Human Anatomy - Kotsan I. Y. 2009

Skeleton of the Lower Limb
Pelvic Girdle

The pelvic girdle, or pelvis (cingulum pelvicum), connects the Free part of the lower limb to the trunk. Unlike the Pectoral Girdle, it is a single shared Structure for both free lower limbs. The pelvic girdle consists of two hip bones, which in humans are the most massive and possess a unique shape determined by bipedalism.

The hip bone (os coxae) is a paired flat bone (Fig. 65). It performs Functions of support (transferring the weight of the entire upper body to the lower limbs), movement (participating in articulations with the sacrum and Femur), and protection (of the pelvic Organs). Up to the age of 14–16, the hip bone consists of three bones: the ilium, pubis, and ischium, separated by cartilaginous layers that ossify in adulthood. As a result, these three bones fuse into a single, highly durable structure necessary to support the entire trunk and HEAD. At the site of fusion of the bodies of the ilium, pubis, and ischium on the outer surface of the hip bone, the acetabulum is formed (the literal name 'acetabulum' comes from the Latin acetum, meaning vinegar). The acetabulum is deep, bounded along its circumference by the lunate margin of the acetabulum (limbus acetabuli), which is interrupted on its medial side by the acetabular notch (incisura acetabuli). For articulation with the femoral head, the acetabulum features a smooth lunate surface (facies lunata). The center of the acetabulum—the acetabular fossa (fossa acetabuli)—is rough and slightly depressed.

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Fig. 65. Right hip bone

a — external surface: 1 — ilium, 2 — outer lip, 3 — intermediate line, 4 — inner lip, 5 — anterior superior iliac spine, 6 — anterior inferior iliac spine, 7 — lunate surface, 8 — obturator crest, 9 — obturator groove, 10 — acetabular notch, 11 — ischial tuberosity, 12 — lesser sciatic notch, 13 — ischial spine, 14 — acetabular fossa, 15 — greater sciatic notch, 16 — posterior inferior iliac spine, 17 — posterior superior iliac spine, b — internal surface: 1 — iliac fossa, 2 — iliac tuberosity, 3 — auricular surface, 4 — body of ischium, 5 — ramus of ischium, 6 — obturator foramen, 7 — inferior ramus of pubis, 8 — symphyseal surface, 9 — pubic tubercle, 10 — superior ramus of pubis, 11 — pubic crest, 12 — iliopubic eminence, 13 — arcuate line

The ilium (os ilium) is located above the acetabulum. It consists of the body of the ilium (corpus ossis ilii), which participates in The formation of the acetabulum, and the ala of the ilium (ala ossis ilii), which is a broad, curved plate, thinned in the center. The upper margin of the ala is thickened and forms the iliac crest (crista iliaca). Three rough lines for the attachment of the broad Abdominal Muscles are clearly visible on the iliac crest: the outer lip (labium externum), inner lip (labium internum), and intermediate line (linea intermedia). The iliac crest terminates anteriorly in the anterior superior iliac spine (spina iliaca anterior superior) and posteriorly in the posterior superior iliac spine (spina iliaca posterior superior), below which are the anterior inferior iliac spine (spina iliaca anterior inferior) and posterior inferior iliac spine (spina iliaca posterior inferior), respectively. The iliac spines serve for the attachment of muscles and ligaments. The lower spines are separated from the upper ones by notches. Slightly anterior and inferior to the anterior inferior iliac spine, at the site of fusion of the ilium and pubis, lies the iliopubic eminence (eminentia iliopubica).

On the gluteal (external) surface (facies glutealis) of the iliac ala, three faint rough lines are visible: the anterior, posterior, and inferior gluteal lines, from which the gluteal muscles originate. The anterior gluteal line (linea glutealis anterior) is the longest; it begins at the anterior superior iliac spine and arches toward the greater sciatic notch of the ischium. The posterior gluteal line (linea glutealis posterior) is considerably shorter, running almost vertically and parallel to the posterior part of the previous line. The inferior gluteal line (linea glutealis inferior) is the shortest. It begins between the anterior superior and anterior inferior iliac spines and arches above the acetabulum toward the greater sciatic notch. At the intersection of the anterior gluteal line and the outer lip of the iliac crest (about 5 cm behind the anterior superior iliac spine) is the iliac tubercle (tuberculum iliacum), which is important for topographical orientation on the anterior abdominal wall.

On the internal surface (facies interna) of the iliac ala lies a depression—the iliac fossa (fossa iliaca), which Supports the Internal Organs. The lower margin of the iliac fossa is bounded by the arcuate line (linea arcuata), which separates the greater and lesser pelvis.

The sacropelvic surface (facies sacropelvica) of the ilium features the auricular surface (facies auricularis), through which the ilium articulates with the corresponding surface of the sacrum, and the iliac tuberosity (tuberositas iliaca), to which the interosseous ligaments attach.

The pubis (os pubis) consists of the body of the pubis (corpus ossis pubis) and two rami: the superior ramus of the pubis (ramus superior ossis pubis) and the inferior ramus of the pubis (ramus inferior ossis pubis). The body of the pubis participates in forming the acetabulum. The pubic rami are angled relative to each other. At the transition from the superior to the inferior ramus, near the medial margin, lies the oval-shaped symphyseal surface (facies symphysialis), which serves for articulation with the pubic bone of the opposite side. The upper margin of the superior pubic ramus is sharp and called the pubic crest (pecten ossis pubis). The anterior PARTS OF THE crest terminate in the pubic tubercle (tuberculum pubicum). Posteriorly, the pubic crest transitions into the arcuate line of the ilium. The pubic rami, together with the ischium, bound the obturator foramen (foramen obturatum), which lies inferior and medial to the acetabulum and has a triangular shape with rounded edges. The obturator foramen is closed by a fibrous plate—the obturator membrane (membrana obturatoria). The upper margin of the obturator foramen features a broad obturator groove (sulcus obturatorius) running from back to front and medially, transmitting the vessels and nerve of the same name. The obturator groove is bounded anteriorly by the anterior obturator tubercle (tuberculum obturatorium anterius) and posteriorly by the inconstant posterior obturator tubercle (tuberculum obturatorium posterius). Above the obturator groove, between the pubic tubercle and the acetabulum, extends the obturator crest (crista obturatoria). Medially from the pubic tubercle to the symphyseal surface runs a short pubic crest (crista pubica), to which the rectus abdominis Muscle attaches.

The ischium (os ischii) is located inferior to the acetabulum. It consists of the thickened body of the ischium (corpus ossis ischii), which inferiorly completes the acetabulum, and the ramus of the ischium (ramus ossis ischii), which, together with the pubic bone, bounds the obturator foramen. The body of the ischium and its ramus form an angle open anteriorly. In the region of this angle, the bone forms a thickening—the ischial tuberosity (tuber ischiadicum)—to which muscles and ligaments attach. Superior to the ischial tuberosity, projecting from the posterior margin of the bone's body, is the ischial spine (spina ischiadica), which separates the greater sciatic notch (incisura ischiadica major) from the lesser sciatic notch (incisura ischiadica minor).