A white, shiny, flexible band of fibrous tissue that holds joints together and connects the various bones, including the following:. The joint capsule is a group of ligaments that connect the humerus to the socket of the shoulder joint on the scapula to stabilize the shoulder and keep it from dislocating. The roof highest point of the shoulder that is formed by a part of the scapula.
The tough cords of tissue that connect muscles to bones. The rotator cuff tendons are a group of tendons that connect the deepest layer of muscles to the humerus. A closed space between 2 moving surfaces that has a small amount of lubricating fluid inside; located between the rotator cuff muscle layer and the outer layer of large, bulky muscles.
Rotator cuff. Composed of tendons, the rotator cuff and associated muscles hold the ball tightly within the glenohumeral joint at the top of the upper arm bone humerus. 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. 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. 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.
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.
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 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.
The differences between the adult female and male pelvis relate to function and body size. 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 either lower limb whenever the other limb is not bearing weight.
Thus, the immobility of the pelvis provides a strong foundation for the upper body as it rests on top of the mobile lower limbs. Figure 1. The pelvic girdle is formed by a single hip bone. The hip bone attaches the lower limb to the axial skeleton through its articulation with the sacrum.
The right and left hip bones, plus the sacrum and the coccyx, together form the pelvis. The hip bone, or coxal bone, forms the pelvic girdle portion of the pelvis. The paired hip bones are the 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 2.
These names are retained and used to define the three regions of the adult hip bone. Figure 2. The Hip Bone. The adult hip bone consists of three regions. The ilium forms the large, fan-shaped superior portion, the ischium forms the posteroinferior portion, and the pubis forms the anteromedial portion. 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 1. 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 2. 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.
Posterior views of the lumbar spine and pelvis. A View of bones and bony landmarks. Figure 6. Anterior view of the lumbar spine and pelvis. The prominent bones and bony landmarks have been labeled. Note: This is the first in a series of 8 blog post articles on the anatomy and physiology of the lumbar spine and pelvis. This series of blog posts will present a review of the essential anatomy and physiology of the low back and pelvis.
The lumbar spine is composed of five vertebrae. Landmarks of the lumbar spine that are particularly important for stretching and joint mobilization techniques are the spinous processes and laminae. Each lumbar spinal joint level has two paired facet joints and a disc joint. The lumbar spine moves very well in all ranges of motion except rotation.
Structurally, the musculature of the low back can be divided into four quadrants: anterior right, anterior left, posterior right, and posterior left. Functionally, the muscles of the low back can be divided into six major mover groups: flexors, extensors, right and left lateral flexors, and right and left rotators. Structurally, the muscles of the pelvis can be divided into three categories: muscles crossing the lumbosacral joint from the trunk onto the pelvis, muscles crossing the hip joint from the lower extremity onto the pelvis, and pelvic floor muscles.
As with the muscles of the trunk, pelvic muscles that cross the hip joint can also be divided into four quadrants: anterior, posterior, lateral, and medial. Functionally, these muscles are usually considered from their open chain action on the thigh.
However, their closed chain action on the pelvis is likely more important; certainly, it is with regard to their effect on the posture of the pelvis and therefore the lumbar spine. Related Terms:. Enter your email to instantly get your FREE video lesson!
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