1. Chapter 17: Blood

2. COMPOSITION OF BLOOD Blood (Figure 17-1) Blood volume
Composed of plasma and formed elements
Complex transport medium that performs vital pickup and delivery services for the body
Keystone of body’s heat-regulating mechanism
Blood volume
Young adult male has approximately 5 L of blood
Blood volume varies according to age, body type, sex, and method of measurement

5. FORMED ELEMENTS OF BLOOD
Red blood cells (RBCs), also called erythrocytes
Description of mature RBCs (Figure 17-4)
Have no nucleus and shaped like tiny biconcave disks
Do not contain ribosomes, mitochondria, or other organelles typical of most body cells
Primary component is hemoglobin
Most numerous of the formed elements
Function of RBCs
Critical role in the transport of oxygen and carbon dioxide depends on hemoglobin

6. FORMED ELEMENTS OF BLOOD (cont.)
Hemoglobin (Figure 17-5)
Within each RBC are approximately 200 to 300 million molecules of hemoglobin
Hemoglobin is composed of four globin chains, each attached to a heme group
Hemoglobin is able to unite with four oxygen molecules to form oxyhemoglobin to allow RBCs to transport oxygen where it is needed
Males have a greater amount of hemoglobin than females
Anemia: a decrease in number or volume of functional RBCs in a given unit of whole blood

7. FORMED ELEMENTS OF BLOOD (cont.)
Formation of RBCs (Figures 17-6 and 17-7)
Erythropoiesis: entire process of RBC formation
Formation begins in the red bone marrow as hematopoietic stem cells and goes through several stages of development to become erythrocytes; entire maturation process requires approximately 4 days

8. FORMED ELEMENTS OF BLOOD (cont.)
Destruction of RBCs (Figure 17-8)
Life span of a circulating RBC averages 105 to 120 days
Macrophage cells phagocytose the aged, abnormal, or fragmented RBCs
Hemoglobin is broken down and amino acids, iron, and bilirubin are released

9. FORMED ELEMENTS OF BLOOD (cont.)
White blood cells (WBCs), also called leukocytes (Table 17-1)
Granulocytes
Neutrophils: approximately 65% of total WBC count in a normal blood sample; highly mobile and active phagocytic cells
Eosinophils: 2% to 5% of circulating WBCs; numerous in lining of respiratory and digestive tracts; weak phagocytes; provide protection against infections caused by parasitic worms and allergic reactions (Figure 17-10)
Basophils: only 0.5% to 1% of circulating WBCs; motile and capable of diapedesis; cytoplasmic granules contain histamine and heparin (Figure 17-11)

10. FORMED ELEMENTS OF BLOOD (cont.)
Agranulocytes (Figures and 17-13)
Lymphocytes: smallest of the WBCs;
second most numerous WBC;
account for approximately 25% of circulating WBCs;
T lymphocytes and B lymphocytes have an important role in immunity:
T lymphocytes directly attack an infected or cancerous cell, and
B lymphocytes produce antibodies against specific antigens

11. FORMED ELEMENTS OF BLOOD (cont.)
Monocytes: largest leukocytes; mobile and highly phagocytic cells
WBC numbers: 1 mm3 of normal blood usually contains 5000 to 9000 leukocytes, with different percentages for each type;
WBC numbers have clinical significance because they change with certain abnormal conditions (Figure 17-14)

12. FORMED ELEMENTS OF BLOOD (cont.)
Platelets (Figure 17-12)
Structure
In circulating blood, platelets are small, pale bodies that appear as irregular spindles or oval disks
Functions of platelets
Important role in hemostasis and blood coagulation; secondary role in defending against bacterial attacks
Hemostasis: refers to stoppage of blood flow; however, if injury is extensive, the blood-clotting mechanism is activated to assist

13. BLOOD TYPES: BLOOD GROUPS
The ABO system (Figures to 17-18)
Every person’s blood belongs to one of four ABO blood groups
Named for antigens on RBC membranes
Type A: antigen A on RBCs
Type B: antigen B on RBCs
Type AB: both antigens A and B on RBCs; known as universal recipient
Type O: neither antigen A nor B on RBCs; known as universal donor

17. BLOOD TYPES: BLOOD GROUPS (cont.)
The Rh system (Figure 17-19)
Rh-positive: Rh antigen is present on the RBCs
Rh-negative: RBCs have no Rh antigen present
Anti-Rh antibodies are not normally present in blood; anti-Rh antibodies can appear in Rh-negative blood if it has come in contact with Rh-positive RBCs

19. BLOOD PLASMA Plasma: liquid part of blood; clear, straw-colored fluid;
composed of 90% water and 10% solutes (Figure 17-20)
Solutes: 6% to 8% of plasma solutes are proteins, consisting of three main compounds
Albumins: help maintain osmotic balance of the blood
Globulins: essential component of the immunity mechanism
Fibrinogen: key role in blood clotting
Plasma proteins have an essential role in maintaining normal blood circulation

21. BLOOD CLOTTING: COAGULATION
Mechanism of blood clotting: goal of coagulation is to stop bleeding and prevent loss of vital body fluid in a swift and sure method (Figure 17-21)
Conditions that oppose clotting
Clot formation in intact vessels is opposed
Several factors oppose clotting
Perfectly smooth surface of the normal endothelial lining of blood vessels does not allow platelets to adhere

22. BLOOD CLOTTING: COAGULATION (cont.)
Conditions that hasten clotting
Rough spot in the endothelium
Abnormally slow blood flow
Clot dissolution (Figure 17-23)
Fibrinolysis: physiological mechanism that dissolves
Fibrinolysin: enzyme in the blood that catalyzes the hydrolysis of fibrin, causing it to dissolve
Additional factors are presumed to aid clot dissolution (e.g., substances that activate profibrinolysin)

24. THE BIG PICTURE: BLOOD AND THE WHOLE BODY
Blood plasma transports substances, including heat, around the body, linking all body tissues together
Substances can be transported between almost any two points in the body
Blood tissue contains formed elements—blood cells and platelets
RBCs assist in the transport of oxygen and carbon dioxide
WBCs assist in the defense mechanisms of the whole body
Platelets prevent loss of the fluid that constitutes the internal environment
No organ or system of the body can maintain proper levels of nutrients, gases, or water without direct or indirect help from blood
Other systems assist the blood
Blood is useless unless it continues to transport, defend, and maintain balance