blood summary document | Study notes Anatomy

Chapter 14 Blood Summary

14.1 Characteristics of Blood

Blood is a type of connective tissue in which cells are suspended in a liquid extracellular matrix, called plasma.

Red blood cells, white blood cells, and platelets are formed elements. Blood is more viscous than water and

has a slightly alkaline pH. Blood volume varies with body size, percent adipose tissue, and fluid and electrolyte

balance. Whole blood can be separated into formed elements (mostly red blood cells) and plasma. The percent

of red blood cells is called the hematocrit.

14.2 Formed Elements

1. The origin of formed elements

a. Blood cells develop from hematopoietic stem cells, or hemocytoblasts, in red bone marrow.

b. Blood cells descended from stem cells respond to hematopoietic growth factors to specialize.

2. Red blood cells

a. Red blood cells are biconcave discs with shapes that provide increased surface area and place their

cell membranes close to oxygen-carrying hemoglobin.

b. Red blood cells contain hemoglobin, which combines loosely with oxygen.

c. The mature form lacks nuclei and mitochondria, but contains enzymes needed for glycolysis.

3. Red blood cell counts

a. The red blood cell count equals the number of cells per microliter (µL) of blood.

b. The average count may range from approximately 4,000,000 to 6,000,000 cells per microliter.

c. Red blood cell count determines the oxygen-carrying capacity of the blood and is used in diagnosing

and evaluating the courses of certain diseases.

4. Erythropoiesis (Red blood cell production) and control of erythropoiesis

a. During fetal development, red blood cells form in the yolk sac, liver, and spleen; after birth, red

blood cells are produced by the red bone marrow.

b. In a person in good health, the number of red blood cells remains relatively stable.

c. A negative feedback mechanism involving erythropoietin from the kidneys and liver controls rate

of red blood cell production.

1) Erythropoietin is released in response to low oxygen levels.

2) High altitude, loss of blood, extreme exercise, or chronic lung disease can lower oxygen

concentration in the blood.

5. Dietary factors affecting red blood cell production

a. The availability of vitamin B12, iron, and folic acid affects red blood cell production.

b. The rate of iron absorption, needed for hemoglobin synthesis, varies with the amount of iron in the

body.

6. Death and destruction of red blood cells

a. Red blood cells are fragile and are damaged while moving through capillaries.

b. Macrophages in the spleen and liver phagocytize damaged red blood cells.

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Chapter 14 Blood Summary 14.1 Characteristics of Blood Blood is a type of connective tissue in which cells are suspended in a liquid extracellular matrix, called plasma. Red blood cells, white blood cells, and platelets are formed elements. Blood is more viscous than water and has a slightly alkaline pH. Blood volume varies with body size, percent adipose tissue, and fluid and electrolyte balance. Whole blood can be separated into formed elements (mostly red blood cells) and plasma. The percent of red blood cells is called the hematocrit. 14.2 Formed Elements

The origin of formed elements a. Blood cells develop from hematopoietic stem cells , or hemocytoblasts , in red bone marrow. b. Blood cells descended from stem cells respond to hematopoietic growth factors to specialize.
Red blood cells a. Red blood cells are biconcave discs with shapes that provide increased surface area and place their cell membranes close to oxygen-carrying hemoglobin. b. Red blood cells contain hemoglobin, which combines loosely with oxygen. c. The mature form lacks nuclei and mitochondria, but contains enzymes needed for glycolysis.
Red blood cell counts a. The red blood cell count equals the number of cells per microliter (μL) of blood. b. The average count may range from approximately 4,000,000 to 6,000,000 cells per microliter. c. Red blood cell count determines the oxygen-carrying capacity of the blood and is used in diagnosing and evaluating the courses of certain diseases.
Erythropoiesis (Red blood cell production) and control of erythropoiesis a. During fetal development, red blood cells form in the yolk sac, liver, and spleen; after birth, red blood cells are produced by the red bone marrow. b. In a person in good health, the number of red blood cells remains relatively stable. c. A negative feedback mechanism involving erythropoietin from the kidneys and liver controls rate of red blood cell production. 1) Erythropoietin is released in response to low oxygen levels. 2) High altitude, loss of blood, extreme exercise, or chronic lung disease can lower oxygen concentration in the blood.
Dietary factors affecting red blood cell production a. The availability of vitamin B 12 , iron , and folic acid affects red blood cell production. b. The rate of iron absorption, needed for hemoglobin synthesis, varies with the amount of iron in the body.
Death and destruction of red blood cells a. Red blood cells are fragile and are damaged while moving through capillaries. b. Macrophages in the spleen and liver phagocytize damaged red blood cells.

c. Hemoglobin molecules are decomposed, and nearly all the iron from the heme portion is recycled. d. Biliverdin and bilirubin are pigments, released from the heme portion, excreted in bile. e. The globin portion is broken down into amino acids metabolized by macrophages or released into the blood.

White blood cells a. Interleukins and colony-stimulating factors are small proteins (some can have endocrine/hormone- like function) (Zhang, J-M. & An, J., 2009) that stimulate white blood cell production. b. Diapedesis allows while blood cells to leave circulation. c. Leukocytes move by ameboid motion. d. Chemicals released by damaged cells attract ( chemotaxis ) and stimulate leukocytes. e. An accumulation of leukocytes, bacteria, and damaged cells is pus.
Types of white blood cells and their functions a. Granulocytes include neutrophils , eosinophils , and basophils. (NEB or BEN) b. Agranulocytes include monocytes and lymphocytes. c. Neutrophils are most numerous and phagocytize foreign particles, particularly bacteria. d. Eosinophils attack parasitic worms and help control inflammation and allergic reactions. e. Basophils are the least numerous and release biochemicals that dilate local blood vessels and that inhibit blood clotting. f. Monocytes are the largest in size and become highly phagocytic macrophages after leaving circulation. g. Lymphocytes are the second most abundant and are important in immunity.
White blood cell counts a. Normal total white blood cell counts vary from 3,500 to 10,500 cells per microliter of blood. b. The number of white blood cells may change in abnormal conditions such as infections, emotional disturbances, or excessive loss of body fluids. c. Because relative proportions of white blood cells may change in diseases, the differential white blood cell count, which indicates the percentages of various types of leukocytes, is a useful test.
Platelets a. Platelets are fragments of megakaryocytes (stem cell) that enter the circulation. b. Platelets have many roles that include closing breaks and repairing breaks in blood vessels, promoting clot formation, and mediating inflammation. c. The normal count varies from 150,000 to 400,000 platelets per microliter. d. A high platelet count increases risk of blood clots, while a low platelet count increases risk of bleeding. 14.3 Plasma Plasma is the liquid part of the blood that is composed of water and a mixture of organic and inorganic substances. It carries nutrients and gases, helps regulate fluid and electrolyte balance, and helps maintain stable pH.
Plasma proteins

a. Blood coagulation or clotting, the most effective means of hemostasis, is a series of reactions wherein each reaction stimulates the next (cascade), which may be initiated by extrinsic or intrinsic mechanisms. b. The major event of coagulation is the conversion of soluble fibrinogen into insoluble fibrin. c. The extrinsic clotting mechanism (tissue factor pathway) is triggered when blood contacts damaged tissue. d. The intrinsic clotting mechanism (contact activation pathway) is triggered when blood contacts a foreign surface. e. Clot formation reflects balance between clotting factors that promote or inhibit clotting. f. A formed clot retracts and pulls the edges of a broken blood vessel closer together. g. A thrombus is an abnormal blood clot in a blood vessel; an embolus is a clot or fragment of a clot or any particle (fat globule, bone chip, air bubble) that moves in a blood vessel. h. Fibroblasts of connective tissue invade a clot, forming connective tissue throughout. i. Protein-splitting enzymes may eventually destroy a clot, plasmin is one.

Prevention of coagulation a. The smooth inner lining of blood vessels discourages the accumulation of platelets. b. As a clot forms, fibrin adsorbs thrombin and prevents the reaction from spreading. c. Antithrombin interferes with the action of excess thrombin. d. Some cells secrete heparin, an anticoagulant. 14.5 Blood Groups and Transfusions Blood is typed based on the surface structures (proteins or carbohydrates) of its erythrocytes. Blood type compatibility is determined by looking for agglutination (clumping) of cross match blood mixtures under the microscope.
Antigens and antibodies a. An antigen is any molecule that triggers an immune response. b. Antibodies are protein molecules produced by B lymphocytes (B cells) or by plasma cells in an immune response to an encounter with an antigen that is not found on the body’s own cells.
ABO blood group a. Blood can be grouped according to the presence or absence of antigens A and B, which are carbohydrates. b. Wherever antigen A is absent, anti-A antibody is present; wherever antigen B is absent, anti-B antibody is present. c. Preventing the mixing of red blood cells that have an antigen with plasma that contains the corresponding antibody avoids a transfusion reaction. d. Transfusion reactions are adverse reactions are due to agglutination (clumping) of the red blood cells caused by antibodies.
Rh blood group a. Rh antigens (proteins) are present on the red blood cell membranes of Rh-positive blood; they are absent in Rh-negative blood.

b. An individual with Rh-negative blood exposed to Rh-positive blood produces anti-Rh antibodies in response. c. Mixing Rh-positive red cells with plasma that contains anti-Rh antibodies agglutinates the positive cells. d. If a Rh-negative female is pregnant with a Rh-positive fetus, some of the positive cells may enter the maternal blood at the time of birth and stimulate the maternal tissues to produce anti-Rh antibodies. e. Anti-Rh antibodies in maternal blood can cross the placental membrane and react with the erythrocytes of a Rh-positive fetus. Zhang, J-M. & An, J. (2007). Cytokines, Inflammation and Pain. Int Anesthesiol Clin. 45(2), 27-37. doi: 10.1097?AIA.0b013e318034194e

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