Chapter 17 Blood and Hematology Flashcards
Blood and 3 Elements It’s Composed of:
A fluid connective tissue composed of:
o Plasma: non-living fluid matrix that is 90% water plus dissolved solutes.
o Formed Elements are the living blood cells:
o Erythrocytes: Red Blood Cells
o Leukocytes: White Blood Cells
o Thrombocytes: Platelets which are pieces of cells
Hematocrit:
The amount of red blood cells in blood or percent blood volume of RBC’s.
o Typically 47% + or – 5% for males and 42% + or – 5% for females.
Physical Characteristics and Volume of Blood:
o Blood is a sticky, opaque fluid with a metallic taste (iron).
o Color is scarlet (oxygen rich) to dark red (oxygen poor).
o Osmolarity: 280-296 mOsm/L= the concentration solute or particles in a given volume of solution. The number of particles translates to the ability to attract H2O
o pH 7.35-7.45, or alkaline
o 38 degrees C (100.4 degrees F)
o ~8% of body weight.
o Average volume: 5-6 L for males and 4-5 L for females.
Ways of Withdrawing Blood:
o Venipuncture: Shoot for antecubital region ( Median cubital vein). Walls of veins are thinner. Blood pressure is lower in veins than arteries.
o Arterial Puncture: To measure blood gases.
o Capillary Sticks: Fingers, Ear Lobes, Heel. (For Diabetics)
Functions of Blood:
Transport of
o O2 and nutrients to body cells.
o Metabolic Wastes to lungs (CO2) and kidneys (uric acid) for elimination.
o Hormones from endocrine organs to target organs.
o Certain blood proteins transport fats and cholesterol.
Functions of Blood:
Regulation of
o Body Temperature: by absorbing and distributing heat (vasodilation/vasoconstriction of BVs) through blood shunting.
o Normal pH (7.35-7.45) using buffers (from solutes in blood).
o Adequate fluid volume in circulatory system ( blood proteins and salts keep fluid within blood vessels due to osmolarity=water wants in?)
Functions of Blood:
Protection Against
o Blood Loss: Plasma proteins (fibrinogen) and platelets initiate clot formation.
o Infection: Antibodies, Complement proteins (initiate and enhance the inflammatory response and work with antibodies against antigens), and WBCs/Leukocytes (defend against foreign invaders).
Components of Blood Plasma:
o Blood plasma contains plasma proteins ( 8% of blood plasma) that are 90% produced by the liver
o Blood plasma is 90% water by volume with over 100 substances dissolved in it (straw color) =
o 1) 60% Albumin (3.5 – 5.4g/dl = protein made in liver & major contributor to blood osmotic pressure, blood buffering, and blood viscosity
o > too large to move out of the blood vessels à creates osmotic pressure gradient inside the blood vessels
o > transport fatty acids, hormones, ions and nutrients, Vita D, bilirubin
o 2) 36% Globulins
o > Alpha & Beta globulins made in the liver for transport of iron, lipid, fat
o > Gamma globulins (or immunoglobulins) = are antibodies & made by plasma cells not liver (differentiated WBC)
o 3) 4% Fibrinogen = made in liver and essential in blood clotting (hemostasis)
o 4) Nitrogen by-products of metabolism—lactic acid, urea, creatinine.
o 5) Nutrients—glucose, carbohydrates, amino acids
o 6) Electrolytes—Na+, K+, Ca2+, Cl–, HCO3 for normal osmotic pressure and pH
o 7) Respiratory gases—O2 and CO2
o 8) Regulatory proteins such as hormones, enzymes
Hypoproteinemia:
o Causes: Extreme starvation, diets severely deficient in protein, liver disease interfering with protein synthesis, kidney disease that allows proteins to leak from blood into the urine, severe burns, severe trauma.
o Consequences: Decreased osmolarity of blood (blood doesn’t attract to water as much, water diffuses into the interstitial spaces between cells), edema= excess fluid in interstitial spaces, and ascites= excess fluid in peritoneal cavity.
Erythrocytes (Red Blood Cells):
o Biconcave discs, anucleate, essentially no organelles.
o Filled with hemoglobin for gas transport.
o Contain the plasma membrane spectrin and other protein.
o Spectrin: Provides flexibility for RBCs to change shape as necessary to fit through the smallest capillary.
o RBC’s are the major factor contributing to blood viscosity.
o Structural characteristics contribute to gas transport both O2 to tissues and CO2 to lungs
o Biconcave shape—huge surface area relative to volume where cytoplasm is close to cell surface
o >97% hemoglobin (not counting water)
o Plasma membrane have antigens (glycoproteins/lipids) on surface which determines different blood groups (A, B, AB,O) and Rh factor.
o Men have more RBC’s than women
o No mitochondria; ATP production is anaerobic; no O2 is used in generation of ATP (RBC’s don’t’ steal oxygen away for themselves!!)
o HbA1-C test: measures amount of glucose sticking to erythrocyte during its’ 3 month lifetime…should be less than 7%
Functions of Erythrocytes:
o One Hemoglobin (Hb) molecule is made up of:
o 1) Protein globin = four polypeptide chains (2 alpha and 2 beta chains)
o 2) Four heme (red pigment) groups bonded to protein globin chains
o An iron atom is centered in each heme group: each heme group can bind to one O2 molecule
o So, each Hb molecule can transport four O2
o Each erythrocyte contains 250 million molecules of Hb
o Number of O2 molecules held by each RBC = 250 million Hb X 4 O2= 1 billion O2 molecules carried per erythrocyte
Hemoglobin:
o O2 loading in the lungs: Produces oxyhemoglobin (ruby red)
o O2 unloading in the tissues: Produces deoxyhemoglobin or reduced hemoglobin (dark red, port wine)
o CO2 loading from the tissues: Produces carbaminohemoglobin (carries only 20% of CO2 in the blood)
Hematopoiesis/Hemopoiesis:
o Hematopoiesis (or hemopoiesis) is blood cell formation of RBCs, leukocytes, thrombocytes (*called the formed elements)
o Before birth: this occurs in the yolk sac, liver, spleen, thymus, lymph nodes
o After birth: red bone marrow = sternum, ribs, clavicle, scapula, illium of os coxae, vertebrae, and proximal epiphyses of humerus and femur.
o Hemocytoblasts are hematopoietic which are stem cells which are in the red bone marrow
o Gives rise to all “formed elements” = erythrocytes, leukocytes (WBCs), and thrombocytes (platelets)
o Hormones and growth factors interact with the hemocytoblasts (hemocytoblasts have special receptors on their plasma membranes) that cause a specific pathway of blood cell differentiation
o RBC formation is caused by hormone erythropoietin (EPO)
o The formation of new blood cells occur in blood sinusoids (large, wide blood vessels found in bone marrow) and eventually are released into the blood stream.
Erythropoiesis:
o Erythropoiesis = red blood cell production
o A hemocytoblast (or stem cell) differentiates into a proerythroblast (has a nucleus and organelles)
o Proerythroblasts develop into early erythroblasts which produce lots of ribosomes (manufactures protein)
o Hb is synthesized by ribosomes along with the insertion of iron—–the new cell type that is formed is called a late erythroblast
o Late erythroblast becomes a normoblast
o Normoblasts ejects the nucleus and organelles to form reticulocytes (ribosomes is still present to manufacture lots of Hb)
o Reticulocytes then become a biconcave cell
o Reticulocytes then become mature erythrocytes after ribosomes are completely broken down and removed
o Reticulocytes make up 1-2% of all erythrocytes: Recticulocyte Count (retic count)= a blood test that measures how fast reticulocytes are being made by the bone marrow. (usually 1-2 days)
o For Example: a higher reticulocyte count might be indicative of anemia (not enough RBCs) and used as a quick way to check if the anemia is being resolved.
Regulation of Erythropoiesis:
o Too few RBCs leads to tissue hypoxia
o Too many RBCs increases blood viscosity
o Balance between RBC production and destruction depends on:
o Hormonal controls
o Adequate supplies of iron, amino acids, and B-12
Hormonal Control of Erythropoiesis:
o Erythropoietin (EPO) = Hormone responsible for stimulus for erythropoiesis (RBC formation) à Produced and released by the kidneys (renal cortex) in response to hypoxia o HIF (hypoxic-inducible factor) = it accumulates in kidney cells when oxygen levels have decreased which triggers production and release of EPO in the kidneys o Effects of Erythropoietin =More rapid maturation of committed bone marrow cells through hematopoiesis. Increased circulating reticulocyte count in 1–2 days o Testosterone: also enhances EPO production, resulting in higher RBC counts in males
Causes of Hypoxia:
o Hemorrhage or increased RBC destruction reduces RBC numbers
o Insufficient hemoglobin (e.g., iron deficiency)
o Reduced availability of O2 (e.g., high altitudes) = altitude sickness (above 8,000 ft.)
Homeostasis of Normal Blood Oxygen Levels:
o 1) Hypoxia occurs: Low blood oxygen carrying ability due to: decreased RBC count, decreased amount of hemoglobin, or decreased availability of O2.
o 2) Kidney (and liver to a smaller extent): release erythropoietin.
o 3) Erythropoietin stimulates red bone marrow.
o 4) Enhanced erythropoiesis increases RBC count.
o 5) O2 carrying ability of blood increases.
Dietary Requirements for Erythropoiesis:
o Nutrients—amino acids, lipids, vitamins, and carbohydrates
o Iron: Stored in Hemoglobin (= 65%), the rest in the liver, spleen, and bone marrow
o Since free iron is toxic, it is stored in cells as ferritin and hemosiderin (proteins that hold and store iron in cells)
o In blood it is transported loosely bound to the protein transferrin to developing erythrocytes for Hb formation
o Vitamin B12 and folic acid (B9)—necessary for DNA synthesis for cell division of the hematocytoblasts (2 million erythocytes per second are made)!
Fate and Destruction of Erythrocytes:
o Life span: 100–120 days
o Old RBCs become fragile, and Hb begins to degenerate
o Loose flexibility, and get stuck in the spleen where macrophages engulf dying RBCs (breakdown also occurs in liver and bone marrow)
o Old and damaged RBCs are broken down by macrophages of the spleen, liver, bone marrow
o Hemoglobin is broken down = Heme + Globin (catabolism)
o Iron is salvaged, stored for reuse as ferritin and hemosiderin (mostly stored within cells of liver….but also spleen and bone marrow )
o Iron is released into blood attached to transferin
o The remaining Heme is degraded to a yellow pigment called bilirubin which binds to albumin and transported to the liver via the blood from the spleen and bone marrow
o Bilirubin is excreted in bile by the liver and stored in the gall bladder bile is then secreted into the small intestine
o Degraded pigment leaves the body in feces as stercobilin (produced by intestinal bacteria)
o Globin is broken down into amino acids (catabolism).
Anemia:
o Blood has abnormally low O2 carrying capacity.
o A sign or condition rather than a disease itself.
o Low blood O2 levels cannot support normal metabolism.
o Accompanied by fatigue, paleness, shortness of breath, and chills.
Causes and Types of Anemia:
o 1) Insufficient numbers of erythrocytes caused by:
o Hemorrhagic anemia: acute blood loss(trauma) or chronic loss of blood (ulcers)
o Hemolytic anemia: RBCs rupture prematurely(caused by faulty hemoblobin, mismatched blood, bacteria, parasites)
o Aplastic anemia: destruction or inhibition of red bone marrow (due to chemo, radiation, viruses): stem cell transplanting.
o 2) Low hemoglobin content in RBCs caused by:
o Iron-deficiency anemia = most common
o Secondary result of hemorrhagic anemia or Inadequate intake of iron-containing foods or impaired iron absorption
o Erythrocytes with low Hb due to iron-deficiency are called microcytes.
o 3) Abnormal Hemoglobin:
o Thalassemias (of mediterranean ancestry)
o Absent or faulty in alpha or beta globin chain in hemoglobin
o RBCs are become thin, delicate, and deficient in hemoglobin
o If severe, blood transfusions indicated
Pernicious Anemia:
o Deficiency of vitamin B12 prevents the proper formation of RBCs (RBCs become large, pale and called macrocytes)
o There is a lack of intrinsic factor in stomach mucosa needed for small intestine absorption of B12
o Autoimmune destruction of “parietal cells” in stomach lining (which produce intrinsic factor)
o Chronic gastritis seen in elderly people which atrophies stomach lining & destroys parietal cells
o Treated by intramuscular injection of B12 or application of Nascobal (nasal lining gel)
Sickle-Cell Anemia:
o Results from a change of a single amino acid in the beta-globin molecule which causes abnormal hemoglobin (HbS = sickle hemoglobin): globin beta chains links together in low 02 conditions.
o Causes RBCs to become sickle or crescent shaped in low-oxygen, infection, dehydration situations & stick to capillary walls.
o RBCs rupture easily, blood capillaries blocked, oxygen transport compromised, causing stroke/massive infection.
o Sickle Cell Trait = one defective gene (heterozygous), resistant to malaria (plasmodium parasite from saliva of mosquitoes)
o Sickle Cell Anemia = two defective genes (homozygous)
Definition and Types of Polycythemia:
o Excess RBCs that increase blood viscosity (Hct generally >55%). Can result in increased viscosity, increased BP, stroke, embolism, heart failure
o Types:
o Polycythemia vera = bone marrow cancer
o Secondary polycythemia—when less O2 is available (high altitude) or when EPO production increases. Athletes train at a higher elevation to increase RBCs
o Blood doping = athletes own RBCs are harvested and re-introduced just before endurance competition = form of secondary polycythemia
Leukocytes (White Blood Cells):
o Make up less than 1% of total blood volume.
o Can leave capillaries via “diapedesis” unlike RBCs (circulatory system is the “subway” system to for WBCs to get to areas for inflammatory or immune responses)
o Move through tissue spaces by ameboid motion and positive chemotaxis (follows chemicals released by damaged tissue = “bloodhounds”)
o Leukocytosis = excessive numbers of WBCs = Body speeds up production of WBC count for infection = over 11,000 WBCs/uL (norm is 5,000-10,000)
o Leukopenia = insufficient numbers of WBCs
