1. Jeanne A Pawitan Histology of the skeletal muscle Jeanne Adiwinata Pawitan Dept. of Histology FMUI

2. Jeanne A Pawitan Muscle tissue Striated muscle – characteristic striation – specific arrangement of myofilament (contractile protein in a myofibril)  parallel arrays  interdigitating °skeletal muscle °cardiac muscle Smooth muscle  Myoepithelial cells –glandular unit in glands  Myofibroblast – wound contraction, tooth eruption

3. Jeanne A Pawitan Unique terms – in muscles sarcolemma= cell membrane sarcoplasm= cytoplasm sarcoplasmic reticulum= smooth surfaced endoplasmic reticulum sarcosome= mitochondria muscle fiber= muscle cell

4. Jeanne A Pawitan Skeletal muscle investments °Epimysium – muscle – irregular dense collagenous connective tissue °Perimysium – fascicles (bundles) - < dense °Endomysium – muscle fiber (cell) - reticular fiber, basal lamina / external lamina cell °Skeletal muscle fibers – striated – parallel °Satellite cells

5. Jeanne A Pawitan Sel/serat otot rangka Perkembangan: mioblas – berjajar  uj –uj  menyatu  myotube – membentuk miofibril  serat otot rangka Bentuk: panjang seperti tabung – Ø 10-100μm Di antara serat: endomisium + kapiler kontinu – paralel otot Sel/serat otot rangka – tak bercabang -bercorak - berinti banyak (multinucleated) Inti – berderet - di perifr – tepat di dalam membran sel (sarkolema) ME: Sarkolema masuk ke dalam  T tubule (transverse tubule)

6. Jeanne A Pawitan Sarkoplasma: di dalamnya Banyak miofibfril Ø-1-2 μm –longitudinal – sepanjang serat otot – tersusun teratur  gambaran lurik pada potongan longitudinal: °Pita A – (anisotropik dengan chy polarisasi  gelap) °Pita I – (isotropik dengan chy polarisasi  terang) ME: Sarkoplasmik retikulum = retikulum endoplasma halus °Berupa jalinan di sekeliling miofibril °Fungsi: menyimpan Ca intrasel (tu sisterna terminal) °Pada perbatasan pita A-I –melebar  sisterna terminal membrannya mengandung junctional feet (= voltage gated Ca release channels) – berhubungan dengan T tubule °Sisanya = longitudinal sarcotubule + cabangnya

7. Jeanne A Pawitan T tubule Invaginasi tubular –transversal – bercabang- anastomosis - saling silang dengan miofibril Letak: pada satu bidang - perbatasan pita A dan I  ada 2 pada tiap sarkomer Ke arah ekstra sel terbuka Berhubungan dengan sarkoplasmik retikulum Fungsi: fasilitasi konduksi gelombang depol sepanjang sarkolema T tubule + 2 buah sisterna terminal  triad °fungsi: penyebaran gelombang depol – cepat – dari sarkolema -ke seluruh sel –sp. sisterna terminal

8. Jeanne A Pawitan Miofibril Pita A (gelap) – pita H – pucat – garis M (M line) Pita I (terang) – garis Z (Z line, Z disk) –gelap Sarkomer = daerah miofibril di antara 2 garis Z = unit kontraktil serat otot skelet Kontraksi: °Pita I memendek °Pita H hilang °Pita A tetap °Garis Z saling mendekat

9. Jeanne A Pawitan Satellite cells Satellite cells = regenerative cells Small cell – location: shallow depression – muscle cell’s surface External lamina – shared with muscle cell → inside external lamina Nucleus-one - > dense - > coarse

10. Jeanne A Pawitan Myotendinuous junction Connective tissue–muscle – tendon – continuous °Cells tapered – fluted (deeply folded) °Collagen fibers-tendon – penetrate Infoldings Endomysium – continuous – reticular fibers

11. Jeanne A Pawitan Innervation of skeletal muscle Motor nerve fibers (α motor neurons –axon- myelinated) branching – unmyelinated (Schwann cells +) – terminal dilated - myoneural junction (motor end plate) °Axon terminal °Synaptic cleft °Muscle cell membrane Sensory nerve fibers °muscle spindles – among muscle cells –stretch Rx °Golgi tendon organ (neurotendinuous spindle)– inhibitory feedback - α motor neurons - relax

12. Jeanne A Pawitan Regeneration of skeletal muscle Skeletal muscle fiber ≠ mitosis Satellite cells °Injury: satellite cells mitosis – hyperplasia °Muscle building: satellite cells fused with skeletal muscle fibers  mass increased  hypertrophy