Blood is carried away from the heart to provide oxygen to rest of the body by the

poor water quality affects most estuarine organisms, including commercially important fish and shellfish. the pollutants that have the greatest impact on the health of estuaries include toxic substances like chemicals and heavy metals, nutrient pollution (or eutrophication), and pathogens such as bacteria or viruses.

the sphincter muscles at the end of the digestive tract is the anus.