Composition of Blood Formed Elements Formed Elements 1. Erythrocytes. 2. Leukocytes. 3. Platelets. Plasma. Plasma.

Plasma Straw-colored liquid. Straw-colored liquid. Consists of H 2 0 and dissolved solutes. Consists of H 2 0 and dissolved solutes. Ions, metabolites, hormones, antibodies. Ions, metabolites, hormones, antibodies. Na + is the major solute of the plasma. Na + is the major solute of the plasma.

Plasma Proteins Constitute 7-9% of plasma. Constitute 7-9% of plasma. Provide the colloid osmotic pressure needed to draw H 2 0 from interstitial fluid to capillaries. Provide the colloid osmotic pressure needed to draw H 2 0 from interstitial fluid to capillaries.  Maintain blood pressure. Albumin: Albumin:  Accounts for 60-80% of plasma proteins.

Plasma Proteins Globulins: Globulins:  globulin:  globulin:  Transport lipids and fat soluble vitamins.  globulin:  globulin:  Transport lipids and fat soluble vitamins.  globulin:  globulin:  Antibodies that function in immunity.

Plasma Proteins Fibrinogen: Fibrinogen:  Constitutes 4% of plasma proteins.  Important clotting factor.  Converted into fibrin during the clotting process.

Formed Elements of Blood Include 2 types of blood cells: Include 2 types of blood cells:  RBCs (red blood cells):  Most numerous of the two.  WBCs (white blood cells). Platelets

Diagram showing formed elements

Erythrocytes(RBC) Flattened biconcave discs. Flattened biconcave discs. Provides increased surface area through which gas can diffuse. Provides increased surface area through which gas can diffuse. Lack nuclei and mitochondria. Lack nuclei and mitochondria. Live for approximately 120 days Live for approximately 120 days Contain 280 million hemoglobin with 4 heme chains (contain iron). Contain 280 million hemoglobin with 4 heme chains (contain iron).

Leukocytes Contain nuclei and mitochondria. Contain nuclei and mitochondria. Move in amoeboid fashion. Move in amoeboid fashion.  Can squeeze through capillary walls (diapedesis). Almost invisible, so named after stains. Almost invisible, so named after stains. Neutrophils are the most abundant WBC. Neutrophils are the most abundant WBC.  Accounts for 50 – 70% of WBCs. Involved in immune function. Involved in immune function.

Platelets Also called thrombocytes. Also called thrombocytes. Smallest of formed elements. Smallest of formed elements.  Are fragments of megakaryocytes.  Lack nuclei. Have amoeboid movement. Have amoeboid movement. Important in blood clotting: Important in blood clotting: Constitute most of the mass of the clot. Constitute most of the mass of the clot.  Release serotonin to reduce blood flow to area. Secrete growth factors Secrete growth factors  Maintain the integrity of blood vessel wall.

Function of Platelets Platelets normally repelled away from endothelial lining by prostacyclin (prostaglandin). Platelets normally repelled away from endothelial lining by prostacyclin (prostaglandin). Do not want to clot normal vessels. Do not want to clot normal vessels.

Circulation of blood The human circulatory system is really a two- part system whose purpose is to bring oxygen- bearing blood to all the tissues of the body. When the heart contracts it pushes the blood out into two major cycle: The human circulatory system is really a two- part system whose purpose is to bring oxygen- bearing blood to all the tissues of the body. When the heart contracts it pushes the blood out into two major cycle: 1.Pulmonary cycle. 1.Pulmonary cycle. 2.Systemic cycle 2.Systemic cycle

Systemic cycle In the systemic loop, the blood circulates into the body’s systems, bringing oxygen to all its organs, structures and tissues and collecting carbon dioxide waste. In the systemic loop, the blood circulates into the body’s systems, bringing oxygen to all its organs, structures and tissues and collecting carbon dioxide waste. The systemic cycle is controlled by the left The systemic cycle is controlled by the left side of the heart side of the heart

The systemic loop begins when the oxygen-rich blood coming from the lungs enters the upper left chamber of the heart, the left atrium The systemic loop begins when the oxygen-rich blood coming from the lungs enters the upper left chamber of the heart, the left atrium As the chamber fills, it presses open the mitral valve and the blood flows down into the left ventricle. As the chamber fills, it presses open the mitral valve and the blood flows down into the left ventricle. When the ventricles contract during a heartbeat, the blood on the left side is forced into the aorta. When the ventricles contract during a heartbeat, the blood on the left side is forced into the aorta.

The blood leaving the aorta brings oxygen to all the body’s cells through the network of ever smaller arteries and capillaries. The blood leaving the aorta brings oxygen to all the body’s cells through the network of ever smaller arteries and capillaries. The used blood from the body returns to the heart through the network of veins. The used blood from the body returns to the heart through the network of veins. All of the blood from the body is eventually collected into the two largest veins: All of the blood from the body is eventually collected into the two largest veins: i) the superior vena cava, which receives blood from the upper body. i) the superior vena cava, which receives blood from the upper body. ii) the inferior vena cava, which receives blood from the lower body region.

Both venae cavae empty the blood into the right atrium of the heart. Both venae cavae empty the blood into the right atrium of the heart. Systemic arteries contains oxygen rich blood and appears bright red. Systemic arteries contains oxygen rich blood and appears bright red. Systemic veins contains oxygen poor blood and appears dark maroon. Systemic veins contains oxygen poor blood and appears dark maroon.

Diagram showing systemic circulation of blood

Pulmonary cycle In the pulmonary loop, the blood circulates to and from the lungs, to release the carbon dioxide and pick up new oxygen. In the pulmonary loop, the blood circulates to and from the lungs, to release the carbon dioxide and pick up new oxygen. The pulmonary cycle is controlled by the right side of the heart. The pulmonary cycle is controlled by the right side of the heart. Blood collected in right atrium passes into right ventricle through the tricuspid valve. When the ventricle contracts, the blood is pushed into the pulmonary arteries. Blood collected in right atrium passes into right ventricle through the tricuspid valve. When the ventricle contracts, the blood is pushed into the pulmonary arteries.

Pulmonary arteries divide into arterioles of the lungs. These arterioles take blood to the pulmonary capillaries where carbon dioxide and oxygen is exchanged. The blood then enters the pulmonary venules and flows through the pulmonary veins back to the left atrium. Pulmonary artries contain oxygen poor blood. Pulmonary veins contain oxygen rich blood.

Diagram showing pulmonary cycle