Circulatory system

• why do we need a circulatory system?


  transportation of materials within the body and exchange of materials with the external environment
• Why do simple animals lack specialized systemfor transport and distribution of materials?


  Many or all cells are in direct contact with the external environment
• How do simple animals transport and exchange materials


  Exchange of materials over the body surface through direct diffusion is sufficient for their needs and materials can be transported bydiffusion through short distance within the body
• Why diffusion is not sufficient to transport materials in complex animals?


  As organism increase in size and complexity the amount of materials moving in and out of the body also increases. The distance that materials have to be transported also increases and many cells are not in direct contact with the external environment.
• How materials are transported in complex animals?

  circulatory system has evolved in such organisms to exchange materials between cells and their immediate surroundings.
• What are the substances that are transported within the body?

  Respiratory gases (oxygen, carbon dioxide)

  nutrients (glucose, amino acids, fatty acids, vitamins etc.)

  waste products of metabolism ( urea, ammonia)

  hormones

  antibodies
• What are the three basic components of a circulatory system?


  muscular pumping device (heart)

  Interconnected vessels

  circulatory fluid ( blood, hemolymph)
• How does circulatory fluid flows through the vessels?

  mainly due to the pressure generated by the heart
• How does the circulatory fluid functionally connects the fluid environment of the body cells to the organs that exchange gases, absorb nutrients and dispose of wastes?

  by transporting fluids throughout the body.
• what are the two types of circulatory systems among the animals?

  Open circulatory system

  closed circulatory system
• What is the open circulatory system?

  in which a fluid called hemolyph which bathes tissues and organs directly.
• To where does the heart pumps hemolymph?

  Into the spaces ( interconnected sinuses) which surround body tissues.
• How does the chemical exchange occurs?


  Directly between the hemolymph and body cells
• How does the back flow of the hemolymph takeplace?

  via the pores (Ostia) with valves found in the heart during the relaxation.
• In which animals have the open circulatory system has evolved?

  invertebrate phyla such as arthropoda and mollusks.
• What is the closed circulatory system?

  In which blood is restricted to vessels and kept apart from the interstitial fluid
• To where the blood is pumped to?

  into large vessels. These large vessels branches into small vessels and they penetrate into the organs
• In which kind of animals can closed circulatory system can be found


  Vertebrates and invertebrates such as annelids
• How does the chemical exchange occur?


  between blood and interstitial fluid and interstitial fluid and body cells
• What are the tree main types of blood vessels?

  arteries

  veins

  capillaries
• What are arteries?


  Blood vessels which can carry blood from heart to organs
• What are arterioles?


  When arteries branches into smaller vessels within organs. They pass blood into capillaries.
• what are capillaries? 


  They are microscopic vessels with thin and porous walls and these are the places where materials exchange occurs between blood and interstitial fluid surrounding body cells through diffusion
• What are veins?


  capillaries converge into venules and they converge into veins which carry blood back to the heart
• What is single circulation?


  In a complete circulation through the entire body blood passes through the heart only once.
• How many chambers in the heart of animals that demonstrate single circulation?

  Two chambers ; atrium and ventricle
• What is the process of a single circulation?

  oxygen poor blood returning from the body enters atrium and pass into the ventricles. Then the ventricle is contracted and blood passes into the capillary beds in the gills. There gas exchange occurs between the capillaries and the external environment. The oxygen is diffused into the blood while carbon dioxide is removed from the blood. Next the oxygen blood circulates throughout the body and reaches the body cells through body capillaries.
• What are the examples for animals that have single circulation?


  Bony fishes, cartilaginous fishes such as rays and sharks.
• what is double circulation?

  In a complete circulation through the entire body blood passes through the heart twice.
• What are the two circuits in the double circulation?

  Pulmonary and systemic circuit in which blood passes through the heart after completing each cycle.
• What are the examples for animals having double circulation.?

  Reptiles, Aves, mammals and amphibians
• How many hearts in amphibians and reptiles?

  Three chambered heart. Two atria and one ventricle
• How about the heart of the aves and mammals?

  They have a four chambered heart where heart is completely divided into right and left side which allows complete separation of oxygen enriched and oxygen poor blood.
• What is the process of double circulation?

  The oxygen poor blood from the systemic circulation flows to the right atrium and pass into the right ventricle. Right ventricle pumps blood into the lungs. Oxygen enriched blood from the lungs reaches the left atrium and pass to the left ventricle. The left ventricle pumps oxygen enriched blood into the systemic circulation.
• Why is double circulation is more effective in supplying blood to organs and tissues especially brain and muscle?


  Due to the higher pressure generated by the heart in the systemic circulation. this in contrast to single circulation where blood flows under reduced pressure from the gas exchange organs to other organs.