[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Histology](https://durgical.com/en/histology/) › [Muscle tissue](https://durgical.com/en/histology/#a-muscle) › Muscle injury, repair and satellite cells [Histology](https://durgical.com/en/histology/) · [Muscle tissue](https://durgical.com/en/histology/#a-muscle) # Muscle injury, repair and satellite cells - Process Skeletal muscle repairs itself with its own stem cells, the satellite cells; heart muscle mostly scars; smooth muscle regrows best. Updated 2026-11-01 **See it in 3D:** [Biceps (long head)](https://durgical.com/en/anatomy/biceps-brachii-long-head/) · [Gastrocnemius (inner head)](https://durgical.com/en/anatomy/medial-head-of-gastrocnemius/) · [Rectus femoris](https://durgical.com/en/anatomy/rectus-femoris-muscle/) ## Key points - Satellite cells: between sarcolemma and basal lamina; Pax7; source of skeletal muscle repair. - Regenerating fibres: small, basophilic, central nuclei. - Regeneration: smooth > skeletal > cardiac. - Large defects heal by fibrosis that cannot contract. - Myocardial infarct = scar, not new muscle. ## What it is When skeletal muscle fibres are torn, crushed or poisoned, they undergo a predictable sequence of necrosis, cleanup and regeneration driven by satellite cells, small stem cells that sit between the fibre's sarcolemma and its basal lamina. If the basal lamina and blood supply survive, regeneration can be good; if damage is extensive, fibroblasts fill the gap with scar that cannot contract. The three muscle types differ sharply in how well they regenerate. ## Key facts - Satellite cells lie between the sarcolemma and the basal lamina; they express the transcription factor Pax7. - Central nuclei in adult skeletal fibres are a sign of regeneration or myopathy. - Cardiac muscle has very limited regeneration; infarcted myocardium heals by scar. - Smooth muscle regenerates best: its cells divide and pericytes of small vessels can become smooth muscle cells. - Exercise causes hypertrophy of existing fibres; satellite cells add nuclei to growing fibres. ## Step by step - Injury tears the sarcolemma; calcium floods in and the damaged segment becomes necrotic. - Neutrophils arrive first, then macrophages that remove the necrotic fibre and release growth factors. - Satellite cells, quiet under the basal lamina, are activated and divide. - Their daughters become myoblasts that fuse with each other or with surviving fibre ends. - Regenerating fibres are small and basophilic with central nuclei in rows; the nuclei move to the periphery as the fibre matures. - If the gap is large or the basal lamina is destroyed, fibroblasts lay down collagen and a scar forms. ## Clinical notes - Muscle strains (for example hamstring) tear fibres near the musculotendinous junction and heal with a mix of regeneration and scar. - Compartment syndrome and crush injury cause widespread necrosis; rhabdomyolysis releases myoglobin that can injure the kidneys. - In Duchenne muscular dystrophy repeated cycles of necrosis exhaust satellite cells, so fibres are replaced by fat and fibrosis. - Ageing muscle loses fibres and satellite cell function (sarcopenia); resistance exercise slows the loss. ## Memory aid Satellites wait in the shadow of the sheath: when the fibre breaks, they wake, multiply and weld. ## Test yourself Think of the answer, then tap the question to see it. ## Where exactly do satellite cells sit? Between the sarcolemma of a skeletal muscle fibre and its surrounding basal lamina. ## How do regenerating skeletal muscle fibres look under the microscope? Small, basophilic fibres (rich in RNA) with large central nuclei, often in rows; the nuclei move to the periphery as the fibres mature. ## How do the three muscle types rank from best to worst at regenerating? Smooth muscle regenerates best, skeletal muscle partially through satellite cells, and cardiac muscle very poorly, healing by scar. ## Why does muscle that heals with a scar lose strength? The scar is collagen made by fibroblasts; it has no contractile proteins, so it transmits force poorly and cannot generate any. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/histology/muscle-injury-repair-and-satellite-cells/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Biceps (long head)](https://durgical.com/en/anatomy/biceps-brachii-long-head/) - [Gastrocnemius (inner head)](https://durgical.com/en/anatomy/medial-head-of-gastrocnemius/) - [Rectus femoris](https://durgical.com/en/anatomy/rectus-femoris-muscle/) ## Related - [Skeletal muscle: sarcomere and contraction](https://durgical.com/en/histology/skeletal-muscle-sarcomere-and-contraction/) - [Cardiac muscle: intercalated discs](https://durgical.com/en/histology/cardiac-muscle-intercalated-discs/) - [Smooth muscle](https://durgical.com/en/histology/smooth-muscle/) - [Cell adaptations: hypertrophy, hyperplasia, atrophy, metaplasia](https://durgical.com/en/histology/cell-adaptations-hypertrophy-hyperplasia-atrophy-metaplasia/) - [Wound healing: phases and scar](https://durgical.com/en/histology/wound-healing-phases-and-scar/) ## Related conditions - [Hamstring Strain](https://durgical.com/en/conditions/hamstring-strain/) - [Acute compartment syndrome](https://durgical.com/en/conditions/acute-compartment-syndrome/) - [Myocardial Infarction (Heart Attack)](https://durgical.com/en/conditions/myocardial-infarction/) [← All of histology](https://durgical.com/en/histology/) Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice. Sources: [10.9 Development and Regeneration of Muscle Tissue](https://openstax.org/books/anatomy-and-physiology-2e/pages/10-9-development-and-regeneration-of-muscle-tissue) (OpenStax, 2022); [10.2 Skeletal Muscle](https://openstax.org/books/anatomy-and-physiology-2e/pages/10-2-skeletal-muscle) (OpenStax, 2022). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/histology/muscle-injury-repair-and-satellite-cells/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/histology/muscle-injury-repair-and-satellite-cells/