Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

The Science of Viscera (Splanchnology)
Digestive System
Esophagus

The esophagus is a cylindrical tube 30 cm long, beginning at the border between the V and VII cervical vertebrae and ending at the level of the XI thoracic vertebra by opening into The Stomach. The cervical, thoracic, and abdominal PARTS OF THE esophagus are distinguished. The cervical part lies posterior to the Trachea and adjacent to the spine. The thoracic part gradually diverges from the spine, lies adjacent to the posterior aorta, and is accompanied by the right and left vagus nerves. The abdominal part is the shortest (1.0–1.5 cm) and is located below the Diaphragm. The esophagus enters the Abdominal cavity along with the vagus nerves through the esophageal hiatus of the diaphragm. Along its path to the stomach, the esophagus presents three constrictions. The first constriction is located at the very beginning of the esophagus, at the pharyngoesophageal junction; the second is where the esophagus passes close to the left main bronchus, at the border between the IV and V thoracic vertebrae; the third constriction is found at the level of the esophageal hiatus of the diaphragm.

The wall of the esophagus consists of a mucous membrane ( mucosa ), submucosa, muscular layer ( muscularis externa ), and adventitia. The esophageal mucosa is lined with non-keratinized stratified squamous epithelium, which transitions into simple columnar epithelium at the gastroesophageal junction. The submucosa is well developed. Due to the thick submucosa, the mucous membrane forms longitudinal folds, giving the esophagus a stellate (star-like) appearance in cross-section. Numerous proper esophageal glands are located within the submucosa. The muscular layer consists of two layers: an inner circular and an outer longitudinal layer. In the upper part of the esophagus, the muscular layer is formed by striated Muscle fibers, which are gradually replaced by smooth myocytes in the middle part. In the lower part, the muscular layer consists entirely of smooth myocytes. The outer adventitial coat is formed by loose Fibrous Connective Tissue.

Review and Self-Assessment Questions:

1. Describe The Structure of the walls of tubular Internal Organs.

2. List the organs belonging to the Digestive System and provide a brief functional description of each.

3. Describe the STRUCTURE OF THE Oral Cavity and the organs located within or near it (Tongue, Salivary Glands, Teeth).

4. State the eruption times for deciduous and permanent teeth. Write the dental formulas for permanent and deciduous teeth.

5. Describe the structure of the pharyngeal and esophageal walls.