Blood Chapter 12

Blood Specialized CT Transports materials Maintains stability of interstitial fluid Distributes heat Amount varies with body size, fluid concentration changes, electrolyte concentration changes ~8% of body weight ~5L = adult blood volume

Blood Cells Form mostly in the red bone marrow Includes: – Red Blood Cells (RBCs) – White Blood Cells (WBCs) – Platelets (cell fragments) Blood cells form from: Hemocytoblasts in the red marrow Hematopoietic stem cells in the red marrow

Plasma = 55% Capillary tube Plug Buffy coat Red cells = 45% (hematocrit) Leukocytes & platelets (<1%) Mostly water, solutes (like proteins, electrolytes, some gases)

Blood (4.8%) (95.1%) (0.1%) Plasma Hormones Monocytes Basophils EosinophilsNeutrophils (54–62%)(1–3%) (<1%) (3–9%) (25–33%) Globulins Albumins (92%)(7%) N2N2 O2O2 CO 2 Platelets Red blood cells Proteins NutrientsGases 45%55% Wastes Water White blood cells Electrolytes Vitamins Lymphocytes Fibrinogen Formed elements

Red Blood Cells (Erythrocytes) Biconcave discs One-third hemoglobin Lack nuclei and mitochondria RBC count = the number of RBCs in a cubic millimeter or microliter of blood

RBC Production Low blood oxygen signals kidneys & liver to release erythropoietin (EPO) – Stimulates RBC production – Feedback mechanism? New RBCs appear in the circulating blood within a few days FactorSourceFunction Vitamin B 12 Absorbed from small intestineDNA synthesis IronAbsorbed from small intestine; conserved during RBC destruction Hemoglobin synthesis Folic acidAbsorbed from small intestineDNA synthesis

Types of Anemia TypeCauseDefect Aplastic anemiaToxic chemicals, radiation Damaged bone marrow Hemolytic anemiaToxic chemicalsRBCs destroyed Iron deficiency anemia Dietary lack of ironHb deficient Pernicious anemiaInability to absorb B12 Excess of immature cells Sickle cell diseaseDefective geneMisshapen RBCs ThalassemiaDefective geneHb deficient; RBCs short-lived

White Blood Cells (Leukocytes) Protect against disease Five types of WBCs (two categories): – Granulocytes Neutrophils Eosinophils Basophils – Agranulocytes Lymphocytes Monocytes

Neutrophils Light purple granules when in neutral (acid-base) stain Lobed nucleus First to arrive at infections Phagocytic 54-62% of leukocytes Elevated in bacterial infections

Eosinophils Deep red granules in acid stain Bi-lobed nucleus Moderate allergic reactions Defend against parasitic worms 1-3% of leukocytes Elevated in parasitic worm infections and allergic reactions

Basophils Deep blue granules in basic stain Releases heparin and histamine Less than 1% of leukocytes Similar to eosinophils in size, nucleus shape

Monocytes Largest of all blood cells Spherical Nucleus can be kidney-shaped, ovalular, or lobed May leave bloodstream to become macrophages 3-9% of leukocytes Phagocytic

Lymphocytes Slightly larger than RBCs Large, spherical nuclei surrounded by thin rim of cytoplasm T cells and B cells – Immunity – (B cells produce antibodies) 25-33% of leukocytes

WBC Functions Protect against infection Squeeze between the cells of capillary wall and the space outside the blood vessel Blood capillary Leukocyte Connective tissue

Epidermis Dermis Blood vessels 1 Splinter punctures epidermis Injured cells release histamine, causing blood vessels to dilate Bacteria multiply Bacteria are introduced into the dermis Neutrophils destroy bacteria by phagocytosis Neutrophils move through blood vessel walls and migrate toward bacteria

WBC Counts Counts number of WBCs per cubic millimeter of blood Typically 5,000 – 10,000 per cubic millimeter of blood Leukopenia – low WBC count (<5,000) Typhoid fever, flu, measles, mumps, chicken pox, AIDS Leukocytosis – high WBC count (>10,000) Acute infections, vigorous exercise, loss of body fluid Differential WBC count Lists percentages of each type of leukocyte May change in particular diseases

Blood Platelets Platelets = thrombocytes Cell fragments of megakaryocytes Lack nucleus; half the size of a RBC 130, ,000 per cubic mm of blood Repair damaged blood vessels by sticking to broken surfaces

Blood Plasma Liquid portion of blood; straw-colored 55% of blood volume 92% water Transports nutrients, gases, vitamins Regulates fluid & electrolyte balance, maintains pH

Plasma Proteins The most abundant dissolved substances (solutes) in plasma

Non-protein Substances Gases, nutrients Nitrogenous substances – Urea – product of protein catabolism (~50%) – Uric acid – product of nucleic acid catabolism – Amino acids – product of protein catabolism – Creatine – stores phosphates – Creatinine – product of creatine metabolism – BUN – blood urea nitrogen (kidney health indicator)

Hemostasis Stoppage of bleeding Actions: – Blood vessel spasm (smooth muscle of vessel contracts) Triggered by pain receptors, platelet release, or serotinin – Platelet plug formation (platelets adhere to surface) Triggered by exposure of platelets to collagen – Blood coagulation Causes formation of blood clot via a cascade of reactions Triggered by cellular damage, blood contact with foreign substances

Endothelial liningCollagen fiber PlateletRed blood cell Break in vessel wall Blood escaping through break Platelet plug helps control blood loss Platelets adhere to each other, to end of broken vessel, and to exposed collagen Platelet Plug Formation

Extrinsic Clotting Mechanism Chemical outside blood vessel triggers coagulation Triggered when blood contacts a damaged blood vessel wall or tissues Positive feedback mechanism

Intrinsic Clotting Mechanism Chemical inside blood triggers blood coagulation Triggered when blood contacts a foreign substance

Fate of Blood Clots After a blood clot forms it retracts and pulls the edges of a broken blood vessel together while squeezing the fluid serum from the clot Smooth muscle cells and fibroblasts stimulated to repair damaged blood vessel walls Plasmin digests the blood clots Thrombus = abnormal blood clot Embolus = blood clot moving through the blood vessels

Prevention of Coagulation Smooth lining of blood vessels discourages accumulation of platelets & clotting factors As clot forms fibrin absorbs thrombin, prevents clot from spreading Anti-thrombin inactivates additional thrombin to block unnecessary clotting Basophils and mast cells can secrete heparin (anti-coagulant)

Arteriosclerosis/Atherosclerosis Arteriosclerosis – Thickening and loss of elasticity in artery walls Atherosclerosis – Specifically, fat plaques that are filled with cholesterol, other lipids, form in the artery

Hypertension Persistently elevated arterial pressure – High sodium intake, obesity, stress, arteriosclerosis – Left ventricle works harder to pump blood – The myocardium thickens – Coronary blood vessels cannot support this overgrowth, and heart muscle can die, replaced with fibrous tissue – Enlarged, weakened heart will eventually die Also contributes to atherosclerosis – plaque can accumulate and cause coronary thrombosis or embolism, or stroke in the brain

Blood Types – Terms to Know Agglutination – clumping of RBCs in response to reaction between an antibody and antigen Antigens – a chemical that stimulates cells to produce antibodies Antibodies – a protein that reacts against a specific antigen

ABO Blood Group Type A, B, or O Based on presence/absence of either of two major antigens on the RBC cell membrane: – Antigen A – Antigen B

Type B blood Type AB bloodType O blood Red blood cell Anti-B antibody Antigen A Anti-A antibody Anti-B antibody Red blood cell Antigen A Antigen B Red blood cell Anti-A antibody Antigen B Type A blood

Red blood cell Anti-B antibody (a)(b) Agglutinated red blood cells Anti-A antibody Antigen A

Rh Blood Group Rhesus monkey Rh positive or negative – Presence/absence of “Antigen D” or other Rh antigens Fetus can develop erythroblastosis fetalis (hemolytic disease) – Can happen in Rh-negative mother on the second or subsequent Rh-positive pregnancy