Anatomy and Physiology 'Blood'

Composition of Blood:

• Blood makes up  ~8% of total body weight

• ~55% plasma

• ~45% formed elements

• 4 to 5 liters for average females

• 5 to 6 liters for average males

(the higher percent body fat the less blood you have per kilogram of weight

Plasma:

• 90% water

• 10% solutes (salts and minerals)

Formed Elements:

• Red Blood Cells; RBCs; erythrocytes

• White Blood Cells; WBCs; leukocytes

• Platelets; thrombocytes

(RBCs make up about 45% of blood volume, WBCs and platelets make up about 1%

Red Blood Cells (erythrocytes):

• Mature cells lack a nucleus and most organelles

• Hemoglobin, red pigment, makes up ⅓ of cell volume

• RBCs are highly flexible because of spectrin protein

• Flexibility can determine the speed of blood flow

• Men have more RBCs because of the influence of testosterone

Hematocrit tubes:

Hematocrit tubes show normal, anemic, and polycythemia

Function of RBCs:

• Hemoglobin and carbonic anhydrase both work to transport O2 and CO2

• Total surface area of all of an adult’s RBCs is about as big as a football field

Hemoglobin:

• Made up of 4 protein chains called globins

• Each chain is bound to a heme group which contains one Fe

• The iron can bind to one O2

• Each globin can bind to one CO2

Formation of RBCs:

• Erythropoiesis begins with hematopoietic stem cells in red bone marrow

• New red blood cells take 4 days to mature

• Sickle cell anemia- inherited defect, causes a defective hemaglobin. Cells become sickle shaped and can clog blood vessels

• Decreased levels of oxygen stimulate the production of RBCs by secreting erythropoietin (EPO) from the kidneys

Destruction of RBCs:

• ~200 million RBCs are formed each day to replace the equal amount destroyed

• Lifespan of RBCs is 105-120 days 

• Lining of blood vessels in liver and spleen destroy damaged or fragmented RBCs

• Components of the cells are broken and reused to make more RBCs

• Bone marrow must have a constant supply of iron, B12, and amino acids to make new RBCs

• B12 is called the antianemic principle

White Blood Cells (leukocytes)

• Granulocytes

• Agranulocytes

Granulocytes:

• Neutrophils (multi lobed)

• Make up about 65% of WBC count

• Move from blood vessels into tissues through diapedesis

• Eosinophils (orangish)

• Fight infection caused by parasitic worms and allergic reactions

• Basophils (dark purple)

• Granules contain histamine and heparin (anticoagulant)

Agranulocytes:

• Lymphocytes (eyes)

• Destroy infected or cancerous cells

• Create antibodies

• Monocytes (mongo kidney shaped lobe)

• Largest of the leukocytes

• Ingest infected cells

White blood cells numbers:

• Differential white blood cell count can indicate different types of infections

• Certain drugs can cause leukopenia (low WBC count)

Platelets:

• Are small cells with special characteristics- agglutination, adhesiveness, and aggregation

• Once they leave the blood vessels they become misshapen and clump together

Platelet Action:

• Platelets have two roles, hemostasis (blood flow stoppage) and coagulation (blood clotting)

• Hemostatic action will occur when a platelet encounters a tear in a capillary. It will form a platelet plug to stop blood from flowing into the tissue.

• Coagulation occurs when sticky platelets release chemicals to cause the blood to clot

• Platelets have a lifespan of ~7 days

Blood Clotting:

• Clotting factors in the blood, in blood cells, and in tissues combine in a metabolic cascade when damage to cells or tissues occurs

• Factors in the blood are called intrinsic

• Factors in tissues are called extrinsic

• Prothrombin -> thrombin -> fibrinogen -> fibrin -> clot

• As platelets bind to injury site they releASe chemicals that trigger the clotting process

• Fibrin forms at site of injury and entangle RBCs

• Calcium in the blood and vitamin K are an important cofactors in coagulation

• Arteriosclerosis can increase clotting because platelets stick to rough patches

• Applying a rough surface such as gauze, heat or pressure as well as direct application of clotting agents can speed up clotting

Clot Dissolving:

• After a while, the clot must dissolve

• Fibrinolysis

• Heparin is major anticoagulant produced in by the liver

Blood Disorders:

• Anemia inability of blood transport O2

• Aplastic anemia caused by destruction of bone marrow, drugs, radiation, or idiopathic

• Pernicious anemia results from lack of vitamin B12

• Folate deficiency anemia results from lack of folic acid, common in alcoholics

• Acute blood loss anemia occurs after serious injury

• Clotting disorders

• Thrombus is a localized blood clot, thrombosis

• Embolus is when a clot circulates in blood stream, embolism

• Hemophilia is an inherited (sex linked) disorder where the blood has difficulty clotting. No factor VIII

• Thrombocytopenia is bleeding that occurs throughout the body because of low platelets usually caused by destruction of bone marrow

Blood Types:

• Blood type is determined by the type of antigens found on the outside of RBCs

• Blood plasma will then contain antigens only for the type not found on the person’s RBCs

Agglutination:

Agglutination will only occur when antibodies encounter foreign antigens