B. Arterial System. 



Distend the oesophagus with a piece of cotton wool or paper to show 

 the blood vessels more clearly. Trace out the anterior part of the arterial 

 system, made up of two branches of the truncus arteriosus each of which 

 divides into : — 



(a) The carotid arch passing to the head region. 



(b) The systemic arch curving round the oesophagus. 



(c) The pulmo-cutaneous arch to the lungs and the skin. 



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