Detailed Study Notes on Bone Structure and Development

Functional microscopic unit of long bone
- Compact bone (Osteon)
- Haversian system
Functional unit of spongy bone
- Trabeculae: Latticework forming the microscopic structural unit of spongy bone
- Gaps between trabeculae filled with blood vessels condensed into red marrow
  - Red marrow is involved in hematopoiesis (blood formation)

Blood supply and nerve supply originate from the periosteum
Nutrient foramen: Openings through which blood vessels and nerves enter the compact bone
Perforating canals: Canals that run perpendicular to the central canal, connecting osteons
Central canal: The center of the osteon, containing blood vessels and nerves
- Connects to the medullary cavity in the diaphysis
- In the epiphyses, connects to trabecular spaces filled with red marrow

Functions of arteries in bone:
- Supply nutrients and oxygen (including glucose and minerals) to bone tissue
Functions of veins in bone:
- Drain metabolic waste produced by bone cells
Nerves in bones primarily sense pain

Ossification: The process of bone formation
- Starts during the sixth or seventh week of embryonic development
- Embryonic skeleton consists of fibrous membranes and hyaline cartilage, without osseous tissue

Intramembranous ossification (IO): Bone develops between membranes, forming compact and spongy bone
Endochondral ossification (EO): Bone replaces cartilage templates
- IO involves flat bones of the face and cranial bones, as well as the clavicles

Mesenchymal tissue forms into bone through osteogenic pathways:
- Osteogenic: Literally means "creation of bone"
During ossification, osteoblasts secrete osteoid (uncalcified matrix) which matures into bone
After calcification, trapped osteoblasts become osteocytes within lacunae

Cartilage is composed of hyaluronic acid, chondroitin sulfate, and collagen
Differences between cartilage and bone:
- Bone is harder due to higher mineral density (calcium carbonate) and lower water content
By birth, most of the cartilage skeleton has been replaced by bone, but certain areas remain (e.g. skull and clavicles)

Intramembranous ossification process:
- Begins with mesenchymal cells differentiating into osteoblasts, forming ossification centers
- Osteoblasts secrete osteoid, forming bone matrix which eventually traps the osteoblasts
- Spongy bone forms at the center, and the periosteum develops from osteoblasts at the surface
Endochondral ossification process:
- Mesenchymal cells differentiate into chondrocytes forming a cartilage template
- The process involves calcification of cartilage, leading to cell death and replacement by bone
- Primary ossification centers develop in the diaphysis during early fetal development, with secondary ossification centers emerging post-birth

Longitudinal growth occurs at the epiphyseal plates
Cartilage remains in joints as articular cartilage and in growth plates
- This cartilage is responsible for adding length to long bones
As long bones develop into adulthood, remnant cartilage contributes to continued growth and remodeling

Fracture Definition: When bone breaks
General types:
- Open fracture: Pierces through the skin (higher infection risk)
- Closed fracture: Does not pierce the skin
Specific types of fractures:
- Transverse fracture: Straight across the bone
- Oblique fracture: At an angle to the long axis
- Spiral fracture: Caused by twisting force
- Comminuted fracture: Bone breaks into multiple pieces due to crushing forces
- Impacted fracture: Bone fragments are pushed together
- Greenstick fracture: Hairline fracture typical in children

Review for upcoming examinations, focusing on the axial skeleton and bone development processes.
Preparation strategies discussed before exams relate to understanding intricate details in lecture topics.