--- module: 075-02 language: en chapter: 75 title: "Anatomical Language, Body Plans, Fascia, Compartments, and Imaging Anatomy" module_title: "Fascia, compartments, neurovascular pathways, and mechanical integration" source_sha256: f3a92829cbcee0f21d02f1a4b7323294a8baaa99bc55f701eed809bec428a3e0 --- # Fascia, compartments, and pathways ## Connective tissue as a mechanical network ### Matrix components #### Collagen tensile strength, elastin recoil #### Proteoglycans bind water ### Fibroblasts remodel matrix under load #### Matrix is active, not inert packing ### Loose tissue permits movement ### Dense regular fibres align with force #### Orientation reflects loading history ### Single fascial chain claims exceed evidence #### Local mechanical relations are established ## Superficial, deep, and visceral fascia ### Superficial fascia beneath dermis #### Skin mobility, energy storage, insulation #### Dense and tethered in scalp, palm, sole ### Deep fascia forms septa and compartments #### Openings can become entrapment sites ### Visceral fascia suspends organs #### Some spaces real, some conceptual planes #### Describe boundaries and contents ## Compartments as pressure-volume systems ### Bounded by relatively unyielding tissue ### Rising volume raises pressure #### Impairs venous outflow and perfusion #### Impairs nerve conduction and muscle viability ### Acute compartment syndrome #### Commonly follows fracture or crush #### Early: disproportionate pain, stretch pain #### Pulses may remain #### Compelling syndrome needs urgent decompression ### Abdominal compartment syndrome #### Reduces renal perfusion and venous return #### Decompress, optimise fluid, drain, operate ### Intracranial and orbital enclosure #### Nonlinear once compensation is exhausted ##### Swelling becomes secondary injury ## Arterial pathways ### Elastic, then muscular arteries, then arterioles ### End arteries versus functional end arteries ### Collaterals depend on anastomoses and time #### Gradual stenosis allows enlargement #### Acute occlusion may still infarct ### Watershed zones vulnerable to hypoperfusion ### Protected planes, compression at tunnels ### Surgical exposure protects perforators ## Venous pathways ### Superficial and deep systems #### Perforators connect, valves direct flow ### Muscle contraction and breathing aid return ### Valveless plexuses allow two-way spread #### Vertebral veins: metastasis and infection #### Facial veins reach intracranial sinuses ### Portal systems: two capillary beds in series #### Portal hypertension enlarges anastomoses ##### Varices can bleed lethally ## Peripheral nerves ### Roots form plexuses #### Each nerve carries several roots #### Localise by motor, sensory, reflex patterns ### Nerves need blood supply and gliding #### Compression impairs axonal transport #### Entrapment at retinacula and tunnels ### Endoneurium, perineurium, epineurium #### Perineurium: blood-nerve barrier #### Intrafascicular injury despite continuity ### Autonomic fibres follow vessels and nerves ### Referred pain from afferent convergence ## Lymph and fascial spread ### Superficial with veins, deep with arteries ### Blocked routes divert to other basins ### Lymphoedema: inadequate lymphatic transport #### Inflammation drives fat and fibrosis ### Spread along low-resistance planes #### Deep neck infection to mediastinum #### Shaped by gravity, pressure, openings ## Muscles as functional compartments ### Shared innervation and broad action ### Either attachment can be fixed ### Line of pull and moment arm set torque ### Agonist, antagonist, synergist, fixator ### Eccentric, concentric, isometric contraction ### Biarticular muscles cross two joints #### Active insufficiency: too shortened #### Passive insufficiency: cannot lengthen enough ### Ask what bounds, traverses, communicates