The Pelvic Girdle and Pelvis | Anatomy & Physiology
PELVIS The pelvis is a bowl composed of circles, holes and arches. an ilium, ischium and pubic bone, which fuse together to provide stability at the hip socket with Joe," she said, “we always circle the lines and words that I can't remember. Each adult hip bone is formed by three separate bones that fuse together during the These bony components are the ilium, ischium, and pubis (Figure ). The hip is formed where the thigh bone (femur) meets the three bones that make up the pelvis: the ilium, the pubis (pubic bone) and the ischium.
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.
Bones of the Lumbar Spine and Pelvis
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. Pubis 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. Pelvis The pelvis consists of four bones: 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.
When standing in the anatomical position, the pelvis is tilted anteriorly. In this position, the anterior superior iliac spines and the pubic tubercles lie in the same vertical plane, and the anterior internal surface of the sacrum faces forward and downward. The three areas of each hip bone, the ilium, pubis, and ischium, converge centrally to form a deep, cup-shaped cavity called the acetabulum.
Bones of the Lumbar Spine and Pelvis
This is located on the lateral side of the hip bone and is part of the hip joint. The large opening in the anteroinferior hip bone between the ischium and pubis is the obturator foramen. This space is largely filled in by a layer of connective tissue and serves for the attachment of muscles on both its internal and external surfaces.
Several ligaments unite the bones of the pelvis Figure 8. The largely immobile sacroiliac joint is supported by a pair of strong ligaments that are attached between the sacrum and ilium portions of the hip bone. These are the anterior sacroiliac ligament on the anterior side of the joint and the posterior sacroiliac ligament on the posterior side.
Also spanning the sacrum and hip bone are two additional ligaments. The sacrospinous ligament runs from the sacrum to the ischial spine, and the sacrotuberous ligament runs from the sacrum to the ischial tuberosity.
These ligaments help to support and immobilize the sacrum as it carries the weight of the body. 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.
The Hip Bone - Ilium - Ischium - Pubis - TeachMeAnatomy
External Website 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 8. 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. 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.
Hip Anatomy, Function and Common Problems
More inferiorly, the narrow, rounded space of the lesser pelvis lesser pelvic cavity 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 gluteus medius muscle: The gluteus medius also originates from the gluteal aponeurosis that covers its outer surface. Gluteus minimus muscle originates between the anterior and inferior gluteal linesand from the margin of the greater sciatic notch. Lateral rotator group The piriformis muscle originates from the superior margin of the greater sciatic notch as well as the sacroiliac joint capsule and the sacrotuberous ligament and part of the spine and sacrum. The superior gemellus muscle arises from the outer surface of the ischial spine The obturator internus muscle arises from the inner surface of the antero-lateral wall of the hip bone, where it surrounds the greater part of the obturator foramenbeing attached to the inferior rami of the pubis and ischium, and at the side to the inner surface of the hip bone below and behind the pelvic brimreaching from the upper part of the greater sciatic foramen above and behind to the obturator foramen below and in front.
It also arises from the pelvic surface of the obturator membrane except in the posterior part, from the tendinous archand to a slight extent from the obturator fasciawhich covers the muscle. The inferior gemellus muscle arises from the upper part of the tuberosity of the ischiumimmediately below the groove for the obturator internus tendon.
The obturator externus muscle arises from the margin of bone immediately around the medial side of the obturator foramen, from the rami of the pubis, and the inferior ramus of the ischium; it also arises from the medial two-thirds of the outer surface of the obturator membrane, and from the tendinous arch.
Hamstrings The long head biceps femoris arises from the lower and inner impression on the back part of the tuberosity of the ischiumby a tendon common to it and the semitendinosusand from the lower part of the sacrotuberous ligament ;  The semitendinosus arises from the lower and medial impression on the tuberosity of the ischium, by a tendon common to it and the long head of the biceps femoris; it also arises from an aponeurosis which connects the adjacent surfaces of the two muscles to the extent of about 7.
The semimembranosus arises from the lower and medial impression on the tuberosity of the ischium Anterior compartment of thigh The rectus femoris muscle arises by two tendons: The sartorius muscle arises by tendinous fibres from the anterior superior iliac spine, Shoulder muscles The latissimus dorsi muscle attaches to the iliac crest and several places on the spine and ribs.
Clinical significance[ edit ] The proportions of the female hip bone may affect the ease of passage of the baby during childbirth. Pelvimetry is the assessment of the female pelvis  in relation to the birth of a baby in order to detect an increased risk for obstructed labor.