🦴 Cartilage and Bones
Osteology – Study of Bones
- Human skeletal system consists of cartilage and bones
- Skeleton acts as a framework supporting soft tissues
- Osteocytes are bone cells that secrete gel-like matrix
- Matrix contains collagen fibers hardened by calcium phosphate crystals
- Ossification/calcification requires Vitamin D for calcium absorption
| Features | Cartilage | Bone |
|---|---|---|
| Definition | Relatively less rigid connective tissue | Most rigid connective tissue |
| Collagen | Loosely packed, Type II | Densely packed, Type I |
| Types | Hyaline, Elastic, Fibrocartilage | Compact, Spongy |
| Cells | Chondrocytes (one type) | Osteoblasts, Osteoclasts, Osteocytes |
| Blood Supply | Absent (diffusion only) | Present |
| Healing | No | Yes |
🌟 Critical Concept: Cartilage has no blood supply and gets nutrients by diffusion. Living cells are called chondrocytes.
💀 Divisions of Human Skeleton
Skeletal Composition
- Infant: ~350 bones
- Adult: 206 bones (fusion occurs)
- Axial Skeleton: 80 bones (skull, vertebral column, rib cage)
- Appendicular Skeleton: 126 bones (limbs and girdles)
Rib Cage Classification
- True Ribs (7 pairs): Connect directly to sternum
- False Ribs (3 pairs): Connect via costal cartilage
- Floating Ribs (2 pairs): No anterior attachment
🌟 Epiphyseal Closure: Bone growth stops between ages 18-25 when epiphyseal plates ossify.
🦾 Types of Joints
Arthrology – Study of Joints
- Joints give mobility to skeleton
- Hold skeletal parts together
- Structural classification: Fibrous, Cartilaginous, Synovial
- Functional classification: Immovable, Slightly movable, Freely movable
| Joint Type | Structure | Mobility | Examples |
|---|---|---|---|
| Fibrous | Bones connected by fibrous tissue | Immovable | Skull sutures |
| Cartilaginous | Bones united by cartilage | Slightly movable | Pubic symphysis |
| Synovial | Joint cavity with synovial fluid | Freely movable | Shoulder, knee |
Arthritis
- Inflammation of joints with tissue degeneration
- Causes: Hereditary, viral infection, injury, aging
- Osteoarthritis: Progressive cartilage softening
- Rheumatoid arthritis: Auto-immune disorder
💪 Types of Muscles
Myology – Study of Muscles
- Muscles transform ATP into mechanical energy
- Functions: Movement, posture, fluid movement, heat production
- Evolution: Smooth → Cardiac → Skeletal muscles
| Features | Smooth Muscle | Cardiac Muscle | Skeletal Muscle |
|---|---|---|---|
| Appearance | Unstriped/Non-striated | Irregular stripes | Regular stripes/Striated |
| Cell Shape | Spindle | Branched | Spindle/Cylindrical |
| Nuclei | One per cell | One per cell | Many per cell |
| Control | Involuntary | Involuntary | Voluntary |
| Location | Blood vessels, GIT | Heart only | Attached to bones |
| Special Feature | Slow contraction | Intercalated discs | T-tubules, SR stores Ca²⁺ |
🌟 Cardiac Biomarker: Troponin release indicates myocardial infarction. Cardiac muscles have intercalated discs.
🏃 Mechanism of Muscle Contraction
Sliding Filament Model (Huxley, 1954)
- Thin filaments slide past thick filaments
- Actin and myosin overlap increases
- Z-lines move closer together
- I-band shortens, H-zone disappears
- Cross bridges attach to actin binding sites
Contraction Requirements
- Nerve impulse at neuromuscular junction
- Energy from ATP hydrolysis
- Calcium ions from sarcoplasmic reticulum
- Troponin-tropomyosin complex movement
Energy Sources
- ATP: Immediate energy source
- Creatine phosphate: High-energy storage
- Glycogen breakdown: Aerobic/anaerobic pathways
- Oxygen debt: Oxygen needed to remove lactic acid
🌟 Rigor Mortis: Stiffening after death due to ATP depletion. Onset: 10 min – 3 hours post-mortem. Useful for determining time of death.
🚀 Study Strategies
Master the Comparisons
Create side-by-side tables for: Cartilage vs Bone, Three muscle types, Joint classifications. Use color coding.
Learn the Sequence
Muscle contraction pathway: Nerve impulse → Ca²⁺ release → Troponin shift → Cross-bridge cycling → ATP hydrolysis.
Anatomy Memory Tricks
Use mnemonics: “Some Lovers Try Positions That They Can’t Handle” for carpal bones (Scaphoid, Lunate, Triquetrum, etc.)