Explain airway and alveolar tissue adaptations for gas exchange and protection using evidence from each question and mark scheme.
Smooth muscle is a tissue composed of smooth muscle cells. The cells contain cytoplasm packed with proteins that are involved in contraction and relaxation.
Smooth muscle is present in the airways of the gas exchange system.
Explain how smooth muscle cells in the walls of the bronchioles contribute to the function of these airways.
any two from:
1 (by) contracts / contracting / contraction, and, relaxes / relaxing / relaxation ;
must be in context of bronchioles
R if includes ref. to stretch / expand / recoil
R if in context of bronchus or trachea (then ecf in subsequent mps)
2 diameter / lumen size, can be, controlled / changed ;
AW
A contraction, decreases diameter (of lumen) / constricts
A relaxation (after contraction) increases diameter (of lumen) / widens / dilates / expands
R vasoconstriction/vasodilation
3 idea of, controls / regulates, flow of air / volume of air flowing ;
AW
I statements such as 'lets air in' / 'allows inhalation and exhalation'
A oxygen in / carbon dioxide out, instead of air flow
R oxygen out and carbon dioxide
4 AVP ;
e.g. contract to, reduce air movement / prevent entry of contaminants idea of normally relaxed but can, contract / cause constriction, when needed
Marking guidance:
max 1 if response relates function to inhalation and exhalation
O marks if incorrectly stated as elastic tissue or elastic fibres