Logan Steele
Striated muscle tissue is made up of two types of tissue: skeletal muscle and cardiac muscle. Skeletal muscle is the tissue that most muscles attached to bones are made of, while cardiac muscle is found on the walls of the heart. Both types of muscle have a 'striated' appearance under a microscope due to their densely packed myofibrils. Each myofibril contains filaments of the proteins myosin and actin, which slide past one another as the muscle contracts and expands.
| Characteristics | Values |
|---|---|
| Structure | Long fine fibres, each of which is a bundle of myofibrils |
| Myofibrils | Filaments of the proteins myosin and actin |
| Appearance | Densely packed myofibrils give striated muscles a striated appearance |
| Sarcomeres | The basic contractile unit of striated muscle |
| Z-lines | Dark bands where actin and myosin filaments overlap |
| T-tubules | Enable the release of calcium ions from the sarcoplasmic reticulum |
| Skeletal muscle fibres | 20-100 µm thick and up to 20 cm long |
| Development | Embryologically, striated muscles develop by the chain-like fusion of myoblasts |
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What You'll Learn
The structure of striated muscle
Striated muscle tissue consists of long, fine fibres, each of which is a bundle of myofibrils. These myofibrils are made up of filaments of the proteins myosin and actin. When a muscle contracts and expands, these filaments slide past one another.
Myofibrils are densely packed, giving striated muscles their striated appearance under a microscope. Each myofibril has regularly occurring dark bands, called Z lines, where actin and myosin filaments overlap. The region between two Z lines is called a sarcomere, which is the primary structural and functional unit of muscle tissue. Sarcomeres span from Z-line to Z-line and consist of a central A-band flanked by two half I-bands. The A-band contains mostly 'thick' filaments of myosin, while the lighter I-bands contain 'thin' actin filaments. The thin filaments also contain the proteins tropomyosin and troponin, which together form a complex that inhibits actin-myosin interactions in resting muscle.
Striated muscle tissue features repeating functional units of sarcomeres, which are visible along muscle fibres under a microscope, giving the tissue its striated appearance. There are two types of striated muscle: skeletal muscle and cardiac muscle. Skeletal muscle is the tissue that most muscles attached to bones are made of, while cardiac muscle is the muscle found on the walls of the heart. Skeletal muscle fibres are around 20-100 µm thick and up to 20 cm long. Embryologically, striated muscle develops by the chain-like fusion of myoblasts. About 200-250 muscle fibres are surrounded by endomysium, forming the functional unit of the muscle, the primary bundle.
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The two types of striated muscle
Striated muscle tissue consists of long, fine fibres, each of which is a bundle of myofibrils. These myofibrils are made up of filaments of the proteins myosin and actin, which slide past each other as the muscle contracts and expands.
There are two types of striated muscle: skeletal muscle and cardiac muscle. Skeletal muscle is the tissue that most muscles attached to bones are made of. Cardiac muscle, on the other hand, is the muscle found on the walls of the heart. Both types of muscle have a striated appearance under a microscope due to their densely packed myofibrils. However, they differ in their histology and physiology.
Skeletal muscle fibres are around 20-100 µm thick and up to 20 cm long. Each fibre is composed of a parallel arrangement of myofibrils, which are made up of sarcomeres in series. Sarcomeres are the basic contractile units of striated muscle, spanning from Z-line to Z-line. The Z-lines are dark bands where actin and myosin filaments overlap. The region between two Z-lines is called a sarcomere and can be considered the primary structural and functional unit of muscle tissue. Sarcomeres contain "thick" filaments composed mainly of myosin and "thin" actin filaments. The thin filaments also contain the proteins tropomyosin and troponin, which form a complex that inhibits actin-myosin interactions in resting muscle.
Skeletal muscle is wrapped in epimysium, which maintains the structural integrity of the muscle during contractions. The perimysium organises the muscle fibres, which are encased in collagen and endomysium, into fascicles. Embryologically, striated muscle develops by the chain-like fusion of myoblasts. Around 200-250 muscle fibres are surrounded by endomysium to form the functional unit of the muscle, the primary bundle.
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How striated muscle develops
Striated muscle tissue is made up of two types of tissue: skeletal muscle and cardiac muscle. Both types of tissue have a 'striated' appearance under a microscope due to their densely packed myofibrils.
Skeletal muscle is the tissue that most muscles attached to bones are made of. Each skeletal muscle fibre is composed of a parallel arrangement of myofibrils, which are composed of sarcomeres in series. The sarcomere is the basic contractile unit of striated muscle and is defined as spanning from Z-line to Z-line. The region between two Z-lines is called a sarcomere; sarcomeres can be considered the primary structural and functional unit of muscle tissue. The Z-lines can be seen under a microscope as dark bands where actin and myosin filaments overlap. The A-band contains the 'thick' filaments composed of mostly myosin, while the lighter I-bands contain the 'thin' actin filaments.
Cardiac muscle, on the other hand, is the muscle found on the walls of the heart.
Embryologically, striated muscle develops by the chain-like fusion of myoblasts. About 200-250 muscle fibres are surrounded by endomysium, forming the functional unit of the muscle, the primary bundle.
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The contractile unit of striated muscle
Striated muscle tissue consists of long, fine fibres, each of which is a bundle of myofibrils. These myofibrils are composed of sarcomeres, which are the basic contractile unit of striated muscle. Sarcomeres span from Z-line to Z-line and consist of a central A-band flanked by two half I-bands. The A-band contains 'thick' filaments composed of mostly myosin, while the lighter I-bands contain 'thin' actin filaments.
The filaments of myosin and actin slide past one another as the muscle contracts and expands. On each myofibril, regularly occurring dark bands, called Z lines, can be seen where actin and myosin filaments overlap. The region between two Z lines is called a sarcomere, which can be considered the primary structural and functional unit of muscle tissue. Sarcomeres are visible along muscle fibres, giving a striated appearance to the tissue.
There are two types of striated muscle: skeletal muscle and cardiac muscle. Skeletal muscle is the tissue that most muscles attached to bones are made of. Cardiac muscle, on the other hand, is the muscle found on the walls of the heart. Microscopically, both the skeletal and cardiac musculature have a 'striated' appearance due to their densely packed myofibrils.
Each skeletal muscle fibre is composed of a parallel arrangement of myofibrils, which are composed of sarcomeres in series. Skeletal muscle fibres are around 20-100 µm thick and up to 20 cm long. About 200-250 muscle fibres are surrounded by endomysium, forming the functional unit of the muscle, the primary bundle.
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The appearance of striated muscle
Striated muscle tissue consists of long, fine fibres, each of which is a bundle of myofibrils. These myofibrils are composed of sarcomeres, which are the primary structural and functional unit of muscle tissue. Sarcomeres are visible along muscle fibres, giving a striated appearance to the tissue.
The sarcomere spans from Z-line to Z-line, and consists of a central A-band flanked by two half I-bands. The A-band contains 'thick' filaments composed of mostly myosin, while the lighter I-bands contain 'thin' actin filaments. The actin and myosin filaments slide past one another as the muscle contracts and expands. On each myofibril, regularly occurring dark bands, called Z lines, can be seen where actin and myosin filaments overlap.
Striated muscle tissue contains T-tubules which enable the release of calcium ions from the sarcoplasmic reticulum. Skeletal muscle fibres are surrounded by endomysium, which forms the functional unit of the muscle, the primary bundle. Skeletal muscle fibres are around 20-100 µm thick and up to 20 cm long.
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Frequently asked questions
Striated muscle is a type of muscle tissue that features repeating functional units called sarcomeres.
Under a microscope, striated muscle has a 'striated' appearance due to its densely packed myofibrils.
Striated muscle is made up of two types of tissue: skeletal muscle and cardiac muscle. Skeletal muscle is the tissue that most muscles attached to bones are made of, while cardiac muscle is the muscle found on the walls of the heart.
Striated muscle develops embryologically by the chain-like fusion of myoblasts.
