McKinley_A&P_4e_Chap018_PPT_Accessible

Functions of Blood

• Blood: a connective tissue that:

  • Moves gases, nutrients, wastes, and hormones.

  • Is circulated by the heart through the cardiovascular system.

  • Composed of formed elements (erythrocytes, leukocytes, platelets) and plasma.

Components of Blood

• Formed Elements:

  • Erythrocytes: transport respiratory gases.

  • Leukocytes: defend against pathogens.

  • Platelets: aid in blood clotting.

• Plasma: the fluid portion of blood containing proteins and solutes.

Functions of Blood

• Transportation:

  • Transports formed elements, molecules, and ions.

  • Carries oxygen and carbon dioxide, nutrients, hormones, heat, and waste.

• Protection:

  • Leukocytes and plasma proteins protect against pathogens.

  • Platelets prevent blood loss through clot formation.

• Regulation:

  • Maintains body temperature, pH, and fluid balance.

Physical Characteristics of Blood

• Color: depends on oxygenation (bright red = oxygen-rich, dark red = oxygen-poor).

• Volume: average adult has 4 to 6 liters.

• Viscosity: 4-5 times thicker than water.

• pH: slightly alkaline (7.35-7.45).

Plasma Composition

• Components:

  • Water (92%), Plasma proteins (7%), Solutes (1%).

• Plasma proteins: include albumins, globulins, and fibrinogen, which help maintain osmotic pressure and prevent fluid loss.

Hematopoiesis

• Definition: production of blood formed elements in red bone marrow.

• Stem cells: Hemocytoblasts, can differentiate into myeloid and lymphoid lines.

• Erythropoiesis: process of red blood cell production requiring iron and vitamins.

• Leukopoiesis: process of white blood cell production.

• Thrombopoiesis: process of platelet production from megakaryocytes.

Erythrocytes

• Structure: small, flexible, biconcave, lack nucleus, rich in hemoglobin.

• Hemoglobin: binds oxygen and carbon dioxide, consisting of globins with heme groups.

Blood Types

• ABO System: determined by presence of A/B antigens.

  • Type A: A antigen, anti-B antibodies.

  • Type B: B antigen, anti-A antibodies.

  • Type AB: both antigens, no antibodies.

  • Type O: no antigens, both antibodies.

• Rh Factor: determines positive/negative blood type.

  • Rh- individuals develop antibodies when exposed to Rh+ blood.

Clinical Considerations

• Anemia: reduced erythrocyte count or function, causing symptoms such as lethargy.

• Leukemia: malignancy in leukocyte-forming cells, leading to abnormal leukocyte proliferation.

• Hemostasis: mechanism to stop bleeding, involving vascular spasms, platelet plug formation, and coagulation cascade.