A common theme in biology is how shape affects function. Just as the shape of many things in biology determines the job for which it is used, so does the shape of cells. Below are examples of how the shapes of particular kinds of cells help those cells perform their specialized job (function) within a multicellular organism.
Nerve cells- Nerve cells contain long spindles that are called axons. These axons need to be long because they relay electrical impulses all over the body - from the head to the lower extremities!
Red blood cells- Red blood cells are shaped like a flat disc which contains a divot in the center. This allows the blood to be "squishy" in order to be squeezed throughout the veins and arteries so that it can transport gases and nutrients throughout the body.
Intestinal lining- Cells located within the intestine are covered with many cilia. This increases their surface area so that more nutrients can be absorbed from the food that is passing.
Hopefully, these examples illustrate how the shapes of cells allow them to function within their specialized roles in an organism.