Oesophagus is a musculo-membranous tube, which extends from the pharynx to the stomach. It is divided into cervical and thoracic parts
The cervical part begins at median line above the cranial border of the cricoid cartilage of larynx
At the level of the fourth cervical vertebra, it passes to the left of the trachea and continues this relation on the left side of the neck and enters the thoracic cavity
The thoracic part begins at the level of the first rib. At the level of third thoracic vertebra it gains the dorsal face of the trachea passes backwards and crosses the right side of aortic arch
It continues its course through the mediastinum between the lungs backwards and slightly upwards inclines to the left, reaches the hiatus oesophagi of the diaphragm
It passes through it and immediately terminates on the dome-like rumino-reticular wall -the atrium ventriculi
Directions : At first downward and backward till the thoracic inlet; upward to the dorsal face of trachea backwards and upwards between the lungs
Relation at the origin : Dorsally, the ventral straight muscles of the head. Ventrally cricoid cartilage. Laterally, carotid arteries
About the middle of the neck : Dorsally, left longus colli. Medially, trachea. Laterally, Left carotid artery, vagus and sympathetic nerves and recurrent laryngeal nerve
In the thoracic cavity In the cranial mediastinum: dorsally longus colli. Ventrally, trachea. Left side, Aorta, right side right vagus
In the caudal mediastinum: Oesophageal trunks of vagus lie above and below it
Sheep and Goat
The lumen is about an inch when moderately distended
Otherwise it resembles that of ox
Horse
It is longer, being about 125 to 150 cm. It has a small abdominal part. At its origin it is related to the guttural pouches
It is narrower and less dilatable
The muscle is striped till the level of the base of the heart and plain thereafter. There is a short abdominal part of oesophagus, about 2 to 3 cm
Pig
Short and nearly straight
The potential caliber is wide
Except the terminal part the muscular coat is striated
It has a small abdominal part
There are numerous tubulo-alveolar glands are present in the cranial part of the tube
Dog
Wide and relatively more dilatable except at the origin where there is a constriction
Muscular tissue is striated
Rabbit
The tube is 8 cm long and thin walled
The cervical part is longer than the thoracic part
It has a considerable length of abdominal part, which is little more than 1cm
Fowl
It extends from the pharynx to the proventriculus
It is greatly dilatable
It is at first dorsal to the trachea, then inclines to the right and presents at the thoracic inlet a ventral dilatation called the crop. Both inlet and outlet are on the internal face of the crop
It joins the cranial extremity of the proventriculus
