CH 18 & 20 Blood & Blood Whatever

Blood (definition)

Fluid connective tissue made of plasma (nonliving fluid matrix) and formed elements (RBCs, WBCs, platelets); pH 7.35-7.45; about 100.4 F (slightly above body temp); 5-6 L in males, 4-5 L in females; about 8% of body weight

Normal pH of blood

7.35 to 7.45

Functions of blood

Transports gases, nutrients, hormones, wastes; regulates pH and ion composition; restricts fluid loss at injury sites; defends against toxins and pathogens; stabilizes body temperature

Plasma

46-63% of blood volume; 90% water; proteins made by the liver (albumin, globulins, fibrinogen); also wastes, nutrients, electrolytes, gases, hormones

Albumin

Plasma protein that carries molecules, buffers pH, and keeps water in the bloodstream

Globulins

Plasma proteins that bind lipids, metal ions, and fat-soluble vitamins; include antibodies

Fibrinogen

Plasma protein that forms fibrin threads for clotting

Erythrocytes (RBCs)

Biconcave discs with no nucleus or organelles; lifespan about 120 days; carry oxygen on hemoglobin

Hemoglobin

Protein (globin) bound to heme with an iron atom; each molecule carries 4 O2; each RBC has about 250 million hemoglobin (about 1 billion O2)

Oxyhemoglobin vs deoxyhemoglobin

Oxyhemoglobin = loaded with O2, bright red (lungs); deoxyhemoglobin = O2 released, dark red (tissues)

Carbaminohemoglobin

Hemoglobin carrying CO2 (about 20% of the blood's CO2; most CO2 is carried in plasma)

Hematopoiesis

Blood cell formation; occurs in red bone marrow of the axial skeleton

Hemocytoblast

The hematopoietic stem cell (blood stem cell); gives rise to myeloid and lymphoid stem cells

Erythropoiesis

Red blood cell production; takes about 15 days (proerythroblast > erythroblasts > normoblast > nucleus ejected > reticulocyte > erythrocyte)

Erythropoietin (EPO)

Hormone from the kidneys (and a little from the liver) released when O2 is low; speeds RBC maturation in the red marrow; testosterone also boosts EPO

Causes of tissue hypoxia that trigger EPO

Hemorrhage, iron deficiency, reduced O2 (e.g., high altitude)

Fate of RBCs

Live 100-120 days; macrophages in the spleen engulf old RBCs; iron is recycled, heme becomes bilirubin (secreted in bile; leaves in feces as stercobilin), globin becomes amino acids

Hematocrit

Percent of blood volume that is RBCs; males 47% +/- 5; females 42% +/- 5

Buffy coat

Layer of leukocytes and platelets in a centrifuged blood sample (less than 1% of blood)

Leukocytes (WBCs)

Complete cells, larger than RBCs; protect against pathogens, toxins, tumor cells; less than 1% of blood volume

Leukocytosis

WBC count over 11,000/mm3; normal response to bacterial or viral invasion

Leukopenia

Low WBC count (e.g., drug-induced in cancer patients)

Granulocytes

WBCs with granules: neutrophils, eosinophils, basophils

Agranulocytes

WBCs without granules: lymphocytes and monocytes

Neutrophils

"Bacteria slayers"; most numerous WBC; 3-6 lobed nucleus; active phagocytes in injured and infected tissue

Eosinophils

Red-staining, telephone-handle nucleus; digest parasitic worms; seen with allergies; release chemicals that reduce inflammation

Basophils

Rarest WBC; release histamine (inflammatory vasodilator that attracts other WBCs) and heparin

Lymphocytes

Crucial to immunity; T cells attack infected and tumor cells; B cells produce antibodies

Monocytes (macrophages)

Largest leukocytes; phagocytize viruses and bacteria; seen in chronic infections; activate lymphocytes

Platelets

Cell fragments with no nucleus; formation controlled by thrombopoietin; form the platelet plug; degenerate in about 10 days

Steps of hemostasis

1) Vascular phase (vasoconstriction, about 30 min) 2) Platelet phase (platelets stick to collagen, release chemicals, positive feedback, plug forms) 3) Coagulation phase (starts about 30 sec; fibrin mesh traps cells)

Coagulation

Blood changes from liquid to gel: prothrombin activator forms > prothrombin becomes thrombin > thrombin changes fibrinogen into fibrin mesh

Clot retraction

Platelet actin and myosin pull the cut edges together within 30-60 min, squeezing serum out of the clot; PDGF and VEGF drive vessel repair

Fibrinolysis

Plasmin digests unneeded clots (starts within 2 days)

Clot-prevention in healthy vessels

Endothelial cells make prostacyclin and nitric oxide to keep platelets inactive; heparin (from basophils and mast cells) inhibits thrombin

Anemia (disease)

WHAT: blood has low O2-carrying capacity (a sign of other problems, not a disease itself) | CAUSE: too few RBCs (hemorrhagic, hemolytic, aplastic), low hemoglobin (iron-deficiency, pernicious), abnormal hemoglobin (thalassemia, sickle-cell) | SYMPTOMS: fatigue, paleness, shortness of breath, chills

Megaloblastic anemia

Lack of vitamin B12 or folic acid impairs DNA synthesis so RBCs are enlarged and abnormal

Sickle-cell anemia

Anemia from abnormal hemoglobin (congenital)

Polycythemia (disease)

WHAT: excess RBCs that raise blood viscosity (hematocrit up to 80%) | CAUSE: polycythemia vera (bone marrow cancer) or secondary (low O2/high altitude, more EPO); blood doping | SYMPTOMS: itching and pain in fingers/toes, night sweats, weight loss; risk of embolisms and hemorrhages

Leukemia (disease)

WHAT: cancer of WBCs | TYPES: myeloid (abnormal granulocytes) or lymphoid (abnormal lymphocytes); acute leukemia involves blast cells and mostly affects children | EFFECT: abnormal WBCs crowd out normal cells

Thrombus (disease)

WHAT: clot in an unbroken blood vessel; blocks circulation and causes tissue death | SYMPTOMS: swelling, pain, tenderness in the leg or along a vein; warmth and red/discolored skin | PREVENTION: aspirin, heparin

Embolus (disease)

WHAT: a thrombus (or other mass) freely floating in the bloodstream | EXAMPLES: pulmonary embolus (shortness of breath, pain on deep breathing, coughing blood, rapid heart rate); cerebral embolus causes stroke

Embolism

Blockage of a vessel by an embolus; pulmonary embolism impairs gas exchange in the lungs

Thrombocytopenia (disease)

WHAT: deficiency of platelets | SYMPTOMS: widespread hemorrhaging, petechiae (purple spots on skin) | TREATMENT: platelet transfusion

Hemophilia (disease)

WHAT: hereditary bleeding disorders; each type lacks a clotting factor (A = factor VIII, most common; B = IX; C = XI, mild) | SYMPTOMS: prolonged bleeding, especially into joint cavities | TREATMENT: plasma transfusions and injections of the missing factor

Vitamin K and clotting

Vitamin K deficiency or liver problems (cirrhosis, hepatitis) impair prothrombin synthesis and cause bleeding problems

Hemolytic disease of the newborn (disease)

WHAT: Rh- mother's antibodies destroy the RBCs of an Rh+ baby | CAUSE: mother exposed to Rh+ blood in the first pregnancy makes anti-D; in a 2nd pregnancy antibodies cross the placenta | TREATMENT: transfusions before/after birth; RhoGAM prevents sensitization

Blood antigens and antibodies

Antigens = identifier proteins on RBC surfaces (A, B); antibodies are inherited and cause agglutination when they meet their target antigen

Type A blood

A antigens; anti-B antibodies

Type B blood

B antigens; anti-A antibodies

Type AB blood

A and B antigens; no anti-A or anti-B antibodies (universal recipient with Rh+)

Type O blood

No A or B antigens; anti-A and anti-B antibodies (universal donor if Rh-)

Universal donor

Type O negative

Universal recipient

Type AB positive

Rh factor

Rh+ means the D antigen is present; Rh- people do not have innate anti-D antibodies but form them after exposure to Rh+ blood (transfusion or childbirth); a second exposure causes a transfusion reaction

Agglutination

Clumping of RBCs when antibodies meet matching antigens

Reading a blood typing card

Add anti-A, anti-B, and anti-Rh serum to blood drops; agglutination (clumping) = positive reaction = that antigen is present

Transfusion reaction

Donor cells attacked by recipient antibodies; small vessels clog; donor cells rupture and release hemoglobin into the kidneys, which can cause renal shutdown; can be fatal

Blood tests

Hematocrit, differential WBC count, complete blood count (CBC), prothrombin time and platelet count (assess hemostasis), blood chemistry profile

Arteries

Carry blood away from the heart; most carry oxygenated blood (exception: pulmonary arteries carry deoxygenated blood to the lungs)

Veins

Carry blood toward the heart; thinner walls and larger lumens than arteries; lower pressure; capacitance vessels

Flow through vessels

Heart > arteries > arterioles > capillary beds > venules > veins > heart

Three tunics of vessel walls

Tunica intima (endothelium, smooth lining; forms valves in veins), tunica media (smooth muscle and elastin; controls vasoconstriction and vasodilation), tunica externa (collagen; protects, reinforces, anchors; has nerves and lymphatic vessels)

Elastic (conducting) arteries

Large thick-walled arteries near the heart (aorta and major branches); elastin in all 3 tunics; act as pressure reservoirs by expanding and recoiling

Muscular (distributing) arteries

Farther from the heart; deliver blood to organs; thick tunica media with lots of smooth muscle; active in vasoconstriction

Arterioles

Smallest arteries; resistance vessels; vasodilation and vasoconstriction control flow into capillary beds

Capillaries

Walls are tunica intima only (one cell thick); one RBC at a time; exchange vessels for gases, nutrients, wastes, hormones; absent in cartilage, epithelia, cornea, and lens

Precapillary sphincters

Regulate blood flow into true capillaries (controlled by local chemicals and nerves)

Venules

Formed when capillary beds unite; very porous (fluid and WBCs move into tissues); postcapillary venules are where WBCs attach during inflammation

Veins as capacitance vessels

Large lumens and distensible; hold up to 65% of the blood at any time (blood reservoirs); valves (part of tunica intima) prevent backflow, most abundant in limbs

Varicose veins (disease)

WHAT: dilated, twisted veins | CAUSE: sustained increased pressure makes the valves fail (obesity, pregnancy, heavy lifting, standing, age over 50) | RISK: more common in women

Arteries vs veins

Arteries: blood pumped from the single aorta; deep and protected; distinct pathways; predictable supply. Veins: return via venae cavae and coronary sinus; deep and superficial; many interconnections