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Immagini e concetti della biologia Sylvia S. Mader Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

C5 – Circulation and blood Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

The circulatory system The function is to transport O2 and nutrients to the cells of the body and to carry away CO2 and other wastes. To do this, the system must keep blood constantly circulating. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Single-loop circulation Fish have a single-loop circulatory pathway: the heart has a single atrium and a single ventricle. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Two-circuits circulation Amphibians and most reptiles have a two-circuits circulatory pathway, with the heart divided into two atria and one ventricle. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Two-circuits circulation Birds and mammals have a two-circuits circulatory pathway with the heart divided into two atria and two ventricles. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

The cardiovascular system A circulatory system consists of a pump (the heart), a fluid (the blood) and a series of blood vessels (the vascular system). All together those elements form the cardiovascular system. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

The heart The heart has four chambers: two atria and two ventricles. A cardiac septum separates the heart into right and left halves. right ventricle right atrium left ventricle left atrium septum Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

The heart An artery carries blood away from the heart while a vein takes the blood to the heart. Cardiac valves keep blood moving in the correct direction. superior vena cava semilunar valve atrioventricular valve inferior vena cava pulmonary veins pulmonary artery aorta Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

The heartbeat Electric rhythmic impulse move the heart. The contraction is called systole, the relaxation of the chambers is diastole. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

The cardiac conduction system The heartbeat starts from the sinoatrial node (SA), the impulse-generating (pacemaker) tissue. The atrioventricular node (AV) causes the ventricle contraction. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Blood vessels Arteries Blood pressure in arteries and arterioles carries blood away from the heart. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Blood vessels Veins Skeletal muscle contractions return blood in veins and venules to the heart. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Blood vessels Capillaries Thin-walled capillaries permit exchange of materials and gas with the tissues. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Pulmonary and systemic circuits Cardiovascular systems includes two circuits. Pulmonary circuit: pulmonary arteries take O2-poor blood to lungs while pulmonary veins return O2-rich blood to the heart. Systemic circuit: left ventricles send O2-rich blood to aorta; vena cava takes O2-poor blood back to the right atrium. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Pulmonary and systemic circuits Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Blood pressure Blood velocity depends on pressure and on capillaries area. Systolic pressure: is the pressure in arteries during ventricular systole. Diastolic pressure: is the pressure in arteries during ventricular diastole. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Vascular diseases A stroke (or cerebral ictus) occurs when a small cranial arteriole bursts or is blocked by an embolus. A heart attack occurs when a coronary artery (the artery that brings O2-rich blood to capillaries of the heart) is completely blocked. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Vascular diseases Healthy life style can help to prevent vascular diseases: refraining from smoking no drugs controlling weight healthy diet monitoring cholesterol exercising Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Vascular diseases Cholesterol is an essential component of cell membranes and is carried by plasmic proteins (LDL and HDL). Anomalies in quantities of LDL or HDL can lead to the formation of cholesterol plaque in blood vessels. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Blood functions Transports substances to and from capillaries where exchanges occur. Helps the organism defend against pathogens. Helps regulate body temperature. Forms clots to prevent hemorrhages. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Blood composition Blood is composed of a liquid portion called plasma and formed elements: red and white blood cells, and platelets. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Clotting Blood clotting involves platelets that release clotting factors at the site of the blood vessel damage. Fibrin threads provide a meshwork for a blood clot. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Blood stem cells Hematopoietic stem cells (HSCs), are multipotent stem cells, found in the bone marrow of adults, that can produce all the blood cell types. HSCs can be easily transplanted from pelvic bone. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Capillary exchange Between the arterial end and the venus end, substances diffuse according to the concentration gradient: CO2 and waste produced by the cells move in; C6H12O6, amino acids and O2 spread out. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

Capillary exchange Lymphatic capillaries collect excess tissue fluid (called lymph) and return it to the vascular system. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

AB0 classification system RBC membranes carry specific carbohydrates and proteins that behave as antigens when transplanted in incompatible organisms. Those antigens are classified as A and B and determine the type of blood. RH factor is another important antigen in matching blood types. Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

AB0 classification system Agglutination: clumping of RBC in the presence of an antibody that binds multiple antigens and joins the cells. No agglutination Agglutination Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018