Pelvic Girdle

The adult pelvic61 girdle is composed of four bones: a right and left os coxae (plural, ossa coxae), the sacrum, and the coccyx (fig. 8.35). Another term for the os coxae—arguably the most self-contradictory term in anatomy—is the innominate62 (ih-NOM-ih-nate) bone, "the bone with no name." The pelvic girdle supports the trunk on the legs and encloses and protects viscera of the pelvic cavity—mainly the lower colon, urinary bladder, and reproductive organs.

Each os coxae is joined to the vertebral column at one point, the sacroiliac joint, where its auricular surface

61 pelv = basin, bowl

Chapter 8 The Skeletal System 277

matches the one on the sacrum. On the anterior side of the pelvis is the pubic symphysis,63 the point where the right and left pubic bones are joined by a pad of fibrocartilage (the interpubic disc). The symphysis can be palpated immediately above the genitalia.

The pelvic girdle has a bowl-like shape with the broad greater (false) pelvis between the flare of the hips and the narrower lesser (true) pelvis below. The two are separated by a somewhat round margin called the pelvic brim. The opening circumscribed by the brim is called the pelvic inlet—an entry into the lesser pelvis through which an infant's head passes during birth. The lower margin of the lesser pelvis is called the pelvic outlet.

The os coxae has three distinctive features that will serve as landmarks for further description. These are the iliac64 crest (superior crest of the hip); acetabulum65 (ASS-eh-TAB-you-lum) (the hip socket—named for its resemblance to vinegar cups used in ancient Rome); and obturator66 foramen (a large round-to-triangular hole below the acetabulum, closed by a ligament called the obturator membrane in life).

The adult os coxae forms by the fusion of three childhood bones called the ilium (ILL-ee-um), ischium (ISS-kee-um), and pubis (PEW-biss), identified by color in figure 8.36. The largest of these is the ilium, which extends from the iliac crest to the superior wall of the acetabulum. The iliac crest extends from a point or angle on the anterior side, called the anterior superior spine, to a sharp posterior angle, called the posterior superior spine. In a lean person, the anterior superior spines form visible anterior protrusions, and the posterior superior spines are sometimes marked by dimples above the buttocks where connective tissue attached to the spines pulls inward on the skin.

Below the superior spines are the anterior and posterior inferior spines. Below the posterior inferior spine is a deep greater sciatic (sy-AT-ic) notch, named for the sciatic nerve that passes through it and continues down the posterior side of the thigh.

The posterolateral surface of the ilium is relatively rough-textured because it serves for attachment of several muscles of the buttocks and thighs. The anteromedial surface, by contrast, is the smooth, slightly concave iliac fossa, covered in life by the broad iliacus muscle. Medially, the ilium exhibits an auricular surface that matches the one on the sacrum, so that the two bones form the sacroiliac joint.

The ischium forms the inferoposterior portion of the os coxae. Its heavy body is marked with a prominent spine. Inferior to the spine is a slight indentation, the

63sym = together + physis = growth

64ili = flank, loin + ac = pertaining to

65acetabulum = vinegar cup

66obtur = to close, stop up + ator = that which

Saladin: Anatomy & I 8. The Skeletal System I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

278 Part Two Support and Movement

Table 8.7 Anatomical Checklist for the Pectoral Girdle and Upper Limb

Pectoral Girdle

Table 8.7 Anatomical Checklist for the Pectoral Girdle and Upper Limb

Pectoral Girdle

Clavicle (fig. 8.30)

Scapula ffig. 8.31)—(Cont.)

Sternal end

Suprascapular notch

Acromial end

Spine

Conoid tubercle

Fossae

Scapula (fig. 8.31)

Subscapular fossa

Borders

Supraspinous fossa

Superior border

Infraspinous fossa

Medial (vertebral) border

Acromion

Lateral (axillary) border

Coracoid process

Angles

Glenoid cavity

Superior angle

Olecranon

Inferior angle

Lateral angle

Upper Limb

Humerus (fig. 8.32)

Ulna (fig. 8.33)—(Cont.)

Proximal end

Radial notch

Head

Styloid process

Anatomical neck

Interosseous border

Surgical neck

Interosseous membrane

Greater tubercle

Carpal Bones ffig. 8.34)

Lesser tubercle

Proximal group

Intertubercular sulcus

Scaphoid

Shaft

Lunate

Deltoid tuberosity

Triquetrum

Distal end

Pisiform

Capitulum

Distal group

Trochlea

Trapezium

Lateral epicondyle

Trapezoid

Medial epicondyle

Capitate

Olecranon fossa

Hamate

Coronoid fossa

Bones of the Hand (fig. 8.34)

Radial fossa

Metacarpal bones I-V

Radius (fig. 8.33)

Base

Head

Body

Tuberosity

Head

Styloid process

Phalanges I-V

Articular facets

Proximal phalanx

Ulnar notch

Middle phalanx

Ulna (fig. 8.33)

Distal phalanx

Trochlear notch

Coronoid process

Saladin: Anatomy & I 8. The Skeletal System I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Chapter 8 The Skeletal System 279

Posterior Features Pelvic Girdle

Ilium Ischium Pubis

- Iliac crest

Inferior gluteal line

Posterior gluteal line

Posterior superior— spine of ilium

Posterior inferior spine of ilium Greater sciatic notch

Posterior gluteal line

Posterior Gluteal Line

Anterior superior spine of ilium

Anterior inferior spine of ilium

Body of ilium

Anterior gluteal line

Anterior superior spine of ilium

Anterior inferior spine of ilium

Body of ilium

Acetabulum

Spine of ischium-

Lesser sciatic notch -

Body of ischium Ischial tuberosity —

Superior ramus of pubis

Body of pubis

Inferior ramus of pubis

Obturator foramen

Ramus of ischium

Figure 8.36 The Right Os Coxae, Lateral View. The three childhood bones that fuse to form the adult os coxae are identified by color.

Saladin: Anatomy & I 8. The Skeletal System I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

280 Part Two Support and Movement lesser sciatic notch, and then the thick, rough-surfaced ischial tuberosity, which supports your body when you are sitting. The tuberosity can be palpated by sitting on your fingers. The ramus of the ischium joins the inferior ramus of the pubis anteriorly.

The pubis (pubic bone) is the most anterior portion of the os coxae. It has a superior and inferior ramus and a triangular body. The body of one pubis meets the body of the other at the pubic symphysis. The pubis and ischium encircle the obturator foramen.

The female pelvis is adapted to the needs of pregnancy and childbirth. Some of the differences between the male and female pelves are described in table 8.8 and illustrated in figure 8.37.

Pregnancy And Childbirth

Pregnancy And Childbirth

If Pregnancy Is Something That Frightens You, It's Time To Convert Your Fear Into Joy. Ready To Give Birth To A Child? Is The New Status Hitting Your State Of Mind? Are You Still Scared To Undergo All The Pain That Your Best Friend Underwent Just A Few Days Back? Not Convinced With The Answers Given By The Experts?

Get My Free Ebook


Responses

  • Felix
    How are the os coxae joined to the vertebral column?
    6 years ago
  • duenna oldbuck
    What is the functions of pelvic girdle?
    3 years ago
  • dahlak
    What is trunk in pelvis girdle?
    2 years ago

Post a comment