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PELVIC WALL JOINTS OF THE PELVIS PELVIC FLOOR Slide 2 PELVIC WALL Slide 3 Dr. L. Tchakarov3 The pelvis is the region of the trunk that lies below the abdomen. Although the abdominal and pelvic cavities are continuous, the two regions are described separately. Slide 4 The Pelvis Slide 5 5 The bony pelvis provides a strong, stable connection between the trunk and the lower extremities. Slide 6 6 The main functions of the pelvis are: transmit the weight of the body from the vertebral column to the femurs; contain, support, and protect the pelvic viscera; and provide attachment for trunk and lower limb muscles. The main functions of the pelvis are: transmit the weight of the body from the vertebral column to the femurs; contain, support, and protect the pelvic viscera; and provide attachment for trunk and lower limb muscles. Slide 7 Dr. L. Tchakarov7 The bony pelvis is composed of four bones: the two hip bones, which form the lateral and anterior walls, and the sacrum and the coccyx, which are part of the vertebral column and form the back wall. Slide 8 Dr. L. Tchakarov8 The two hip bones articulate with each other anteriorly at the symphysis pubis and posteriorly with the sacrum at the sacroiliac joints. The bony pelvis with its joints form a strong basin-shaped structure that contains and protects the lower parts of the intestinal and urinary tracts and the internal organs of reproduction. Slide 9 Dr. L. Tchakarov9 The pelvis is divided into two parts by the pelvic brim. Above the brim is the false pelvis, which forms part of the abdominal cavity. Below the brim is the true pelvis. Slide 10 Dr. L. Tchakarov10 The pelvic brim is formed by: the sacral promontory (anterior and upper margin of the first sacral vertebra) behind, the ileopectineal lines (a line that runs downward and forward around the inner surface of the ileum) laterally, and the symphysis pubis (joint between bodies of pubic bones) anteriorly. Slide 11 ORIENTATION OF THE PELVIS Slide 12 Dr. L. Tchakarov12 In the standard anatomic position, the front of the symphysis pubis and the anterior superior iliac spines lie in the same vertical plane. This means that the pelvic surface of the symphysis pubis faces upward and backward and the anterior surface of the sacrum is directed forward and downward. Slide 13 FALSE PELVIS Slide 14 Dr. L. Tchakarov14 The false pelvis is bounded behind by the lumbar vertebrae, laterally by the iliac fossae and the iliacus muscles, and in front by the lower part of the anterior abdominal wall. The false pelvis flares out at its upper end and should be considered as part of the abdominal cavity. It supports the abdominal contents and after the third month of pregnancy helps support the gravid uterus. During the early stages of labor, it helps guide the fetus into the true pelvis. Slide 15 TRUE PELVIS Slide 16 Dr. L. Tchakarov16 Knowledge of the shape and dimensions of the female pelvis is of great importance for obstetrics, because it is the bony canal through which the child passes during birth. Slide 17 Dr. L. Tchakarov17 The true pelvis has: an inlet, an outlet, and a cavity. Slide 18 Dr. L. Tchakarov18 The pelvic inlet, or pelvic brim, is bounded posteriorly by the sacral promontory, laterally by the iliopectineal lines, and anteriorly by the symphysis pubis. Slide 19 Dr. L. Tchakarov19 The pelvic outlet is bounded: coccyx,posteriorly by the coccyx, ischial tuberosities,laterally by the ischial tuberosities, and pubic arch.anteriorly by the pubic arch. Slide 20 Dr. L. Tchakarov20 The pelvic outlet does not present a smooth outline but has three wide notches: Anteriorly, the pubic arch is between the ischiopubic rami, and, laterally, are the sciatic notches. Slide 21 Dr. L. Tchakarov21 The sciatic notches are divided by the sacrotuberous and sacrospinous ligaments into the greater and lesser sciatic foramina. Slide 22 Dr. L. Tchakarov22 From an obstetric standpoint, because the sacrotuberous ligaments are strong and relatively inflexible, they should be considered to form part of the perimeter of the pelvic outlet. Thus the outlet is diamond shaped, with the ischiopubic rami and the symphysis pubis forming the boundaries in front and the sacrotuberous ligaments and the coccyx forming the boundaries behind. Slide 23 Dr. L. Tchakarov23 The pelvic cavity lies between the inlet and the outlet. It is a short, curved canal, with a shallow anterior wall and a much deeper posterior wall. Slide 24 Structure of the Pelvic Walls Slide 25 Dr. L. Tchakarov25 The walls of the pelvis are formed by bones and ligaments that are partly lined with muscles covered with fascia and parietal peritoneum. The pelvis has anterior, posterior, and lateral walls and an inferior wall or floor. Slide 26 ANTERIOR PELVIC WALL Slide 27 Dr. L. Tchakarov27 The anterior pelvic wall is the shallowest wall and is formed by the posterior surfaces of the bodies of the pubic bones, the pubic rami, and the symphysis pubis. Slide 28 POSTERIOR PELVIC WALL Slide 29 Dr. L. Tchakarov29 The posterior pelvic wall is extensive and is formed by the sacrum and coccyx and by the piriformis muscles and their covering of parietal pelvic fascia. Slide 30 Sacrum Slide 31 Dr. L. Tchakarov31 The sacrum consists of five rudimentary vertebrae fused together to form a single wedge- shaped bone with a forward concavity. The upper border or base of the bone articulates with the fifth lumbar vertebra. The narrow inferior border articulates with the coccyx. Slide 32 Dr. L. Tchakarov32 Laterally, the sacrum articulates with the two iliac bones to form the sacroiliac joints. The anterior and upper margins of the first sacral vertebra bulge forward as the posterior margin of the pelvic inletthe sacral promontory which is an important obstetric landmark used when measuring the size of the pelvis. Slide 33 Dr. L. Tchakarov33 The vertebral foramina together form the sacral canal. sacral hiatus.The laminae of the fifth sacral vertebra, and sometimes those of the fourth, fail to meet in the midline, forming the sacral hiatus. Slide 34 Dr. L. Tchakarov34 The sacral canal contains the anterior and posterior roots of the lumbar, sacral, and coccygeal spinal nerves; the filum terminale; and fibrofatty material. Slide 35 Dr. L. Tchakarov35 The sacral canal also contains the lower part of the subarachnoid space down as far as the lower border of the second sacral vertebra. Slide 36 Dr. L. Tchakarov36 The anterior and posterior surfaces of the sacrum possess on each side four foramina for the passage of the anterior and posterior rami of the upper four sacral nerves. Slide 37 Dr. L. Tchakarov37 The sacrum is usually wider in proportion to its length in the female than in the male. Slide 38 Dr. L. Tchakarov38 The sacrum is tilted forward so that it forms an angle with the fifth lumbar vertebra, called the lumbosacral angle. Slide 39 Coccyx Slide 40 Dr. L. Tchakarov40 The coccyx consists of four vertebrae fused together to form a small triangular bone, which articulates at its base with the lower end of the sacrum. The coccygeal vertebrae consist of bodies only, but the first vertebra possesses a rudimentary transverse process and cornua. The cornua are the remains of the pedicles and superior articular processes and project upward to articulate with the sacral cornua. Slide 41 Piriformis Muscle Slide 42 Dr. L. Tchakarov42 The piriformis muscle arises from the front of the lateral masses of the sacrum and leaves the pelvis to enter the gluteal region by passing laterally through the greater sciatic foramen. It is inserted into the upper border of the greater trochanter of the femur. Slide 43 Dr. L. Tchakarov43 Action: It is a lateral rotator of the femur at the hip joint. Nerve supply: It receives branches from the sacral plexus. Slide 44 LATERAL PELVIC WALL Slide 45 Dr. L. Tchakarov45 The lateral pelvic wall is formed by part of the hip bone below the pelvic inlet, the obturator membrane, the sacrotuberous and sacrospinous ligaments, and the obturator internus muscle and its covering fascia. Slide 46 Hip Bone Slide 47 Dr. L. Tchakarov47 In children, each hip bone consists of the ilium, which lies superiorly; the ischium, which lies posteriorly and inferiorly; and the pubis, which lies anteriorly and inferiorly. The three separate bones are joined by cartilage at the acetabulum. At puberty, these three bones fuse together to form one large, irregular bone. Slide 48 Dr. L. Tchakarov48 The hip bones articulate with the sacrum at the sacroiliac joints and form the anterolateral walls of the pelvis; they also articulate with one another anteriorly at the symphysis pubis. Slide 49 49 On the outer surface of the hip bone is a deep depression, the acetabulum, which articulates with the hemispherical head of the femur. Behind the acetabulum is a large notch, the greater sciatic notch, which is separated from the lesser sciatic notch by the spine of the ischium. Slide 50 Dr. L. Tchakarov50 The sciatic notches are converted into the greater and lesser sciatic foramina by the presence of the sacrotuberous and sacrospinous ligaments. Slide 51 Dr. L. Tchakarov51 The ilium, which is the upper flattened part of the hip bone, possesses the iliac crest. The iliac crest runs between the anterior and posterior superior iliac spines. Below these spines are the corresponding anterior and posterior inferior iliac spines. Slide 52 Dr. L. Tchakarov52 On the inner surface of the ilium is the large auricular surface for articulation with the sacrum. The iliopectineal line runs downward and forward around the inner surface of the ilium and serves to divide the false from the true pelvis. Slide 53 Dr. L. Tchakarov53 The ischium is the inferior and posterior part of the hip bone and possesses an ischial spine and an ischial tuberosity. Slide 54 Dr. L. Tchakarov54 The pubis is the anterior part of the hip bone and has a