Bones and Skeletal Tissues

Skeletal Cartilage Basics

Skeletal cartilage is a specialized connective tissue that provides support and flexibility to the skeletal system. It is primarily composed of water, which contributes to its resilience and ability to withstand compression.

• Chondrocytes: These are the cells found within cartilage, residing in small cavities called lacunae within a jelly-like extracellular matrix.

• Perichondrium: Cartilage is surrounded by a dense irregular connective tissue membrane called the perichondrium, which supplies nutrients since cartilage is avascular (lacks blood vessels).

• Nutrient Diffusion: Nutrients diffuse from the perichondrium to the chondrocytes.

Types of Skeletal Cartilage

There are three main types of cartilage found in the human body, each with distinct structural and functional properties.

Hyaline Cartilage

• Function: Provides support, flexibility, and resilience.

• Structure: Most abundant type; contains only collagen fibers.

• Locations: Articular (joints), costal (ribs), respiratory (larynx and airways), and nasal cartilage (external nose).

• Example: The cartilage at the ends of long bones in synovial joints.

Elastic Cartilage

• Function: Flexible and resilient, similar to hyaline cartilage but with added elasticity.

• Structure: Contains both collagen and elastic fibers.

• Locations: External ear and epiglottis.

• Example: The cartilage that maintains the shape of the ear.

Fibrocartilage

• Function: Withstands pressure and stretch; strongest type of cartilage.

• Structure: Contains thick collagen fibers.

• Locations: Menisci of knee, pubic symphysis, intervertebral discs.

• Example: The cartilage found between vertebrae in the spine.

Growth of Cartilage

Cartilage grows by two mechanisms, both important during development and healing.

• Appositional Growth: Growth occurs outward, adding new layers to the surface of cartilage.

• Interstitial Growth: Expansion from within, as chondrocytes divide and secrete new matrix.

• Growth Limitation: Cartilage growth typically ends during adolescence.

Functions of Bones

Bones serve multiple essential functions in the human body, contributing to both structure and physiology.

• Support and Protection: Bones form the framework of the body and protect vital organs (e.g., skull protects the brain, rib cage protects thoracic organs).

• Anchorage and Movement: Skeletal muscles attach to bones via tendons, enabling movement.

• Mineral and Growth Factor Storage: Bones store minerals such as calcium and phosphate, releasing them as needed for physiological processes.

• Blood Cell Formation (Hematopoiesis): Occurs in red marrow cavities, producing red and white blood cells.

• Fat and Hormone Storage: Yellow marrow stores triglycerides (fat), and bones produce the hormone osteocalcin, which regulates insulin, glucose, and metabolism.

Additional info: Osteocalcin is a hormone produced by osteoblasts that plays a role in bone mineralization and metabolic regulation.