Esophagus

Esophagus
The esophagus is the upper part of the digestive tract, connecting the oral cavity to the stomach. The major function of the esophagus is to provide passage for food from the mouth to the stomach. The luminal surface of the esophagus is lined by nonkeratinized stratified squamous epithelium. Mucous glands called esophageal glands are located in the submucosa of the esophagus. The muscularis externa consists of two layers of muscle: inner circular and outer longitudinal layers. Both skeletal and smooth muscle fibers are found in the muscularis externa of the esophagus. The proportions of skeletal and smooth muscle fibers are different in different regions of the esophagus. Swallowing begins with voluntary muscle action but finishes with involuntary peristalsis
The esophagus can be divided into three regions:
The upper esophagus, middle esophagus, and lower esophagus(Fig,4).
1. The upper esophagus connects the oropharynx to the middle esophagus,this segment contains numerous esophageal glands in the submucosa. these glands secrete mucus to lubricate the esophageal wall so that food will pass through easily, the upper esophagus contains only skeletal muscle fibers in the muscularis externa. These are voluntary muscle fibers and are innervated by the glossopharyngeal nerve (cranial nerve ).
2. The middle esophagus has mucosa similar to that of the upper esophagus, the esophageal glands in the submucosa are less numerous than in the upper esophagus ,the muscularis externa contains both skeletal and smooth muscles.
3. The lower esophagus connects the esophagus to the cardiac of the stomach,this region contains large numbers of mucous glands in the lamina propria and
Dr.Hameda abdulmahdi College of Medicine /Dep. of anatomy &
histology 2nd stage
2
submucosa,these are called esophageal cardiac glands and produce mucous secretions to protect the lower esophagus from being damaged by reflux of acidic gastric juices from the stomach, the lower esophagus contains only smooth muscle fibers in the muscularis externa, these are controlled by the enteric branches of the vagus nerve.
(Figur,4):The four layers of esophageal wall include mucosa, submucosa,muscularis externa and serosa /adventitia.
The upper esophagus connects the oropharynx to the middle esophagus. This segment contains numerous esophageal glands in the submucosa. These glands secrete mucus to lubricate the esophageal wall so that food will pass through easily. The upper esophagus contains only skeletal muscle fibers in the muscularis externa. These are voluntary muscle fibers and are innervated by the glossopharyngeal nerve (cranial nerve [CN] IX)