Blood & Blood Vessels Anatomy & Physiology/Cardiovascular System

Functions of Blood  Blood transports everything that must be carried from one place to another within the body.  For example:  Nutrients  Waste  Body Heat  Oxygen  Carbon Dioxide

Functions of Blood  In order to transport these things, blood flows through a vast and complex system of closed tubes called blood vessels.  Types of blood vessels include:  Arteries- large, thick vessels that carry oxygen and nutrient rich blood from heart/lungs to the body  Veins- large, but thinner vessels that carry oxygen and nutrient depleted blood from the body to the heart/lungs  Capillaries- small, very thin vessels that form woven networks of arterioles and venules (mini arteries and veins) and where a direct exchange occurs between blood and body tissue cells.

Composition of Blood  Blood is unique in that it is the only fluid body tissue.  Blood is a connective tissue composed of solid elements suspended in a fluid called plasma.  About 55% of blood is made up of plasma, with the remaining 45% made up of the solid elements.

Solid Elements of Blood  Erythrocytes- red blood cells that function in oxygen transport and make up the large majority of the solid matter of the blood. The mass of erythrocytes in a blood sample is also referred to as the hemocrit.  Leukocytes- white blood cells that function as part of the body’s defense system.  Platlets- Cell fragments that function in blood clotting.

Plasma  Over 90% of plasma is water.  However, dissolved in the plasma are many important elements being transported by the blood.  When placed in a centrifuge and spun at high speed, plasma rises to the top of any blood sample.

Composition of Erythrocytes  Erythrocytes, also known as red blood cells, are unusual cells because they do not contain a nucleus or mitochondria.  The lack of mitochondria means that they do not require oxygen and therefore do not use up any of the oxygen that they transport throughout the body.  Erythrocytes ultimately are sacs of an oxygen binding protein called hemoglobin.

Hemoglobin  Hemoglobin is an oxygen binding protein.  Hemoglobin contains iron, which is what gives red blood cells their color.  The more hemoglobin molecules a red blood cell contains, the more oxygen the cell is able to carry.  The amount of hemoglobin produced by the body can vary dependent on elevation and physical training.

Composition of Leukocytes  Leukocytes, also known as white blood cells, do contain nuclei and the usual organelles of a cell.  White blood cells have the unique ability to slip in and out of blood cells and in this way can move throughout the body, depending on where they are needed.  When white blood cells are needed to defend against a foreign agent, the body speeds up their production.

Hematopoiesis  Hematopoiesis is the process of blood cell formation, which occurs in red bone marrow.  The rate of red blood cell formation is controlled by a hormone called erythropoietin.  The rate of white blood cell formation is controlled by hormones called colony stimulating factors.  The rate of platelet production is controlled by hormones called interleukins.

Hemostasis  Hemostasis is the process that results in blood clotting when the wall of a blood vessel breaks.  This process involves three main stages: 1.Platelet plug forms: The platelets become sticky and cling to the damaged site. 2.Vascular spasms occur: Platelets release serotonin causing the blood vessel to spasm and narrow. 3.Coagulation events occur: After time, the clot retracts from the damaged site and releases serum which pulls together the ruptured ends of the blood vessel.

Hemostasis Video  htm