The cells are bound together by the glycoproteins, specialized junctions, and the wavy membranes contours. The glycolipids and the glycoproteins form the glycocalyx. This acts as the adhesive holding the cells together. The specialized junctions formed between the cells also function to hold the cells closely to each other. The wavy contours of the cells fit together with the contours of the other cells in the tongue-and-groove fashion.
Hence, the answer is glycoproteins, specialized junctions, and the wavy membranes contours.