Question

Innominate or hip bone is formed by the fusion of how many bones? (a) 2 (b) 3 (c) 4 (d) 5

Short answer

The innominate or hip bone is formed by the fusion of 3 bones.

Step-by-step solution

Understand the Question

This multiple choice question is asking for the number of bones that fuse together to form one hip or innominate bone.

Refer to Anatomy Knowledge

By referring to anatomical knowledge, it can be remembered that the hip or innominate bone is formed by the fusion of three bones: the ilium, ischium, and pubis.

Match the Answer

Comparing this knowledge with the given options, it can be seen that the answer matches with option (b), which states that three bones fuse together to form the innominate or hip bone.

Key concepts

Innominate Bone

The innominate bone, also known as the hip bone, is a large, complex structure that plays a crucial role in human skeletal anatomy. This bone is unique because it is formed by the fusion of three separate bones during childhood and adolescence. Understanding this bone is essential for students studying human anatomy, particularly the skeletal system.

• The innominate bone serves as a connection between the lower limb and the axial skeleton.
• It consists of three sections: the ilium, ischium, and pubis.
• Each section contributes to the formation and functionality of the pelvic girdle.

As we grow, these three bones gradually fuse to become a single structure by the time we reach adulthood. This fusion provides stability and strength necessary for movements such as walking, running, and sitting.

Ilium

The ilium is the largest and most superior part of the innominate bone. It forms the broad, flared section that is easily felt when you place your hands on your hips. The ilium has several important functions and distinctive features:

• Acts as the main supporter for the weight of the body, distributing it across the pelvis.
• Features the iliac crest, which is the curved superior margin of the ilium and an important landmark in anatomy.
• Provides attachment sites for several important muscles, including those forming the abdominal wall and hip flexors.

The ilium's broad surface also provides space for organs in the pelvic cavity, further demonstrating its importance in both structural and protective roles.

Ischium

The ischium forms the lower and posterior portion of the innominate bone. You might be familiar with it as the bone that we sit on, known for forming a part of the sitting bones.

• Provides support when sitting and critical shock absorption.
• Contains the ischial tuberosity, a roughened area that is a major weight-bearing surface and muscle attachment site.
• Plays a role in forming the acetabulum, the socket for the hip joint.

The ischium's robust structure is pivotal not only for seating comfort but also for supporting movements involving the legs and lower body.

Pubis

The pubis is the anterior portion of the innominate bone and contributes to forming the pelvis's structure. It is the smallest of the three bones but is crucial for specific functions and anatomical features:

• Forms the front portion of the pelvic girdle and meets the opposite pubic bone at the symphysis pubis.
• Involved in forming the obturator foramen, an important passageway for nerves and blood vessels.
• Contributes to the stability and strength of the pelvis during various activities like standing and lifting.

Although smaller, the pubis plays a vital role in forming the pelvic ring and maintaining pelvic integrity.