Chapter 17: Blood

Fluid connective tissue

• Plasma on top (55%)
• WBCs and platelets in buffy coat (<1%)
• Erythrocytes on bottom (45%)

• Percent of blood volume that Erythrocytes (RBCs)
• 42-52% for males
• 37-47% for females

• Sticky, opaque fluid with metallica taste
• Color: high O2 - scarlet / low O2 - dark red
• pH: 7.35-7.45
• 8% of body weight
• Average volume: 5-6 L males / 4-5 L females

• Distribution
• Regulating blood levels of substances
• Protection (antibodies - WBCs)

• Maintaining body tempt by absorbing and distributing heat (warm - dilate / cold - constrict)
• Maintain normal pH using buffers
• Maintaining adequate fluid volume in circulatory system

• Preventing blood loss - plasma proteins and platelets initiate clot formation
• Preventing infection - antibodies, compliment proteins, WBCs

90% water with over 100 dissolved solutes - nutrients, gases, hormones, wastes, inorganic ions

• Only WBCs are complete cells
• RBCs have no nuclei or other organelles
• Platelets are cell fragments
• Most formed elements survive in bloodstream only few days (with the exception of Erythrocytes)
• Most blood cells originate in bone marrow and do not divide

• biconcave discs, anucleate
• Diameters larger than some capillaries
• Major factor contributing to blood viscosity
• Filled with hemoglobin (hb) for gas transport

having a thick, sticky consistency between solid and liquid

Hemoglobin binds reversibly with oxygen

• Globin: composed of 4 polypeptide chains
• Heme: pigment bonded to each globin chain (contains iron)
• Each Hb molecule can transport 4 O2 (each Iron atom carries one O2 molecule)
• Each RBC contains 250 million Hb molecules

• O2 loading in lungs - produces oxyhemoglobin (ruby red)
• O2 unloading in tissues - produces deoxyhemoglobin or reduced hemoglobin (dark red)
• O2 loading in tissues - 20% of CO2 in blood binds to Hb (carbaminohemoglobin)

Blood cell formation in red bone marrow (in axial skeleton, girdles, and proximal epiphyses of humerus and femur)

• Hemocytoblasts
• Give rise to all formed elements
• Hormones and growth factors push cell toward specific pathway of blood cell development

• Too few RBCs leads to tissue hypoxia
• Too many RBCs increases blood viscosity
• Balance between RBC production and destruction depends on (hormonal controls - adequate supplies of iron, amino acids, and B vitamins

• 1. Hypoxia: body is deprived of adequate oxygen supply
• 2. Kidney releases erythropoietin
• 3. Erythropoietin stimulates red bone marrow
• 4. Enhances erythropoiesis increases RBC count
• 5. O2- carrying ability of blood rises

• Life span: 100-120 days
• Old RBCs become fragile; Hb begins to degenerate
• Get trapped in smaller circulatory channels especially in spleen
• Macrophages engulf dying RBCs in spleen

• Abnormally low O2-carrying capacity
• Blood O2 levels cannot support normal metabolism
• Accompanied by fatigue, pallor, shortness of breath, chills

• Blood Loss
• Low RBC Production
• High RBC Destruction

• Causes: rapid blood loss
• Treatment: blood replacement

Cause: slight but persistent blood loss

• Cause: hemorrhagic anemia, low intake or impaired absorption
• Treatment: iron supplements

• Cause: Lack of Erythropoietin
• Treatment: synthetic erythropoietin
• often accompanies renal disease

• Cause: Autoimmune disease - Lack of intrinsic factor needed to absorb B12 (deficiency of vitamin B12)
• Treatment: B12 injections or nasal gel
• also caused by low dietary B12 (vegetarians)

Cause: Hb abnormalties - incompatible transfusions - infections

• Cause: Hemoglobin S - one amino acid wrong in a globin beta chain
• RBCs crescent shaped when unload O2 or blood O2 low
• Poor O2 delivery - pain

• Make up of less than 1% of total blood volume
• Function in defense against disease (can leave capillaries)

• WBC count over 11,000 cells per nanoliter
• normal response to infection

• Granulocytes
• Agranulocytes

• Visible cytoplasmic granules
• Neutrophils, Esoinophils, Basophils

• No visible cytoplasmic granules - spherical or kidney-shaped nuclei
• Lymphocytes, Monocytes

• Most numerous WBCs
• Structure: 3-6 lobes in nucleus; twice size of RBCs - granules stain lilac; contain hydrolytic enzymes or defensins
• Very phagocytic - "bacteria slayers"

• Structure: red-staining granules - bilobed nucleus - granules lysosome-like
• Role in: allergies and asthma - modulating immune response

• Rarest WBCs
• Structure: nucleus deep purple with 1-2 constrictions - large, purplish-black granules contain histamine
• functionally similar to mast cells

• Second most numerous WBC
• Structure: large, dark purple, circular nuclei with thin rim of blue cytoplasm
• Located in: mostly in lymphoid tissue - few circulate in blood
• Crucial to immunity

• Largest leukocytes
• Structure: abundant pale-blue cytoplasm - dark purple-staining, U- or kidney-shaped nuclei
• Actively phagocytic cells (crucial against, viruses, intracellular acterial parasites, and chronic infections)
• Activate lymphocytes to mount an immune response

form lymphocytes

Forms Monocytes, Neurophils, Eosinophils, Basophils

Abnormally low WBC count - drug induced

• Cancer - overproduction of abnormal WBCs
• Named according to abnormal WBC clone involved
• Cancerous leukocytes fill red bone marrow
• Immature nonfunctional WBCs in bloodstream
• Death usually from internal hemorrhage; overwhelming infections
• Myeloid leukemia: involves myeloblast descendants
• Lymphocytic leukemia: involves lymphocytes

• Highly contagious viral disease - Epstein-Barr virus
• High numbers atypical agranulocytes
• Symptoms - tired, ach, chronic sore throat, low fever
• Runs course with rest

• Cytoplasmic fragments of megakaryocytes
• Blue-staining outer region; purple granules
• Normal = 150,000-400,000 platelets /mL of blood
• Form temporary platelet plug that helps seal breaks in blood vessels

Hematopoietic stem cell - megakaryoblast - megakaryocyte - platelets

• Fast series of reactions for stoppage of bleeding
• Requires clotting factors, substances released by platelets and injured tissues

• 1. Vascular spasm - smooth muscle contracts
• 2. Platelet plug formation - injury to lining of vessel exposes collagen fibers; platelets adhere - platelets release chemicals that make nearby platelets sticky; platelet plug forms
• 3. Coagulation - fibrin forms a mesh that traps red blod cells and platelets, forming the clot