Page 122 - Biology Form Two
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Biology for Secondary Schools







                                                                Capillaries in the lung

             Pulmonary artery
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                                         Pulmonary
                                         circulation
                                                                Pulmonary vein

                                                                Left auricle

                                                                Left ventricle


                                                                Aorta

                    Vena cava            Systemic
                                         circulation                     Oxygenated blood

                                                                         Deoxygenated blood

                                                                Capillaries in the body


                                     Figure 5.14: Double circulation in human beings


              The left auricle then pumps the blood  aorta.  The  deoxygenated  blood  from
              into the left ventricle. The left ventricle  different parts of the body is brought
              has strong muscles that pump blood to  into the right auricle through the vena
              all parts of the body through the aorta.  cava.
              After delivering the requrements to     Formation of tissue fluid
              the  tissues,  the  blood  flows back to   Tissue fluid is a kind of fluid formed
              the heart through the vena cava. This   from blood plasma by a diffusion and
              movement of blood between the heart     filtration  process.  This  fluid  occupies
              and various parts of the body is called   much  of the  intercellular spaces in
              the systemic cycle. Therefore, systemic   the  body and blood  capillaries.  They
              circulation  is the circulation  of blood   form  a  connecting  link  for  transport
              between the heart and all other parts of   of nutrients, gases and other materials
              the body, except the lungs. Oxygenated   between blood capillaries, tissues, and
              blood from the left ventricle is pumped   lymphatic vessels.
              to various parts of the body through the






            116                                                      Student’s Book - Form Two



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