gas exchange

Describe the gross structure of the human has exchange system

• trachea branches into two main bronchi;

• correct sequence from bronchus to bronchioles to alveoli;

• further detail eg. trachea has C-shaped, incomplete rings of cartilage / diameters of respiratory tube decrease towards alveoli;;

Suggest and explain how the oxygenator carries out the functions of gas exchange that normally occur in the lungs

• oxygen moves into blood, carbon dioxide moves from blood;

• by diffusion, down concentration gradient;

• counter current maintains steep diffusion gradient;

• short diffusion pathway;

• membrane has large surface area;

Suggest how the steep diffusion gradient for oxygen is maintained at the gas exchange surface.

• ventilation / inhalation brings in oxygen;

• blood flow in pulmonary capillaries removes oxygen;

• oxygen bind to haemoglobin / forms oxyhemoglobin;

• deoxygenated blood arriving;

Describe the defence mechanisms of the gas exchange system and explain how bacteria in inhaled air are prevented from entering cells of the gas exchange system

• production of mucus by goblet cells;

• sticky / traps pathogens;

• acts as a barrier;

• increase distance to reach cells;

• ciliated epithelium;

• cilia move mucus; away from alveoli / towards mouth;

Describe the role of cartilage in the gas exchange system

• prevent collapse of airways;

• allow flexibility;

• incomplete rings allow trachea to widen when inhaling;

State the main effects of tar on the cells lining the gas exchange system that are related to lung cancer and to chronic bronchitis

• carcinogen;

• causes mutations;

• AVP eg. protooncogenes to oncogenes / cell cycle checkpoints disabled / no programmed death;

• paralyses cilia;

• consequence to cilia action; eg. cannot waft away mucus / loss of synchronous rhythm

• goblet cells enlarged; excess mucus produced;

Suggest why there is an improvement in total lung SA:V after surgery has been carried out to remove diseased lung tissue

• alveoli burst to produce one large air sac;

• removed tissue has large air sacs;

• remaining tissue has healthy alveoli;

Suggest one reason why smoking tobacco, even after only a short time, may cause a decrease in the volume of air per breath moving towards the alveoli.

• in context of airways

• diameter of lumen decrease / smooth muscle contracts;

• inflammation;

Explain why smoking tobacco causes a decrease ibn the ability of red blood cells to carry oxygen

• carbon monoxide binds to haemoglobin;

• ref. competitive / permanent binding;

• presence of carbon monoxide lowers affinity of haemoglobin for oxygen;

• ref. carboxyhemoglobin formed;

• comparatively less haemoglobin per red blood cell to bind oxygen;

Suggest how thicker mucus interferes with the maintenance of healthy gas exchange surfaces in the lungs

• cilia have difficulty moving mucus;

• pathogens build up; lead to infection

Suggest and explain how the effect of phagocytes on tissues in the lungs leads to people feeling tired all the time

• elastase breaks down alveolar walls;

• alveoli cannot stretch and recoil / overstretch;

• alveoli burst / single large air sac formed;

• surface area reduced;

• less oxygen absorbed / not enough oxygen for aerobic respiration;

Describe and explain how the oxygen dissociation curve show some of the health benefits of stopping smoking

In lungs

• more oxygen taken up by haemoglobin / more saturated;

• ref. comparative data;

• carbon monoxide no longer binding to haemoglobin;

• more sites on haemoglobin available to take up oxygen;

In respiring tissue

• more oxygen dissociates from haemoglobin at lower partial pressures;

• ref. comparative data;

• ref. increase in allosteric effect;

health benefits

• more oxygen delivered to body / reach tissue;