Overview
This lecture covers age-related changes in the urinary, immune, and reproductive systems, emphasizing how different organ systems age at different rates and the functional consequences of these changes.
Urinary System and Aging
- Kidneys remove metabolic waste and balance blood electrolytes (sodium, potassium, calcium, chloride) to maintain pH and blood pressure.
- Kidney function loss with age is mainly due to blood vessel narrowing or loss, not kidney tissue itself.
- Average renal blood flow declines about 10% per decade after age 30, reducing filtration efficiency.
- Decreased kidney function causes increased blood pressure and reduced waste elimination in older adults.
- Water reabsorption in kidneys is regulated by antidiuretic hormone (ADH).
Immune System and Aging
- The immune system is divided into innate (present at birth) and acquired (developed after exposure) branches.
- Innate immunity acts quickly and non-specifically; key cells include neutrophils and macrophages, responsible for inflammation and phagocytosis.
- Acquired immunity uses lymphocytes: T cells (mature in thymus, helper and cytotoxic roles) and B cells (produce antibodies).
- Memory cells from acquired immunity enable faster and stronger responses to previously encountered antigens (basis of vaccines).
- With age, phagocytic function declines, slowing wound healing and immune response, though neutrophil and macrophage numbers remain unchanged.
- Thymus shrinks ~90% by age 70, reducing T cell production; B cell production also drops, weakening new immune responses and vaccine effectiveness.
Reproductive System and Aging
- Menopause in women results from decreased estrogen and progesterone production, causing ovarian and uterine shrinkage and affecting body temperature regulation and disease protection.
- Menopause is diagnosed after one year without menstruation.
- Male fertility declines slightly with age, mainly due to reduced seminiferous tubule cell function and lower testosterone, termed andropause.
- Sperm quality decreases in older men, increasing risk of genetic disorders in offspring.
- Age-related changes in reproductive organs do not necessarily impair sexual performance, though discomfort and injury risk may increase.
Key Terms & Definitions
- Phagocytosis — process by which immune cells engulf and destroy pathogens.
- Innate immunity — non-specific, fast immune defense present at birth.
- Acquired immunity — specific, adaptive immune defense developed after exposure to antigens.
- Menopause — permanent cessation of menstruation due to reduced ovarian hormone production.
- Andropause — age-related decline in male testosterone and fertility.
Action Items / Next Steps
- Review diagrams of kidney function, immune pathways, and reproductive anatomy.
- Read assigned textbook sections for Chapter 8 (urinary, immune, reproductive systems).