Transport in Animals

• Open circulatory

  Blood is pumped into a haemocoel where it bathes the tissue / organ and returns slowly to the heart with little control over the direction of flow. Blood is not contained in blood vessels.
• Closed circulatory

  Blood is pumped into a series of vessels; blood flow is rapid and direction of flow is controlled. Organs are not bathed by blood but by tissue fluid that leaks from capillaries
• Single circulation

  Blood passes once through the heart in each circulation
• Double circulation

  Blood passes twice through the heart twice in each circulation. Once in the pulmonary circulation (lungs) and then again through the systemic circulation (body).
• Pulmonary circulation

  Heart to the lungs
• Systemic circulation

  Heart to the body
• Circulation in Insects

  • Open circulatory system
  • Dorsal tube shaped heart
  • No respiratory pigment in blood as lack of respiratory gases in blood due to tracheal gas exchange system
• Circulation in earthworm

  • Closed circulatory system
  • 5 pseudohearts
  • Respiratory pigment as haemoglobin carries respiratory gases in blood
• Circulation in Fish

  • Closed, single circulatory system
  • Blood pumped to gills from heart, then to the body
  • Lower pressure and slower flow around the body
• Circulation in mammals

  • Closed, double circulatory system
  • High blood pressure to deliver oxygen quickly
  • Lowers pressure to lungs, prevents hydrostatic pressure forcing tissue fluid into and reducing efficiency of alveoli
• Mammalian heart

  • Superior vena cava
  • Right atrium
  • Tricuspid valve
  • Right ventricle
  • Pulmonary artery
  • Pulmonary veins
  • Biscupid valve
  • Left atrium
  • Left ventricle
  • Semi lunar valve
• Superior vena cava

  Carries deoxygenated blood to the heart
• Right atrium

  Controls and pumps deoxygenated blood into the right ventricle
• Tricuspid valve

  Pressure of the contraction of the atrium opens this valve which then closes preventing back flow to the right atrium when the right ventricle contracts
• Pulmonary artery

  Takes deoxygenated blood to lungs from right ventricle
• Semi lunar valve

  Prevents blood flowing back into ventricle between heart beats
• Pulmonary vein

  Returns oxygenated blood from lungs to left atrium
• Bicuspid valve

  Prevents back flow of blood into the left atrium when the ventricles contract
• Left ventricle

  Thicker muscular wall, compared to right ventricle, to produce a higher pressure to push oxygenated blood around the body
• Aorta

  Carries oxygenated blood from the left ventricle to the body
• structure of blood vessels

  • Tunica externa
  • Tunica media
  • Endothelium
• Tunica externa

  A tough collagen outer coat to prevent overstretching
• Tunica media

  • Contains elastic fibres and smooth muscle.
  • It is thicker in arteries than in veins
  • Elastic fibres allow stretching to accommodate changes in blood flow and pressure as blood is pumped from the heart
  • Contraction of smooth muscle regulates blood flow and maintains blood pressure as the blood is transported further from the heart
• Arteries

  Take blood away from the heart
• Arterioles - Form when large arteries begin to narrow as they approach organs
• Vein

  Takes blood back to the heart
• venules

  Form when capillaries reunite to leave the organ
• Capillaries

  Take blood through the tissue
• The cardiac cycle

  Sequences of events which occur in one heart beat
• Stages of the cardiac cycle

  1. Atrial systole
  2. Ventricular systole
  3. Diastole
• Atrial systole

  Atrium walls contract and blood pressure increases

  This pushes the blood through the tricuspid and bicuspid valves down into ventricles
• Ventricular systole

  - Ventricle walls contract causing and increase the blood pressure in the ventricles

  - When the pressure in the ventricle is greater than the pressure in the atria the atrioventricular valves close

  - Blood is forced into aorta and the pulmonary artery
• Diastole

  • Ventricles relax
  • Volume in ventricle increases, pressure in the ventricles decrease
  • When ventricular pressure falls below the aortic pressure, the semi lunar valve closes
• Valves - Prevent back flow of blood. Operates by closing under high pressure
• Control of heartbeat

  Contraction of cardiac muscle is myogenic
• Sino atrial node (SAN)

  Specialised cardiac cells which act as a pacemaker sending waves of excitation across the atria causing them to contract simultaneously
• Atrio ventricular node (AVN)

  The wave of contraction cannot pass from the atrial walls to the ventricle walls, because the two chambers are separated by fibrous tissue.

  The wave of contraction does reach a second patch of excitable tissue at the at the top of the septum between the atrium and ventricles.
• Bundle of His

  When the impulses reach the AVN it is carried down the septum in a block of fibres.

  This takes the impulses to the bottom of the ventricles