Injury and againg

By the end of this section, you will be able to:
- Understand that tissues of all types are vulnerable to injury and aging.
- Recognize how understanding tissue responses can guide repair strategies.
- Explain how the impact of aging can inform ways to diminish its effects.

Inflammation: Initial response of the body to injury, regardless of cause (biological, chemical, physical, radiation).
- Limits injury, eliminates cause, initiates repair and regeneration of damaged tissue.
Necrosis: Accidental cell death leading to inflammation.
Apoptosis: Programmed cell death; normal process that does not initiate an inflammatory response.
Acute Inflammation: Resolves over time with healing;
Chronic Inflammation: Persists and leads to diseases (e.g., arthritis, tuberculosis).
Suffix "-itis" denotes inflammation (e.g., peritonitis, meningitis).

Redness
Swelling
Pain
Local Heat
Loss of Function: Fifth sign often associated with inflammation.
Historical Note: Cornelius Celsus documented these signs in the 1st century AD.

Damaged Cells: Release inflammatory chemicals that:
- Cause vasodilation (widening of blood vessels).
- Result in redness and heat due to increased blood flow.
Mast Cells: Degranulate and release histamine, a potent vasodilator.
Leaky Blood Vessels: Histamine and other mediators allow neutrophils, macrophages, and fluid to enter the interstitial spaces, causing edema.
Pain Sensation: Caused by squeezed pain receptors and prostaglandins (activated pain neurons).
NSAIDs: Reduce pain by inhibiting prostaglandin synthesis; high doses also reduce inflammation.
Antihistamines: Block histamine receptors, decreasing allergic responses.

Removal of Toxins and Waste: Initiates repair.
Clotting: Reduces blood loss, forms fibrin network to trap blood cells and bind wound edges.
Scab Formation: Dried clot reduces infection risk.
Pus: Mixture of dead leukocytes and fluid may accumulate.
Fibroblasts: Replace lost collagen and extracellular material.
Angiogenesis: Formation of new blood vessels, leading to granulation tissue.
Wound Healing Types:
- Primary Union: Healing with edges close together.
- Secondary Union: Healing with gaping wounds requiring longer refilling time with cells.
- Sutures recommended for deep wounds to promote primary union.
- Regeneration: Addition of new cells of the same type during healing.

Impact of Aging: Functions of the body decline with age.
- Skin and tissues thin and dry; reduced elasticity leads to wrinkles.
- Hair grays due to decreased melanin production.
- Muscle tone loss leads to flabby appearance, joint stiffness, and reduced mobility.
Sensory Deterioration: Glasses and hearing aids become necessary due to decreased elasticity.
Height Reduction: Bones lose calcium; intervertebral disks lose fluid.
Cellular Changes: All cells undergo changes with aging, impacting division and regeneration (telomere shortening).
- Impaired transport of oxygen and nutrients due to membrane alterations.
Older Individuals: Experience slower wound healing and greater infection risk due to weakened immune system.

Aging Effects: Cells lose mass, transmit signals less effectively, affecting thought clarity and memory.
Diseases Associated with Aging: Those worsening with age (e.g., arthritis, certain cancers) may also be related to lifestyle choices.

Cancer Definition: Uncontrolled cell growth and invasion.
- Tumors can rob blood supply from normal organs.
Mutations: Permanent DNA changes that can cause cancerous cells.
- Epigenetic Modifications: Change how DNA is decoded without altering the code itself.
Tumors: Masses of abnormal cells; can be benign or malignant.
- Carcinomas: Cancers from epithelial cells.
- Myelomas: Cancers in blood cells.
- Leukemias: Cancers of white blood cells.
- Sarcomas: Derived from connective tissue.
Cancer Stem Cells: Uncontrolled growth subtype; tumors exhibit their own structures contrary to previous assumptions of disorganization.

Traditional Approaches: Surgery, radiation, chemotherapy, hormonal therapy aimed at removing or killing rapidly dividing cancer cells.
Limitations: Difficulty in targeting cancer cells alone can lead to healthy tissue destruction.
Future Directions: Research focusing on drugs targeting specific proteins in cancer-related pathways.