Adv. Anatomy & Physiology | Blood

Functions of blood

• Primary transportation fluid in the body (hormones, gases, wastes)

• Regulates pH, temp, fluid volume

• Provides protection from infection and blood loss

Composition of blood

• Made up of a liquid with cells and cell fragments in it

  • Liquid = plasma

  • Cell fragments = formed elements

• Average volume is 5-6 L (1.5 gallons) for males, slightly less for females

• Color varies from scarlet (oxygen rich) to dark red (oxygen poor)

Plasma

* Made up of water with many dissolved substances
* Hormones are transported in the plasma
* Food and salts are dissolved
* Wastes are also dissolved in the blood

Formed Elements

• Red Blood Cells (RBC) & White Blood Cells (WBC)

• Platelets

Red Blood Cells (Erythrocytes)

• Function: Transport oxygen and carbon dioxide

• Live about 120 days

• Each hemoglobin molecule in red blood cells contains four heme pigments, each of which contain iron which bind to oxygen molecules

Anemia

• Inability of the blood to carry sufficient oxygen

• Causes a feeling of tiredness along with other symptoms including decreased cellular function

• Caused by many conditions:

  • Low RBC count

  • Lack of hemoglobin

  • Genetic mutation

  • Iron deficiency

White Blood Cells (Leukocytes)

• Function: Defend and attack!

• They make up approximately 1% of blood

• Live about 3 to 4 days

WBC: Lymphocyte

• Function: Antibody production and cellular immune response in response to microbes

• T-cells

• Agranular

• 20-25%

WBC: Monocytes

• Function: Immune defense through phagocytosis (cell eating)

• Agranular

• 3-8%

WBC: Basophils

• Function: Inflammatory Response

• Granular

• .5-1%

WBC: Neutrophils

• Function: Immune defense through phagocytosis

• Granular

• 60-70%

WBC: Eosinophils

• Function: Defense against parasites

• Granular

• 2-4%

Platelets

• Function: Clot blood to stop bleeding

• Last only 4 days

Hemostasis

• Prevention of blood loss

• 3 major phases to hemostasis

  • Vascular spasms

  • Coagulation

  • Clot retraction and repair

Vascular Spasms

* Vessels constrict to slow blood and platelets in the presence of damaged vessels start to stick together forming a platelet plug

Coagulation

• During this phase, blood is transformed from a liquid to a gel.

• Clotting factors (proteins and enzymes that enhance clot formation) join molecules called fibrinogen together forming a fibrin mesh which traps more platelets and RBCs which effectively seals the hole in the vessel.

Clot Retraction

• Platelets in the clot contract, pulling the edges of the tear closer together.

• Cells in the vessel are stimulated and multiply and restore the vessel wall.

Blood types

• Most common is O-positive (38%) and A-positive (34%)

• Least common is AB-negative (1%)

• Universal donor is O-negative

• Universal recipient is AB-positive

• People over age 69 receive half of all transfusions of whole blood