Cow pelvic bone

The cow’s right and left pelvic bones, sacrum, and one or two caudal vertebrae form its bony pelvis. Here, I will discuss on the details osteological features of the cow pelvic bone with diagrams.

Quick answer: Cow pelvic bone consists of the ilium, ischium, and pubis bones. Pelvic bones from the right side join with the left side at the ventral pelvic symphysis.

Here, I will describe the anatomy of the ilium, ischium, and pubis bones from the cow’s pelvis separately. You will also learn the key differentiating points of the pelvic among cow, horse, and dog perfectly.

Cow pelvic bone

The cow’s pelvic bone is the most complex but easily identifiable bone in the skeleton. It is the first bone of the cow’s hindlimb and forms the hip/pelvic segment.

The pelvic is called a complex bone as it consists of the ilium, ischium, and pubis bones. These bones have no demarcation and are fused to form a single hip/pelvic joint in the cow on both sides.

Here, Figure 1 shows the location and parts of the pelvic bone of the cow’s hindlimb.

This figure also shows that the right and left pelvic joints join together at the ventral aspect with the pelvic symphysis.

During learning this cow’s pelvis, you will get familiar with the following terms –

• Pelvis and hemipelvis,
• Os coxae / pelvic bone/ hip bone, and
• Ossa coxarum,

First, let’s describe these terms briefly from the cow’s pelvic bone.

• Pelvis: it means the circle of bones by which the pelvic limbs (hindlimbs) articulate with the vertebral column.
• Hemipelvis: it is the half of a pelvis that comprises the three flat bones: ilium, ischium, and pubis.

Here, the fused form of the hemipelvis is known as the os coxae/pelvic bone/hip bone. Again, the right and left hemipelvis are collectively known as the ossa coxarum.

Figure 2 shows the pelvis, hemipelvis, os coxae, and ossa coxarum from the cow’s pelvic bone.

Cow pelvic bone identification

Now, I will help you to identify all the osteological features of the cow’s pelvis. This is the best strategy to learn the details of a complex bone like cow’s pelvic easily.

Here, I have identified all the cow’s pelvic osteological features from its dorsal view (cranial to caudal), lateral view, cranial, and ventral views.

From the dorsal view, the cow’s pelvic present the followings –

• Sacral tuber/tuber sacrale,
• Coxal tuber/tuber coxae,
• Gluteal surface with gluteal line,
• Greater ischiatic notch (first notch from the cranial aspect of the bone),
• Psoas tubercle (medial to greater ischiatic notch),
• Superior ischiatic spine (after greater ischiatic notch),
• Inferior/ lesser ischiatic notch (caudally),
• Tuber ischii/ ischial tuberosity,
• Ischial arch (curved, caudally located),
• The pelvic floor with the pelvic symphysis, and
• Oval obturator foramen (right and left),

Here, Figure 3 shows all the above-mentioned osteological features from the cranio-dorsal view of cow pelvic bones. I have also used the lateral view to identify some of the features clearly from the cow’s pelvic bone.

The lateral view of cow’s pelvic presents the following osteological features –

• Acetabulum/cotyloid cavity, and
• Small acetabular notch,

Finally, the cranio-ventral view of the cow’s pelvic present the followings osteological features –

• Triangular articular surface for articulation with the wing of the sacrum bone,
• Supra acetabular fossa (above the acetabulum),
• Ilio pectineal eminence/ ilio-pubic eminence, and
• Ventral tubercle on pelvic symphysis (caudally),

Here, Figure 4 shows the cow’s pelvic osteological features from its lateral and cranio-ventral views. (Lateral and ventral views of cow’s pelvic bones)

Great, now you know most of the features of the cow’s pelvic bones. Thus, it will be easy for you to describe each flat bone separately with its important features.

Description of cow pelvic bones

To describe these three flat bones (ilium, ischium, and pubis) from the cow’s pelvis, you might know their extension. But, as they are fused bones, it is very hard to identify their limit/extension.

Thus, you may consider the acetabulum as the landmark to identify their extension roughly. Here, the ilium, ischium, and pubis bones together form the boundary of the acetabulum. It means the ilium ends on the acetabulum, whereas the ischium and pubis start from the acetabulum.

The schematic presentation of the ilium, ischium, and pubis from a cow pelvic bone is shown in Figure 5. It might help you to understand the shape and extension of these pelvic bones perfectly.

Great, now you know the followings on the cow’s pelvic bone –

• All osteological features of the pelvic bone,
• Shape and extension of ilium, ischium, and pubis bone,

Again, all these are flat types of bones; thus, you should describe their surfaces, borders, and angles with specific osteological features.   

Thus, while describing the features of ilium, ischium, and pubis, you may follow the format below –

• Location and shape of the bones,
• Surfaces, borders, and angles with their key identifying features in descriptive form,

The ilium of the cow’s pelvic

The ilium is the largest part of the cow’s pelvis and is located on the craniolateral aspect of the pelvis. It is triangular in shape, like the cow scapula bone, and presents –

Two surfaces: gluteal (dorsal) and pelvic (ventral) surfaces,

Three borders: anterior, internal/medial, and external/lateral borders, and

Three angles: internal/sacral angle, external/coxal angle, and posterior/acetabular angle.

Here, Figure 6 shows the schematic presentation of the cow ilium bone along with the real bone. It shows the three borders and three angles of the cow’s ilium bone.

The gluteal surfaces of the cow’s ilium bone

The gluteal surface of the cow’s ilium bone faces upward, backward, and downward. This bone is smooth, flat, wide, and concave in front, whereas it is narrower and convex behind.

Here, the flat cranial part of this ilium is known as the wing. Again, the distal narrow part is considered the body of the cow’s ilium.

You will see a curved gluteal line on the gluteal surface of the cow’s ilium that runs parallel to the lateral border. This gluteal line continues distally with the superior ischiatic spine.

The gluteal surface provides attachment to the middle and deep gluteus muscles in the cow. But the deep gluteus muscle is absent in small ruminants like the sheep and goat.

Here, Figure 7 shows the gluteal surface, line, and other features from the gluteal surface of the cow’s ilium bone.

Pelvic surface of the cow’s ilium

The pelvic surface of the cow’s ilium bone faces towards the pelvic cavity. This surface is convex and consists of two distinct parts –

• Inner triangular rough part: it bears an irregular facet for the articulation with the wing of the cow’s sacrum.
• Outer quadrilateral part: it is smooth and crossed by the ilio-pectineal line.

Here, the ilio-pectineal line begins below the articular surface and continues on the shaft. Finally, it joins with the anterior border of the cow’s pubic bone caudally.

This line is interrupted by a furrow for ilioco-femoral vessel. Again, below this interruption on the line, you will find a psoas tubercle. The psoas tubercle gives attachment to the cow’s psoas minor muscle.

Here, Figure 8 shows the features from the pelvic surface of the cow’s ilium bone.

Borders of the cow’s ilium bone

The anterior border of the cow’s ilium bone faces the craniodorsal aspect. It is concave, thick, and rough in cow’s ilium bone.

The internal border of the cow’s ilium is deeply concave. Its middle part forms the lower boundary of the greater ischiatic foramen in the cow.

Finally, the internal border continues caudally with the superior/greater ischiatic spine.

The external border is also concave in cow’s ilium bone. It is rough, and the groove crosses its cranial part. You will find some nutrient foramina at the caudal part of this border.

Angles of the cow ilium

The internal angle is blunt and curves upward and a little backward close to the first sacral spine. This angle forms the highest point of the cow’s skeleton.

The blunt internal angle is generally known as the tuber sacrale/sacral tuber.

The external angle forms the basic point of the cow’s pelvic bones. This angle is known as the tuber coxae (coxal tuber).

It is a large quadrilateral mass which remain roughen for the muscle attachment.

The posterior angle is also known as the acetabular angle. It meets the other two bones at the acetabulum.

The upper prominent border of the posterior angle forms the superior ischiatic spine. There is a fossa at the anterior aspect of this posterior angle, which is known as the supra-acetabular fossa.

Here, Figure 9 shows the borders and angles of the cow’s ilium bone.

Body of the cow ilium bone

The body of the cow’s ilium bone is a three-sided prismatic form. It presents the external, pelvis, and ventral surfaces.

Here, the external surface of the body of cow’s ilium is convex and rough. It gives attachments to the deep gluteus muscle of the cows.

Again, the pelvic surface of the body of cow’s ilium is smooth. It is grooved for passes obturator vessels and nerves.

Finally, the ventral surface of the body is crossed by different grooves.

The ischium of cow pelvic bone

The ischium is a flat quadrilateral plate of the cow pelvic bone that forms the floor of the bony pelvis. It is located behind the pubis and slopes a little downward and inward.

As an irregular quadrilateral bone, the ischium presents two surfaces, four borders, and four angles for description.

• Surfaces: superior (pelvic), and inferior (ventral),
• Borders: anterior, posterior, external, and internal, and
• Angles: antero-internal, antero-external, postero-internal, and postero-external angles.

Here, Figure 10 shows the schematic presentation of the four borders, four angles, and the extension of the cow ischium bone.

Surfaces of the cow ischium bone

The superior surface of the cow ischium bone is smooth and slightly concave from side to side. It presents an impression of the obturator internus muscle close to the obturator foramen.

The inferior surface of the cow ischium bone is convex. It is rough and provides attachment for the adductor muscle.

Here, Figure 11 shows the superior and inferior surfaces of the cow’s ischium bone.

Borders of the cow ischium bone

The anterior border of the cow’s ischium is concave and thin. It forms the posterior margin of the obturator foramen of cow’s hip.

The posterior border of the cow’s ischium is thick and rough. It slopes oblique inward and forward to meet the border of the other side.

Thus, the posterior borders of both the right and left sides form the ischial arch.

The external border is thick and rounded, and also concave in its length. It forms the inferior ischiatic notch in the cow’s pelvis. This border also forms the lower boundary of the obturator foramen of the cow’s pelvis.

The internal border of the cow’s ischium is almost straight and meet to the similar border of the opposite side. Thus, the right and left internal borders of the ischium bones form the ischial symphysis.

Here, the ischial symphysis is the part of the pelvic symphysis. Another part of the pelvic symphysis is formed by the pubic bone, which is known as the pubic symphysis. Thus, pelvic symphysis = ischial symphysis + pubic symphysis.

At the ventral aspect of the ischial symphysis, you may find a ventral prominence. This prominence in the cow’s ischium is known as the ventral tubercle. But, this feature is not ideal for all pelvic bones of the cows.

Here, Figure 12 shows the different borders of the cow ischium bone.

Angles of the cow’s ischium bone

The antero-internal angle of the cow’s ischium is narrow and joins with the posterior angle of the pubis. This angle forms the inner boundary of the obturator foramen in the cow’s pelvis.

The antero-internal angle of the cow’s ischium is also known as the anterior symphyseal angle.

The antero-external angle is wide and joins with the posterior angle of the ilium and the external angle of the pubis at the acetabulum. Superiorly, it contains the part of the superior ischiatic spine. This angle is also internally grooved for passess the obturator vessels.

The postero-internal angle of the cow’s ischium bone joins with the similar angle of other ischia at the middle of the ischial arch. It is also known as the posterior symphyseal angle and forms the middle part of the ischial arch.

Finally, the postero-external angle is a thick, three-sided, expanded mass. This trifid structure of the ischium is known as the cow’s tuber ischii. Another name for the tuber ischii is the ischial tuberosity.

The lateral prominent part of the tuber ischii of the cow’s ischium is known as the pin bone. The lower border of the postero-external angle of the cow’s ischium forms the inferior ischiatic spine. The biceps femoris and semitendinosus muscles attach to the inferior ischiatic spine of the cow’s pelvis.

Here, Figure 13 shows the different angles of the cow ischium bone with their key identifying features.

The pubis of the cow’s pelvic bone

The pubis is the smallest of the three parts of the cow pelvic bone. It is located at the anteromedial aspect of the cow’s pelvic floor.

Here, the cow’s pubis is a small triangular bone that presents two surfaces, three borders, and three angles.

• Surfaces of the pubis: superior (pelvic), and inferior (ventral).
• Borders: anterior, internal, and posterior, and
• Angles: internal, external, and posterior angles.

The schematic presentation of the borders and angles of the cow pubis bone is shown in Figure 14. It also shows the contribution of the cow’s pubis to the cranial part of the pelvic floor.

Surfaces of the cow pubis bone

The superior surface, which is also known as the pelvic surface, is convex in the calf. Whereas this surface is concave in the cow and hosts the urinary bladder on it.

The inferior surface of the cow’s pubis, which is also known as the ventral surface, is convex. Most of this surface is rough for muscle attachment.

You will find a sub-pubic groove at the anterior aspect of the inferior surface of the cow’s pubis. Its inner part is occupied by the large vessels and the outer part by the pubo-femoral ligament.

Borders of the cow pubis bone

The anterior border of the cow pubis bone is thin. Its inner part forms the pecten ossis pubis at the inner aspect.

You will see an ilio-pectineal eminence at the external part of this anterior border. Behind this eminence, this border is continuous with the ilio-pectineal line. Another name for the ilio-pectineal eminence of the cow’s pelvis is the ilio-pubic eminence.

The internal border of the cow’s pubis is almost straight. It joins with the similar border of the opposite bone and forms the pubic symphysis.

Finally, the posterior border of the cow’s pubis is concave and thin. It forms the anterior margin of the obturator foramen of the cow’s hip. This border is also marked by an obturator groove externally.

Angles of the cow pubis bone

The anterior angle joins with the similar angle of the opposite bone at the anterior aspect of the symphysis. Actually, the right and left anterior angles of the cow’s pubis bones form the pecten ossis pubis.

The external angle of the cow’s pubis joins with the ilium and ischium bones at the acetabulum. Thus, this angle is also known as the acetabular angle of the pubis bone.

Again, the posterior angle of the cow’s pubis joins with the antero-internal angle of the ischium. This angle forms the inner boundary of the cow’s obturator foramen.

Here, Figure 15 shows the borders and angles of the cow pubis bone along with their key osteological features.

What is the acetabulum in the cow’s pelvis?

The acetabulum is a cotyloid cavity that is formed by the union of the corresponding angles of the ilium, ischium, and pubis. It faces downward and inward and accommodates the head of the cow’s femur bone.

The cow’s acetabulum possess a outer smooth articular and a non-articular part –

• Articular part of the acetabulum: this part is notched at the posterior medial aspect. It is known as the acetabular notch of the cow’s acetabulum.
• Non-articular part: it is located in the middle and deep to the fossa? A small depression is found in the acetabulum, which is known as the acetabular fossa.

This acetabular fossa is also connected with the acetabular notch. Sometimes a smaller secondary notch can be found at the anterio-medial aspect of the acetabular cavity.

Here, Figure 16 shows the acetabulum cavity, acetabular notch, and acetabular fossa from the cow’s pelvic bone.

How is the pelvis formed in a cow?

The cow’s bony pelvis is formed by the ossa coxarum, sacrum, and first three caudal vertebrae. Let’s see the boundary of the cow’s bony pelvis –

• Dorsal wall: it is also known as the roof of the bony pelvis. It is formed by the sacrum and the first three caudal vertebrae.
• Ventral wall: it is also known as the floor of the bony pelvis. The ischium and pubis bones of the cow pelvis form it.
• Lateral wall: the right and left lateral walls of the cow’s bony pelvis are formed by the ilium and the acetabular part of the ischium bones.

In fresh condition, you will also find the sacro-sciatic ligaments and semimembranosus muscles at the lateral wall of cow’s pelvis.

The cranial elliptical opening of the cow’s pelvis is known as the pelvic inlet. This inlet is formed by the base of the sacrum dorsally, the ilio-pectineal line laterally, and the anterior border of the pubis ventrally.

Again, the posterior opening of the cow’s pelvis is known as the pelvic outlet. It is much smaller and incomplete in the skeleton.

The cow’s pelvis outlet is formed by the third caudal vertebrae dorsally and the ischial arch and tuberosity ventrally. Here, the outer encloser with the sacro-sciatic ligament and the semimembranosus muscle is known as the perineum.

Conjugate and transverse diameters in the cow pelvis

In the cow’s pelvis inlet, you will find two important diameters –

• Conjugate diameter: this diameter is measured from the sacral promontory (body of the sacrum) to the anterior end of the pubic symphysis. Another name for the cow hip’s conjugate diameter is sacro-pubic diameter.
• Transverse diameter: it is the distance between the two psoas tubercles of the cow pelvic bone.

Here, Figure 17 shows the boundary of the cow’s pelvis. It also shows the conjugate and transverse diameters of the cow’s pelvic inlet.

Comparative anatomy of pelvic bones of cow, horse, and dog

You may easily compare the pelvic bones among the cows, horses, and dogs with their key differentiating features. Here, Table 1 shows the comparative osteological features of the pelvic bones of cow, horse, and dog –

Features	Cow pelvic bones	Horse pelvic bones	Dog pelvic bones
Apperance	Inclined downward and backward	More inclined forward	Height is more
Ilium bones	Triangular Faces dorsally and caudally	Similar to cow	Ilium bones are parallel to each other
Gluteal line	Prominent	Not prominent	Not prominent (Gluteal surface is concave)
Tuber sacrale	Prominent	Inclined backward	Ill-developed
Psoas tubercle	Developed	Underdeveloped	Ill-developed
Ischium bones	Large, directed obliquely	Quadrilateral	Twisted
Ischiatic spine	Sharp	Not sharp	Blunt
Ischiatic notches	Deep	Deep	Shallow
Acetabulum cavity	Deep and small	Deep and wide	Shallow and wide
Acetabular notch	Narrow	Wide	Wide
Second acetabular notch	Present	Absent	Absent
Supra acetabular fossa	Deep	Shallow	Shallow
Tuber ischii	Trifid	Not trifid	Flat
Ventral tubercle	Present	Absent	Absent

So, the major comparison of pelvic bones between cow and horse is found in their appearances, gluteal surface, ischiatic spines, and notches. The acetabulum cavity with notches also shows major differences between the cow’s and horse’s pelvic bones.

Cow’s trifid tuber ischii is the unique feature of its pelvic compared to the horse and dog. Again, the dog pelvis is totally different than the cow hip as their ilium bones run parallel with concave gluteal surfaces.

Here, Figure 18 shows the key comparison of the pelvic bones of cow, horse, and dog.

FAQ’s on cow pelvis

Conclusion

So, each hemipelvis bone, which consists of three flat bones – ilium, ischium, and pubis- is fused to form the pelvic bone in a cow. The right and left cow pelvic bones are joined together ventrally with the pelvic symphysis.

The ilium is the largest irregular triangular flat and most dorsal of the cow’s pelvic bones. Again, the ischium of the cow’s pelvic projects backward and ventrad from the acetabulum. It forms much of the floor of the cow’s pelvic cavity.

Here, the pubis is the smallest of the three pelvic bones of the cow. It forms the cranial part of the pelvic floor and enters into the formation of the acetabulum with the other two parts of the cow’s pelvic bone.

References

• Chaurasia, D., Morphometrical Characterization of Hip Bone of Sahiwal Cattle. Indian Journal of Veterinary Anatomy, 2022; 33(2).
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