UoB Medicine

Introduction Kidney - organ of excretion and body fluid regulation Produces urine dependent on the condition of the body Regulation of EC fluid - osmolarity/ plasma blood volume Production of hormones eg. renin (regulates blood volume) In the body - 14L Interstitial fluid 28L Intracellular fluid H2O is lost and gained from the body in a variety of ways.  However, this can vary in a number of ways and the kidney must adapt to support this, H2O intake: type of food, water availability H2O output: lactation, exercise, environmental conditions, disease The most common causes of fluid loss are: Sweating Diarrhoea Vomiting Hyperventilation Fever Hyponatremia: low Na+ therefore plasma is too dilute and H2O moves into cells causing them to swell. Leads to a person becoming irrational/comatose  Low K+ : cardiac arrhythmia Low Ca2+ : Fatigue/weakened + can soften bones/rickets/osteomalacia   Low Mg2+: Causes muscles to twitch uncomfort

The Limbs Over Time Sarcopaenia: Loss of muscle mass and strength as you age With age: SA of muscles decreases Infiltration of non contractile tissue into muscles - increase in adipose tissue Muscle strength decreases Reduction in motor units  Change in type of motor neurones - deinnervation of fast motor neurones therefore increased innervation of slow motor neurones Factors that contribute to Sarcopaenia Nutritional Hormonal Metabolic Immunological This leads to  Reduced motor units Decreased muscle fibres Atrophy  Loss in muscle mass/strength Reduced physical activity = risk of falls Osteopoenia  Bone loss Reduced bone mineral density Bones become more fragile Vertebrae, hip and wrist most at risk Previous fracture, increases risk of fracture Cortical and trabecular bone are affected differently with age.  • cortical bone strength ↓ by 2% per decade, from age 20 yrs • toughness ↓ by 7% per decade (bone becomes mo