Bone Structure and Joint Types

Types of Bone Tissue
- Compact Bone: Dense outer layer; provides strength.
- Spongy Bone: Lighter, porous inner layer; contains bone marrow.
Bone Cells
- Osteoblasts: Build new bone.
- Osteocytes: Maintain bone tissue.
- Osteoclasts: Break down old bone.
Bone Matrix
- Composed of collagen fibers and mineral salts (mainly calcium phosphate).
- Provides rigidity and strength.
Bone Classification
- Long Bones: Longer than wide (e.g., femur).
- Short Bones: Cube-shaped (e.g., carpals).
- Flat Bones: Thin, flattened (e.g., skull).
- Irregular Bones: Complex shapes (e.g., vertebrae).

Fibrous Joints
- No movement (e.g., sutures in the skull).
Cartilaginous Joints
- Limited movement; connected by cartilage (e.g., intervertebral discs).
Synovial Joints
- Freely movable; characterized by a joint capsule and synovial fluid.
- Types include:
  - Hinge Joints (e.g., elbow)
  - Ball-and-Socket Joints (e.g., hip)
  - Pivot Joints (e.g., neck)
  - Saddle Joints (e.g., thumb)

Embryonic Development
- Begins around the 6th week of gestation.
- Two types of bone formation: Intramembranous (directly from mesenchyme) and Endochondral (from cartilage).
Growth Stages
- Infancy: Rapid growth and ossification.
- Adolescence: Growth plates open and close with puberty.
- Adulthood: Bone remodeling occurs; peak bone mass is reached.

Support
- Provides structural support for the body.
Protection
- Shields vital organs (e.g., skull protects the brain, rib cage protects the heart).
Movement
- Serves as levers for muscles to facilitate movement.
Mineral Storage
- Reservoir for minerals, particularly calcium and phosphorus.
Blood Cell Production
- Hematopoiesis occurs in the bone marrow.

Osteoporosis
- Characterized by decreased bone density; increases fracture risk.
Arthritis
- Inflammation of joints; includes osteoarthritis (degenerative) and rheumatoid arthritis (autoimmune).
Fractures
- Breaks in bone; types include simple, compound, and comminuted fractures.
Osteomyelitis
- Bone infection, often caused by bacteria.
Paget's Disease
- Abnormal bone remodeling leading to enlarged and weakened bones.

Types of Bone Tissue
- Compact Bone: Forms the dense outer layer, offering strength and support.
- Spongy Bone: A lightweight, porous interior containing bone marrow, facilitating blood cell production.
Bone Cells
- Osteoblasts: Cells responsible for bone formation and mineralization.
- Osteocytes: Mature bone cells that maintain and monitor the bone matrix.
- Osteoclasts: Cells that break down bone tissue, playing a crucial role in bone resorption.
Bone Matrix
- Composed of collagen fibers and mineral salts, primarily calcium phosphate, providing structural integrity and strength.
Bone Classification
- Long Bones: Exceed length compared to width, such as the femur, contributing to movement.
- Short Bones: Cube-shaped, like carpals, providing stability and support.
- Flat Bones: Thin and flattened, such as the skull, protecting internal organs.
- Irregular Bones: Have complex shapes, as seen in vertebrae, serving varied functions.

Fibrous Joints
- Immovable joints held together by connective tissue, exemplified by sutures in the skull.
Cartilaginous Joints
- Allow limited movement; connected by cartilage, seen in intervertebral discs.
Synovial Joints
- Freely movable joints characterized by a joint capsule and synovial fluid for lubrication.
- Types include:
  - Hinge Joints: Allow bending and straightening, such as the elbow.
  - Ball-and-Socket Joints: Enable rotational movement, like in the hip.
  - Pivot Joints: Allow rotation around a single axis, exemplified by the neck.
  - Saddle Joints: Allow movement along two axes, demonstrated by the thumb.

Embryonic Development
- Initiates around the 6th week of gestation, involving two main bone formation processes:
  - Intramembranous: Bone develops directly from mesenchymal tissue.
  - Endochondral: Bone is formed from pre-existing cartilage.
Growth Stages
- Infancy: Characterized by rapid bone growth and ossification.
- Adolescence: Growth plates open during growth spurts; they eventually close at puberty.
- Adulthood: Bone remodeling occurs continuously, peaking with maximum bone mass.

Support
- Provides a framework that supports the body and maintains shape.
Protection
- Safeguards vital organs, with the skull shielding the brain and the rib cage protecting the heart.
Movement
- Bones act as levers, enabling movement when muscles contract and exert force.
Mineral Storage
- Acts as a reservoir for essential minerals, particularly calcium and phosphorus, critical for various bodily functions.
Blood Cell Production
- The process of hematopoiesis occurs in bone marrow, generating red and white blood cells.

Osteoporosis
- A condition marked by reduced bone density, significantly increasing the risk of fractures.
Arthritis
- Joint inflammation, which can be classified into degenerative osteoarthritis or autoimmune rheumatoid arthritis.
Fractures
- Breaks in bone categorized into types such as simple (closed), compound (open), and comminuted (multiple fragments).
Osteomyelitis
- An infection of the bone often caused by bacterial pathogens, leading to inflammation and tissue death.
Paget's Disease
- A disorder causing abnormal bone remodeling, resulting in enlarged, weakened bones that are more susceptible to fractures.