<prompt> Which of the following is true about esophagus except:Serosa not presentMiddle lower third made up of striated muscleLower oesophageal sphincter is a zone of relatively high pressureIn achalia cardia LOS tone is increased so that food can not pass below  <response>: Answer-B Middle lower third made up of striated muscleEpithelium 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 Laimers tringle which is filled with circular muscle fiber 