transportation and excretion in substances

• The circulatory system transports blood throughout the body, delivering oxygen and nutrients to cells and removing waste products.
• in unicellular organisms , the transportation of materials takes place through diffusion
• circulatory system is responsible for

  transportation of nutrients and other substances

  transportation of respiratiory gases

  removal of waste products formed during the various processes of that occur inside the body
• blood vessels are tubes that carry blood from one part of the body to another
• arteries have thick walls with elastic tissue which allows them to expand when filled with blood
• veins have thinner walls than arteries but they contain valves that prevent backflow of blood
• arteries take blood away from the heart
• veins bring blood back towards the heart
• capillaries connect arteries with veins and allow exchange between tissues and blood
• the heart pumps blood around the body by contracting and relaxing
• capillaries are tiny blood vessels where exchange between blood and tissues occurs
• the heart pumps blood into the arteries and receives it from the veins
• heart has four chambers - two atria (upper) and two ventricles (lower)
• the liquid part of the blood is called blood plasma
• the solid component is called blood cells
• red blood cells carry oxygen
• blood carries oxygen, nutrients, hormones and waste products to/from organs
• platelets clot blood to prevent excessive bleeding
• the blood plasma is a colourless liquid
• white blood cells are responsible for fighting infection
• the blood plasma consists of 90% water and 10% of minerals , dissolved food, waste products and some proteins
• the types of blood cells

  platelets

  wbc

  rbc