Chapter 12 Blood Type of connective tissue Cells suspended in a liquid extracellular matrix Vital in transporting substances between body cells and the external environment Promotes homeostasis Whole blood is Heavier than water 3-4 times more viscous than water Cells form mostly in red bone marrow Red blood cells that carry oxygen White blood cells fight infections Platelets help blood clot

Formed Elements and Plasma Cells and platelets found in blood are called formed elements Red blood cells (RBCs) make up about 45% of blood Percentage of RBCs in a blood sample is called the hematocrit White blood cells (WBCs) and platelets make up less than 1% and are sometimes called the buffy coat Liquid portion of blood is called plasma Normally straw colored and clear Makes up about 55% of blood Mixture of water, amino acids, proteins, carbohydrates, lipids, vitamins, hormones, electrolytes, and cellular waste

Origins of Blood Cells

Red Blood Cells Also called erythrocytes Biconcave discs Increased surface area No nucleus in mature RBCs Life span about 120 days Adapted to transport gases (O2 & CO2) Contains a protein called hemoglobin Makes up about 1/3 of RBCs Binds to oxygen in blood Oxyhemoglobin bright red when oxygen present Deoxyhemoglobin darker color when oxygen absent Oxygen-carrying capacity increases as numbers of RBCs increase Normal RBC count: Males: 4.6 – 6.2 million cells per microliter Females: 4.2 – 5.4 million cells per microliter

Red Blood Cells A person with a decreased oxygen-carrying capacity Has hypoxia May appear bluish in color and be cyanotic Sickle cell disease Genetic disorder causes an abnormal form of hemoglobin to be produced Hemoglobin crystallizes into a “sickled” shape when oxygen levels are low Blocks circulation and causes severe pain More common in people of African descent

White Blood Cells Also called leukocytes Protect against disease Transported to sites of infection by blood Leave bloodstream to fight infection Two main types of WBCs: Granulocytes Have granular cytoplasm Include neutrophils, eosinophils, and basophils About twice the size of RBCs Agranulocytes No cytoplasmic granules Include monocytes and lymphocytes Normal WBC count: 4,500 – 10,000 cells per microliter

White Blood Cells – Neutrophils Have fine cytoplasmic granules that appear light purple in a neutral stain The nuclei of older cells are lobed and have 2-5 segments Sometimes called “segs” Nuclei attached by thin strands of chromatin The nuclei of younger cells usually have a C – shape Sometimes called “bands” Account for 54 – 62% of WBCs in an adult Phagocytize bacteria and other small particles

White Blood Cells – Eosinophils Contain coarse cytoplasmic granules that appear deep red in an acid stain The nucleus usually has only two lobes (bilobed) Make up about 1-3% of WBCs Kill parasites Help control inflammation Increase in number with allergic reactions

White Blood Cells – Basophils Similar to eosinophils in size and shape of nuclei Contain fewer cytoplasmic granules that stain deep blue in a basic stain Usually account for less than 1% of WBCs in adults Release heparin and histamines Increased count may indicate a problem such as cancer

White Blood Cells – Monocytes Largest blood cells 2 – 3 times larger in diameter than an RBC Nuclei vary in shape from spherical to lobed Account for 3 – 9% of WBCs in an adult Phagocytize larger particles May live for several weeks or even months

White Blood Cells – Lymphocytes Usually only slightly larger than RBCs Contain a large round nucleus surrounded by a thin rim of cytoplasm Account for about 25 – 33% of WBCs in an adult Provide immunity in the form of antibodies Proteins that attack foreign particles in the blood Usually increase in number when an individual has a viral infection Ex: mononucleosis or EBV 2 main types: T-cells and B-cells T-cell counts drop to almost zero in AIDS patients May live for years

White Blood Cells Leukocytosis Increased WBC count over 10,000 cells per microliter May indicate acute infection Number of neutrophils increases with bacterial infections Number of lymphocytes increases with viral infections Leukopenia Decreased WBC count under 5,000 cells per microliter May accompany influenza, measles, mumps, AIDS, or chickenpox Leukemia Cancer of WBCs

Platelets Also called thrombocytes Fragments of cells Arise from very large cells called megakaryocytes Lack nuclei Less than half the size of an RBC May live for about 10 days Normal platelet count 130,000 – 360,000 per microliter Help close breaks in damaged blood vessels Initiate formation of blood clots Inactivated by the use of aspirin for up to a week

Blood Plasma Clear, straw-colored liquid portion of blood Cells and platelets are suspended Approximately 92% water Contains a complex mixture of organic and inorganic biochemicals Functions Transporting nutrients, gases, and vitamins Help regulate fluid and electrolyte balance Maintain normal pH

Plasma Proteins Most abundant of the dissolved substances in plasma All are made in the liver Albumins (60%) Smallest plasma proteins Important in maintaining osmotic pressure Globulins (36%) Can be subdivided into alpha, beta, and gamma globulins Alpha & beta globulins transport lipids and fat-soluble vitamins Gamma globulins make antibodies that fight foreign substances in the body (viruses, transplanted organs) Fibrinogen (4%) Functions in blood coagulation One of the largest plasma proteins

Plasma Proteins

Gases and Nutrients Most important plasma gases: Oxygen (O2) – needed for cellular respiration Carbon dioxide (CO2) – waste product Other plasma gases: Nitrogen (N2) – no function Plasma nutrients: Absorbed from digestive tract Include: Amino acids, simple sugars, nucleotides, lipids Nonprotein Nitrogenous Substances Products of protein metabolism Include: Amino acids, urea, and uric acid

Gases and Nutrients Plasma electrolytes Absorbed from the intestines Released as by-products of cellular metabolism Include ions of: sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate, and sulfate Bicarbonate ions are important in maintaining Osmotic pressure Plasma pH

Hemostasis The stoppage of bleeding Important after damage to blood vessels Actions that limit blood loss include: Blood vessel spasms Also called vasospasms and result from contractions of smooth muscles in blood vessels Platelet plug formation Platelets adhere to rough surfaces and collagen in connective tissue Platelets adhere to each other Controls blood loss in small breaks Blood coagulation Formation of a blood clot Uses biochemicals called clotting factors Fibrinogen converts to fibrin to help form blood clot

Hemostasis Plasma vs. serum Plasma contains clotting factors Serum contains no clotting factors Thrombus – a blood clot that forms abnormally in a blood vessel Embolus – a clot that dislodges or a fragment of a clot that breaks loose and is carried away by blood flow A blood clot that forms in a vessel that supplies a vital organ may be fatal Coronary thrombosis Cerebral thrombosis A blood clot that travels and then blocks a blood vessel may be fatal Pulmonary embolism Myocardial infarction

Blood Groups Agglutination – clumping of RBCs following a transfusion reaction Antigens - molecules on the surface of RBCs Also called agglutinogens Identify RBCs as belonging to a person More than 260 different antigens can be found on RBCs Important antigens include those of the ABO and Rh blood groups Antibodies – proteins made by the body to attack foreign antigens Also called agglutinins Carried in plasma

ABO Blood Group Based on the presence or absence of two major protein antigens on red blood cell membranes Antigen A Antigen B Inherited ABO blood types: Only antigen A – blood type A Produce antibody B Only antigen B – blood type B Produce antibody A Both antigen A & B – blood type AB Produce no A or B antibodies Neither antigen A or B – blood type O Produce antibodies to both A & B

ABO Blood Group

ABO Blood Group Antibodies to antigens A & B form about 2 – 8 months following birth. An antibody of one type will react with an antigen of the same type and clump (or agglutinate) RBCs

Coagulation Disorder – Hemophilia A Results from a lack of clotting factor VIII Sex-linked recessive allele Usually males are affected Symptoms: Severe hemorrhage following minor injury Frequent nosebleeds Large intramuscular hematomas Blood in the urine Achieved notoriety when factor VIII pooled from blood donations were shown to transmit HIV (1985) 90% of those who used factor VIII in the few years prior to 1985 developed AIDS

Rhesus Blood Group Named after the rhesus monkey in which it was first studied In humans, this group includes several Rh antigens Most prevalent is antigen D If the D antigen is present on RBCs, the blood is said to be Rh-positive If the D antigen is absent on RBCs, the blood is said to be Rh-negative Exposure to Rh-positive blood can cause a person with Rh-negative blood to form anti-D antibodies

Hemolytic Disease of the Fetus & Newborn If an Rh-negative mother with an Rh-positive husband has a baby If the baby is Rh-negative, no problem If the baby is Rh-positive, the mother can form antibodies to the baby. The first baby is usually not harmed The second and any following babies may have agglutination of RBCs May cause lack of oxygen and permanent damage or death May need a transfusion of blood that is compatible with the mother’s blood Rh-negative mothers that may have Rh-positive babies receive RhoGam at 28 weeks of pregnancy Contains Anti-D Fools mother’s body into thinking it’s already formed Anti-D

Hemolytic Disease of the Fetus & Newborn