Pelvic Girdle and Lower Limbs 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 Lesser trochanter Large process below the head Provide attachments for muscles of the lower limbs Lesser trochanter 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) Instep (metatarsus) 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