Anatomy of Pelvis, Leg, and Foot Bones

Pelvis and Leg Bone Anatomy Q&A

1. Which bones form the pelvic girdle?
   The pelvic girdle is formed by the two innominate bones (hip bones), the sacrum, and the coccyx.
2. What is the pubic symphysis?
   It is the cartilaginous joint connecting the left and right pubic bones.
3. Which bones fuse to form the innominate (hip) bone?
   The ilium, ischium, and pubis fuse to form each innominate bone.
4. What is the function of the iliac crest?
   It serves as an important attachment point for abdominal and hip muscles.
5. Where does the femoral head articulate with the innominate bone?
   The head of the femur articulates within the acetabulum, a socket on the innominate bone formed by the fusion of the ilium, ischium, and pubis.
6. What is the function of the greater and lesser trochanters of the femur?
   They serve as major insertion points for muscles acting on the hip and thigh, particularly those involved in rotation and movement of the thigh.
7. What is the role of the linea aspera on the femur?
   It is a prominent ridge on the posterior shaft of the femur that serves as an attachment site for several thigh muscles (adductors, extensors, flexors).
8. Which femoral structures articulate with the tibia?
   The medial and lateral condyles of the femur articulate with the corresponding condyles of the tibia.
9. Which tibial structures articulate with the femoral condyles?
   The superior articular facets located on the medial and lateral condyles of the tibia articulate with the femoral condyles.
10. Where is the tibia located in the leg?
    The tibia is located on the medial (inner) side of the lower leg.
11. What tibial structures facilitate articulation with the femur?
    The concave superior articular surfaces (facets) on the tibial condyles receive the convex femoral condyles. Menisci (cartilage discs) also aid articulation.
12. Where can the crest of the tibia be felt?
    The anterior crest (shin) of the tibia is subcutaneous and can be easily palpated along the front of the lower leg.
13. With which bone does the distal end of the tibia articulate?
    The distal tibia articulates primarily with the talus (a tarsal bone) to form part of the ankle joint.
14. With which bones does the fibula articulate?
    The fibula articulates proximally with the tibia (just below the knee) and distally with both the tibia and the talus (at the ankle joint).
15. What is another name for the bony prominence on the outer ankle?
    The lateral malleolus, which is the distal end of the fibula.

Foot Bone Anatomy Q&A

1. Where are the tarsal bones located, and what are they?
   The tarsal bones form the posterior part of the foot (ankle and heel area). They are the calcaneus (heel bone), talus, cuboid, navicular, and three cuneiform bones (medial, intermediate, and lateral).
2. With which bones do the metatarsals articulate?
   The bases (proximal ends) of the metatarsals articulate with the distal row of tarsal bones (cuneiforms and cuboid). The heads (distal ends) articulate with the proximal phalanges of the toes.
3. What are the names of the phalanges in the toes?
   Each toe has three phalanges: proximal, middle, and distal, except for the great toe (hallux), which only has two: proximal and distal. They are often referred to as phalanx (singular) or phalanges (plural).

Bone Formation and Structure

Bone Formation (Osteogenesis)

The process by which bones form is called osteogenesis or ossification. This can occur through direct (intramembranous) or indirect (endochondral) ossification.

General Bone Structure

Key components of a typical long bone include:

• Periosteum: A tough, protective membrane covering the outer surface of the bone. It contains blood vessels, nerves, lymphatic vessels, and bone-forming cells (osteoblasts), contributing to growth, repair, and nutrition.
• Compact Bone: The dense, hard outer layer providing strength and support.
• Spongy (Cancellous) Bone: Found inside the compact bone, especially at the ends (epiphyses). It consists of a network of trabeculae, providing strength while reducing weight, and contains red bone marrow.
• Endosteum: A thin membrane lining the inner surfaces of bone, including the marrow cavity and trabeculae of spongy bone. It contains bone-resorbing cells (osteoclasts) and osteoblasts.
• Marrow Cavity (Medullary Cavity): The central cavity within the shaft (diaphysis) of long bones, containing yellow bone marrow (primarily fat) in adults.

Microscopic Structure: Vascular Canals

Compact bone contains microscopic canals for blood vessels and nerves:

• Haversian Canals (Central Canals): Run longitudinally through the bone, parallel to the long axis. Each canal is surrounded by concentric layers of bone matrix (lamellae) forming an osteon (Haversian system).
• Volkmann's Canals (Perforating Canals): Run transversely or obliquely, connecting Haversian canals to each other and to the periosteum and marrow cavity, allowing vessels and nerves to penetrate the compact bone.