Yup. For anatomy purposes the lumen of the digestive tract is external the body(debatable I am sure). It’s a bit confusing but kinda makes sense considering the anus and mouth both open to the external environment. If you think about it a step further you also have blood in an area where it cannot deliver oxygen and remove waste, rather it gets digested. At this point the blood is not doing it job and the person can be considered anemic because low Blood levels are based of serum concentration.