Sentence:  This vessel could be followed to the parenchyma where it directly provided bronchial arterial <WSD>blood</WSD> to the alveolar capillary bed ( figs. 17 , 18 ) . 
Meaning of the word marked with <WSD> tags:  the fluid (red in vertebrates) that is pumped through the body by the heart and contains plasma, blood cells, and platelets