Supportive Connective Tissue

• Types of Supportive Connective Tissue:
    - Bone
      - Divided into Axial Skeleton and Appendicular Skeleton.
        - Axial Skeleton: Includes the trunk.
        - Appendicular Skeleton: Includes limb bones, articulating or forming joints that come from the trunk.
    - Cartilage
      - Subdivided into three types:
        1. Hyaline Cartilage
        2. Elastic Cartilage
        3. Fibrocartilage

Cartilage

• Types of Cartilage
    - Hyaline Cartilage:
      - Description: Most abundant type of cartilage. Provides support, flexibility, and is extremely resilient. Comprised mainly of collagen fibers.
      - Cells: Chondrocytes (mature cartilage cells) located in spaces called Lacunae.
      - Function: Protects bones against crushing when they move, found at the ends of bones.
    - Elastic Cartilage:
      - Description: Similar to hyaline cartilage but contains elastic fibers in addition to collagen fibers. Less abundant.
      - Function: Provides flexibility and resilience; for example, found in the external part of the ear (pinna).
    - Fibrocartilage:
      - Description: Second most abundant cartilage type, characterized by very thick collagen fibers.
      - Function: Provides tensile strength and absorbs shock; found between vertebrae (intervertebral discs) and in joint structures.

• Cells Making Cartilage:
    - Chondrocytes: Mature cartilage cells found in the Lacuna.
    - Chondroblasts: Immature cells in the perichondrium (a dense irregular connective tissue surrounding cartilage).

Functions of Cartilage

• Protection: Cushions joints and supports skeletal structure.
• Movement: Facilitates smooth movement across joints.

Structure of Cartilage

• Extracellular Matrix: The non-living portion secreted by chondrocytes, primarily composed of collagen fibers.
• Perichondrium: Protects against expansion, contains chondroblasts for cartilage growth and maintenance.

Growth of Cartilage

• Types of Growth:
    - Appositional Growth:
      - Occurs at the perichondrium where chondroblasts secrete new matrix on the outer surface.
      - Chondroblasts push inward to form Lacunae, becoming chondrocytes as they mature.
    - Interstitial Growth:
      - Involves division of chondrocytes within Lacunae.
      - Results in expansion of the cartilage tissue internally as new matrix is formed.

Important Notes

• Slow Growth: Cartilage grows slowly due to lack of blood vessels; healing is a lengthy process.
• Trauma to Cartilage: When damaged, cartilage calcifies but does not transform into bone.

Bone

• Bone Functions:
    - Provides support and shape to the body.
    - Protects internal organs.
    - Facilitates movement by serving as attachment points for muscles.
    - Stores minerals and growth factors (e.g., calcium).
    - Houses adipose tissue and produces red blood cells (hematopoiesis).

• Types of Bone:
    - Compact Bone: Dense and solid, provides strength.
    - Spongy Bone: Contains trabecular (branched) structures and spaces for blood vessels and marrow.

Bone Cells

• Osteocytes: Mature bone cells residing in Lacunae, involved in the maintenance of bone tissue.
• Osteoblasts: Bone-forming cells that secrete collagen and minerals to form the extracellular matrix.
• Osteoclasts: Cells responsible for bone resorption; they dissolve bone tissue.

Structure of Bone

• Periosteum: A fibrous membrane covering the bone, consisting of dense irregular connective tissue.
    - Contains blood vessels and nerve fibers.
    - Contains the osteogenic layer made of osteoblasts.
• Endosteum: A thin layer surrounding spongy bone, contains osteoblasts and osteoclasts.

Bone Anatomy

• Gross Anatomy of Bones
    - Observed with the naked eye; includes bones and their markings.
• Microscopic Bone Anatomy
    - Involves looking under a microscope at bone structure and composition.

Bone Growth

• Appositional and Interstitial Growth: Similar to cartilage growth; osteoblasts push inward and mature to osteocytes.
• Osteons: The structural and functional units of compact bone, forming the Haversian system.
    - Comprised of concentric lamellae surrounding a central canal containing blood vessels.

Lamella Types in Bone

• Concentric Lamella: Forms the osteon around the central canal.
• Interstitial Lamella: Incomplete lamella found between osteons.
• Circumferential Lamella: Extends around the entire circumference of the bone beneath the periosteum.

Nutrient Supply in Bone

• Central Canals and Canaliculi: Osteocyte projections extend through canaliculi, allowing for nutrient exchange between cells and the central canal containing blood vessels.

Cartilage vs. Bone

• Cartilage does not contain blood vessels, grows slowly, and is more flexible, while bone is vascularized, grows quickly, and is rigid.

Conclusion

• The support provided by connective tissue (both cartilage and bone) is essential for body structure, protection, and mobility. Understanding the differences between these connective tissues is crucial for studying their specific functions and structures in the body.