Blood is a fluid connective tissue that includes plasma, blood cell and platelets.Plasma is a fluid substance that transports gases, nutrients, nitrogenous waste.Haemoglobin is a respiratory pigment which carries oxygen through red blood cells. The amount of haemoglobin varies in different animals.Blood vessels are tube like and forming a intricate net work to transport blood to various parts of body. They are mainly arteries and veins.Arteries carry oxygenate blood from heart to different parts of body.Veins carry deoxygenated blood from body parts to heart. Capillaries are the fine branches of blood vessels which are deeply innervated into the tissues, organs and organ systems.Platelets prevents bleeding of blood from blood vessels and body parts by forming a blood clot. Lymph is a colourless tissue fluid which contains less proteins than plasma and lacks RBC.Structure of heart consists of two atria and two ventricles in mammals. Fishes are able to extract 80% of the oxygen contained in water passing over their gills.Heart is a pumping organ for blood in animals. It has structural differences in animals.Blood circulation - Deoxygenated blood carried to right atrium, and oxygenated blood carried to left atrium.
Right ventricle pumps deoxygenated blood to lungs and left ventricle pumps oxygenated blood to body organs. The force applied by blood in blood vessels is called Blood pressure. The pressure exerted by blood against the wall of the artery during ventricular contraction or systole is called systolic pressure.