transport in animals

• Transport in animals involves circulatory systems adapted to meet their needs
• Transport in animals

  1. Circulatory systems are adapted to meet the needs of each animal

  2. All circulatory systems transport gases and nutrients around an organism in a transport liquid, for example, blood

  3. The liquid is transported around in vessels with a pump, for example, the heart
• Open circulatory system

  • Seen in invertebrates like insects
  • Transport medium is hemolymph pumped directly to the body cavity called the hemoseal
  • Few transport vessels
  • Pumped at low pressure
  • Transports food and nitrogenous waste but not gases
• Closed circulatory system


  • Seen in all vertebrates and some invertebrates like annelid worms
  • Transport medium is blood that remains inside blood vessels
  • Gas and small molecules can leave the blood by diffusion or due to high hydrostatic pressure
• Single closed circulatory system

  • Blood passes through the heart once per cycle
  • One circuit that the blood takes
  • Example: fish
• Double closed circulatory system

  • Blood passes through the heart twice per cycle
  • Two separate circuits
  • Example: birds and most mammals
• Blood vessels

  • Arteries
  • Arterioles
  • Capillaries
  • Venules
  • Veins
• Capillaries

  • Form capillary beds with many branch capillaries connected
  • Found at exchange surfaces such as the outside of the alveoli
  • Have a narrow diameter to slow down blood flow
  • Made up of one single layer in their endothelium, enabling tissue fluid formation
  • Liquid and small molecules can be forced out of the capillaries due to high pressure, forming tissue fluid
• Hydrostatic pressure


  Pressure exerted by a liquid
• Oncotic pressure


  Tendency of water to move into the blood by osmosis
• Tissue fluid formation

  1. Blood enters the capillaries from the arterioles with a wider diameter, resulting in high hydrostatic pressure

  2. High hydrostatic pressure forces out water and small molecules such as glucose, amino acids, fatty acids, ions, and oxygen, forming tissue fluid
• Tissue fluid reabsorption

  1. Interaction of hydrostatic and oncotic pressure

  2. Water and small molecules are reabsorbed back into the blood
• Formation of tissue fluid

  Hydrostatic pressure is higher than the oncotic pressure at the arterial end of the capillaries, leading to the net movement of water and small molecules out to form tissue fluid
• Reabsorption of water

  Large molecules like soluble plasma proteins remain in the capillaries, lowering the water potential of the blood and leading to a higher oncotic pressure, resulting in the net movement of liquid back into the capillaries at the venule end
• Formation of lymph


  Final parts of tissue fluid get absorbed into the lymphatic system, forming lymph which is similar to plasma but without large plasma proteins and some blood cells
• The mammalian heart is made up of cardiac muscle and is responsible for pumping blood around the body
• Cardiac muscle

  • Myogenic (automatically contracts and relaxes), does not fatigue, has coronary arteries supplying oxygenated blood for aerobic respiration
• Pericardial membranes

  • Inelastic membranes surrounding the heart to prevent it from filling and swelling with blood
• Left ventricle


  • Thicker muscular wall to pump blood at higher pressure to the rest of the body
• Right ventricle


  • Thinner cardiac muscle wall as it pumps blood to the lungs at lower pressure
• Atria


  • Thinner cardiac muscle as they push blood to the ventricles, which are close and below
• Cardiac cycle


  Can be split into three key stages: diastole, atrial systole, ventricular systole
• During diastole


  Both Atria and ventricles relax, leading to a larger volume in the chambers and a drop in pressure
• During atrial systole

  Atria contract, forcing blood from Atria into ventricles
• During ventricular systole

  Ventricles contract, causing higher pressure in ventricles compared to Atria, leading to the closure of atrioventricular valves and opening of semilunar valves
• Ventricles contracting

  1. Higher pressure in the ventricles compared to the Atria causes the atrioventricular valves to shut

  2. When pressure is high enough from ventricular contraction, the semilunar valves open, causing blood to be pushed out of the pulmonary artery and the aorta
• Diastole

  1. Muscles are relaxed, blood enters the Atria via the vena cava and the pulmonary vein, pressure in the Atria slightly increases

  2. Atrial systole: Atria muscles contract, pressure increases further, atrioventricular valves open, causing blood to flow into the ventricles

  3. After a short delay, the ventricles contract, pressure increases beyond that of the Atria, atrioventricular valves close, and semilunar valves open
• Cardiac outputs

  • Volume of blood leaving one ventricle in one minute, calculated using heart rate times stroke volume
• Cardiac outputs


  Calculated using the formula heart rate times stroke volume
• Controlling the cardiac cycle

  1. Cardiac muscle is myogenic, contracts on its own accord, rate of contraction is controlled by a wave of electrical activity

  2. Sinoatrial node (SAN) located in the right atrium acts as the pacemaker

  3. Atrioventricular node (AVN) located near the border of the right and left ventricle

  4. Bundle of His runs through the septum, Perkinje fibers branch into the walls of the ventricles

  5. SAN releases a wave of depolarization across the Atria, AVN releases another wave once the first wave reaches it

  6. Non-conductive layer between Atria and ventricles forces depolarization wave to move down the bundle of His

  7. Depolarization wave moves up through the Perkinje fibers, causing the Apex and walls of the ventricle to contract efficiently

  8. Diastole occurs when repolarization occurs and the cardiac muscle relaxes
• • Electrocardiogram (ECG) measures waves of depolarization in the heart, detects differences in electrical activity in the skin caused by heart's electrical activity
  • ECG can diagnose irregularities in heart rhythms
• Abnormal heart rhythms

  • Tachycardia (heart beating over 100 bpm)
  • Bradycardia (heart beating less than 60 bpm)
  • Fibrillation (irregular heart rhythm)
  • Ectopic heartbeat (additional irregular heartbeats)
• • Hemoglobin is a group of globular proteins responsible for transporting oxygen, made up of four polypeptide chains
  • Some organisms also have myoglobin, made up of one polypeptide chain, often found in muscle tissues in vertebrates
• Oxyhemoglobin dissociation curve is a way to view the percentage saturation of hemoglobin
• Oxyhemoglobin dissociation curve

  Way to view the percentage saturation of hemoglobin with oxygen against different partial pressures of oxygen
• High partial pressures of oxygen

  Hemoglobin is about 100% saturated with oxygen
• Low partial pressures of oxygen


  Lower percentage saturations indicate that oxygen is being unloaded, typically representing different parts of the body
• In respiring cells or tissues

  Low partial pressure of oxygen because they're using up the oxygen, leading to less saturation of hemoglobin
• In the alveoli with high partial pressure of oxygen


  High saturation of hemoglobin to transport oxygen around
• Affinity


  Referring to the attraction, high partial pressures of oxygen result in high affinity for oxygen, while low partial pressures result in lower affinity