exchanging surfaces and breathing

Question 1

Outline the structure and function of each type of tissue found in the lungs. (6)

Answer 1

Cartilage supports trachea / bronchi / prevents collapse of trachea;
Cartilage is made of C shaped rings for flexibility / allow oesophagus to expand when swallowing;

Smooth muscle contracts to constrict airway;
Smooth muscle controls flow of air / prevents harmful substances entering;

Elastic fibres recoil (when muscle relaxes);
To return airway to normal size / dilate airway;

Goblet cells / glandular tissues secrete mucus;
Goblet cells / glandular tissues trap dirt / dust / bacteria;

Ciliated epithelium are hair-like structures / protrusions;
Ciliated epithelium waft / move mucus back up to the throat

Question 2

Compare and contrast the mechanisms of ventilation in mammals, insects and bony fish (5)

Answer 2

All three have a large surface area
All three have short diffusion distance / good blood supply;
Mammals breathe with lungs, fish through gills and insects through spiracles;
Mammals breathe due to pressure changes in the thorax (described);
Fish use counter-current flow (described);
Fish irrigate their gills by opening their mouth and operculum alternately;
Insects have a muscular valve to change pressure;
Insects pump thorax / abdomen to exhale

Question 3

Describe the journey of an oxygen molecule from the alveoli in the lungs to a muscle cell in the leg

Answer 3

Oxygen diffuses into blood / capillary;
Oxygen enters erythrocyte / RBC;
Oxygen combines with haemoglobin to form oxyhaemoglobin;
Enters left side of heart / left atrium;
Enters through pulmonary vein;
Leaves through aorta;
Oxygen dissociates from haemoglobin;
Oxygen diffuses into tissue fluid;
Oxygen diffuses into cell