Cow thyroid gland is associated with the proximal part of the trachea near the thyroid cartilage of the larynx. It is a very vascular, ductless gland and is firm in texture.
Here, I will describe the detailed anatomy of the cow’s thyroid gland with hand-drawn diagrams and real pictures.
Quick answer: The cow thyroid gland consists of two triangular lobes with 3 surfaces and 3 borders, and it is related to the trachea and larynx.
As a ductless gland, this organ is also described under the endocrine system. But from my experience, it is better to learn this thyroid gland along with the organs of the respiratory system.
However, the appearance of the thyroid varies widely with the species. Thus, at the end of this guide, I will show the basic differences of the thyroid gland in various species.
Where is the cow’s thyroid gland located?
Figure 1 shows the location of the cow’s thyroid gland in the cranial part of the neck region. This hand-drawn presentation indicates the tracheal rings and the lateral lobe and ventral isthmus of the thyroid gland.
Location: Thus, according to the figure, the thyroid gland is located on each side of the cow’s trachea, in close contact with the larynx.
However, the right and left lateral lobes of the gland vary slightly in location (Getty, 1970; Ryan Jennings). They extend on either side of the first and second, or second and third rings of the trachea.
However, these lateral lobes are loosely attached to these tracheal rings. Again, the cranial portion of the lateral lobes is connected with the thyroid cartilage of the cow’s larynx.
Their position indicates the angle formed by the jugular and external maxillary veins. However, this area is also known as the laryngotracheal junction between the cow’s larynx and trachea.
Cow thyroid gland anatomy
Figure 2 shows an overview of the cow’s thyroid gland anatomy. I made this figure by combining a hand-drawn diagram of the thyroid gland with the real picture.
Thus, the anatomy of the cow’s thyroid requires the description of the following –
- Lateral lobes: The cow’s thyroid consists of two lateral flattened triangular lobes: right and left lobes.
- Isthmus: The right and left lobes of the thyroid are connected by a thin transverse strip of connective tissue. This is the isthmus of the cow’s thyroid gland.
However, each of these lateral lobes of the cow’s thyroid gland presents 3 surfaces and 3 borders –
Surfaces: They are superficial, deep, and lateral surfaces.
Borders: They are cranial, dorsal, and caudoventral borders.
Shape and color of the cattle’s thyroid: The thyroid glands are pale in the cow, whereas they are dark red in the calf. However, the shape of the cattle/ruminant’s thyroid is like a butterfly.
Now, I will describe the lateral lobes and isthmus of the thyroid gland with the diagrams. However, you might memorize at least the unique anatomical features of these structures that I already indicated in the figures.
Lateral lobes of the cattle’s thyroid glands
Figure 3 highlights the shape, surfaces, and borders of the two lateral lobes of the cattle’s thyroid gland. Each of the lobes is oval or triangular in outline and is about as large as the plum/walnut of a medium size.
However, Table 1 shows the average length, height, and weight of each lobe of the cow’s thyroid.
| Length of the lobe | Height of the lobe | Weight of the lobe |
| 8 centimeters | 5 centimeters | 15 grams |
Surfaces of the thyroid’s lobes
Superficial surface: The superficial surface of the lateral lobe is convex and faces dorsally. It is covered by the cervical angle of the cow’s parotid salivary gland.
However, the cow’s neck muscles, such as the proximal part of the sternocephalicus and omohyoideus,, also cover the superficial surface. Here, Figure 4 shows the relationship of the lateral lobe of the cattle’s thyroid gland to the parotid gland and neck muscles.
Deep surface: The deep surface of the cattle/cow’s thyroid gland is concave and related to the trachea.
Lateral surface: Here, the lateral surface of each lobe of the thyroid gland is related to the following –
Cervicohyoid muscles: Sternothyrohyoideus and sternocephalicus muscles,
Vessels: Carotid artery and internal jugular vein, and
Nerves: Vagus and sympathetic nerves.
Borders of the lateral lobe of the cattle’s thyroid gland
Figure 5 highlights the dorsal, cranial, and caudo-ventral borders of the thyroid gland’s lobes.
Dorsal border: This border lies on the cow’s esophagus.
Cranial border: The cranial border of the thyroid lobe is almost straight. It is related to the cricopharyngeus and cricothyroideus muscles (Figure 6) and also to the thyrolaryngeal artery.
Caudoventral border: This border of the lateral lobe is concave and lies on the cow’s trachea.
Isthmus of the cow’s thyroid gland
Figure 7 presents the isthmus of the cow’s thyroid gland that extends across the ventral face of the trachea. However, it connects the two lateral lobes at the level of the second tracheal ring.
Again, the isthmus of the cow’s thyroid is narrow and may often be reduced in great part.
Structure of the cow’s thyroid gland
The lobes and isthmus of a cow’s thyroid gland consist of numerous globular sacs called follicles. However, they are well understood and viewable through the microscopic figure.
Figure 8 shows the follicles from the lobes and isthmus, follicular and parafollicular cells from the cow’s thyroid.
A thin fibro-elastic capsule covers the whole thyroid gland. However, many trabeculae extend from the capsule and pass between the lobes.
Each follicle is lined with epithelial or follicular cells (cuboidal shape). However, a basement membrane surrounds a central lumen of the follicle, which fills with colloid.
You will also find the parafollicular cells within the connective tissue, close to the follicles. However, they are arranged in clusters in the interfollicular space.
Vessels and nerves of the cattle’s thyroid gland
Vessels: In the cattle/cow thyroid gland, the arteries and veins are relatively large. There are usually two thyroid arteries that arise from the carotid artery.
However, the thyroid branch of the thyrolaryngeal arteries has two branches –
Superficial branch: It courses down along the cranial border of the thyroid gland. Again, it eventually disappears at the junction of the lobe and isthmus of the thyroid gland.
Larger deep branches: They course to the surface of the lobes and also send other small branches to the cow’s esophagus.
Veins: The largest vein leaves the thyroid gland at its caudoventral border. However, it (the large vein) goes to the cow’s jugular vein.
Nerves: It is innervated by sympathetic fibers from the cervical ganglion and parasympathetic fibers from the recurrent laryngeal nerve.
FAQ’s on the cow’s thyroid gland
The sheep thyroid’s lobes are elliptical in outline, whereas the cow’s are triangular. Again, the sheep’s thyroid is dark red, whereas the cow’s thyroid is pale (Figure 9).
The two lateral lobes of the cattle’s thyroid are unsymmetrical. They are variable in size and position, but the anatomical structures are similar.
Here, the right lobe is commonly in contact with the cricopharyngeus muscle, but may be about 2 centimeters from the larynx. However, the left lobe may be 4 centimeters from the larynx.
The lobules of the thyroid tissue are variable and sometimes become larger. They may be found near the cranial extremity of the lateral lobes.
However, they may be seen along the course of the cranial thyroid artery or on the trachea. They may even be seen at a considerable distance from the cow’s thyroid gland. These larger lobules are termed accessory thyroids in animals.
Conclusion
The cow thyroid gland is a ductless gland consisting of two triangular lateral lobes connected by a ventral isthmus. Each of these two lateral lobes has 3 surfaces and 3 borders.
However, these lobes lie dorsal to the cow’s tracheal rings and are connected by the narrow ventral isthmus. Structurally, the lobes and isthmus consist of numerous follicles and are covered by a thin capsule.
References
- Ghosh, R. K.: Primary Veterinary Anatomy, 2nd Ed.Current Books International, Kolkata.
- Nyberg, J. A., et al. Morphological Studies of the Thyroid Gland in Cattle. Acta Vet Scand 9, 151–167 (1968).
- Rowen D. Frandson, W. Lee Wilke, and A. Dee: Anatomy and physiology of farm animals, 4th edn.Wiley-Blackwell, USA.
- Eppe J, et al. (2024) From ultrasound to microscopy in thyroid investigation in cattle. PLoS ONE 19(5): e0302997.
- Getty, R. Sission and Grossman’s The anatomy of the domestic animals, 5th Edn. W. B. Saunders and Co., Philadelphia (USA).
- Huszebucza, G., et al. (2002). Endocrinology of the thyroid gland in ruminants. Veterinární medicína, 47(7), 199-210. doi: 10.17221 /5824-VETMED
- Nickel, R., Schummer, A. and Seiferle, E.: The anatomy of domestic animals, 1st Edn. Verlag Paul Parey, Berlin.
- Eppe, J., et al. (2026). Exploring thyroid function in main domestic ruminants: a scoping review of physio-anatomy, diseases and diagnostic tools. Veterinary Quarterly, 46(1).
- 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
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