All are true about esophagus except ?

Ans. is 'd' i.e., Lower third contains only skeletal muscleImpoant features of esophagusEpithelium is stratified squamous non-keratinized epithelium.Muscularis mucosa contains only longitudinal layer and no circular layer.Mucosa is the toughest and strongest layer.Serosa is absent.Muscularis externa is made up of skeletal muscle fibers only in the upper third, smooth muscles only in the lower third and both types of muscle fibers in middle third. At upper end the longitudinal coat splits into two bundles and the triangular interval between them is called Laimer's tringle which is filled with circular muscle fibers.