Describe the bones of the pelvic girdle, and describe how the pelvis unites the lower limbs with the axial skeleton. The two hip bones also called coxal bones or os coxae are together called the pelvic girdle hip girdle and serve as the attachment point for each lower limb. When the two hip bones are combined with the sacrum and coccyx of the axial skeleton , they are referred to as the pelvis.
The right and left hip bones also converge anteriorly to attach to each other at the pubic symphysis Figure 8. Unlike the bones of the pectoral girdle, which are highly mobile to enhance the range of upper limb movements, the bones of the pelvis are strongly united to each other to form a largely immobile, weight-bearing structure. This is important for stability because it enables the weight of the body to be easily transferred laterally from the vertebral column, through the pelvic girdle and hip joints, and into the weight bearing lower limb s.
Thus, the immobility of the pelvis provides a strong foundation for the upper body as it rests on top of the mobile lower limbs. The hip or coxal bones form the pelvic girdle portion of the pelvis. The hip bones are large, curved bones that form the lateral and anterior aspects of the pelvis.
Each adult hip bone is formed by three separate bones that fuse together during the late teenage years. These bony components are the ilium, ischium, and pubis Figure 8. These names are retained and used to define the three regions of the adult hip bone.
The ilium is the fan-like, superior region that forms the largest part of the hip bone. It is firmly united to the sacrum at the largely immobile sacroiliac joint see Figure 8. The ischium forms the posteroinferior region of each hip bone. It supports the body when sitting. The pubis forms the anterior portion of the hip bone.
The pubis curves medially, where it joins to the pubis of the opposite hip bone at a specialized joint called the pubic symphysis. When you place your hands on your waist, you can feel the arching, superior margin of the ilium along your waistline see Figure 8. This curved, superior margin of the ilium is the iliac crest. The rounded, anterior termination of the iliac crest is the anterior superior iliac spine. This important bony landmark can be felt at your anterolateral hip.
Inferior to the anterior superior iliac spine is a rounded protuberance called the anterior inferior iliac spine. Both of these iliac spines serve as attachment points for muscles of the thigh.
Posteriorly, the iliac crest curves downward to terminate as the posterior superior iliac spine. More inferiorly is the posterior inferior iliac spine. This is located at the inferior end of a large, roughened area called the auricular surface of the ilium. The auricular surface articulates with the auricular surface of the sacrum to form the sacroiliac joint. Both the posterior superior and posterior inferior iliac spines serve as attachment points for the muscles and very strong ligaments that support the sacroiliac joint.
The shallow depression located on the anteromedial internal surface of the upper ilium is called the iliac fossa. The inferior margin of this space is formed by the arcuate line of the ilium , the ridge formed by the pronounced change in curvature between the upper and lower portions of the ilium.
The large, inverted U-shaped indentation located on the posterior margin of the lower ilium is called the greater sciatic notch. The ischium forms the posterolateral portion of the hip bone see Figure 8. The large, roughened area of the inferior ischium is the ischial tuberosity. This serves as the attachment for the posterior thigh muscles and also carries the weight of the body when sitting.
You can feel the ischial tuberosity if you wiggle your pelvis against the seat of a chair. Projecting superiorly and anteriorly from the ischial tuberosity is a narrow segment of bone called the ischial ramus. The slightly curved posterior margin of the ischium above the ischial tuberosity is the lesser sciatic notch. The bony projection separating the lesser sciatic notch and greater sciatic notch is the ischial spine.
The central body of the ischium connects the ischial tuberosity, the acetabulum and the ischial spine. The pubis forms the anterior portion of the hip bone see Figure 8. The enlarged medial portion of the pubis is the pubic body.
Located superiorly on the pubic body is a small bump called the pubic tubercle. The superior pubic ramus is the segment of bone that passes laterally from the pubic body to join the ilium. The narrow ridge running along the superior margin of the superior pubic ramus is the pectineal line of the pubis. The pubic body is joined to the pubic body of the opposite hip bone by the pubic symphysis. Extending downward and laterally from the body is the inferior pubic ramus.
The pubic arch is the bony structure formed by the pubic symphysis, and the bodies and inferior pubic rami of the adjacent pubic bones. The inferior pubic ramus extends downward to join the ischial ramus. Together, these form the single ischiopubic ramus , which extends from the pubic body to the ischial tuberosity.
The inverted V-shape formed as the ischiopubic rami from both sides come together at the pubic symphysis is called the subpubic angle Figure 8. The pelvis consists of four bones: the right and left hip bones, the sacrum, and the coccyx see Figure 8.
The pelvis has several important functions. Its primary role is to support the weight of the upper body when sitting and to transfer this weight to the lower limbs when standing. It serves as an attachment point for trunk and lower limb muscles, and also protects the internal pelvic organs.
What's special about this particular head is its role as the ball in the ball-and-socket hip joint. The pubis, ischium, and ilium have a hand in creating the acetabulum, the deep, hemispherical, cup-shaped depression the socket with which the head of the femur articulates. The head of the femur fits perfectly in this cavity; its ball shape allows it to roll the femur, rotating it in a way that facilitates walking.
Ligaments hold the bones together. In addition to supporting the vertebral column and allowing you to walk, the pelvic girdle—along with the sacrum and the coccyx—forms the walls of the pelvic cavity, which contains and protects some of the reproductive, digestive, and urinary organs. The pelvic girdle is delicate and shallower in the female pelvis than the male—the ilia are less sloped, and the superior aperture is more circular.
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Use the links at the bottom of any email to manage the type of emails you receive or to unsubscribe. See our privacy policy for additional details. Welcome to the Visible Body Blog! Okay, let's take a look at the pelvic girdle, its relationship with the femur, and its responsibilities in the body. Bones of the Pelvic Girdle When we're born, we have over bones. Ligaments of the Pelvis. The posterior sacroiliac ligament supports the sacroiliac joint.
The sacrospinous ligament spans the sacrum to the ischial spine, and the sacrotuberous ligament spans the sacrum to the ischial tuberosity. The sacrospinous and sacrotuberous ligaments contribute to the formation of the greater and lesser sciatic foramens. Watch this video for a 3-D view of the pelvis and its associated ligaments. What is the large opening in the bony pelvis, located between the ischium and pubic regions, and what two parts of the pubis contribute to the formation of this opening?
The sacrospinous and sacrotuberous ligaments also help to define two openings on the posterolateral sides of the pelvis through which muscles, nerves, and blood vessels for the lower limb exit.
The superior opening is the greater sciatic foramen. This large opening is formed by the greater sciatic notch of the hip bone, the sacrum, and the sacrospinous ligament. The smaller, more inferior lesser sciatic foramen is formed by the lesser sciatic notch of the hip bone, together with the sacrospinous and sacrotuberous ligaments. The space enclosed by the bony pelvis is divided into two regions Figure 4.
The broad, superior region, defined laterally by the large, fan-like portion of the upper hip bone, is called the greater pelvis greater pelvic cavity; false pelvis. This broad area is occupied by portions of the small and large intestines, and because it is more closely associated with the abdominal cavity, it is sometimes referred to as the false pelvis.
More inferiorly, the narrow, rounded space of the lesser pelvis lesser pelvic cavity; true pelvis contains the bladder and other pelvic organs, and thus is also known as the true pelvis. The pelvic brim also known as the pelvic inlet forms the superior margin of the lesser pelvis, separating it from the greater pelvis.
The pelvic brim is defined by a line formed by the upper margin of the pubic symphysis anteriorly, and the pectineal line of the pubis, the arcuate line of the ilium, and the sacral promontory the anterior margin of the superior sacrum posteriorly. The inferior limit of the lesser pelvic cavity is called the pelvic outlet.
This large opening is defined by the inferior margin of the pubic symphysis anteriorly, and the ischiopubic ramus, the ischial tuberosity, the sacrotuberous ligament, and the inferior tip of the coccyx posteriorly. Because of the anterior tilt of the pelvis, the lesser pelvis is also angled, giving it an anterosuperior pelvic inlet to posteroinferior pelvic outlet orientation.
Figure 4. Male and Female Pelvis. The female pelvis is adapted for childbirth and is broader, with a larger subpubic angle, a rounder pelvic brim, and a wider and more shallow lesser pelvic cavity than the male pelvis.
The differences between the adult female and male pelvis relate to function and body size. The greater sciatic notch of the male hip bone is narrower and deeper than the broader notch of females. Because the female pelvis is adapted for childbirth, it is wider than the male pelvis, as evidenced by the distance between the anterior superior iliac spines see Figure 4.
The ischial tuberosities of females are also farther apart, which increases the size of the pelvic outlet. Because of this increased pelvic width, the subpubic angle is larger in females greater than 80 degrees than it is in males less than 70 degrees. The female sacrum is wider, shorter, and less curved, and the sacral promontory projects less into the pelvic cavity, thus giving the female pelvic inlet pelvic brim a more rounded or oval shape compared to males.
The lesser pelvic cavity of females is also wider and more shallow than the narrower, deeper, and tapering lesser pelvis of males. Because of the obvious differences between female and male hip bones, this is the one bone of the body that allows for the most accurate sex determination.
Table 1 provides an overview of the general differences between the female and male pelvis. A forensic pathologist also known as a medical examiner is a medically trained physician who has been specifically trained in pathology to examine the bodies of the deceased to determine the cause of death.
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