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Chapter 7: Circulation and Blood The Importance of the Circulatory System The circulatory system carries: nutrients and oxygen to cells waste away from the cell chemical messages fro cells in one part of the body to distant target tissues distributes heat through the body along with kidneys, maintains acceptable levels of body fluid helps defend against invading organisms permits the transport of immune cells throughout the body transports waste The Circulatory system consists of: The heart The blood vessels: arteries, veins, and capillaries Blood: red, white, and platelets There are two types of circulatory systems: 1. Open Circulatory system 2. Closed Circulatory System The Open Circulatory System (p. 243) Found in snails, insects, and crustaceans There is no distinction between the blood and the interstitial fluid system Blood carrying oxygen and nutrients is pumped into body cavities where it bathes the cells directly. The Closed Circulatory System Found in earthworms, squids, octopuses, and vertebrates. The blood is contained within blood vessels Components of Blood 45% of blood is composed of blood cells 55% of blood is composed plasma, which is the fluid part. 90% of the plasma is water The plasma contains: proteins, glucose, vitamins, minerals, dissolved gases, and waste products. The large plasma proteins help maintain homeostasis and these are: 1. Albumins: maintain body fluid levels by regulating osmotic balance 2. Globulins: provide protection against invading microbes 3. Fibrinogens: important in blood clotting Components of Blood The red, the white, the platelets are produced by stem cells found in the bone marrow. 60% of the stem cells become red blood cells, 30% become white blood cells, 5% become platelets, and the rest 5% are indiscernible. 1. Red Blood Cells or Erythrocytes The primary function of red blood cells id to transport oxygen The red blood cells carry oxygen with the help of an iron containing protein called hemoglobin. The presence of hemoglobin increases the ability of blood to carry oxygen by a facto of 70. An estimated 280 million hemoglobin molecules are found in a single red blood cell. Four iron atoms attach to the folded protein structure and bind with oxygen molecules. The oxyhemoglobin gives blood its red color. The deoxhemoglobin makes blood appear blue because of the change in shape of the hemoglobin. Red blood cells live only about 120 days At least 5 million red blood cells are produced every minute. Red blood cells lose their nucleus as they enter the blood stream. Enucleation helps red blood cells accommodate as many hemoglobins as they can so that they transport oxygen more efficiently. 2. White Blood Cells or Leukocytes There is one white blood cell for every 700 red blood cells. Their main functions are defending against foreign invaders, cleaning up dead cells, and foreign matter at injury cites. All white blood cells are colourless and are larger than red blood cells. All white blood cells have district nuclei. There are 5 different types of white blood cells: 1. Neutrophil: when pneumonia is present their count increases by 25% 2. Eosinophil: play major role in allergic reactions 3. Basophil: their numbers increase when Leukemia is present 4. Monocyte: when tuberculosis is present their count increases by 500%. 5. Lymphocytes (T and B cells): produce custom made antibodies to destroy foreign substances such as protein coats of viruses. 3. Platelets Platelets are small fragments of larger cells found in bone marrow. Platelets do not contain nucleus. There is 1 platelet for every 20 red blood cells Platelets initiate blood clotting The rupturing of platelets membranes during an injury releases a substance that reacts with the plasma proteins such as fibrinogen to form a mesh of fibers.