Untitled Quiz

Skeletal System Functions

• Provides support for the body, soft tissues, and organs
• Stores minerals like calcium and phosphate
• Yellow bone marrow stores lipids
• Red bone marrow inside long bones produces red blood cells, white blood cells, and platelets
• Protects vital organs like the heart, lungs, brain, and spinal cord

Bone Classification

• Bones are classified by shape, bone markings, and internal tissues.
• Five shapes: long, flat, irregular, short, and sesamoid.
• Long bones such as femur and humerus are found in arms, legs, hands, and feet.
• Flat bones like the skull, sternum, ribs, and scapula are thin with parallel surfaces.
• Irregular bones are complex shapes like vertebrae and pelvic bones.
• Short bones like the ankles and wrist bones are small and thick.
• Sesamoid bones are small and flat, found inside tendons near joints like knees, hands, and feet.
• Bone markings are depressions, projections, and tunnels that serve specific functions.
• Depressions and grooves along the bone surface provide pathways for blood vessels and nerves.
• Projections are points where tendons and ligaments attach, or points of articulation (joining) with other bones.
• Tunnels allow blood vessels and nerves to enter the bone.

Bone Structure

• Diaphysis (shaft) of the bone is composed of compact bone with a marrow cavity inside containing bone marrow.
• Epiphysis (ends) of the bone are wider and made of spongy bone. They are the points where the bone articulates (joins) with other bones.
• Metaphysis is the region between the diaphysis and epiphysis.

Bone Tissue

• Dense matrix composed of calcium salts and bone cells.
• Bone cells are located within cavities called lacunae and organized around blood vessels.
• Canaliculi connect lacunae, providing pathways for blood vessels and exchange of nutrients and waste.
• Calcium phosphate is the main mineral component of bone, constituting 2/3 of the bone matrix.
• Collagen protein fibers make up 1/3 of the bone matrix.

Bone Cells

• Only 2% of bone mass is composed of cells.
• Osteocytes are mature bone cells that maintain the bone matrix by regulating its protein and mineral content and helping repair damage. They do not divide.
• Osteoblasts are immature bone cells that secrete matrix compounds (osteogenesis), building new bone.
• Osteoprogenitor cells are immature cells that can differentiate into osteoblasts. They are responsible for bone growth and repair.
• Osteoclasts are responsible for breaking down bone tissue, called bone resorption, to release minerals or to remodel bone.

Types of Bone

• Compact bone has a dense, solid appearance. It contains parallel osteons (structural units of bone).
• Osteons are composed of concentric layers of osteocytes surrounding a central canal containing blood vessels.
• Spongy bone is lighter with a lattice-like structure called trabeculae. Trabeculae are meshworks of supporting fibre bundles that provide strength with minimal weight.