Control & Coordination Part 1 The Respiratory System Year 9 Science 2013 Control & Coordination Part 1 The Respiratory System

Gas Exchange Oxygen and carbon dioxide need to be exchanged with the environment

Diffusion The process of gas exchange is always by diffusion between the external and internal environment of the organism.

Surface Area: Volume For single-celled and small organisms this is not a problem because of their high surface area to volume ratio.

Multicellular Organisms Large organisms rely on specialised respiratory surfaces.

Features of Respiratory Surfaces Large surface area Thin, moist and easily penetrable surface. Adequate ventilation. Efficient transport of carrier fluid (blood) across respiratory surface.

Alveoli The site of gaseous exchange Increases the surface area for gas exchange. http://www.bmu.unimelb.edu.au/examples/gasxlung/

Breathing Contraction & relaxation of the diaphragm muscle results in changes in pressure within the lung cavity, forcing air in & out.

Epiglottis The epiglottis prevents food from travelling down the trachea and blocking the passage of air.

Gas exchange relies on diffusion, therefore concentration gradients need to be maintained.

For oxygen to continually diffuse into capillaries around alveoli, oxygen needs to be transported away from the site

Respiratory pigments such as haemoglobin carry oxygen in the blood from lungs and release oxygen into cells.

Rhythmic pumping of the heart ensures continuous flow of blood along capillaries surrounding the alveoli.

Haemoglobin and oxygen bind in a reversible reaction.