Cardio and Respiratory system

• Adaptations for gas exchange

  • All gas exchange surfaces have features to increase the efficiency of gas exchange including:
  • Large surface area to allow faster diffusion of gases across the surface
  • Thin walls to ensure diffusion distances remain short
  • Good ventilation with air so that diffusion gradients can be maintained
  • Good blood supply (dense capillary network) to maintain a high concentration gradient so diffusion occurs faster
• The Ribs:

  • Bone structures that surround and protect the lungs
  • They also aid in breathing
• Diaphragm:

  • sheet of connective tissue and muscle at the bottom of the thorax, that help change the volume of the thorax to allow inhalation and exhalation
• Trachea:

  • a windpipe that connect the mouth and the nasal cavity to the muscle at the bottom of the thorax
  • its lined with goblet cells, that produce mucus, and epithelial cells, that contain cilia that move mucus up to the mouth.
• Bronchus, Plural for bronchi:

  • Large tubes that connect to the trachea to each bronchus for each lung
  • they are lined up with goblet cells and ciliated epithelial cells
• Bronchioles:

  • The bronchi splits into smaller tubes called the bronchioles in the lungs connected to the alveoli
• Alveoli:

  • tiny moist air sacs where the gas exchange takes place
  • Each alveolus is pact with capillaries
• Circulatory system


  1. Right side pumps blood to the lungs for gas exchange (pulmonary circuit)

  2. Left side pumps blood under high pressure to the body (systemic circulation)
• Pathway of blood through the heart

  1. Deoxygenated blood enters via vena cava, flows to right atrium

  2. Flows down through atrioventricular valves to right ventricle

  3. Pumped up through pulmonary artery to lungs for gas exchange

  4. Oxygenated blood returns via pulmonary vein to left atrium

  5. Flows down through atrioventricular valves to left ventricle

  6. Pumped up through aorta to body
• Adaptations of the heart


  • Walls of ventricles much thicker than atria as they pump blood out of the heart at higher pressure
  • Wall of left ventricle much thicker than right as it pumps blood at high pressure around the body
  • Two sets of valves (atrioventricular and semilunar) prevent backflow of blood
  • Septum prevents mixing of deoxygenated and oxygenated blood
• Cardiac muscle tissue


  Does not fatigue like skeletal muscle
• Coronary arteries supply the tissue of the heart with oxygenated blood - the heart needs a constant supply of oxygen (and glucose) for aerobic respiration to release energy to allow continued muscle contraction
• Pacemaker


  The role is to coordinate the contraction of the heart muscle, therefore it regulates the heart rate
• Pacemaker function


  1. Sends out an electrical impulse

  2. Impulse spreads to the surrounding muscle cells

  3. Muscle cells contract
• Artificial pacemakers


  • Electrical devices used to correct irregularities in the heart rate
  • Implanted just under the skin
  • Wire delivers an electrical current to the heart to help it contract regularly
• Types of blood vessels


  • Arteries
  • Veins
  • Capillaries
• Arteries


  Transport blood away from the heart (usually at high pressure)
• Veins


  Transport blood to the heart (usually at low pressure)
• Capillaries


  Have thin walls which are "leaky", allowing substances to leave the blood to reach the body's tissues
• The blood vessels form a continuous network; the structure of each allows it to carry out its function
• Arteries


  • Must be able to withstand high pressures generated by the contracting heart, and maintain these pressures when the heart is relaxed
  • The wall of the artery is relatively thick with layers of collagen, smooth muscle and elastic fibres
  • The elastic fibres allow the artery wall to expand around blood surging through at high pressure when the heart contracts, these fibres then recoil when the heart relaxes – this alongside a narrow lumen maintains high blood pressure
• Veins


  • Receive blood that has passed through capillary networks; blood is at very low pressure and must be returned to the heart
  • The wall of the vein is relatively thin with thinner layers of collagen, smooth muscle and elastic fibres
  • The lumen of the vein is much larger than that of an artery
  • Veins contain valves that prevent the backflow of blood, helping return blood to the heart
• Capillaries


  • The wall is only one cell thick – this reduces the diffusion distance for oxygen and carbon dioxide between the blood and the tissues of the body
  • The cells of the wall have gaps called pores which allow blood plasma to leak out and form tissue fluid
• Components of human blood


  • Plasma
  • Red blood cells
  • White blood cells
  • Platelets
• Red blood cells (RBCs)


  • Distinctive biconcave disc shape
  • No nucleus
  • Large surface to volume ratio to maximise the efficiency of diffusion of gases
• Haemoglobin


  Protein in the cytoplasm of RBCs that oxygen binds reversibly to, forming the red pigment oxyhaemoglobin
• White blood cells (WBCs)


  • Part of the immune system, responsible for defending the body from infection by recognising and destroying pathogens
  • Phagocytes engulf and digest pathogens
  • Lymphocytes produce specific antibodies that help enhance phagocyte activity
  • Some lymphocytes produce antitoxins to neutralise toxic substances
• Platelets


  • Fragments of cells (they contain cytoplasm but no nucleus)
  • Involved in forming a blood clot to prevent blood loss
• Individuals with insufficient platelets cannot clot their blood effectively – this can be life-threatening if excessive damage occurs