Section 39: Muscle – Micro-and Macro-Structure

39-1

MicroscopicMicroscopic-Macroscopic pStructure of

Sk l t lSkeletal MuscleMuscle

39-2 From: Brown

Muscle Structure• Structural unit of skeletal muscle is the

multinucleated muscle cell or fiber (thickness: 10-100 μm, length: 1-30 cm

• Muscle fibers consist of myofibrilsMuscle fibers consist of myofibrils (sarcomeres in series: basic contractile unit of muscle)unit of muscle)

• Myofibrils consist of myofilaments (actin and myosin)and myosin)

39-3 From: Brown

Muscle Architecture - Micro

• Key Words:• sarcomere• Actin -double strand, woundActin double strand, wound• Myosin- twisted golf clubs, heads

facing out in a spiral fashion down the bundled tails

• titan• Z- line , M - line• cross bridges • Contractile mechanism

39-4 From: Legh

Muscle Structure (continued)• Composition of sarcomere

– Z line to Z line (≅ 1.27-3.6 μm in length)e to e ( 3 6 μ e gt )– Thin filaments (actin: 5 nm in diameter)– Thick filaments (myosin: 15 nm inThick filaments (myosin: 15 nm in

diameter)– Myofilaments in parallel with sarcomereMyofilaments in parallel with sarcomere– Sarcomeres in series within myofibrils

39-5 From: Brown

Microsoft® Encarta® Online Encyclopedia 2004 http://encarta.msn.com© 1997 2004 Microsoft Corporation All Rights Reserved© 1997-2004 Microsoft Corporation. All Rights Reserved.

39-6 From: GarnerMarieb, 1997

39-7 From: GarnerMarieb, 1997

39-8 From: GarnerMarieb, 1997

39-9 From: GarnerMarieb, 1997

39-10 From: GarnerNigg & Herzog, 1998

Muscle Architecture - Micro

• Key Words:• sarcomere• Actin -double strand, woundActin double strand, wound• Myosin- twisted golf clubs, heads

facing out in a spiral fashion down the bundled tails

• titan• Z- line , M - line• cross bridges • Contractile mechanism

39-11 From: Legh

39-12 From: Garner