Units 4 & 5

• Syllabus Focus Points

  • Lifestyle choices, including being active or sedentary, the use of drugs and type of diet, can compromise body functioning in the short term and may have long-term consequences
  • The exchange of gases between the internal and external environments of the body is facilitated by the structure and function of the respiratory system at the cell, tissue and organ levels
  • The efficient exchange of gases in the lungs is maintained by the actions of breathing, blood flow and the structure of the alveoli
• The circulatory and respiratory systems work together to ensure cells have a constant supply of oxygen and CO2 is continually removed
• Structures of the Respiratory System

  • Nasal Cavity: Lined by mucous membranes, Filters, warms and moistens air, Hairs and mucus trap debris which prevents it from reaching the lungs
  • Pharynx: Region from the nasal cavity to the top of the trachea and oesophagus, Air travels through the pharynx before being diverted into the trachea by the epiglottis
  • Epiglottis: A flap of elastic cartilage, During inhalation, it covers the oesophagus so that air goes into the trachea, When swallowing food, it closes off the larynx to prevent food from entering the lungs
  • The Larynx (voice box): Cartilage, Joins the pharynx and the trachea, Contains vocal cords
  • The Bronchial Tree: Larynx, Trachea, Bronchus, Bronchiole
  • Trachea (windpipe): Carries air into and out of the lungs, Made of C-shaped cartilage rings, Ensures that it always stays open, Lined with a mucus membrane – traps dust and debris, Cilia push mucus with dust up to pharynx to be swallowed
  • The Ciliated Lining Tissue: Mucus-secreting goblet cells, Cilia
  • Bronchi: Two primary bronchi, one for each lung, These split into secondary bronchi which take air into each lobe, These divide into tertiary bronchi, Made of C-shaped cartilage rings
  • Bronchioles: Smaller tubes branching off the tertiary bronchi, End in terminal bronchioles, Made of smooth muscle and elastin (not cartilage), Controls the flow of air in the lungs, Cilia and mucous present to protect from contaminants
  • Alveoli: Tiny air sacs – make up most of lungs, One cell thick, Surrounded by capillaries, Allow for good gas exchange
  • The Lungs: Left lung: two lobes, Right lung: three lobes, Pleura – covers the surface of the lungs and lines the inside of the chest, Pleural fluid – thin layer of fluid between the two layers of membrane, Holds the lungs against the inside of the chest wall, Allows the lungs to slide when breathing
  • Ribs: Form chest framework
  • Intercostal Muscles: Lie between the rib bones, Move rib cage up and out to increase volume of chest cavity
  • Diaphragm: Separates the chest/abdomen, Contracts/flattens downwards to increase the chest cavity
• Mechanics of Breathing

  • Ventilation: process where air is moved into and out of lungs, Air flows from higher pressure to lower pressure, If the pressure in your lungs is high (lungs are smaller in volume) then air will flow from inside your lungs to air outside your body
  • Respiration: transport of oxygen from the air to the tissues
• Process where air is moved into and out of lungs

  1. Air flows from higher pressure to lower pressure

  2. If the pressure in your lungs is high (lungs are smaller in volume) then air will flow from inside your lungs to air outside your body
• Inspiration

  The process of taking air into the lungs (inspiration/inhalation)
• Respiration

  Transport of oxygen from the air to the tissues and the transport of carbon dioxide in the opposite direction
• For air to flow into the lungs, the pressure of air in the lungs must be less than the atmospheric pressure outside the body
• Effects of Lifestyle and Environment: Emphysema Causes: Long term exposure to irritating particles in the air such as smoke particles (smokers), dust, asbestos
• Gas Exchange

  There must be a concentration gradient for diffusion of gases into and out of the blood. This means that there needs to be a difference in gas concentration (carbon dioxide and oxygen) between the air in the alveoli and the blood in the capillaries
• Concentration gradient is maintained by: Constant flow of blood through the capillaries. Movement of air into and out of the alveoli as we breathe in and out
• Expiration

  The process of expelling air out of the body (breathing out/exhalation)
• Effects of Lung Cancer
• Emphysema damages the Alveoli as they

  Lose elasticity, Replaced with fibrous tissue, May break down, reducing the internal surface area of the lung
• Structure of the alveoli contributes to the efficiency of gas exchange

  Describing how the structure of the alveoli contributes to the efficiency of gas exchange
• Due to the loss of elasticity of the lung tissue in Emphysema, the lungs are constantly inflated, and breathing out no longer occurs passively but requires voluntary effort
• Good hygiene practices help to reduce the spread infections
• When infected people cough, sneeze or spit, tiny droplets of moisture containing the bacteria, viruses or fungi may be inhaled by others, so spreading the infection
• Most lung infections are spread by droplets (tuberculosis and pneumonia)
• Asthma is an allergic response to foreign substances that enter the body
• Pneumonia


  • Infection of the lungs caused by bacteria, viruses, fungi or other organisms, The surface area available for exchange of gases is reduced, The inflammation resulting from the infection causes secretion of fluid and mucus into the alveoli, thus reducing the amount of air that they can contain, Breathing difficulty is a symptom of many types of pneumonia
• Substances that may trigger an asthma attack include animal skins, feathers, bird excreta, house dust mites, pollen grains, and some substances in food
• During an asthma attack, muscles that surround the bronchioles go into spasm, narrowing the air passage, secretion of excessive mucus, reduced volume of air going into and out of the lungs, blood does not carry the usual amount of oxygen, gas exchange is impaired
• Asthma occurs due to smooth muscles contracting and narrowing the airway, inflammation causing the lining of the airways to thicken, and mucus filling the airway
• Transport of materials throughout the body

  Facilitated by the structure and function of the circulatory system at the cell, tissue, and organ levels
• Lymphatic system functions

  Return tissue fluid to the circulatory system and assist in protecting the body from disease
• Circulatory System


  • Body’s main internal transport system
  • Provides cells with substances they need and removes waste products
  • Consists of heart, blood vessels, and blood
• Components of blood

  • Plasma, Erythrocytes, Platelets, Leucocytes
• Functions of Blood

  1. Transport oxygen and nutrients to all cells, carbon dioxide and other wastes away from cells, chemical messengers (hormones) to cells

  2. Regulate pH, body temperature, water content, and ion concentration

  3. Protect against disease-causing micro-organisms, clotting when vessels are damaged
• Components of Blood

  • Plasma, Red blood cells (erythrocytes), White blood cells (leucocytes), Platelets (thrombocytes)
• Leucocytes (WBC)


  • Larger than RBC, protect the body from infection, remove dead or injured cells and invading micro-organisms, live from a few minutes to years
• Leucocyte Types

  • Neutrophils, Monocytes, Lymphocytes, Basophils, Eosinophils
• Erythrocytes (RBC)


  • Most abundant cell in blood, biconcave discs, no nucleus, live for about 120 days, produced in bone marrow, destroyed in liver and spleen
• Blood Plasma


  • Makes up 55% of blood volume
  • Consists of 91% water, dissolved substances like sugar and salts
  • Function is to transport the other components of the blood
• Transport of Oxygen

  3% carried in blood plasma, 97% carried with hemoglobin as oxyhaemoglobin
• Platelets (thrombocytes)


  • Small cell fragments, no nucleus, formed in red bone marrow, live for about 7 days, important for blood clotting
• Transport of Oxygen by Red Blood Cells

  • Contain hemoglobin, no nucleus for more room for hemoglobin, biconcave shape for increased surface area for oxygen exchange
• Oxygenated blood/Oxyhaemoglobin


  Red in arteries
• Deoxygenated blood/Haemoglobin

  Dark red in veins
• Transport of Carbon Dioxide

  Diffuses into the plasma due to concentration difference, some dissolves in plasma, some combines with hemoglobin, most reacts with water to form carbonic acid which then dissociates into hydrogen and bicarbonate ions