Bone Tissue and Joints

• Compact bone is dense tissue forming the outer bone layer, crucial for strength and structure.
• Spongy bone is a lighter, less dense tissue inside bones, especially in epiphyses, aiding shock absorption with its trabeculae.
• Trabeculae are small beams within spongy bone that provide structural support.
• Osteons, or Haversian systems, are the basic units of compact bone, featuring concentric lamellae, osteocytes, and a central canal.
• The central canal, also known as the Haversian canal, contains blood vessels and nerves within the osteon.
• Lacunae are small cavities in bone tissue where osteocytes reside.
• Canaliculi are tiny channels in bone that connect lacunae, facilitating nutrient exchange.

Bone Cells

• Osteocytes are mature cells that maintain the bone matrix.
• Osteoblasts build new tissue by secreting osteoid.
• Osteoprogenitor cells are stem cells that become osteoblasts.
• Osteoclasts break down tissue during remodeling.

Joint Types

• Synarthrosis joints are immovable, such as skull sutures.
• Diarthrosis joints are freely movable, examples being the knee and shoulder.
• Synovial joints have a synovial cavity filled with synovial fluid, such as the knee and elbow.
• Amphiarthrosis joints are slightly movable, like the pubic symphysis.
• Syndesmosis joints are fibrous joints connected by ligaments, such as between the radius and ulna.
• Symphysis joints are cartilaginous joints connected by fibrocartilage, like intervertebral discs.
• Gomphosis is a peg-in-socket joint, such as teeth attached to sockets.

Bone Markings

• A fossa is a shallow depression or cavity in the bone.
• A sulcus is a groove or furrow in the bone.
• A facet is a smooth, flat surface for articulation.
• A foramen is a hole for nerves and blood vessels.
• A process is a projection or outgrowth from the bone.
• A condyle is a rounded, articular surface at the end of a bone.

Skeletal Regions

• The axial skeleton includes the skull, vertebral column, and rib cage.
• The appendicular skeleton includes limbs and girdles (shoulder and pelvic).

Compact Bone Function

• Compact bone offers strength, mineral storage, and facilitates movement.

Spongy Bone Function

• Spongy bone aids in shock absorption.
• Spongy bone supports red bone marrow.
• Spongy bone helps reduce overall bone weight.

Medullary Cavity Function

• It stores bone marrow, red for blood cell production and yellow for fat storage.
• It helps reduce the bone’s overall weight.

Bone Remodeling

• Bone remodeling is where old tissue is replaced by new tissue.
• Osteoclasts break down old bone.
• Osteoblasts build new bone.

Bone Cell Roles

• Osteocytes' role involves maintaining bone matrix.
• Osteoblasts produce bone tissue.
• Osteoclasts break down tissue.
• Osteoprogenitor cells differentiate into osteoblasts.

Atlas (C1)

• It supports the skull, allowing a nodding motion.

Axis (C2)

• The axis allows head rotation, featuring a dens (odontoid process) that fits into the atlas.

Bone Composition

• Hydroxyapatite provides hardness and strength; without it, bones become brittle.
• Collagen provides flexibility; without it, bones break easily.

Vitamin D

• Vitamin D aids the body in absorbing calcium, crucial for bone mineralization.
• A deficiency leads to rickets in children.
• A deficiency leads to osteomalacia in adults.

Bone Fractures

• Simple fractures mean the bone breaks but does not pierce the skin.
• Compound fractures mean the bone breaks and pierces the skin.
• Comminuted fractures involve the bone breaking into several pieces.
• Greenstick fractures are incomplete, often in children.
• Spiral fractures are caused by a twisting motion.
• Repair involves hematoma formation as well as callus formation.
• Ossification occurs followed by bone remodeling.

Synovial Joints

• Synovial joints contain synovial fluid and a synovial membrane.
• Synovial joints Allow for free movement.

Types of Synovial Joints

• Monaxial joints move in one plane, such as hinge joints.
• Biaxial joints move in two planes, such as condylar joints.
• Triaxial joints move in three planes, such as ball-and-socket joints.

Common Joint Movements

• Flexion decreases the angle between bones.
• Extension increases the angle between bones.
• Abduction moves away from the midline.
• Adduction moves toward the midline.
• Rotation is movement around an axis (internal/external).
• Pronation is palm down, supination is palm up.
• Circumduction is circular motion at a joint.

Bone Development

• Endochondral ossification is when bone replaces hyaline cartilage, such as in long bones.
• Intramembranous ossification is when bone forms directly from mesenchyme, such as in skull bones.

Vertebrae

• Cervical vertebrae feature transverse foramina for blood vessels.
• Thoracic vertebrae have heart-shaped bodies with facets for rib attachment.
• Lumbar vertebrae have large bodies to support weight.

Bone Diseases

• Osteopenia is the condition of low bone mass that can lead to osteoporosis.
• Osteoporosis is a condition where bone density decreases, making bones fragile and prone to fractures.

Skeletal Functions

• Support provides structural support for the body.
• Movement is due to muscle attachments to bones enabling movement.
• Protection is for vital organs (e.g., brain, heart).
• Mineral storage is for calcium and phosphorus.
• Blood cell production by red bone marrow occurs.
• Energy storage via yellow bone marrow is for fat storage.