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BIOL 301
Vivian Dayeh

CHAPTER 19 – THE HEART THE CIRCULATORY SYSTEM − Circulatory system is made up of: o Cardiovascular system (double circuit  pulmonary and systemic)  Heart (pump that contracts)  Blood vessels (vasculature)  Blood (fluid) o Lymphatic system  Vessels  Lymphatic fluid (extracellular fluid/plasma) − Cardiovascular system o Because humans are multi-cellular organisms a system is needed to distribute critical cargo (gases, nutrients) throughout the body  From external environment to the tissues, between and from the tissues to the external environment o This is accomplished by the heart, blood vessels and blood. BLOOD − Blood is specialized connective tissue. − Contains: o Ground substance/fluid  plasma o Buffy coat in between plasma and RBCs  leukocytes and platelets o Formed elements  cells of the blood (erythrocytes)  Plasma • Primarily water (~90%) • Contains dissolved material: proteins (albumin, globulins, fibrinogen), electrolytes (e.g., Na), nutrients (e.g., glucose), gas (e.g., C2 ) • Makes up 50% of blood  Formed elements • Blood cells are scattered in the plasma • Erythrocytes  RBCs o Biconcave discs that have no nucleus  anucleate o Main protein  hemoglobin  Gas transport o Makes up 40-50% of blood o Originates in red bone marrow and lives up to 120 days • Leukocytes  WBCs o Less than 1% of blood o Nucleated o Can change their shape  Can leave blood vessels  diapedesis  squeezing through capillaries to get to infection sites  Help the body defend against infection o Originate in red bone marrow and live up to a few hours to years o Can be divided into 2 groups:  Granulocytes - contain cytoplasmic granules (All Phils) • Eosiniphils, neutrophils, basophils (become mast cells)  Agranulocytes  no cytoplasmic granules (All Cytes) • Monocytes, lymphocytes • Thrombocytes  platelets o Fragments of a cell  Contain cytoplasmic granules  Involved in blood clotting o Derived from larger cell called megakaryocyte o Anucleate o Originate in red bone marrow and love up to a few days − Blood cell formation o All blood cells are formed in process called hematopoiesis  all cells are derived from a single cell type o Occurs in bone marrow o 2 types of bone marrow  Red bone marrow  site of blood cell generation • At birth, all marrow is red type • In adult, it remains in trabeculae of spongy bone in axial skeleton, girdles, and proximal epiphysis of humerus and femur (the ones interacting with the girdles)  Yellow bone marrow  dormant bone marrow • Between ages of 8 and 18 red bone marrow is replaced with yellow marrow in limbs  contains many fat cells (adipocytes) Blood disorders − Anemia  erythrocytes or hemoglobin levels are low − Sickle cell disease  inherited condition that impacts hemoglobin structure − Leukemia  uncontrolled proliferation of leukocytes lineage − Thrombocytopenia  low level of platelets  inability to form blood clots OVERVIEW OF CIRCULATION − Heart is double pump − There are 2 circuits: o Pulmonary circuit  sends oxygen poor blood to lungs  Right side of heart to lungs via pulmonary arteries o Systemic circuit  sends oxygen rich blood to body  Left side of heart to body organs via aorta LOCATION AND ORIENTATION OF HEART WITHIN THE THORAX − Lies in thorax posterior to sternum and costal cartilages and rests on superior surface of diaphragm, − It’s the largest organ in the mediastinum (region between the lungs) − Has an oblique position: angled to the left and 2/3 is left of the median plane o Apex lies to left of the midline (bottom) o Base is the broad posterior surface (top) − Has 4 corners defined by 4 points projected onto anterior thoracic wall: superior left and right, inferior left and right STRUCTURE OF THE HEART Coverings − Pericardium  triple-layered sac that encloses the heart. o Fibrous pericardium  outer layer of this sac; made of dense CT; attachment point of great vessels, holds heart in place and keeps it from overfilling with blood o Serous pericardium  deep to fibrous pericardium  double-layered  Parietal pericardium  outer layer; continuous with epicardium  Visceral pericardium  lies on the heart;
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