Blood - PDF

Unit 6 Blood Blood Blood transports everything that must be carried from one place to another, such as: ○ Nutrients ○ Wastes ○ Hormones ○ Body heat Components of Blood Blood is the only fluid tissue, a type of connective tissue, in the human body Components of blood ○ Formed...

Unit 6 Blood Blood Blood transports everything that must be carried from one place to another, such as: ○ Nutrients ○ Wastes ○ Hormones ○ Body heat Components of Blood Blood is the only fluid tissue, a type of connective tissue, in the human body Components of blood ○ Formed elements (living cells) ○ Plasma (nonliving fluid matrix) Physical Characteristics Blood characteristics ○ Sticky, opaque fluid ○ Heavier and thicker than water ○ Color range Oxygen-rich blood is scarlet red Oxygen-poor blood is dull red or purple ○ Metallic, salty taste ○ Blood temperature is slightly higher than body temperature, at 38°Celsius or 100.4° Fahrenheit Blood Volume Blood volume ○ About 5–6 liters, or about 6 quarts, of blood are found in a healthy adult ○ Blood makes up 8 percent of body weight Plasma 90% water Straw-colored fluid Includes many dissolved substances ○ Nutrients ○ Salts (electrolytes) ○ Respiratory gases O2 and CO2 ○ Hormones ○ Plasma proteins ○ Waste products Plasma Plasma proteins Albumin—an important blood buffer and contributes to osmotic pressure Clotting proteins—help to stem blood loss when a blood vessel is injured Antibodies—help protect the body from pathogens Formed Elements Erythrocytes ○ Red blood cells (RBCs) Leukocytes ○ White blood cells (WBCs) Platelets ○ Cell fragments Erythrocytes Erythrocytes (red blood cells, or RBCs) ○ Main function is to carry oxygen ○ R B Cs differ from other blood cells No nucleus Shaped like biconcave discs ○ Normal count is 5 million RBCs per cubic millimeter of blood Erythrocytes Erythrocytes ○ Hemoglobin is an iron-bearing protein Binds oxygen Each hemoglobin molecule can bind 4 oxygen molecules Each erythrocyte has 250 million hemoglobin molecules Normal blood contains 12–18 grams of hemoglobin per 100 milliliters (m l) of blood Erythrocytes Homeostatic imbalance of RBCs ○ Anemia is a decrease in the oxygen-carrying ability of the blood due to: Lower-than-normal number of RBCs (i.e. bleeding) Abnormal or deficient hemoglobin content in the RBCs ○ Sickle cell anemia (SCA) results from abnormally shaped hemoglobin Comparison of a Normal RBC to SCA RBC Erythrocytes Polycythemia ○ Disorder resulting from excessive or abnormal increase of RBCs due to: Bone marrow cancer (polycythemia vera) Life at higher altitudes (secondary polycythemia) ○ Increase in RBCs slows blood flow and increases blood viscosity Leukocytes Leukocytes (white blood cells, or WBCs) ○ Crucial in body’s defense against disease ○ Complete cells, with nucleus and organelles ○ Able to move into and out of blood vessels ○ Respond to chemicals released by damaged tissues Leukocytes Leukocytosis ○ Abnormally high WBC count ○ Generally indicates an infection Leukopenia ○ Abnormally low WBC count ○ Commonly caused by certain drugs, such as corticosteroids and anticancer agents Leukemia ○ Bone marrow becomes cancerous ○ Numerous immature WBC are produced Leukocytes Types of leukocytes ○ Granulocytes Include neutrophils, eosinophils, and basophils ○ Agranulocytes Include lymphocytes and monocytes Leukocytes List of the WBCs, Easy way to from most to remember this list least abundant: ○ Never ○ Neutrophils ○ Let ○ Lymphocytes ○ Monkeys ○ Monocytes ○ Eat ○ Eosinophils ○ Bananas ○ Basophils Granulocytes ○ Neutrophils Function as phagocytes at active sites of infection Numbers increase during infection ○ Eosinophils Function is to kill parasitic worms and play a role in allergy attacks ○ Basophils Rarest of the WBCs Contain heparin (anticoagulant) Agranulocytes ○ Lymphocytes Slightly larger than RBCs Reside in lymphatic tissues Play a role in immune response ○ Monocytes Largest of WBCs Important in fighting chronic infection Platelets Platelets ○ Irregularly shaped fragments ○ Needed for the clotting process; initiate clotting cascade to injured area Recap: Characteristics of Formed Elements of Blood Recap: Characteristics of Formed Elements of Blood Recap: Characteristics of Formed Elements of Blood Hematopoiesis (Blood Cell Formation) Hematopoiesis is the process of blood cell formation Occurs in red bone marrow All blood cells are derived from a common stem cell RBCs can live up to 120 days When worn out, R B Cs are eliminated by phagocytes in the spleen or liver Formation of Red Blood Cells Rate of RBC production is controlled by a hormone called erythropoietin Kidneys produce most erythropoietin as a response to reduced oxygen levels in the blood Homeostasis is maintained by negative feedback from blood oxygen levels Mechanism for Regulating the Rate of RBC Production Hemostasis Hemostasis is the process of stopping the bleeding that results from a break in a blood vessel Hemostasis involves three phases 1. Vascular spasms 2. Platelet plug formation 3. Coagulation (blood clotting) Hemostasis Step 1: vascular spasms ○ Immediate response to blood vessel injury ○ Vasoconstriction causes blood vessel to spasm ○ Spasms narrow the blood vessel, decreasing blood loss Hemostasis Step 2: platelet plug formation ○ Collagen fibers are exposed by a break in a blood vessel ○ Platelets become “sticky” and cling to fibers ○ Anchored platelets release chemicals to attract more platelets ○ Platelets pile up to form a platelet plug Hemostasis Step 3: coagulation ○ Injured tissues release tissue factor that triggers a clotting cascade forming a meshwork to make a clot Fibrin Clot Disorders of Hemostasis Undesirable clotting ○ Thrombus A clot in an unbroken blood vessel Can be deadly in areas such as the lungs ○ Embolus A thrombus that breaks away and floats freely in the bloodstream Can later clog vessels in critical areas such as the brain Disorders of Hemostasis Bleeding disorders ○ Thrombocytopenia Insufficient number of circulating platelets Arises from any condition that suppresses the bone marrow Even normal movements can cause bleeding from small blood vessels that require platelets for clotting Evidenced by petechiae (small purplish blotches on the skin) Disorders of Hemostasis Bleeding disorders ○ Hemophilia Hereditary bleeding disorder Normal clotting factors are missing Minor tissue damage can cause life-threatening prolonged bleeding Blood Groups and Transfusions Large losses of blood have serious consequences ○ Loss of 15 to 30 percent causes weakness ○ Loss of over 30 percent causes shock, which can be fatal Blood transfusions are given for substantial blood loss, to treat severe anemia, or for thrombocytopenia Human Blood Groups Blood contains genetically determined proteins known as antigens Antigens are substances that the body recognizes as foreign and that the immune system may attack ○ Most antigens are foreign proteins ○ We tolerate our own “self” antigens Antibodies are the “recognizers” that bind foreign antigens Human Blood Groups ABO blood group ○ Blood types are based on the presence or absence of two antigens 1. Type A 2. Type B Human Blood Groups ABO blood group ○ Presence of both antigens A and B is called type A B ○ Presence of antigen A is called type A ○ Presence of antigen B is called type B ○ Lack of both antigens A and B is called type O Human Blood Groups ABO blood group ○ Type A B can receive A, B, A B, and O blood Type AB is the “universal recipient” ○ Type B can receive B and O blood ○ Type A can receive A and O blood ○ Type O can receive O blood Type O is the “universal donor” ABO Blood Groups ABO Blood Groups Human Blood Groups Rh blood group ○ Named for the Rh antigens ○ Most Americans are Rh+ (Rh-positive), meaning they carry the Rh antigen ○ If an Rh−(Rh-negative) person receives Rh+ blood: The immune system becomes sensitized and begins producing antibodies Second, and subsequent, transfusions involve antibodies attacking donor’s R h+ R B Cs, and hemolysis occurs (rupture of RBCs) Human Blood Groups Rh-related problem during pregnancy ○ Danger occurs only when the mother is Rh−, the father is Rh+, and the child inherits the Rh+ factor ○ RhoGAM shot can prevent buildup of anti-Rh+ antibodies in mother’s blood Human Blood Groups The mismatch of an Rh− mother carrying an Rh+ baby can cause problems for the unborn child ○ The first pregnancy usually proceeds without problems; the immune system is sensitized after the first pregnancy ○ In a second pregnancy, the mother’s immune system produces antibodies to attack the Rh+ blood