Age-Related Anatomical Changes

Age-Related Anatomical Changes - Tiny Time Travelers

• Hallmarks of Cellular Aging:
  • Telomere Shortening: Progressive loss of chromosomal ends, limiting cell divisions (replicative senescence).
  • Cellular Senescence: Irreversible cell cycle arrest; cells secrete Senescence-Associated Secretory Phenotype (SASP) factors, promoting inflammation.
  • Mitochondrial Dysfunction: Leads to ↓ATP production and ↑Reactive Oxygen Species (ROS), causing oxidative damage.
  • Epigenetic Alterations: Changes like DNA methylation & histone modification alter gene expression patterns.
  • Stem Cell Exhaustion: Diminished self-renewal and differentiation capacity, impairing tissue repair and regeneration.
• General Physiological Decline:
  • Homeostenosis: Narrowed range of physiological parameters to maintain homeostasis, especially under stress.
  • Reduced Physiological Reserves: Decreased functional capacity across organ systems, increasing vulnerability.

⭐ The Hayflick limit describes the finite number of times a normal human cell population will divide before cell division stops, typically around 40-60 divisions for human fetal fibroblasts.

Age-Related Anatomical Changes - Bones, Groans & Moans

• Osteoporosis: Systemic skeletal disease with ↓ bone mineral density (BMD) & microarchitectural deterioration.
  • Diagnosis: T-score ≤ -2.5.
  • 📌 Risk Factors (ACCESS): Alcohol, Corticosteroid, Calcium low, Estrogen low, Smoking, Sedentary lifestyle.
• Sarcopenia: Progressive, generalized loss of skeletal muscle mass, strength, & function.
  • Diagnosis: ↓ muscle mass + (↓ muscle strength OR ↓ physical performance).
• Osteoarthritis: Degenerative joint disease.
  • Features: Cartilage degradation, osteophytes (bone spurs), joint space narrowing, subchondral sclerosis.

⭐ Vertebral compression fractures are the most common osteoporotic fractures.

Age-Related Anatomical Changes - Heart & Huff Puffs

Cardiovascular System:

• Arteries: ↑ stiffness, ↑ pulse wave velocity.
  • ↑ Systolic BP (SBP).

  ⭐ Isolated systolic hypertension (SBP ≥140 mmHg, DBP <90 mmHg) is the most common form in elderly.

• Heart:
  • Left Ventricular Hypertrophy (LVH).
  • Diastolic dysfunction (impaired LV filling).
  • Valvular calcification (e.g., aortic stenosis).
  • ↓ Baroreceptor sensitivity (risk of postural hypotension).
  • ↓ SA node pacemaker cells.

Respiratory System:

• Mechanics:
  • ↓ Lung elasticity.
  • ↑ Chest wall stiffness.
• Lung Volumes:
  • ↓ FEV1, ↓ FVC.
  • ↑ Residual Volume (RV), ↑ Functional Residual Capacity (FRC).
  • Total Lung Capacity (TLC) often unchanged.
• Gas Exchange:
  • ↑ Ventilation/Perfusion (V/Q) mismatch.
  • ↓ Diffusing capacity ($D_LCO$).

Age-Related Anatomical Changes - Brain Fades & Sense Shades

Nervous System ("Brain Fades"):

• Structural Changes:
  • Mild cortical atrophy.
  • Ventricular enlargement (often compensatory).
• White Matter: Changes evident as leukoaraiosis.
• Neurotransmitter Levels:
  • ↓ Dopamine (impacting motor control, cognition).
  • ↓ Acetylcholine (crucial for memory).
• Cellular Pathology: Senile plaques and neurofibrillary tangles may be present even in non-demented elderly individuals.

Sensory System ("Sense Shades"):

• 👁️ Presbyopia (Vision): Due to ↓ lens elasticity, leading to impaired near vision.
• 👂 Presbycusis (Hearing): Progressive bilateral sensorineural hearing loss, particularly for high-frequency sounds.

  ⭐ Presbycusis typically affects high-frequency sounds first and is the most common cause of hearing loss in adults.

• 👃👅 Olfaction & Gustation: General decline in the sensitivity of smell and taste.

High‑Yield Points - ⚡ Biggest Takeaways

• Thymic involution begins early, with significant adipose replacement by adulthood.
• Arterial stiffening (arteriosclerosis) from elastin degradation and collagen accumulation.
• Brain atrophy involves neuronal loss, ventricular enlargement, and potential plaque/tangle formation.
• Sarcopenia is the progressive loss of skeletal muscle mass and function.
• Osteoporosis features reduced bone mineral density, increasing fracture susceptibility.
• Presbyopia (age-related farsightedness) due to lens elasticity loss.
• Skin aging includes dermal thinning, reduced elasticity, and impaired wound healing.