U5-6H

Characteristics of Cartilaginous Tissue

Tough, durable supporting connective tissue; ECM rich in GAGs, proteoglycans, collagen, & elastic fibers; provides cushioning in joints, allows bearing mechanical stress, and guides bone growth.

Localization of Cartilaginous Tissue

Found in trachea, articular surfaces of bones, synovium, ligaments, synovial fluid, and fetal skeleton.

Organization of Cartilaginous Tissue

Chondrocytes in lacunae, lacks vascular nerve supply; nutrients diffuse from perichondrium.

Structure of Perichondrium

Outer region with collagen type I fibers and fibroblasts; inner layer contains mesenchymal cells that differentiate into chondrocytes.

Main Cells in Cartilaginous Tissue

Chondrogenic cells, chondroblasts (immature), chondrocytes (mature).

Main Components of ECM in Cartilaginous Tissue

GAGs (chondroitin sulfate), proteoglycans, type II collagen, adhesive proteins.

Location of Hyaline Cartilage

Articular surfaces of joints, respiratory passages (nose, larynx, trachea), rib ends, epiphyseal plates.

Composition of Hyaline Cartilage ECM

Type II collagen, aggrecan, chondroitin sulfate, keratan sulfate, hyaluronan.

Unique Feature of Hyaline Cartilage Perichondrium

Present in most hyaline cartilage, except articular cartilage.

Isogenous Aggregates in Hyaline Cartilage

Groups of up to eight chondrocytes from mitotic divisions of a single chondroblast.

Elastic Cartilage

Similar to hyaline cartilage but with elastic fibers; located in the ear, auditory canals, epiglottis.

Fibrocartilage

Mix of hyaline cartilage and dense connective tissue; found in intervertebral discs, ligament attachments, pubic symphysis.

Difference Between Fibrocartilage and Other Cartilage Types

Lacks distinct perichondrium and has a more acidophilic matrix due to fewer proteoglycans.

Types of Growth in Cartilaginous Tissue

Interstitial growth (mitotic division of chondrocytes) and appositional growth (differentiation of chondroblasts).

Reason for Slow Cartilage Repair

Avascularity and low metabolic rate; repairs often form dense connective tissue scars.

Functions of Bone Tissue

Provides support, protects organs, encloses medullary cavities; reservoir for calcium and phosphate.

Main Cells in Bone Tissue

Osteoblasts (bone-forming), osteocytes (mature), and osteoclasts (resorbing cells).

Composition of Bone Matrix

50% inorganic (calcium hydroxyapatite) and 90% organic matter (type I collagen, proteoglycans).

Function of Osteoblasts

Synthesize organic components of bone matrix and deposit inorganic components.

Function of Osteocytes

Maintain calcified matrix; situated in lacunae, connected by canaliculi.

Function of Osteoclasts

Resorb bone matrix; crucial for growth and remodeling.

Structure of the Periosteum

Outer fibrous layer (collagen, fibroblasts, blood vessels) and inner cellular layer (osteoprogenitor cells).

Types of Bone Based on Structure

Compact (cortical) bone (80% of mass) and spongy (cancellous) bone (20% of mass).

Structure of Compact Bone

Organized into osteons (Haversian systems) with concentric lamellae, central canals, canaliculi.

Structure of Spongy Bone

Network of trabeculae with osteocytes; no Haversian systems.

Intramembranous Ossification

Direct differentiation of osteoblasts from mesenchyme; forms flat bones.

Endochondral Ossification

Replaces hyaline cartilage with bone; primarily forms long bones.

Steps of Endochondral Ossification

Cartilage model → bone collar → primary ossification center → secondary centers → epiphyseal plate → elongation.

Appositional Bone Growth

Osteoblasts deposit bone, enlarging medullary cavity via osteoclast activity.

Stages of Fracture Repair

1. Hematoma formation; 2. Fibrocartilaginous callus; 3. Hard callus formation; 4. Bone remodeling.

Role of Osteonectin in Bone Matrix

Glycoprotein that helps osteoblasts adhere to ECM.

Role of Osteocalcin in Bone Matrix

Calcium-binding protein promoting matrix calcification.

Role of Matrix Vesicles in Bone Formation

Release phosphatases that facilitate matrix calcification.

Role of Epiphyseal Plate in Bone Growth

Allows for bone elongation during childhood.

Difference Between Woven and Lamellar Bone

Woven bone is immature and disorganised; lamellar bone is mature and organised.