Oesophagus/ Esophagus
Esophagus is a fibromuscular tube, lined by mucosa. Through esophagus food and liquid passes from the pharynx into the stomach. Itconnects pharynx to stomach.
Esophagus is 25 cm long and 2 cm in diameter.
Esophagus passes through lower neck and throax. Then passes through diaphragm and joining the stomach. Esophagus runs behind trachea (windpipe) and Heart.
Location of Esophagus
Above - Pharynx
Just below- diaphragm and joint the stomach
Before entering stomach esophagus passes through esophageal hiatus (opening) of diaphragm.
End of esophagus is close by a sphincter muscle (lower esophageal sphincter) and separates esophagus from stomach and beginning of stomach.
Lower part of esophagus that connects to stomach is called gastroesophageal (GE) junction.
Sphincter of Esophagus
Esophagus has two muscular sphincters -
1. Upper or superior esophageal sphincter (UES)
2. Lower or cardiac esophageal sphincter (LES)
1. Upper or Superior Esophageal Sphincter/ Inferior Pharyngeal Sphincter/ Cricopharyngeal Sphincter
Upper esophageal sphincter consist of cricopharyngeal muscle.
UES prevent the reflux of foods from the esophagus into the throat.It open and closes to allow passage of content. Keep food and secretion from going down the windpipe. Create a barrier between esophagus and pharynx.
2. Lower or Cardiac Esophageal Sphincter / Gastroesophageal Sphincter/Gastroesophageal Junction
Lower Esophageal Sphincter (LES) present just superior to diaphragm, lower end of esophagus, where meets stomach.
When LES is closed, prevent HCL acid and stomach content from traveling backwards from stomach and prevent reflux of acidic gastric content into esophagus.
Layers of Esophagus
The wall of esophagus composed of four layers -
1. Mucosa
2. Submucosa
3. Muscularis externa or prorpia
4. Outer fibrous layer; Adventitia
1. Mucosa
Mucosa is inner layer line with mucus membrane, covers esophageal lumen, made up non-keratinized stratified squamous epithelium. Lamina proprio and muscularis mucosa are located under epithelium.
Lamina propria consist of areolar connective tisssue and Muscularis mucosa consists of smooth muscle.
2. Submuosa
Submucosa layer consists of elastic and collagen fibers areolar connective tissue (loose connective tissue), blood vessels, and mucus gland (esophageal glands and meissner plexus (interlacing collection of nerves) and highly vascular.
Mucosa connecting the mucosa to the muscularis.
3. Muscularis externa or propria
Muscularis externa consist of wholly skeletal muscle; upper third of esophagus.
Smooth and skeletal muscle; middle third of esophagus.
Wholly smooth muscle; lower third of esophagus.
4. Outer fibrous layer; Tunica Adventitia
Outer layer of esophagus is called adventitia (lack of epithelial layer).
Function of Esophagus
1. Passage food to stomach
2. Connect pharynx to stomach
3. Propel food, peristaltic movement
4. Transport food and liquid
5. Swept food towards stomach in peristaltic wave
6. Propel food into stomach
7. Esophageal mucosa mucus; lubricate
8. Secrete mucus
9. Lower esophageal sphincter prevents back flow of acid and stomach contents from traveling backwards from the stomach.
10. Serve as dynamic tube pushing food towards stomach
11. Upper esophageal sphincter opens to allow food and liquids to pass into esophagus.
Nerve supply of Esophagus
Esophagus is innervated by the oesophageal plexus formed by parasympathetic vagal trunks and cervical and thoracic sympathetic trunks.
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