Musculoskeletal System

Navigational overlay for bone, skeletal muscle, joints, and their resident cells. Loss of musculoskeletal integrity — declining muscle mass/strength and bone density — is a defining feature of physical aging and the proximate driver of frailty, falls, and fractures. The bone and muscle compartments are mechanically and endocrine-coupled (the “bone-muscle unit”), and both share mesenchymal-progenitor exhaustion as an upstream cause.

Tissues & organs

• bone — remodeling tissue; the bone-vascular axis links it to vascular-calcification
• skeletal-muscle — contractile tissue; site of sarcopenia

Cell types

• osteoblasts — bone-forming; declining number/activity with age
• osteoclasts — bone-resorbing; relative hyperactivity drives net resorption
• osteocytes — mechanosensory hub; SOST/FGF23 source
• satellite-cells — muscle stem cells; exhaustion impairs regeneration
• fibroadipogenic-progenitors — drive fatty/fibrotic muscle degeneration
• mesenchymal-stem-cells — shared osteo/adipo/chondro progenitor (BM-MSCs); fate-drift toward adipogenesis

Aging phenotypes

• sarcopenia — age-related muscle loss
• osteoporosis — low bone density / fragility fractures
• osteoarthritis — joint cartilage degeneration
• frailty — integrative phenotype (musculoskeletal + multisystem)
• intervertebral-disc-degeneration · low-back-pain — spinal-axis degeneration

Key molecular axes

• Bone remodeling regulators: runx2, sost, dkk1, lrp5-lrp6, matrix-gla-protein, fgf23
• Therapeutics: romosozumab (anti-sclerostin), senolytics; vitamin-k (MGP carboxylation)

Auto-aggregated tissue members

LIST FROM "tissues"
WHERE parent-system = "musculoskeletal-system"
SORT file.name

Missing / planned pages

• [[cartilage]], [[tendon]], [[ligament]], [[synovium]], [[intervertebral-disc]], [[joint]] — connective/articular tissues not yet seeded stub
• [[chondrocytes]], [[myofibers]] — cell types not yet seeded stub

See also

• by-organ-system — index of all body-system MOCs
• cardiovascular-system — shares the bone-vascular calcification axis
• stem-cell-exhaustion — the dominant upstream hallmark for both bone and muscle