Chapter 7

Pelvic Girdle and Lower Limbs

Pelvic Girdle

• Consists of two coxae (hipbones) that articulate with each other anteriorly and with the sacrum posteriorly

• Functions:– Supports the trunk of the body (weight is

transmitted through the girdle to the lower limbs and then the ground)

– Provides attachments for the lower limbs– Protects the bladder, the distal end of the large

intestine, and the internal reproductive organs

Coxae

• Each coxa develops from three parts (ilium, ischium, and pubis) that fuse in a depression (called the acetabulum) on the lateral surface of the hipbone that receives the head of the femur

Coxae• Ilium

– Largest and most superior of the coxa– Forms the prominence of the hip– Special features:

• Iliac crest– Margin of the prominence

• Iliac fossa– Smooth, concave surface on the anterior

side

• Sacroiliac joint– Where the iliac joins the sacrum

• Anterior superior iliac spine– Spine the provides attachments for

ligaments and muscles

• Posterior superior iliac spine– Spine on the poster border

• Greater sciatic notch– Indentation below the posterior superior

iliac spine through which nerves and blood vessels pass

Coxae• Ischium– Forms the lowest portion of the

coxa– L-shaped– Special features

• Ischial tuberosity– Angle of the ischium– Points downward and posteriorly– Provides attachments for ligaments

and lower limb muscles– Supports the weight of the body

during sitting

• Ischial spine– Sharp projection located above the

ischial tuberosity, near the junction of the iliam and ischium

Coxae• Pubis– Anterior portion of the coxa– Special features:• Symphysis pubis

– Joint between the 2 pubic bones

• Pubic arch– Formed by the angle of the pubic

bones beneath the symphysis pubis

• Obturator foramen– Largest foramen in the skeleton– Located between the pubis and

ischium bones– Covered a nearly closed by an

obturator membrane

Greater and Lesser Pelves

• Greater pelvis (false pelvis)– Upper part of the pelvis– Bounded posteriorly by the lumbar vertebrae,

laterally by the flared parts of the iliac, and anteriorly by the abdominal wall

– Helps support the abdominal organs

Greater and Lesser Pelves

• Lesser pelvis (true pelvis)– Bounded posteriorly by the sacrum and coccyx

and laterally and anteriorly by the lower ilium, ischium, and pubis bones

– Surrounds the cavity through which an infant passes during the birthing process

Differences between Male and Female Pelves

• Iliac bones in females are usually more flared, creating broader hips

• Pelvic cavity in females is usually wider in all diameters than that of males

• Bones in female pelvis are usually lighter and show less evidence of muscle attachments than those of males

Lower Limbs

• Include femur, tibia, fibula, tarsals, metatarsals, and phalanges

Femur• Longest bone in the body• Extends from the hip to the knee• Special features:– Head

• Located at the proximal end• Projects medially into the

acetabulum of the coxa

– Fovea capitis• Pit on the head that marks the

attachment of a ligament

– Neck• Constriction located just below the

head

Femur• Special features (cont)

– Greater trochanter• Large process below the head• Provide attachments for muscles of the lower

limbs

– Lesser trochanter• Large process below the head• Provide attachments for muscles of the lower

limbs

– Linea aspera• Longitudinal crest in the middle of the femur

that serves as an attachment for muscles

– Lateral and medial condyles• Rounded processes at the distal end that

articulate with the tibia

– Medial and lateral epicondyles• Projections on the distal surface that provide

attachments for muscles

Patella

• Flat sesamoid (round) bone• Located in a tendon that passes anteriorly

over the knee

Tibia• Larger of the two leg bones• Located on the medial side• Articulates with the talus in the ankle• Special features:

– Medial and lateral condyles• Expanded proximal end• Have concave surfaces that articulate with the

condyles of the femur

– Tibial tuberosity• Process on the anterior surface that provides

an attachment for the patellar ligament

– Anterior crest• Extends downward from the tuberosity and

attaches connective tissues in the leg

– Medial malleolus• Expanded prominence on the inner ankle that

forms an attachment for ligaments

Fibula

• Long, slender bone located on the lateral side of the tibia

• Special features:– Head

• Enlarged proximal end• Articulates with the tibia• Doesn’t enter into the knee joint or

bear any body weight

– Lateral malleolus• Enlarged distal end• Articulates with the ankle• Protrudes on the lateral side

Foot• Ankle (tarsus)– Composed of 7 tarsal bones– The talus (your ankle bone) articulates with the tibia and fibula and can

move freely– The calcaneus (your heel bone) helps support the body weight and

serves as an attachment for the muscles that move the foot• Instep (metatarsus)

– Composed of 5 metatarsal bones (numbered 2 to 5 beginning on the medial side)

– Articulates with the tarsus– The heads of the metatarsals at the distal end form the ball of the foot

• The tarsals and metatarsals are bound by ligaments to form 2 arches (longitudinal arch and a transverse arch)

Foot

• Phalanges– Each toe (except the big two – which has two) has

three phalanges (a proximal, middle, and distal phalanx)

– Align and articulate with the metatarsals