Cow esophagus

Cow esophagus is a long, muscular tube that is considered as the important organ of the digestive system. Here, I will describe its parts, courses, and topographic relationship with hand-drawing diagrams and real pictures.

Quick answer: Cow esophagus is a long, musculomembranous tube that extends from the end of the pharynx to the atrium ventriculi with relation to different organs of the neck and thorax.

However, I will also describe the general structure of the cow’s esophagus with proper diagrams.

Cow esophagus

Figure 1 shows the schematic diagram/presentation of the location, parts, and courses/extension of the cow’s esophagus. This hand-drawing diagram might help you to understand the overview of the cow’s esophagus perfectly.

Here, the above figure presents that the cow’s esophagus has the followings features –

• Location: It has a start and end points along with a define course or extension through the neck and thorax.
• Parts: While passing the neck and thorax regions, it is divided into two parts that are identified in Figure 1.
• Relation with other organs: It has a direct or indirect relationship with different organs or parts of the neck and thorax of the cow.
• Structure: Like other tubular organs, the cow’s esophagus also has similar features in its wall.

Thus, I will describe the above-mentioned features while describing the cow’s esophagus anatomy.

First, let’s describe the location and parts of the cow’s esophagus. But I will describe the relation of the esophagus with other organs and its structure separately.

Where is the esophagus located in a cow?

Figure 2 highlights the location of the cow’s esophagus. It also identifies the neck region, thorax region, diaphragm, and the parts of the cow’s stomach from its abdominal cavity.

Location of the cow’s esophagus: It is located between the cow’s pharynx and parts of the stomach. But, you may also describe the cow’s esophagus location as follows –

The cow’s esophagus extends from the pharynx, passes through the neck and then through the thorax. Finally, it pierces the diaphragm and opens into the atrium ventriculi of the stomach inside the abdominal cavity.

Here, the atrium ventriculi is the dome-shaped area between the dorsal sac of rumen and reticulum of the cow’s stomach. Again, the cow’s esophagus enters the abdominal cavity through the esophageal hiatus of the diaphragm.

Here, Figure 3 highlights the atrium ventriculi from the cow’s stomach. However, it also presents the esophageal hiatus of the cow’s diaphragm.

Parts of the cow’s esophagus

Figure 4 presents the different parts of the cow’s esophagus. I have made this figure with the combination of both a hand-drawn diagram and a real picture to make the esophagus understandable.

For anatomical point of view, the cow’s esophagus has 2 major parts –

• Cervical part: The average length of the cervical part of the cow’s esophagus 40 centimeter (cm).
• Thoracic part: The length is about 50 centimeters (cm).

Again, the thickness/diameter of the cow’s esophagus is about 4 centimeters (cm). Again, the diameter of the esophagus increases from the pharynx to the stomach.

Do cow’s esophagus have an abdominal part?

No, there is no abdominal part in the cow’s esophagus. This is because of the close apposition of the cow’s stomach to the diaphragm.

Here, Figure 5 shows that the esophagus open to the shallow vault between rumen and reticulum immediately after passing the diaphragm. Thus, there is no abdominal part in the cow’s esophagus.  

But the other species, like the horse, dog, and pig, have a small abdominal part in their esophagus.

Course and relation of the cow’s esophagus

Now, I will describe the course of the cow’s esophagus through the neck and thorax, that are shown in Figure 6. I will also show the relation of the cervical and thoracic parts of the esophagus with different organs of the neck and thorax, respectively.

Followings things should be kept in mind while you describe the course of the cow’s esophagus –

• From where it arises, and does it have any relationship with other organs?
• When does it change its direction (from dorsal to lateral or lateral to dorsal)?
• How many curves does the cow’s esophagus have before reaching it in its destination?
• Obviously, you might keep in mind the surface and topographic anatomy of these curves or the turning points of the cow’s esophagus.
• How does it enter the abdominal cavity and open on the atrium ventriculi of the cow’s stomach?

However, Table 1 shows the short technique to memorize the course of the cow’s esophagus –

Parts	Course	Curves
Cervical part	Start: cricoid cartilage Left lateral: 3rd to 6th cervical vertebrae Dorsolaterally: at the level of the thoracic inlet	First: at the level of the 3rd cervical vertebra Second: at the level of the 6th cervical vertebra
Thoracic part	Start: at the level of the first rib Courses in: mediastinum Dorsally: at the base of the heart and tracheal bifurcation Course in: caudal mediastinum Passes: esophageal hiatus Open: atrium ventriculi	First: convex ventral curve at the level of the first rib Second: convex dorsal curve (at the level of the base of the heart)

Cervical course of the cow esophagus

In the cervical course, the cow’s esophagus begins in the median plane dorsal to the lamina of the cricoid cartilage of the larynx. Then it passes backwards and downwards on the dorsal surface of the cow’s trachea.

Thus, after origin, the esophagus remains dorsal to the trachea at the cranial third of the cow’s neck.

At the level of the third cervical vertebra, the cow’s esophagus inclines the left surface of the trachea. It continues this position till it reaches the sixth cervical vertebra.

Again, at the level of the first rib, the esophagus goes a little upward and becomes dorsolateral to the trachea again. Here, Figure 7 presents the overview of the course of the cervical part of the cow’s esophagus.

Thus, from origin to the level of the first rib, the cow’s esophagus has the following curvatures –

• First curve: At the level of the third cervical vertebra,
• Second curve: At the level of six cervical vertebra,
• Third curve: At the level of the first rib,

Figure 8 highlights the curvatures of the cow’s esophagus from origin to the level of the first rib/thoracic inlet. Here, I have used both a hand-drawn diagram and a real picture to express these curvatures of the cow’s esophagus.  

Topographic anatomy of the cow’s esophagus

The cervical part of the cow’s esophagus is related to the following organs/structures –

At the origin: It is related to the rectus capitis ventralis major muscle dorsally, and the cricoid cartilage of the larynx ventrally.

First segment at the level of the third cervical: The first segment of the cervical course, the cow’s esophagus is dorsally related to the longus colli muscle of the neck. However, it is ventrally related to the trachea at the level of the third cervical vertebra.

Second segment of the cervical course: It lies to the left of the trachea and is also related dorsally to the longus colli muscle. Again, it is also related ventrally to the ventral cervical muscles (especially to the sternocephalicus and omohyoideus).

Medially, the second segment of the cervical part of the cow’s esophagus is related to the trachea. However, you will find the following organs/structures that have a relationship laterally –

• First, the left common carotid artery,
• Second, the left vagosymphathetic trunk,
• Third, the left recurrent laryngeal nerve,
• Fourth, the deep cervical lymph node, and
• Fifth, the scalenus and brachicephalicus muscles.

Here, Figure 9 presents the overview of the topographic anatomy of the cervical course of the cow’s esophagus.

Thoracic course of the cow’s esophagus

The thoracic part of the cow’s esophagus begins at the level of the first rib, in the continuation of the cervical part. At the junction of neck and thorax, it undergoes a slight curvature with its convexity directed ventrally.

Now, the thoracic part of the cow’s esophagus continues caudally into the cranial mediastinum. It passes dorsal to the base of the heart and bifurcation of the trachea at the level of the third to fourth ribs.

Here, the thoracic part of the esophagus forms a second curvature, which is convex dorsally. It crosses the right face of the aortic arch. However, it then passes straight back to the caudal mediastinum ventral to the thoracic aorta.

Figure 10 shows the summary of the thoracic part and course of the cow’s esophagus.

Thus, from the thoracic inlet (at the level of the first rib) to the caudal mediastinum, you will find two major curvatures –

• First curvature: At the junction of the neck and thorax, and
• Second curvature: At the level of the third to fourth ribs.

How does the cow’s esophagus open into the stomach?

At the level of eight or ninth intercostal space, the cow’s esophagus passes through the esophageal hiatus of the diaphragm. It enters the abdomen and opens into a shallow vault between the rumen and the reticulum. This is known as the atrium ventriculi of the cow’s stomach (Figure 11).

The relation of the thoracic course of the cow’s esophagus

At the junction of the cow’s neck and thorax: Here, the cow’s esophagus is related to the trachea medially and laterally to the first rib. However, it is also laterally related to the common trunk of the vertebral, costocervical, and caudal cervical veins.

Cranial to middle mediastinum areas: Within these areas, it is related to the thoracic duct and aortic arch on the left side. However, it is also related to the right and left longus colli muscles, the common trunk for right costocervical veins, and the right vagus nerve on the right side.

At the caudal mediastinum: Here, the cow esophagus is related to the right and left lung, the vagus nerve, and the bronchial and esophageal arteries on the left.

Here, Figure 12 presents the summary of the relation of the thoracic course of the cow’s esophagus.

Structure of the cow’s esophagus

You may easily understand the structure of the cow’s esophagus through the histological section. Here, the wall of the cow’s esophagus consists of mucosa, submucosa, muscular, and a fibrous layer from inside outward (Figure 13).

The mucosa layer of the cow’s esophagus consists of surface epithelium, lamina propria, and lamina muscularis. Here, the epithelium consists of nonkeratinized stratified epithelium.

In the upper cervical part of the cow’s esophagus, the mucous membrane is extensively thrown into longitudinal folds. Here, the lumen of the cervical part appears to be contracted and almost closed.

In the remaining part, the lumen of the esophagus is quite wide and varies in shape. The shape of the lumen can be oval, circular, or slit-like at different levels.

The submucosa coat contains the plexus of vessels, lymphatics, nerves, and mucous-secreting esophageal glands. However, the muscular coat of the cow’s esophagus consists of two layers of muscles: inner circular and outer longitudinal.

FAQ’s on the cow’s esophagus anatomy

Conclusion

Thus, the cow esophagus is a long, muscular tube that extends from the pharynx to the atrium ventriculi of the stomach. It is one of the major parts of the digestive system of a cow and presents a define courses through the neck and thorax.

However, its topographic anatomy, along with its curvatures, is also important for further applied study.

References

• Ghosh, R. K. : Primary veterinary anatomy, 2nd Edn. Current Books International, Kolkata.
• Rowen D. Frandson, W. Lee Wilke, and A. Dee: Anatomy and physiology of farm animals, 4th edn.Wiley-Blackwell, USA.
• Getty, R. Sission and Grossman’s The anatomy of the domestic animals, 5th Edn. W. B. Saynders and Co., Philadelphia (USA).
• Sravya et all., Surgical retrieval of oesophageal foreign body in 12 cows. Int Jr of Vet Sci and Ani Hus., 2024; SP-9(2): 331-334.
• Nickel, R., Schummer, A. and Seiferle, E.: The anatomy of domestic animals, 1st Edn. Verlag Paul Parey, Berlin.
• Szabo et al., Comparative study on the structure of the esophagus in different animals. Bio Jr of Sci and Tech Res., (53):2, 2023.
• Hermanson et al., Miller and Evan’s Anatomy of the Dog, 5th Edn. Elsevier.
• Mcleod, W. N.: Bovine anatomy, 2nd Edn. Burgess Publishing Co., Minneapolis.
• Dyce, K. M., W. O. Sack and CSG Wensing: Textbook of Veterinary Anatomy, Lea & Febiger. Philadelphia