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Circulation I

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Biological Sciences
BISC 101
Derek Bingham

Week 9 – Circulation I 1 Cardiovascular System vs. Lymphatic System Cardiovascular system  Heart (muscular pump made of atria and ventricles)  Closed system of blood vessels that circulate blood – arteries, veins, and capillaries Lymphatic system  Another series of vessels that plays a role in the body to return tissue fluid to circulation Components of the Cardiovascular System Blood enters the atria of the heart via veins. It is then pumped into the ventricles. The ventricles then pump the blood into arteries which go to the lungs and body. Arteries going to the lungs and body gradually branch into smaller arterioles, then into capillaries, and back into venules. Venules become veins and the body is returned to the heart for the cycle to begin again.  Blood – colloidal fluid that circulates throughout the cardiovascular system  Artery – a vessel carrying blood away from the heart to the lungs and all other body systems; thick and elastic muscular wall  Vein – a vessel carrying blood back to the heart from the lungs and all body regions; thinner muscular and elastic layers compared to arteries  Capillaries – networks of small vessels that intermingle with tissues of the body to allow delivery of nutrients and removal of wastes; intermediate vessel that joins arterioles (small arteries) to venules (small veins).  Atria – two small upper chambers of the heart; receives blood from veins and pumps it into ventricles  Ventricles – two lower larger chambers of the heart; when blood is received from the atria, the ventricles pump it into arteries for distribution to the lungs or rest of the body General Nature and Function of Blood Blood – a connective tissue containing cells and cell fragments in a liquid matrix; 7-8% of body weight, ~6 litres Functions 1. Transport of gases, nutrients, processed molecules (e.g., vitamin D), hormones, and waste materials 2. Regulation of pH, temperature, and osmosis (i.e., fluid and ion balance) 3. Protection. Blood clots to prevent excessive loss; contains WBC’s and defensive proteins (e.g., antibodies) Week 9 – Circulation I 2 Three Components of Blood Cells Red blood cells  Erythrocytes  ~5 million per µL White blood cells  Leukocytes  ~8000 per µL  Many types of WBC’s with varying functions (such as neutrophils, lymphocytes, monocytes, eosinophils, and basophils) Plasma  The acellular fluid component of blood  Pale yellow colloidal fluid Functions 1. Carry cells of blood in circulation 2. Transport nutrients to tissues and carry away waste materials 3. Maintain acid-base balance of blood 4. Effect intercellular communication through transport of hormones 5. Defense functions through clotting and transport of antibodies Platelets  Thrombocytes  Disc-shaped membrane-bound fragments  Derived from megakaryocytes (large resident bone marrow cells)  Contains no hemoglobin and no nuclei  Smallest formed element in blood  Essential role in blood clotting Component Importance Red blood cells Transport gases essential for normal metabolism Most of the oxy
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