Diagram of Skeletal Muscle

Skeletal muscles are voluntary and striated in nature. They are responsible for the movement of appendages and locomotion. Skeletal muscle is formed by 75% of water and 25% of solids. The solid components include proteins and other organic and inorganic substances. All the components of the skeletal muscle contribute toward body movement.

Here let’s learn about the structure of skeletal muscle with a diagram.

Table of Content:

• Labelled Diagram of Skeletal Muscle
• Skeletal Muscle – Description
• Significance
• Frequently Asked Questions

Labelled Diagram of Skeletal Muscle

Skeletal Muscle – Description

• The muscle tissue is composed of a large number of myocytes or muscle cells. These muscle cells are slender and long and are termed as muscle fibres.
• The skeletal muscle fibres are multinucleated. They are arranged parallel to each other, along with some intervening connective tissue.
• The muscle tissue is divided from the neighbouring tissues by fascia. Fascia is a thick fibrous connective tissue layer.
• Beneath the fascia is a connective tissue sheath termed epimysium that covers the muscles.
• The muscle fibres in the muscle are organised in groups called bundles or fasciculi. The connective tissue covering that wraps each fasciculus is termed perimysium. Each muscle fibre is individually wrapped by a connective tissue layer termed the endomysium.
• Each muscle fibre is cylindrical in shape and is enclosed by a cell membrane (beneath endomysium) called sarcolemma. The cytoplasm of the muscle is known as sarcoplasm.
• The myofibrils are the fine parallel filaments present in the sarcoplasm of the muscle cell. These myofibrils run through the entire length of the muscle fibre. The myofibrils are made of repeating units of sarcomere that appear as alternating light and dark bands under the microscope.
• The light band or ‘I’ band and the dark band or ‘A’ band are formed by muscle proteins. In the middle of ‘A’ band, there is a light area called ‘H’ zone. In the middle of ‘H’ zone lies the ‘M’ line that is formed by myosin-binding proteins.
• Further microscopic studies reveal that the sarcomere comprises many thread­like myofilaments made of actin and myosin proteins.
• The actin filaments are thin filaments that run across the ‘I’ band, and myosin filaments are thick filaments that are present in ‘A’ band.
• Other than myofibrils, the sarcoplasm has the nuclei, mitochondria, Golgi, sarcoplasmic reticulum, ribosomes, etc.
• The muscle fibres are attached to a strong cord of connective tissue known as the tendon.
• The tendon is, in turn, connected to the bone.

Significance

The major properties of skeletal muscle are excitability and contractility. Excitability is defined as the response or reaction of tissue to a stimulation. It is a physiochemical change. Contractility is also a response of the muscle to a stimulus. Contraction is typically the thickening or shortening of muscles against a tension or load. The other properties include the ability to stretch and the elasticity of the skeletal muscle.

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