📝 STANDARD DESCRIPTION:
Function: Muscular tube carrying food from pharynx to stomach.
Three parts:
1. Cervical — starts dorsal to larynx, runs LEFT of trachea in the neck.
2. Thoracic — enters chest, runs above trachea in cranial mediastinum, then through middle mediastinum.
3. Abdominal — short; from oesophageal hiatus to cardia of stomach (rumen in cattle).
Wall (Ox): Lined by stratified squamous epithelium. Muscle layer is STRIATED throughout in ox/dog (not smooth). Allows quick voluntary regurgitation for chewing cud.
Four Narrow points (sites of CHOKE):
1. Cricopharyngeal (top of oesophagus).
2. Thoracic inlet.
3. Base of heart.
4. Oesophageal hiatus of diaphragm.
Vagal trunks run on its surface (dorsal & ventral).
📚 DETAILED DESCRIPTION:
THE FOOD-PIPE — OESOPHAGUS
The oesophagus is a muscular tube about 90-105 cm long in ox. It carries food (and water) from the pharynx to the stomach. In ruminants it works in both directions — down for swallowing, up for regurgitating cud.
THREE PARTS:
• Cervical part: Begins at the back of the pharynx and runs down the neck, lying first above the trachea, then deviating to the LEFT side of the trachea about midway down the neck. This is why the jugular furrow on the LEFT side is preferred for oesophageal observations and why a stomach tube is felt running on the left side of the neck.
• Thoracic part: Enters the chest at the thoracic inlet, runs in the cranial mediastinum above the trachea, then in the middle mediastinum it crosses over the heart base and runs along the dorsal surface of the heart, finally reaching the diaphragm.
• Abdominal part: Very short — from the oesophageal hiatus to where it joins the stomach (in cattle, the cardia of the rumen at the reticulo-rumen junction).
WALL STRUCTURE:
• Mucosa: stratified squamous epithelium (tough, like skin lining; resists scratches from rough food).
• Muscularis: This is special — in ox and dog the muscle layer is striated (skeletal) throughout the entire length. In horse, the upper 2/3 is striated and lower 1/3 is smooth muscle. In cat, only the upper part is striated. Striated muscle = voluntary, fast — explains why ruminants can voluntarily regurgitate cud.
FOUR NARROW POINTS — common SITES OF CHOKE (oesophageal obstruction):
1. Just past the pharynx (cricopharyngeal sphincter).
2. Thoracic inlet (at first rib).
3. Base of heart (where the oesophagus crosses over).
4. Oesophageal hiatus of the diaphragm.
NERVE SUPPLY: Vagal (dorsal and ventral vagal trunks lie ON the oesophagus and travel with it through the diaphragm).
// COMPARATIVE ANALYSIS
| OX |
Striated muscle THROUGHOUT — supports cud regurgitation. |
| HORSE |
Upper 2/3 striated, lower 1/3 smooth → why horses CANNOT vomit easily; oesophageal obstruction (choke) is common and serious. |
| DOG |
All striated (like ox); easy regurgitation possible. |
| PIG |
Mostly striated; widely uses pharyngeal swallowing. |
| FOWL |
Has a CROP (large dilation of cervical oesophagus) for storing food; opens into proventriculus. |
CLINICAL RELEVANCE
CHOKE (Oesophageal obstruction): Common in cattle (potato/turnip pieces) and horses (dry pellets, apples). Animal cannot swallow, drools saliva, may bloat (cattle cannot eructate gas → bloat). Common sites = thoracic inlet & heart base.
Megaoesophagus (dog): Loss of oesophageal motility → food stagnates → regurgitation of solid food.
