UoB Medicine

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

Bone Fractures and Healing Covered by periosteum that helps with fracture healing. Contains osteogenic progenitor cells that mature into osteoblasts and therefore increases the thickness.  Two types of bone: CORTICAL and TRABECULAR Cortical bones have a strong outer layer which resists force and weight. It is organised into Haversian systems.                                   Consists of concentric lamallae - rings of calcified matrix.  Contains osteoblasts embedded in lamallae which mature and become osteocytes in lacunae.  Canaliculi - connect lacunae and are used in the movement of nutrients and removal of waste products.  Osteoclasts                                 Has a ruffled border - attaches to the surface of bone and releases lysosomal enzymes and acids which act to digest the proteins found in the bone matrix. These are balanced with osteoblasts.  Osteopetrosis: OC can't create acidic conditions to absorb bone which re

Healthy Bones and Metabolism Bones consists of: Mineral and Organic part Calcium hydroxyapatite  - provides compressive strength - lack of mineral components of bone results in rubbery and flexible bones = osteomalacia                                            - Collagen (tensile strength) (PG- compressive strength) - Proteoglycans   - provides flexible strength- lack of organic results in brittle bone disease  - Osteocalcin (promotes mineralisation)                                    Ca2+ is produced from:    Bone turnover Resorption from kidneys Diet The regulation of Ca2+ is by:  PTH Vitamin D Calcitonin The amount of Ca2+ is instrumental for the bone density - a measure of the mineral present in bone.   Bone density can be affected by a range of factors including: Availability of substrates - Ca2+ intake/absorption and PTH function Physiological - Weight bearing exercise/ Smoking/ Diet + BMI Biochemical - Hormones