This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: CIRCU LATORY SYSTEMS (PART I I) LIFE 49.4 – 49.5 49.4 What are the properties of blood and blood vessels?-Blood is a connective tissue that consists of cells suspended in an extracellular matrix (liquid), so blood is a fluid tissue-cells of the blood can be separated from the fluid matrix, called plasma , by centrifugation (cells move to bottom of tube)- packed-cell volume , or hematocrit , is the percentage of the blood volume made up by cells-two elements in blood: the red blood cells and the platelets , which are pinched-off fragments of cells 49.4.1 Red blood cells transport respiratory gases-Most of the cells in the blood are erythrocytes , or red blood cells // packed w/hemoglobin // shape facilitates gas exchange-RBC generated by stem cells in the bone marrow, particularly in the ribs, breastbone, pelvis, and vertebrae. Red blood cell production is controlled by a hormone , erythropoietin , which is released by cells in the kidney in response to insufficient oxygen — hypoxia 49.4.2 Platelets are essential for blood clotting-bone marrow stem cells also produce megakaryocytes: large cells that remain in the bone marrow and continually break off cell fragments called platelets . A platelet is just a tiny fragment of a cell without cell organelles , but it is packed with enzymes and chemicals necessary for its function: sealing leaks in blood vessels and initiating blood clotting-Damage to a blood vessel exposes collagen fibers. An encounter with collagen fibers activates a platelet . The platelet swells, becomes irregularly shaped and sticky, and releases chemicals called clotting factors , which activate other platelets and initiate the clotting of blood • Cascade: cell damage and platelet activation inactive circulating enzyme , prothrombin , converts to active form, thrombin Thrombin cleaves molecules of fibrinogen , a plasma protein , forming insoluble threads of fibrin fibrin threads form the meshwork that clots the blood, seals the vessel, and provides a scaffold for the formation of scar tissue 49.4.3 Plasma is a complex solution- Plasma , the clear, straw-colored liquid portion of the blood, contains dissolved gases,...
View Full Document
This note was uploaded on 09/02/2009 for the course BIO 315H taught by Professor Payne during the Spring '08 term at University of Texas at Austin.
- Spring '08