How many muscles are in a human's body?

Study of muscles is known as myalogy.There are more than 600 muscles in the human body that make up to 40-50% of the weight of human body.They are composed of contractile fibres which are made up of myofibrils. So this is today's topic for the notes of biology class 12

The muscular system consists of the muscles of skeletal system which are voluntary so it is suitable to discuss three types of muscle fibres. These are

1.Smooth muscles

2.Cardiac muscles

3.Skeletal or striated muscles

These muscle tissues consist of elongated cells known as muscle fibres. These muscle fibres have fine fibrils. known as myofibrils in their cytoplasm. These all muscle tissues possess the physical property of elasticity, contraction, excitation and extension.

1.Smooth muscles - These muscles don't have any striations so these are called smooth muscles. These muscles are also known as visceral muscles as they help in the visceral movements. These muscles are found in the walls of hollow internal organs such as blood vessels,alimentary canal etc.They are not connected with the bones. These muscles are controlled by the autonomous nervous system and are involuntary.

2.Cardiac muscles - These muscles bear striations. These muscles are found in the wall of heart and help in bringing heartbeat. These muscles are not connected with the bones.Fatigue is not caused by these muscles. These cardiac muscles are involuntary. Autonomous nervous system innervates these muscles.

3.Skeletal or striated muscles - These muscles possess striations and have dark and light bands. These muscles are connected to the bones with the help of tendons. They help in the movement of limbs and locomotion. The dark band is also known as the anisotropic band or A-band and is formed from the filaments of the protein myosin.The light band is also known as the isotropic band or I-band and consists of myofibrils. This band is formed from thin filaments of actin protein. A dense line called the Z-line crosses each isotropic band. The area between two Z-lines is known as sacromere. Sacromere is known as the functional and structural unit of the striated muscle fibre. The sacromere consists of two types of filaments. These are thin filaments and thick filaments. In each sacromere the thin filaments are found at both the ends while the thick filaments are found at the centre. There is a boundary of Z- line between the thin filaments of two adjacent sacromeres. Thin and thick filaments are overlapped and are arranged alternatively. The H - zone has only thick filaments and the I-band has only thin filaments. The A-band consists of both thin and thick filaments. These are voluntary muscles and can be controlled according the will of the person.

Hope this topic How many muscles are in a human's body? for biology class 12 would be helpful to you.You may practice this topic using Worksheets for Science.Please comment if you want article on any other topic.

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