The cow trachea is the part of the upper respiratory system just caudal to the larynx. Here, in this guide, I will explain the anatomy of the cow’s trachea with hand-drawn diagrams and real pictures.
Quick answer: Cow trachea anatomy refers to the description of its extension and formation, along with its peculiar features before bifurcation.
I will also show the topographic location of the cow’s trachea while passing through the neck and thorax.
What is the cow’s trachea?
Figure 1 shows a cartilaginous and membranous tubular structure that looks like a flexible pipe. It is the cow’s trachea that connects the pharynx and larynx to the lungs.
This structure allows air to pass from the larynx to the lungs and vice versa during breathing.
Location and extension: Here, Figure 2 shows the hand-drawing schematic presentation of the location and extension of the cow’s trachea.
Thus, according to this figure, the cow’s trachea is located partly in the neck and thorax.
However, it extends from the pharynx to the level of the base of the cow’s heart. Here, it divides into the right and left bronchi and enters the roots of the right and left lungs, respectively.
Length: Typically, the cow’s trachea is about 60 centimeters long and occupies the median position except at its termination. However, before termination, it is pushed a little to the right by the arch of the cow’s aorta.
Cow trachea anatomy
Figure 3 presents an overview of the anatomy of the cow’s trachea. I tried to point out the features that you need to explain while writing the cow’s trachea anatomy in your examination.
The following are the features/topics for the perfect description of the cow’s trachea –
- Location, shape, and length: Includes the topographic and surface location of the trachea, along with its shape and length.
- Formation of the trachea: It is made up of cartilage and membrane.
- Course/extension of the cow’s trachea: It includes the description of its cervical and thoracic parts along with its peculiarities.
How is the cow’s trachea formed?
Figure 4 shows the hand-drawn schematic presentation on the formation of the cow’s trachea. It shows the tracheal rings, annular ligaments, trachealis muscles, bronchi, and other structures.
Thus, the cow’s trachea is formed by a series of C- shaped incomplete rings made of hyaline cartilage. However, this open portion of the trachea is placed dorsally.
The fibroelastic membrane joins the cartilaginous rings. This type of connective tissue membrane is the annular ligament of the cow’s trachea (Figure 4).
The smooth trachealis muscles fill in the gap between the free ends of the C-shaped cartilaginous rings. Thus, the annular ligaments and trachealis muscles form the middle layer of the wall of the cow’s trachea.
Again, the inner layer of the cow’s trachea consists of mucous membrane with ciliated epithelium. It also contains mucosal glands that secrete mucus and trap debris from the filtered air.
However, the outer layer of the cow’s trachea consists of a serous membrane. This membrane is called tunica adventitia in the neck and tunica serosa in the thorax.
Why are the cartilages and trachealis muscles important?
The structural conformation of the cow’s trachea with the hyaline cartilages and muscles is important for the following reasons –
- C-shaped cartilages: They prevent the trachea from collapsing
- Cartilages and muscles: They allow the trachea to adjust in length and diameter due to traction during neck movement. However, they also work during forceful breathing.
Course of the cow’s trachea in neck and thorax
Figure 5 shows the detailed course/extension of the cow’s trachea in the neck and thorax. For descriptive purposes, the course of the trachea of a cow is divided into a cervical and thoracic part.
In each part, you might describe the specific extension of the trachea. However, the topographic relationship of different organs with the cow’s trachea should be explained properly.
Cervical part and course of the trachea
Figure 6 highlights the part and course of the cow’s trachea in the neck region. It shows its limits and relationships with various organs and structures of the neck.
Extension: The cervical part of the cow’s trachea extends from the pharynx to the level of the thoracic inlet. It lies median in position and runs parallel to the cow’s esophagus.
However, the cow’s esophagus lies to the left of the trachea throughout the cervical course. But, from the origin to the level of the third cervical vertebra, the cow’s trachea is related dorsally to the esophagus.
Thereafter, for the rest of the course up to the thoracic inlet, the cow’s trachea is dorsally related to the longus colli muscle. However, the longus colli is a longer and stronger muscle of the cow’s neck.
Organs related to the lateral and ventral aspect of the cow’s trachea
Laterally: The cow’s trachea is laterally related to the following organs –
Glands: The lateral lobe of the thyroid gland and cervical lymph gland,
Vessels: Carotid artery and jugular vein,
Nerves: Vagus, the sympathetic nerves, and recurrent laryngeal nerve, and
Ducts: The tracheal lymph ducts,
Figure 7 highlights organs or structures that are laterally related to the cow’s trachea. In this segment, the esophagus of a cow lies to the left of the trachea.
Ventrally: The cow’s trachea is ventrally related chiefly to the ventral cervical muscles of the neck. Figure 8 presents the major ventral cervical muscles (sternocephalicus, omohyoideus, and sternothyrohyoideus) that have a relationship with the trachea.
- Sternocephalicus muscle: It crosses the cow’s trachea obliquely, passing upward and forwards to reach the angle of the jaw.
- Omohyoideus muscle: It crosses the cervical part of the cow’s trachea in its upper third.
- Sternothyrohyoideus muscle: It also covers the ventral surface of the ox/cattle’s trachea.
Thus, most of the external part of the cow’s trachea in the cervical region is covered by muscles. However, other structures leave a small space on its ventral aspect in the upper third of the cervical course. Finally, the skin and cutaneous muscles cover the trachea externally.
Thoracic part and course of the cow’s trachea
Figure 9 highlights the thoracic part of the cow’s trachea, which is the caudal continuation of the cervical part. It enters the thoracic cavity of the cow through the thoracic inlet.
Location: The thoracic part of the trachea of a cow is located at the dorsal aspect of the cranial and middle mediastinum. However, the cow’s trachea extends from the thoracic inlet to the tracheal bifurcation at the level of the fifth rib.
Relationship with the esophagus: At the beginning of the thoracic course, the trachea lies on the right side of the esophagus. This relationship extends from the thoracic inlet to the level of the third rib or intercostal space.
However, the cow’s trachea slips down ventral to the esophagus and continues at the level of the fifth rib. Here, the cow’s trachea terminates by bifurcating into the right and left bronchi.
Apical bronchus in the cattle’s trachea (Unique features in the ruminant)
The cow’s trachea (and other ruminants like sheep, goats, and buffalo) shows unique features compared with the horse and dog. Figure 10 shows an extra bronchus in the cow’s trachea, which is absent in other species.
This extra bronchus arises from the right side of the trachea at the level of the third intercostal space. It is known as the apical bronchus, which ventilates the apical lobe of the cow’s right lung.
Topographic relationship of thoracic part of the cow’s trachea
Figure 11 shows the topographic relationship of the thoracic part of the cow’s trachea with various organs. I made this figure with both hand-drawn diagrams and real pictures of the cow’s trachea.
Dorsal: The thoracic part of the cattle’s trachea is dorsally related to the longus colli muscle except at its bifurcation. However, at the level of the tracheal bifurcation, it is dorsally related to the esophagus.
Ventral: The thoracic part of the trachea is ventrally related to the following organs or structures –
Vessels: It includes the brachicephalic vein, cranial vena cava, brachiocephalic trunk, right common carotid artery, and right pulmonary artery.
Nerves: It contains the recurrent laryngeal nerve and the right sympathetic cardiac nerve.
Lymph node: It includes only the cranial mediastinal lymph node.
Right and left lateral relationship: Here, Table 1 presents the relationship of the various organs with the cow’s trachea at the right and left lateral aspects.
| Left lateral relationship | Right lateral relationship |
| Dorsolateral to the esophagus, except at the tracheal bifurcation Lateral to the vagus, left sympathetic cardiac nerve Left lateral to the aortic arch and left tracheobronchial lymph nodes | Common trunk of the costocervical, deep cervical, and vertebral arteries Right vagus nerve and right sympathetic cardiac nerve Right lateral ansa subclavia and right tracheobronchial lymph nodes |
FAQ’s on cow’s trachea
The shape of the tracheal ring varies across species such as the cow, sheep, goat, and horse. Here, the cross-section of the cow’s tracheal ring is U-shaped, whereas the horse has a C-shaped tracheal ring (Figure 12).
Again, the goat also has a U-shaped tracheal ring, but the left end overlaps the right end. However, the sheep has a C-shaped tracheal ring where the right end overlaps the left end.
Arterial supply: Branches of the common carotid and broncho-esophageal arteries are the main arterial supply to the cow’s trachea.
Venous supply: Branches of the jugular and broncho-esophageal veins are the main venous supply to the trachea.
Nerve innervation: The recurrent laryngeal nerve and sympathetic nerve fibers from the sympathetic nerve trunks innervate the cow’s trachea.
Conclusion
So, the trachea of a cow is a cartilaginous structure that connects its pharynx and larynx to the lungs. It is made up of C-shaped cartilage, annular ligament, muscles, and membrane.
The course of the cow’s trachea divides into cervical and thoracic parts. Here, the cervical part extends from the larynx to the level of the thoracic inlet. At the same time, the thoracic part is the continuation of the cervical part that extends at the level of the fifth intercostal space.
References
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