Summary BIO 205 Chapter 19 Lecture Notes

CHAPTER 19

LECTURE OUTLINE

I. FUNCTION AND PROPERTIES OF BLOOD
A. Blood inside blood vessels, interstitial fluid around body cells, and lymph inside lymph
vessels constitute one’s internal environment.
B. To obtain nutrients and remove wastes, cells must be serviced by blood and interstitial fluid.
1. Blood, a connective tissue, is composed of plasma and formed elements.
2. Interstitial fluid bathes body cells.
C. The branch of science concerned with the study of blood, blood-forming tissues, and the
disorders associated with them is called hematology.


II. FUNCTIONS OF BLOOD
A. Blood transports oxygen, carbon dioxide, nutrients, heat, wastes, and hormones.
B. It helps regulate pH, body temperature, and water content of cells.
C. It prevents blood loss through clotting and combats toxins and microbes through certain
phagocytic white blood cells or specialized plasma proteins.


III. PHYSICAL CHARACTERISTICS OF BLOOD
A. Blood has a viscosity greater than that of water, a temperature of 38°C (100.4°), and a pH of
7.35 to 7.45.
B. Blood constitutes about 8% of body weight; volume ranges from 4 to 6 liters.
C. Blood samples for laboratory testing may be obtained by venipuncture, finger-stick, or
arterial stick (Clinical Connection).


IV. COMPONENTS OF BLOOD
A. Blood consists of 55% plasma and 45% formed elements (Figure 19.1a).
B. Blood plasma consists of 91.5% water and 8.5% solutes.
1. Principal solutes include proteins (albumins, globulins, fibrinogen), nutrients,
enzymes, hormones, respiratory gases, electrolytes, and waste products.
2. Table 19.1 summarizes the chemical composition of plasma.
C. Formed Elements
1. The formed elements in blood include erythrocytes (red blood cells or RBCs),
leukocytes (white blood cells or WBCs), and thrombocytes (platelets) (Figure 19.2).

, 2. The percentage of total blood volume occupied by red blood cells is called the
hematocrit. A hematocrit measures the percentage of red blood cells in whole blood.
a. A significant drop in hematocrit indicates anemia, due to a lower than normal
number of RBCs.
b. In polycythemia, the percentage of RBC is abnormally high with a higher
than normal hematocrit.


V. FORMATION OF BLOOD CELLS
A. Blood cells are formed from pluripotent hematopoietic stem cells (Figure 19.3).
1. Originating from the pluripotent stem cells are the myeloid stem cells and lymphoid
stem cells.
a. Myeloid stem cells give rise to RBCs, platelets, and all WBCs except for
lymphocytes.
b. Lymphoid stem cells give rise to lymphocytes.
2. Myeloid stem cells differentiate into progenitor cells or precursor cells (blast cells)
which will develop into the actual formed elements of blood.
3. Lymphoid stem cells differentiate into pre-B and prothymocytes which develop into
B-lymphocytes and T-lymphocytes, respectively.
B. This process of hemopoiesis (or hematopoiesis) is stimulated by several hematopoietic
growth factors. These hematopoietic growth factors stimulate differentiation and proliferation
of the various blood cells.
1. Erythropoietin increases the number of RBC precursors.
2. Thrombopoietin increases the number of platelet precursors.
3. Cytokins (colony-stimulating factors and interleukins) increase the number of WBC
precursors.
C. Bone marrow examination is a way to diagnose blood diseases. (Clinical Connection)
D. Growth factors, available through recombinant DNA technology, hold great potential for use
in patients who cannot normally form the blood cells. (Clinical Connection)


VI. RED BLOOD CELLS
A. Red blood cells or erythrocytes (RBCs) contain the oxygen-carrying protein hemoglobin and
number about 5.4 million cells/microliter of blood.
B. RBCs anatomy
1. Biconcave discs without nuclei that contain hemoglobin (Figure 19.4a)