to the damaged area, partially sealing torn blood vessels. Injured tissues release prothrombin activator, which converts prothrombin to thrombin. This step requires calcium ions. Thrombin functions as an enzyme to convert fibrinogen into long threads of insoluble fibrin.

Disorders of Platelets Thrombocytopenia A disorder in which the number of platelets is too low due to not enough being made in the bone marrow or the increased breakdown outside the marrow Thromboembolism A spontaneous clot is called a thrombus if it remains in the vessel; if it dislodges and travels, it is called an embolus. A thromboembolus can result in a heart attack or stroke when the clot plugs a vessel in the heart or brain

Disorders of Platelets Hemophilia Hemophilia is an inherited clotting disorder carried on the X chromosome which results in the deficiency of a clotting factor. Injections of this factor can treat the disease. Victim hemorrages Can die from bleeding internally

Blood Typing A blood transfusion is the transfer of blood from 1 individual to another For transfusions to be safe, blood must be typed so that agglutination (clumping) does not occur Blood typing involves determining the ABO blood group and Rh factor so that the transfusion can be done safely. Blood typing usually involves determining the ABO blood group and whether the individual is Rh- or Rh+

ABO Blood Groups The most common system for typing blood is the ABO system. Blood types A, B, and AB correspond with having specific antigens on the surface of RBCs; type O is an absence of these antigens. All persons have antibodies in their plasma for the A and/or B antigen not carried on their own RBCs. If the corresponding antigen and antibody are combined, clumping, or agglutination, occurs.

Blood typing For example: Type A blood -has A antigen on its surface -has B antibodies in the plasma What can you say about someone with type AB blood?

Blood types Plasma

Determining compatibility for blood transfusion First consider the antigens found on the blood transfusion recipient Second, consider the antibodies found in the donor blood If the antibodies in the donor blood can recognize the antigen on the recipient’s blood then the blood will agglutinate (clump) and cause rejection

Blood Compatibility Type O blood is sometimes called the universal donor because the red blood cells of type O blood lack A and B antigens. Type O blood will not agglutinate regardless of the recipient’s antibodies.

Blood Compatibility Type AB blood is called the universal recipient because the plasma lacks A and B antibodies Type AB recipient blood won’t clump with any type of donor blood

Testing your understanding Can a person with blood type O accept blood type A without agglutination occurring? Why can people with AB blood type accept more blood types than people with type O, A, or B? Which blood type is able to be used most often as a donor blood type?

Rh blood groups The Rh factor is often included when expressing a blood type by naming it positive or negative People with the Rh factor are positive and those without it are negative Rh antibodies only develop in a person when they are exposed to the Rh factor from another’s blood (usually a fetus)

When is Rh Factor Important During pregnancy under these conditions: Mom: Rh- Dad: Rh+ Fetus: Rh+ In this case some Rh+ blood can leak from the fetus to the Mom during birth causing the mother to make Rh antibodies

When is Rh factor Important This can be a problem is the mother has a 2nd fetus that is Rh+ because she now has antibodies that can leak across the placenta and attack the fetus This condition is known as hemolytic disease of the newborn that can lead to death

Hemolytic Disease of Newborn or Erythroblastosis fetalis Can be fatal Can cause jaundice because of degrading hemoglobin in blood

Hemolytic Disease Prevention Rh- women are given an injection of anti-Rh antibodies no later than 72 hours after birth to an Rh+ baby These antibodies attack fetal red blood cells in mother before the mother’s immune system can make antibodies This will have to be repeated if an Rh- mother has another Rh+ baby in case she has later pregnancies

AB incompatibility < 20% of all pregnancies Anti-A and anti-B antibody molecules are IgM and therefore very large Do not cross placenta Do not cause hemolytic disease IgG is occasionally produced and does cross placenta causing hemolytic disease

EC Reports-1 Discuss the problems with athletes and blood doping. Is this legal? What are the advantages? What are the disadvantages? Some athletes have been stripped of their medals because they tested positive for performance-enhancing substances in their blood. Why would someone use such a drug if they knew they could be caught and disqualified from the competition? How do the Olympics keep ahead of the new methods for illegally enhancing performance? Why do so many of our US Olympic teams train at high altitudes?

EC Reports-2 Discuss the use of stem cells from the blood in the treatment of leukemia and other blood diseases. How successful is this? How is it done? What types of stem cells are used? Why would parents choose to save cord blood? What diseases can be treated with cord blood? What are the costs associated with saving cord blood?

EC Reports-3 Read BIOLOGY MATTERS-Health “Aspirin and Heart Disease” on page 122 of the text. Recount the differences between a negative and a positive feedback mechanism. Have students discuss the advantages and disadvantages of inhibiting the activity of thromboxane. If a family member has had a stroke or strokes, would you consider taking daily baby aspirins as you would a vitamin supplement?