Cow abdominal muscles

Cow abdominal muscles form the lateral and ventral walls of its abdomen. Here, I will help you to identify the four abdominal muscles of the cow with diagrams.

Quick answer: the cow abdominal muscles include obliquus externus, obliquus internus, transverse abdominis, and the rectus abdominis.

I will provide the schematic diagrams of these four abdominal muscles from a cow. Thus, you will easily compare their features with the real muscle sample.

However, this is a very practical guide for the identification of the cow’s abdominal muscles.

Cow abdominal muscles

The abdominal muscles are considered the most clinically important part of the cow’s muscle anatomy. They form the lateral and ventral wall of the largest body cavity and extend from the last few ribs to the cranial part of the pelvic bone.

Here, Figure 1 shows the schematic diagram of the location and extension of the cow’s four abdominal muscles. It also presents the fiber directions of the individual muscles of the cow’s abdomen.

Thus, the four muscles from the cow’s abdomen are (Getty, 1972) –

• Obliquus  abdominis externus muscle,
• Obliquus  abdominis internus muscle,
• The transverse abdominis muscle, and
• Straight ventral abdominis muscle.

Knowledge of fiber directions and the exact location is required to identify these muscles from the cow/cattle/sheep/goat’s abdomen. However, you need to remove the skin and abdominal tunic to expose the cow’s abdominal muscles for identification.

While removing the skin from the cow’s abdomen, you will find the cutaneous muscle. Here, the cutaneous muscle of the cow’s abdomen is the continuation of the cutaneous muscle of the thorax.

Again, beneath the cow’s skin, there are two layers of fascia in the abdominal region –

• Superficial fascia: It is next to the skin and is fused with the thoracolumbar fascia.
• Deep fascia: it is especially well-developed as a thick layer of tunic in the ventral region and the adjacent lateral part of the cow’s abdomen.

The deep fascia of the cow’s abdomen is known as the abdominal tunic. It covers the external aspect of the obliquus and ventral straight muscles.

Here, Figure 2 shows the abdominal tunic (deep fascia) of cow’s abdomen.

How to identify muscles in the cow’s abdomen?

Figure 3 shows that the four abdominal muscles of the cow are arranged layer by layer. Thus, you might also go layer by layer to identify the four important muscles of the cow’s abdomen.

So, first, let’s identify the most external muscle of the cow’s abdomen. All these four muscles are named according to the position and direction of their muscle fibers.

Muscle identification from the cow’s abdomen

Here, the most external muscle of the cow’s abdomen is larger than the other muscles. It is irregularly triangular in shape with a narrow part in front and a wide part behind.

However, its fiber passed ventrally and caudally (oblique direction). Thus, it is the obliquus abdominis externus muscle of the cow’s abdomen.

The naming of the muscle is very simple:

Obliquus + abdominis + externus = (oblique direction)+(abdominal muscle)+(located external to the abdomen).

Figure 4 shows the naming strategies of the cow’s abdominal muscles.

Under the obliquus abdominis externus, there is another muscle that fibers ventrally and cranially. As this muscle is internal to the obliquus externus and passes obliquely, it is known as the obliquus abdominis internus.

After removing the obliquus abdominis internus, you will find the most innermost muscle of the cow’s abdomen. It forms the inner layer of the abdomen and is externally covered by the obliquus internus muscle.

However, the fibers of this muscle are directed vertically/ transversely. Thus, this is called the transverse abdominis muscle of the cow.

Finally, a wide band of muscle at the lower abdomen extends from the sternum to the pubis. It forms the floor of the cow’s abdomen and is considered the strongest muscle.

However, it lies between the obliquus abdominis laterally and the transverse abdominis medially. The fibers of this muscle are directed straight from cranial to caudal.

Thus, it is called the straight abdominis muscle (Getty, 1972) of the cow’s abdomen.

All four of these muscles are symmetrically present in both the right and left lateral walls of the cow’s abdomen. However, the identification strategies of the abdominal muscle are also similar to cattle, goats, sheep, and buffalo (major ruminants).

Cow abdominal muscles description

For description of the cow’s abdominal muscle, you might describe the followings –

• Location, shape, and parts (if any) of the specific muscle,
• Fiber directions of the specific abdominal muscle, and
• Origin and insertion of the specific abdominal muscle.

The location, shape, and fiber directions of the cow’s abdominal muscles have already been discussed during identification. Thus, I will focus on the origin, insertion, and point out any special part (if any) in their description with a schematic diagram and a real sample.

But, before the description of the abdominal muscles, you might know the following terminologies –

• Linea alba of a cow’s abdomen, and
• Prepubic tendon of a cow.

What is the linea alba of a cow?

The linea alba of a cow is a white fibrous connective tissue in the ventral part of the abdomen. It is formed by the union of the aponeurotic portions of two oblique and transverse abdominis muscles.

All these aponeurotic portions of muscles meet at the midline of the ventral abdomen, where two straight muscles also meet. Thus, you may say that all the abdominal muscles have direct or indirect involvement in forming the cow’s linea alba (Ghosh, 2000).

Here, Figure 5 shows the linea alba of a cow. It also shows that the linea alba extends from the xiphoid cartilage to the pubis with the prepubic tendon.

Prepubic tendon in cattle, cow, sheep, and goat

The prepubic tendon is essentially the tendon of insertion of the two straight abdominis muscles (Getty, 1972; Ghosh, 2000). But, it is also considered a common tendon of insertion formed by all abdominal muscles, gracilis, and pectineus (Dieudoné et al., 2021).

It is located at the midline of the ventral abdomen and ventral to the abdominal tunic. However, it extends from the xiphoid cartilage of the sternum to the ilipentineal eminence on the cranial border of the pubis.

It has a very thick, strong band-like appearance with a concave lateral border. In the ox, sheep, goat, and buffalo (all ruminants), you will also find a similar type of prepubic tendon.

Here, Figure 6 shows the prepubic tendon from the cow’s ventral abdomen.  

Now, you may describe the cow’s abdominal muscles. Make sure you also have the perfect knowledge of some bones of the cow skeleton, like ribs, lumbar vertebrae, and pelvic bones.

Obliquus abdominis externus of the cow

It is the most extensive muscle of the cow’s abdomen, and the origin and insertion are below –

Origin of obliquus abdominis externus: It originates on –

• The lateral surface of the ribs from the lower part of the fifth intercostal space to above the middle of the last rib.
• Also from the thoracolumbar fascia.

Its fibers pass ventral and caudal before termination by the aponeurosis at the linea alba.

Insertion: it inserts on the linea alba and the prepubic tendon by aponeurosis along with other abdominal muscles. It also inserts on the coxal tuber (tuber coxae) of the cow’s pelvic bone.

Action: This muscle helps in the compression of the abdominal viscera and adds to the abdominal press.

Here, Figure 7 shows the origin, insertion, and fiber direction of the cow’s obliquus abdominis externus muscle.

Obliquus abdominis interus muscle of a cow

This muscle has muscular and apponeurotic parts. Here, the aponeurotic part blends with that of the external abdominal muscle. Then, it attaches to the straight abdominal muscle and finally terminates on the linea alba.

However, the muscular part of this muscle occupies mostly the dorsolateral aspect of the cow’s abdomen.

Origin of the obliquus abdominis externus: it originates by aponeurosis on –

• The external angle of the ilium bone (coxal tuber),
• The adjacent thoracolumbar fascia, and
• Lateral border of the longissimus lumborum muscle,

Insertion: it inserts on the linea alba, prepubic tendon, and lateral surface of the last two/three ribs. It also inserts the cartilages of these last two/three ribs.

Here, Figure 8 shows the obliquus abdominis internus muscle from the cow’s abdominal wall.

Transverse abdominis muscle of a cow

The transverse abdominis is the most thin and innermost muscle of the cow’s abdomen. It also possesses muscular and aponeurotic parts like the other abdominal muscles of a cow.

Here, the muscular part forms the layer of the lateral wall of the cow’s abdomen. In contrast, the aponeurotic part of the muscle forms the ventral part of the abdomen.

Origin of the cow’s transverse abdominis muscle: it originates on –

• The medial surface of the cartilages of the asternal ribs,
• The transverse process of the lumbar vertebrae through the thoracolumbar fascia, and
• Also from the caudo-medial surface of the thirteen ribs.

Insertion: It is inserted by the aponeurosis on the linea alba and the prepubic tendon along with the internal and external oblique muscles.

Here, Figure 9 shows the origin, insertion, and fiber direction of the cow’s transverse abdominis and ventral straight abdominal muscles.

The straight ventral muscle of cow’s abdomen

This is mainly the muscle of the ventral abdomen of the cow. The right and left lateral ventral straight muscles contribute to forming the linea alba in the cow.

Origin of cow’s ventral straight abdominal muscle: it originates from the –

• Lateral border and ventral surface of the cow’s sternum,
• Also from the third to the ninth costal cartilages.

Insertion: it inserts on the linea alba and the pubis bone by the prepubic tendon.

FAQ’s on muscles of the cow’s abdomen

Conclusion

So, the cow’s abdominal muscles include the identification and description of four major muscles of the abdomen. These muscles are: two oblique muscles (obliquus externus and internus), one transverse, and one straight ventral abdominal muscle.

Here, the fiber directions of the oblique externus are ventral and caudal, whereas the transverse fibers present a vertical direction. The individual muscle’s fiber directions and their location are key identifying features for primary identification from cow’s abdomen.  

References

• Dieudoné et al., “Surgical Anatomy and Approach to the Abdominal Wall of Domestic Animals”. Asian Jr of Med and Hel., 2021, 19 (5):11-21. https://doi.org/10.9734/ajmah/2021/v19i530325.  
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• Getty, R,. SG’s The anatomy of the domestic animals, 5th Edn. W. B. Saynders and Co. Philadelphia (USA).
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