7.4 Disorders of Skeleton
This section outlines common disorders affecting the skeletal system, categorizing them based on their causes: hereditary, hormonal, or nutritional. The disorders detailed include their specific pathologies and clinical manifestations.
Slipped Disc (Herniated Disc)
A slipped disc, also known as a herniated disc, is a condition affecting the intervertebral discs of the spine.
Structure of Intervertebral Discs
Intervertebral discs are cushion-like pads located between adjacent vertebrae. Each disc consists of two main components:
- Nucleus Pulposus: The inner, semifluid core that provides elasticity and compressibility. It functions like a rubber ball, allowing the spine to absorb shocks and undergo movement.
- Annulus Fibrosus: A strong outer ring of fibrocartilage that holds successive vertebrae together and contains the nucleus pulposus.
The primary function of intervertebral discs is to act as shock absorbers for the spine.
Herniation Process
- Severe or sudden trauma causes the annulus fibrosus to rupture.
- The inner nucleus pulposus protrudes (herniates) outwards through the tear.
- This protrusion can press on the spinal cord or spinal nerves, causing pain and potential neurological damage.
The term "slipped disc" is misleading, as the entire disc does not slide out of position. Instead, the inner material bulges through the damaged outer ring.
Symptoms
Severe pain and potential damage to nervous structures result from nerve compression.
Spondylosis
Spondylosis is a degenerative condition characterized by the immobility and fusion of vertebral joints.
- Cervical Spondylosis: A common form resulting from chronic degeneration of the cervical (neck) vertebrae, often linked to aging and disc herniation.
Sciatica
Sciatica refers to nerve pain originating from the sciatic nerve.
- Symptoms: Pain, weakness, numbness, or tingling in the leg.
- Cause: Injury to or pressure on the sciatic nerve.
- Common Triggers:
- Slipped disc
- Pelvic injury or fracture
- Tumors
Arthritis
Arthritis is a general term for the inflammation of one or more joints.
General Symptoms
- Pain, especially after walking, which can later occur at rest
- Creaking sounds in the joint
- Difficulty getting up from a chair
- Pain on walking up and down stairs
Types of Arthritis
| Type | Cause | Description | Common Joints Affected |
|---|---|---|---|
| Osteoarthritis | Degenerative ("wear and tear") | Progressive disease where the articular cartilages gradually soften and disintegrate. | Knee, hip, intervertebral joints |
| Rheumatoid Arthritis | Autoimmune Disorder | The body's immune system mistakenly attacks the synovial membrane, causing inflammation. | Hands, feet |
| Gouty Arthritis (Gout) | Metabolic Disorder | High levels of uric acid in the blood lead to the deposition of sodium urate crystals in the joints. | Joint of the big toe is most common. |
Osteoporosis
Osteoporosis is a disease characterized by reduced bone mass (density), leading to an increased risk of fractures.
- Underlying Mechanism: The rate of bone resorption (breakdown) exceeds the rate of bone deposition (formation).
- Bone Mass Lifecycle:
- Bone mass increases during growth, reaching a peak between ages 20 and 25.
- After this peak, bone mass gradually falls in both sexes.
- Prevention: Ingesting adequate amounts of calcium, especially for women in their 20s and 30s, helps build a higher peak bone mass. A higher peak mass provides a greater tolerance for bone loss later in life.
Osteomalacia and Rickets
While not detailed in the original summary table, these nutritional disorders are critical skeletal conditions.
Possible Questions and Answers
Q: What happens during a "slipped disc"? A: The outer ring of the intervertebral disc (annulus fibrosus) ruptures, allowing the soft inner core (nucleus pulposus) to protrude and press on nearby nerves or the spinal cord.
Q: What is the fundamental difference between Osteoarthritis and Rheumatoid Arthritis? A: Osteoarthritis is a degenerative "wear-and-tear" disease where cartilage breaks down. Rheumatoid arthritis is an autoimmune disorder where the body's immune system attacks the joint's synovial membrane.
Q: Why is osteoporosis more than just "weak bones"? A: It is a systemic disease where the balance between bone formation and bone breakdown is disrupted. Specifically, bone resorption (breakdown) outpaces bone deposition (formation), leading to a progressive loss of bone density and structural integrity.
Comparison of Arthritis Types
| Arthritis Type | Primary Cause | Key Feature |
|---|---|---|
| Osteoarthritis | Degeneration | Breakdown of articular cartilage. |
| Rheumatoid Arthritis | Autoimmune | Inflammation of the synovial membrane. |
| Gouty Arthritis | Metabolic | Uric acid crystal deposits in joints. |
Biological Significance: Understanding these common skeletal disorders is crucial for diagnosis, treatment, and prevention. Lifestyle factors such as diet (calcium intake for osteoporosis), managing physical stress (preventing slipped discs), and understanding autoimmune responses are key to maintaining skeletal health throughout life. Related neurological impacts can be explored in Disorders Of The Nervous System→.