Human Skeleton Development

Study Notes

Made of highly resilient, molded cartilage tissue that consists primarily of water
Contains no blood vessels or nerves
Surrounded by perichondrium, a layer of dense connective tissue that helps resist outward expansion and contains blood vessels for nutrient delivery

Hyaline cartilage:
- Provides support, flexibility, and resilience
- Most abundant type; contains collagen fibers only
- Found in articular (joints), costal (ribs), respiratory (larynx), and nasal cartilage (nose tip)
Elastic cartilage:
- Similar to hyaline cartilage, but contains elastic fibers
- Found in external ear and epiglottis
Fibrocartilage:
- Thick collagen fibers; has great tensile strength
- Found in menisci of knee and vertebral discs

Appositional growth:
- Cartilage-forming cells in perichondrium secrete matrix against external face of existing cartilage
- New matrix laid down on surface of cartilage
Interstitial growth:
- Chondrocytes within lacunae divide and secrete new matrix, expanding cartilage from within
- New matrix made within cartilage

Support for body and soft organs
Protection for brain, spinal cord, and vital organs
Movement (levers for muscle action)
Mineral and growth factor storage
Blood cell formation (hematopoiesis)
Triglyceride (fat) storage
Hormone production (osteocalcin regulates insulin secretion, glucose levels, and metabolism)

206 named bones in human skeleton
Divided into two groups based on location:
- Axial skeleton (skull, vertebral column, rib cage)
- Appendicular skeleton (bones of upper and lower limbs, girdles attaching limbs to axial skeleton)
Classified according to shape:
- Long bones
- Short bones
- Flat bones
- Irregular bones

Bones are organs composed of different types of tissues (bone, nervous, cartilage, fibrous connective, muscle, and epithelial)
Three levels of structure: gross, microscopic, and chemical
Compact and spongy bone:
- Compact bone: dense outer layer on every bone that appears smooth and solid
- Spongy bone: made up of a honeycomb of small, needle-like or flat pieces of bone called trabeculae
Structure of short, irregular, and flat bones:
- Consist of thin plates of spongy bone (diploe) covered by compact bone
- Compact bone sandwiched between connective tissue membranes
Structure of typical long bone:
- Diaphysis (shaft), epiphyses (bone ends), and membranes