Skeletal System Overview

Study Notes

Bone comprises multiple tissue types: osseous, cartilage, dense connective, epithelium, adipose, and nervous tissue.
Provides structural support for soft tissues and attachment points for skeletal muscle tendons.
Protects vital internal organs: cranial bones shield the brain, and the rib cage safeguards the heart and lungs.
Assists in movement by acting as levers for muscle contraction.
Red bone marrow in certain bones produces blood cells, with all marrow initially red in newborns, transitioning to yellow with age.
Bone tissue, making up 18% of body weight, stores 99% of the body's calcium and phosphorus, aiding in mineral homeostasis.
Yellow bone marrow primarily consists of adipose cells that store triglycerides for energy reserve.

Long bones consist of two main regions: diaphysis (hollow tubular shaft) and epiphysis (wider end filled with spongy bone).
Periosteum: dense connective tissue covering the bone, involved in growth, nutrient supply, and repair.
Endosteum: thinner connective tissue lining the medullary cavity, functioning in bone remodeling and mineral exchange.
Articular cartilage covers epiphyses at joints, reducing friction between bones.

Compact Bone: characterized by a solid matrix and packed cells.
Cancellous Bone (Spongy Bone): contains trabeculae, delicate rods or plates of bone found in the epiphyses and flat bones.
Osteon (Haversian System): the fundamental unit of bone, composed of concentric rings (lamellae) around a central canal containing blood vessels and nerves.

Joints are connections between two bones, classified functionally based on movement capabilities.
Functional Classifications:
- Synarthrosis: non-movable joints (e.g., skull sutures).
- Amphiarthrosis: slightly movable joints (e.g., pubic symphysis, intervertebral joints).
- Diarthrosis: freely movable joints (e.g., knee joint, limb joints).

Fibrous Joints: joined by fibrous tissue, allowing little to no movement.
Cartilaginous Joints: connected by cartilage, permitting slight movement.
Synovial Joints: freely movable with synovial fluid in a cavity around the ends of articulating bones.

Bone formation, termed osteogenesis or bone ossification, continues until around age twenty-five.
Two types of bone ossification:
- Intramembranous Ossification: mesenchymal cells turn into osteoblasts and cluster into ossification centers, leading to trenching into osteocytes and forming trabecular bone and periosteum.
- Endochondral Ossification: involves the transformation of cartilage into bone, essential for long bone growth.