A 25 cm long muscular tube that carries food from the pharynx to stomach is called esophagus.

        A 25 cm long muscular tube that carries food from the pharynx to stomach is called esophagus. This tube starts from the surface of sixth cervical vertebra, passing downwards through trachea and posterior of heart and reaches to the diaphragm on the tenth thoracic vertebral surface; from where it continues its journey to the eleventh thoracic vertebral surface by making a hole in the diaphragm, here it makes a curve upper side and being opened on the cardiac ends of stomach.    

          The wall of oesophagus is made up of four layers. The innermost layer is covered with mucosa stratified squamous epithelium and secretes mucus. Submucosa layer is present on it that connects the mucosa and muscular layer. In it, blood vessels and nerves are found along with mucus glands too. Muscularis externa is present on it, in which there are two layers of involuntary muscles present. The muscular fibers of external layer are long and the muscular fibers of internal layer are circular in shape. The outermost layer of it is called adventitia and made up of loose fibrous tissues.    

        One-third part of the uppermost muscularis externa of the esophagus is made up of skeletal muscles, one-third part of middle layer is made up of skeletal and smooth muscles and one-third of the lower layer is made up of only smooth muscles. the nerves of the esophagus are made up of Vegas nerve.

        The upper and lower ends of the esophagus remain closed with sphincter muscles. The upper sphincter muscles are called cricopharyngeal sphincter that stops air to enter in the esophagus and the substances of esophagus to come out during breathing. The lower sphincter is called esophageal sphincter. It is a band of smooth muscles, in which the last section of 4 cm, before connecting with stomach, is present. well, this band remains in contractive stage, but is become loose (relax) at the time of entering foods and liquid substances in to the stomach and stops foods and hydrochloric acid to come back in the esophagus from the stomach due to increasing internal pressure of abdomen.