Transport in animals and plants

• in open circulatory systems blood doesn’t flow round the organism but simply bathes the tissues in fluid these tissues are held in a cavity known as a haemocoel
• an example of open respiratory systems is insects

  • They have a long dorsal heart all the way down the body
  • this pumps low pressure blood into the haemocoel which takes in the substances that are needed
  • blood then returns to the heart and then open circulation begins again
• in closed circulatory systems blood moves through the blood vessels
• closed circulation has two types

  1. single circulation
  2. double circulation
• single circulation has the blood move through the heat once
• double circulation has

  • B look passes through heart twice at a time
  • blood pumped by heart muscle at high pressure via aorta
  • organs not in direct contact with blood but bathed in tissue fluid that seeps out of the capillaries
  • Respiratory pigment is haemoglobin
• Vascular system of insects

  • Open circulatory system
  • Dorsal-tube shaped heart
  • Respiratory gases not carried in blood
• Open circulatory system

  • Transport medium pumped by the heart is not contained within vessels, but moves freely
  • Transport fluid comes into direct contact with the cells
• Vascular system of earthworms

  • Vascularisation
  • Closed circulatory system
  • Respiratory gases carried in blood
• Closed circulatory system

  • Blood pumped by the heart is contained within blood vessels
  • Blood does not come into direct contact with the cells
• Advantages of a closed circulatory system

  • Blood pressure can be maintained
  • Blood supply to different organs can vary
  • Lower volumes of transport fluid required
• Circulatory system of fish

  Single circulatory system
• Single circulatory system

  • Circulatory system in which the blood travels one circuit
  • Blood flows through the heart and is pumped around the body before returning to the heart
• Circulatory system of mammals

  Double circulatory system
• Double circulatory system

  • Circulatory system in which the blood flows through the heart twice in two circuits
  • Blood is pumped from the heart to the lungs before returning to the heart. It is then pumped around the body, after which it returns to the heart again
• Benefits of a double circulatory system

  • Maintains blood pressure around the whole body
  • Uptake of oxygen is more efficient
  • Delivery of oxygen and nutrients is more efficient
  • Blood pressure can differ in pulmonary and systemic circuits
• Double circulatory system in humans

  1. Pulmonary circuit

  2. Systemic circuit
• Four chambers of the mammalian heart

  • Left atrium
  • Right atrium
  • Left ventricle
  • Right ventricle
• Structures of the mammalian heart labelled in the diagram
• Pathway of blood around the body, naming the structures of the heart

  Pulmonary vein → Left atrium → Left ventricle → Aorta → Body → Vena cava → Right atrium → Right ventricle → Pulmonary artery → Lungs
• Direction of blood flow through the heart shown on the diagram
• Atrioventricular valves

  • Found between the atria and ventricles
  • Prevent the backflow of blood from the ventricles into the atria
• Types of atrioventricular valves

  • Bicuspid (left side)
  • Tricuspid (right side)
• Semilunar valves

  • Found between the ventricles and arteries
  • Prevent the backflow of blood from the arteries into the ventricles
• Types of blood vessel

  • Arteries
  • Arterioles
  • Capillaries
  • Venules
  • Veins
• Pathway of blood through the blood vessels

  heart → arteries → arterioles → capillaries → venules → veins → heart
• Function of arteries

  Carry blood away from the heart to the tissues, under high pressure
• Structure of arteries

  • Thick, muscular walls to handle high pressure without tearing
  • Elastic tissue allows recoil to prevent pressure surges
  • Narrow lumen to maintain pressure
• Function of veins

  Carry blood towards the heart under low pressure
• Structure of veins

  • Thin walls due to lower pressure
  • Require valves to ensure blood doesn't flow backwards
  • Have less muscular and elastic tissue as they don't have to control blood flow
• Function of capillaries

  Form a large network through the tissues of the body and connect the arterioles to the venules
• Structure of capillaries

  • Walls only one cell thick ∴ short diffusion pathway
  • Very narrow, so can permeate tissues and red blood cells can lie flat against the wall, reducing the diffusion distance
  • Numerous and highly branched, providing a large surface area
• Function of arterioles

  Connect the arteries and the capillaries
• Function of venules

  Connect the capillaries and the veins
• Structure of arterioles and venules

  • Branch off arteries and veins in order to feed blood into capillaries
  • Smaller than arteries and veins so that the change in pressure is more gradual as blood flows to the capillaries
• Arterioles

  Connect the arteries and the capillaries
• Venules

  Connect the capillaries and the veins
• Arterioles and venules

  • Smaller than arteries and veins so that the change in pressure is more gradual as blood flows to the capillaries
  • Branch off arteries and veins in order to feed blood into capillaries
• Cardiac cycle

  The sequence of events involved in one complete contraction and relaxation of the heart
• Cardiac cycle

  1. Atrial systole

  2. Ventricular systole

  3. Diastole