Nicole McCormick - Oil on Canvas
The Muscular System
Each of more than six hundred muscles is served by nerves, which link the muscle to the brain and spinal cord. Skeletal muscules are the body’s most abundant tissue, comprising about 23% of a woman’s body weight and about 40% of a man’s body weight.
Skeletal or voluntary muscle are those muscles that attach to bones and are responsible for movement. Cardiac muscle composes the bulk of the heart and cells in this type of muscle are cylindrical and branch frequently. Nonstriated or smooth muscle cells form an important part of blood vessel walls and of many internal organs, and are also known as visceral muscle. Both involuntary. Muscle cells specialize in contraction or shortening. Skeletal muscle allows for every voluntary movement that we make. Contraction of cardiac muscle cells keep the blood circulating, and smooth muscle contractions move food into and through the intestines, for example.
A skeletal muscle is mainly composed of striated muscle cells and connective tissue. Most muscles attach to two bones that have a moveable joint between them. One of the two bones is usually more stationary in a given movement than the other. The muscle’s attachment to the more stationary bone is called its origin. The attachment to the more moveable bone is called the muscle’s insertion. The rest of the muscle is called the body of the muscle.
Tendons attach muscle to bone. Ligaments attach bone to bone. Muscle tissue consists of muscle fibers that are grouped together in a highly organized way. Each muscle fiber has two kinds of threadlike structures called thick and thin myofilaments. The sarcomere is the basic functional unit of skeletal muscle. The microscopic view of a sarcomere consists of many thick and think myofilaments.
Muscles of the head and neck allow us to communicate many different emotions nonverbally. Contracting the frontal muscle raises the eyebrow. The orbicularis muscle is called the kissing muscle , and the zygomaticus muscle allows us to smile. Muscles of mastication, or chewing are among the strongest muscles in the body. The sternocleidomastoid muscles bring the head to the chest, and the triangular-shaped trapezius muscles help us shrug our shoulders.
Muscles of the upper extremities, like the pectoralis major and latissimus dorsi, perform many movements, including full movement of the upper arm.
Muscles of the trunk include the internal and external obliques, and the transversss and rectus abdominus, which protect the abdomen and assist in flexing the spinal column (bending over).
Muscles of the lover extremities, like the gluteus maximus, or the buttocks, extend the thigh and support the torso. The hamstring muscles flex (bend) the lower leg, and the quadriceps muscles extend the lower leg. The tibialis anterior muscle, located on the front surface of the lower leg, dorsiflexes, or points the foot and toes upward. The gastocnemius is the primary calf muscle, and is responsible for plantar flexion, or pointing the foot and toes downward.
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The Skeletal System The Muscular System The Nervous System The Digestive System The Respiratory System |
The Endocrine System The Lymphatic System The Urinary System The Reproductive System |
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