Bones of the Lower Limbs

Bones of the Lower Limbs

• The pelvic girdle is composed of two innominate bones and one sacrum.
• Each innominate bone is formed by the fusion of three bones: ilium, ischium, and pubis.
• The acetabulum is a deep depression on the outer surface of the innominate bone, creating the hip joint with the femur's head.
• The ilium is the upper, flattened part of the innominate bone, notable for the iliac crest and anterior superior iliac spine.
• The pubis is the anterior part of the innominate bone; it articulates with the other pubis at the symphysis pubis.
• The ischium is the inferior and posterior part of the innominate bone.
• The three components fuse at the acetabulum.

Pelvis

• The pelvis is formed by two innominate bones joined anteriorly at the symphysis pubis and posteriorly with the sacrum at the sacroiliac joints (synovial joints).
• The pelvic brim divides the pelvis into two parts—the greater (false) pelvis above and the lesser (true) pelvis below.
• The pelvic brim is formed by the promontory of the sacrum and the iliopectineal lines of the innominate bones.

Differences between Male and Female Pelves

• The female pelvis is lighter, shallower, more rounded, and roomier compared to the male pelvis.
• This shape is crucial for childbirth, allowing passage of the baby during childbirth.

Lower Limb Bones

• Lower limb bones: femur, tibia, fibula, patella, 7 tarsal bones, 5 metatarsal bones, 14 phalanges.

Femur

• The femur is the longest and strongest bone in the body.
• Its head is almost spherical and fits into the acetabulum of the hip bone.
• A small depression in the femur head's center accommodates a ligament for blood vessel attachment.
• The neck connects the femur head to its shaft.
• The lower-third posterior surface forms the popliteal surface.
• Two articular condyles in the distal extremity meet the tibia and patella to form the knee joint.

Tibia (Shinbone)

• The tibia is the medial bone of the lower leg.
• The proximal extremity is broad and flat with two condyles that articulate with the femur.
• The distal extremity forms the ankle joint with the talus and fibula.
• The medial malleolus is a downward projection of the tibia's medial side at the ankle joint.

Fibula

• The fibula is the long, slender lateral bone of the lower leg.
• The fibula head articulates with the tibia's lateral condyle, creating the proximal tibiofibular joint.
• The distal portion of the fibula forms the lateral malleolus, extending beyond the tibia.

Patella (Kneecap)

• The patella is a roughly triangular sesamoid bone in the knee joint.
• Its posterior surface interacts with the patellar surface of the femur.
• The patella sits within the patellar tendon (the tendon of the quadriceps femoris muscle).

Tarsal Bones (Ankle Bones)

• There are seven tarsal bones forming the posterior part of the foot: talus, calcaneus, navicular, and three cuneiform bones, and one cuboid bone.
• The talus articulates with the tibia and fibula at the ankle joint.
• The calcaneus forms the heel.
• Other tarsal bones connect to each other and the metatarsals.

Metatarsal Bones

• Five metatarsal bones; numbered from the inside (medial) to the outside (lateral); form the major part of the foot's sole.
• Metatarsals connect to the tarsals proximally and phalanges distantly.
• The first metatarsal's enlarged head forms the ball of the foot.

Phalanges (Toe Bones)

• Fourteen phalanges: two in the great toe (hallux) and three in each of the other toes.
• Arrangement is similar to the finger phalanges.

Arches of the Foot

• The foot's bones have a bridge-like pattern and are supported by muscles and ligaments, forming four arches:
  • Medial longitudinal arch (calcaneus, talus, navicular, three cuneiforms, and first three metatarsals)
  • Lateral longitudinal arch (calcaneus, cuboid, and two lateral metatarsals)
  • Two transverse arches (formed by three cuneiforms and cuboid bones)

This quiz covers the anatomy of the lower limbs, focusing on the pelvic girdle and its components. Study the innominate bones, the structure of the femur, and the articulation within the pelvis. Perfect for students of anatomy and related fields.