animal transport

• features of an effective transport system

  • a fluid to carry oxygen and amino acids around the body
  • exchange surfaces that enable oxygen to enter and leave the blood
  • a pump to create pressure and push fluid around the body
  • tubes and vessels to carry blood
  • two circuits
• closed circuit - the fluid remains entirely inside vessels
• open circulatory systems - blood circulates in the body cavity (haemocoel), cells are bathed directly in blood
• single circulatory system - blood flows only through the heart once for each complete circuit of the body
• double circulatory system - blood flows through the heart twice for each complete circuit of the body
• pulmonary circulation - blood is pumped from the heart to the lungs ad then returns to the heart
• systemic circulation - blood is pumped from the heart around the body and returns to the heart
• artery structure

  • narrow lumen to maintain pressure
  • elastic tissue for recoil
  • folded endothelium made of squamous cells which make it smooth
  • thick layer of smooth muscle for constriction and dilation
  • collagen to withstand the pressure
  • lead to arteries which have more smooth muscle and fewer elastic fibres allowing for vasodilation and vasoconstriction
• capillary structure

  • one cell thick wall for exchange
  • walls are leaky allowing for white blood cells to leave the blood
• vein structure

  • join to form venules then veins `
  • carry low pressure blood back to the heart
  • thinner walls than arteries
  • not folded endothelium cells
  • elastic fibers
  • thin layer of smooth muscle
  • mainly collagen
  • contain valves to prevent back flow
• coronary arteries - supply the heart muscle with oxygen and nutrients so the heart can respire aerobically
• cardiac veins - remove waste carbon dioxide
• septum function - separates the two sides of the heart and therefore prevent the mixing of oxygenated and deoxygenated blood
• the atria have thin muscular walls because atria only pump blood to the ventricles
• tendinous chords function - prevent the values turning inside out
• tricuspid valve - the right atrioventricular valve
• bicuspid valve - the left atrioventricular valve
• aorta - from the left ventricle to the body and head
• pulmonary artery - from the right ventricle to the lungs ( the only artery with deoxygenated blood )
• vena cava - from the body and head to the right atrium
• pulmonary vein - from the lungs to the left atrium ( the only vein with oxygenated blood)
• cardiac muscle structure

  • myogenic
  • branched producing cross bridges - helping spread the contraction
  • intercalated discs - enable the synchronised contraction
• atrial systole process

  1. muscle in the walls of the atria contract
  2. increase in pressure opens the atrioventricular valves and fills the ventricles with blood
  3. semi-lunar valves are closed preventing back flow into the vena cava
• ventricular systole

  1. the ventricles contract
  2. increasing the pressure
  3. pressure higher inside the ventricles is higher than the atria so the atrioventricular valves are closed
  4. increase in pressure forces open the semilunar valves forcing blood into the aorta and the pulmonary artery
• diastole

  1. atria and ventricles relax
  2. elastic tissue recoil returns to original size
  3. pressure in ventricles decreases
  4. semilunar valves are closed to prevent back flow
  5. blood from the veins flows into the atria
  6. ventricles are relaxed and so the pressure is higher in the atria
• atrial contraction - controle of the cardiac cycle

  • cardiac cycle initiated by the Sino-atrial node
  • wave of excitation generated
  • walls of the atria contract
  • a band of non-conducting collagen fibres between the atria and the ventricles prevent the electrical wave passing through
• ventricular contraction - control of the cardiac cycle

  • the atrioventricular node in the apex of the heart allows the wave of excitation 0.1s later
  • wave then travels through the purkyne tissue in the septum
  • electrical wave upwards and outwards through the ventricle walls
• ecg

  • qrs complex = the electrical activity causing the ventricles to contract
  • p wave = electrical activity in causing the atria to contract
  • q-t interval = ventricular systole
  • T-P interval = diastole
  • t wave = repolarisation
• bradycardia - when the heart rate slows down to below 60
• tachycardia - when the heart beat is very rapid
• ectopic heartbeat - extra beats that are out of the normal rhythm
• atrial fibrillation - an abnormal rhythm of the heart, the atria contract very rapidly but the ventricles are not in time
• ventricular fibrillation - rapid and irregular activity, ventricles cannot contract in a synchronised manner
• constituents of blood

  • 55% plasma
  • 1% platelets and white blood cells
  • 44% red blood cells
• tissue fluid - the fluid that bathes cells in tissues to prevent them from drying out

  • formed from the plasma that leaks out of capillaries
  • essential for exchange of material between cells and blood
• formation of tissue fluid

  1. at the arteriole end of the capillary blood has high hydrostatic pressure this pushes fluid through gaps in capillary walls
  2. the tissue fluid has a relatively low hydrostatic pressure working in the opposite direction
  3. oncotic pressure is generated by the presence of plasma proteins
  4. at the arteriole end there is a net hydrostatic pressure forcing fluid out of the capillary
• re sending of tissue fluid into the blood

  1. at the venule end of the capillary the hydrostatic pressure is much lower due to the loss of the fluid
  2. the plasma proteins are still too large to fit through caps in capillary walls so the same amount of onctoic pressure is still present
  3. at the venule end of the capillary there is net movement of fluid into the capillary due to oncotic pressure
• lymph

  • the remaining 10% of tissue fluid that is not retuned to the capillary travels through the blood system via lymph vessels
  • relies on the movement of us to pump
  • valves in lymph vessel walls allows tissue fluid in but not out
  • these valves let proteins through which is key as the proteins cannot enter back into the capillary
  • less oxygen, more carbon dioxide and more lymphocytes
• process of lymph formation

  1. lymph is transported to the subclavian veins
  2. contraction of the muscles surrounding lymph vessels aids the movements
  3. lymphocytes are produced in the lymph nodes
• adaptations of ethrocytes

  • small = short diffusion distance, squeeze through capillaries
  • biconcave disc = sa:volume ratio
  • no nucleus, mitochondria, and no er, = more space for haemoglobin