• A circulatory system is found in animals whose body is too large or complex for chemicals to reach all cells by diffusion alone.
• The fluid that is used to carry materials through a circulatory system is called blood.
• Open circulatory system - blood is pumped through open-ended blood vessels and freely circulates through the cells
• Closed circulatory system - blood is moved throughout the organism though blood vessels; nutrients/wastes diffuse through the walls of the vessels
     • The heart, vessels, and blood are known as the cardiovascular system.
     • There are 3 types of blood vessels: arteries, capillaries, veins
• The hearts of vertebrates is composed of 2-4 chambers.
     • The atria receives blood from the body.
     • The ventricle(s) sends blood to the body.
• Animals higher on the evolutionary scale have more advanced systems.
    • Fish have hearts with 2 chambers, amphibians have hearts with 3 chambers, birds and mammals have hearts with 4 chambers.
•  The Human Heart
     1) pumps the blood
     2) about the size of your fist
     3) layers/linings of the heart
     4) chambers of the heart
          a) right atrium - takes in blood from the superior and inferior vena cavae
          b) left atrium - takes in blood from the 4 pulmonary veins
          c) right ventricle - pumps blood to the lungs
          d) left ventricle - pumps blood to the body; strongest chamber of the heart
     Path of blood through the heart
          deoxygenated blood from the body -> superior & inferior vena cava -> right atrium -> thru the tricuspid valve -> right ventricle -> thru the pulmonary semilunar valve -> pulmonary trunk -> pulmonary arteries -> lungs -> pulmonary veins -> left atrium -> thru the bicuspid valve -> left ventricle -> thru the aortic semilunar valve -> aorta -> body
• The sequence of filling and pumping blood is the cardiac cycle.
     • diastole - the heart is relaxed; the lower number for blood pressure
     • systole - the heart is contracting; the higher number for blood pressure
• The pacemaker (sinoatrial node) controls the pumping rate of the heart.
• An electrocardiogram (ECG) is used to record the heart's cycle.
• heart attack - a coronary artery is blocked; also cardiac arrest or myocardial infarction
     • 1/3 of heart attack victims die almost immediately
• arteriosclerosis - blockage of an artery due to build-up on the interior wall

• Blood Vessels
• Arteries: carry blood away from the heart; are under high pressure; located deep
• Capillaries: very small (from 8-10 micrometers in diameter); they are woven together in a network called a capillary beds exchange sites ... where oxygen and nutrients are released from the blood and carbon dioxide and wastes enter the blood
• Veins: carry blood to the heart thin walls; are under low pressure; have one-way valves so that blood doesn’t flow backwards small veins, called venules
• aorta - body's largest artery; exits from the left ventricle
• superior vena cava - collects deoxygenated blood from the upper body
• inferior vena cava - collects deoxygenated blood from the lower body
• Blood pressure (BP) - pressure exerted on the blood vessel by the blood
• Blood pressure can be increased by certain chemicals (epinephrine, ADH, etc.).
• Blood pressure can be lowered by certain chemicals (alcohol, nitric oxide, etc.)
• In the long run, BP is controlled by the kidneys, which regulate how much water is taken from the blood.
• If more water is removed, BP goes down; if more water is retained, BP goes up.
• High blood pressure is known as hypertension.
• Hypertension can be caused by: diet, obesity, age, race, heredity, stress, and smoking.
• Low blood pressure is known as hypotension.  It can be orthostatic (temporary, such as when you stand rapidly) or chronic.
• Pulse is a pressure wave transmitted through the arteries.

• Blood
     • Blood is composed of formed elements and plasma.
     • Blood is a viscous, slightly alkaline fluid
     • You have about 5 liters (about 8% of your weight)
     • Functions of blood:
        A) delivery of oxygen & nutrients to the body tissues
        B) removal of body wastes
        C) transport of hormones
        D) regulation of body temperature
        E) regulation of constant blood pH
        F) regulation of fluid volume
        G) hemostasis (it contains elements that clot the blood when vessels are damaged)
        H) prevention of infection
     • Composition of blood
       • Plasma
          - a straw colored, viscous fluid that is 90% water
          - the remaining 10% is composed of nutrients, respiratory gases, salts, hormones, & proteins
       • Formed elements - make up 45% of the blood; they come from hemocytoblasts in red bone marrow
          1) erythrocytes
              a) also called red blood cells
              b) they have no nucleus and few organelles
              c) their main function is to transport oxygen (oxygen attaches to the hemoglobin in the cell)
              d) there are several disorders related to erythrocytes
                 i) anemia
                   1) insufficient red blood cells
                   2) decrease in hemoglobin (ie. iron deficiency)
                   3) abnormal hemoglobin
                 ii) polycythemia - too many red blood cells
            2) leukocytes
               a) also called white blood cells; <1% of your blood
               b) they have nuclei
               c) there are 2 main types: granulocytes and agranulocytes
               d) granulocytes
                 i) neutrophils - active phagocytes
                 ii) basophils - contain histamine, which help send leukocytes to infected areas
                 iii) eosinophils - attack parasitic worms; quantity increases during allergic reactions
               e) agranulocytes
                 i) lymphocytes ("immune cells")
                 ii) monocytes, which differentiate into macrophages
               f) there are several disorders related to leukocytes
                 i) leukemia - too many leukocytes; "leukocyte cancer"
                 ii) infectious mononucleosis
           3) platelets
              a) fragments of cells formed in the red marrow
              b) help to plug up damages in blood vessels (blood clots)

• Hemostasis (blood clotting)
     1) occurs in 3 phases
          a) vascular spasms - damaged blood vessel tightens
          b) platelet plug formation - platelets form a tempory blockage in the wound
          c) coagulation
               i) prothrombin activator is formed
               ii) the prothrombin activator converts prothrombin (a plasma protein) into thrombin
               iii) thrombin changes fibrinogen into a fibrin mesh, which traps blood cells and seals the wound (= a scab)
     2) Hemostasis disorders
          a) thromboembolytic disorders - unwanted blood clots
          b) thrombocytopenia - not enough platelets
          c) hemophilia - blood won't clot; a genetic disease

• Blood Types
     1) There are 4 blood types
          a) A - has A antigens
          b) B - has B antigens
          c) AB - has A & B antigens
          d) O - has no antigens
     2) you cannot receive blood that has an antigen you don't already have
     3) if a mismatch occurs, agglutination (clumping of the blood) can occur
     4) O - universal donor type
     5) AB - universal recipient type
     6) Rh factors
          a) a variety of antigens that may or may not be present in your blood
          b) if present, you have Rh+ blood
          c) if absent, you have Rh- blood
          d) it is most problematic when an Rh- mother is carrying an Rh+ baby
               i) antibodies in the mother's blood can get into the baby's system and damge the baby
               ii) transfusions of the baby's blood are required to prevent anemia and hypoxia
               iii) if untreated, brain damage and even death may occur

Stem Cells
• Stem cells are unspecialized cells that can turn into different types of cells.  
• The hope is that they can be used to treat diseases.
• Example: bone marrow stem cells can help to repopulate blood and the immune system.