Understanding the Skeletal System: Structure, Function, and Cells
Skeletal System: Bone Tissue and Bones
Bone Classification
Long Bone (e.g., Humerus):
- Longer than they are wide, with one diaphysis and two epiphyses.
- Bones of the limbs: superior (arm, forearm, palm, fingers) and inferior (thigh, leg, sole, toes).
- Mostly compact bone, especially in the epiphysis.
- Plays a role in support.
- Contains a medullary cavity (only type of bone with this feature).
Short Bone (e.g., Talus):
- Small, almost cubic.
- Filled with spongy bone, covered by a thin layer of compact bone.
- Bones of the wrist (carpals) and ankles (tarsals).
Sesamoid Bone:
- Found in tendons, such as the patella, and at the level of the hands and feet (only found in certain individuals).
Flat Bone:
- Thin, flat, slightly curved.
- Filled with spongy bone (diploe), covered by a layer of compact bone.
- Bones of the cranium, sternum, ribs, and scapula.
- Protective role, large surface for muscle attachment.
Irregular Bone:
- Complex shapes and varied composition.
- Spongy bone with a thin layer of compact bone.
- Vertebrae, facial bones, and coxal bones.
Sutural Bones:
- Irregular form.
- Located between sutures of certain cranial bones.
- Especially the lambdoid suture (back of the head).
Structure of Long Bone
Endosteum: Membrane that covers the medullary cavity, trabeculae (spongy bone), and canals that cross compact bone; contains osteoblasts and osteoclasts.
Diaphysis: The body of a long bone; a cylinder of thick compact bone with an interior medullary cavity filled with yellow bone marrow.
Epiphysis: The end of a long bone; filled with spongy bone and covered by a thin layer of compact bone. The part of the epiphysis that participates in the articulation is covered by articular cartilage (hyaline).
