How is the concentration of sodium altered in a cell in the intestines and why is glucose absorption affected?

Imagine a cell like a rectangle, of which one side has finger-like projections (this side faces the intestinal lumen) called the villi, and the other side is flat - the base membrane of that cell that is. On the flat side blood is constantly passing by taking with it some substances that exit from the flat side of the cell. On the finger like membrane there are proteins which pump simultaneously Na ions and Glucose from the intestinal lumen and into the cell. These proteins are called symport proteins. In greek, Sym.=with/together and in latin, port= door. Therefor two things, glucose and sodium, are carried TOGETHER into the cell. On the flat side of the cell we have sodium/potassium pumps. This is an enzyme pump, which takes 3 sodium molecules out of the cell and then pumps two potassium molecules in the cell. To be able to do that it uses ATP. The pump breaks the ATP down to ATP and Pi and uses the energy released to do the pumping. 

Therefore, the pump on the flat side, removes sodium from the intestinal cell and therefore decreases the sodium concentration in the cell. Now, as a result, when we compare the inside of the cell with the intestinal lumen we see that in the intestine there s more sodium. We have what we call a concentration gradient for sodium. So sodium wants to go were there's less sodium, down its concentration gradient, and this is the inside of the intestinal cell. This enables the proteins on the finger-like surface to do what we discussed above.