Pelvic Girdle - Lower Limb Anatomy PDF

PELVIC GIRDLE LOWER LIMB ANATOMY  PELVIC CAVITY The pelvis (L. basin) is the part of the trunk that is inferoposterior to the abdomen, and is the area of transition between the trunk and the lower limbs. The pelvic cavity is the inferiormost part of the abdominopelvic cavity...

PELVIC GIRDLE LOWER LIMB ANATOMY  PELVIC CAVITY The pelvis (L. basin) is the part of the trunk that is inferoposterior to the abdomen, and is the area of transition between the trunk and the lower limbs. The pelvic cavity is the inferiormost part of the abdominopelvic cavity. Anatomically, the pelvis is the part of the body surrounded by the pelvic girdle (bony pelvis), part of the appendicular skeleton of the lower limb. Externally, the pelvis is covered or overlapped by the inferior anterolateral abdominal wall anteriorly, the gluteal region of the lower limb posterolaterally, and the perineum inferiorly.  STRUCTURE OF THE PELVIC GIRDLE In the mature individual, the pelvic girdle is formed by three bones: Right and left hip bones (coxal or pelvic bones): large, irregularly shaped bones, each of which develops from the fusion of three bones, the ilium, ischium, and pubis. Sacrum: formed by the fusion of five, originally separate, sacral vertebrae  STRUCTURE OF THE PELVIC GIRDLE There are four articulations within the pelvis: Sacroiliac joints (x2) – between the ilium of the hip bones, and the sacrum Sacrococcygeal symphysis – between the sacrum and the coccyx. Pubic symphysis – between the pubis bodies of the two hip bones.  HIP BONES The hip bones consist of three separate bones that are united by a triradiate cartilage at the acetabulum, the cup-like depression in the lateral surface of the hip bone, which articulates with the head of the femur. After puberty, the ilium, ischium, and pubis fuse to form the hip bone.  ILIUM The ilium is the superior, fan-shaped part of the hip bone. The ala (wing) of the ilium represents the spread of the fan, and the body of the ilium, the handle of the fan. On its external aspect, the body participates in formation of the acetabulum  ILIUM The iliac crest, the rim of the fan, has a curve that follows the contour of the ala between the anterior and posterior superior iliac spines. The anteromedial concave surface of the ala forms the iliac fossa.  ISCHIUM The ischium has a body and ramus (L. branch). The body of the ischium helps form the acetabulum and the ramus of the ischium forms part of the obturator foramen. The large postero-inferior protuberance of the ischium is the ischial tuberosity.  ISCHIUM The small pointed posteromedial projection near the junction of the ramus and body is the ischial spine. The concavity between the ischial spine and the ischial tuberosity is the lesser sciatic notch. The larger concavity, the greater sciatic notch, is superior to the ischial spine and is formed in part by the ilium.  PUBIS The pubis is an angulated bone with a superior ramus, which helps form the acetabulum, and an inferior ramus, which helps form the obturator foramen. A thickening on the anterior part of the body of the pubis is the pubic crest, which ends laterally as a prominent swelling, the pubic tubercle. The lateral part of the superior pubic ramus has an oblique ridge, the pecten pubis (pectineal line of pubis).  PELVIC CAVITY The osteology of the pelvic girdle allows the pelvic region to be divided into two: Greater pelvis (false pelvis) – located superiorly, it provides support of the lower abdominal viscera (such as the ileum and sigmoid colon). It has little obstetric relevance. Lesser pelvis (true pelvis) – located inferiorly. Within the lesser pelvis reside the pelvic cavity and pelvic viscera. Pelvic cavity The junction between the greater and lesser pelvis is known as the pelvic inlet. The outer bony edges of the pelvic inlet are called the pelvic brim.  PELVIC INLET The pelvic inlet marks the boundary between the greater pelvis and lesser pelvis. Its size is defined by its edge, the pelvic brim. The pelvic inlet determines the size and shape of the birth canal, with the prominent ridges a key site for attachment of muscle and ligaments.  PELVIC INLET The borders of the pelvic inlet: Posterior – sacral promontory (the superior portion of the sacrum) and sacral wings (ala). Lateral – arcuate line on the inner surface of the ilium, and the pectineal line on the superior pubic ramus. Anterior – pubic symphysis.  PELVIC OUTLET The pelvic outlet is located at the end of the lesser pelvis, and the beginning of the pelvic wall. Its borders are: Posterior: The tip of the coccyx Lateral: The ischial tuberosities and the inferior margin of the sacrotuberous ligament Anterior: The pubic arch (the inferior border of the ischiopubic rami). PELVIC OUTLET The angle beneath the pubic arch is known as the sub- pubic angle and is of a greater size in women. By 2024)  FUNCTIONS OF THE PELVIS The pelvic girdle is a basin-shaped ring of bones that connects the vertebral column to the two femurs. The strong and rigid pelvis is adapted to serve a number of roles in the human body. The main functions being: Transfer of weight from the upper axial skeleton to the lower appendicular components of the skeleton, especially during movement. Provides attachment for a number of muscles and ligaments used in locomotion. Contains and protects the abdominopelvic and pelvic viscera (inferior parts of the urinary tracts and the internal reproductive organs).  ADAPTATION FOR CHILDBIRTH The majority of women have a gynaecoid pelvis, as opposed to the male android pelvis. The slight differences in their structures creates a greater pelvic outlet, adapted to aid the process of childbirth. When comparing the two, the gynaecoid pelvis has: A wider and broader structure yet it is lighter in weight An oval-shaped inlet compared with the heart-shaped android pelvis.  ADAPTATION FOR CHILDBIRTH Less prominent ischial spines, allowing for a greater bispinous diameter A greater angled sub-pubic arch, more than 80-90 degrees. A sacrum which is shorter, more curved and with a less pronounced sacral promontory. In addition to the bony adaptations, the sacrotuberous and sacrospinous ligaments can stretch under the influence of progesterone and increase the size of the outlet further. THE END