The human musculoskeletal system (also known as the locomotor system) is an organ system that gives humans and animals the ability to move using the muscular and skeletal systems. The musculoskeletal system provides form, stability, and movement to the human and animal body.

It is made up of the body's bones (the skeleton), muscles, cartilage, tendons, ligaments, joints, and other connective tissue (the tissue that supports and binds tissues and organs together). The musculoskeletal system's primary functions include supporting the body, allowing motion, and protecting vital organs.^[1] The skeletal portion of the system serves as the main storage system for calcium and phosphorus and contains critical components of the hematopoietic system.^[2]

This system describes how bones are connected to other bones and muscle fibers via connective tissue such as tendons and ligaments. The bones provide the stability to a body in analogy to iron rods in concrete construction. Muscles keep bones in place and also play a role in movement of the bones. To allow motion different bones are connected by joints. Cartilage prevents the bone ends from rubbing directly on to each other. Muscles contract (bunch up) and extend (stretch) to move the bone attached at the joint.

There are, however, diseases and disorders that may adversely affect the function and overall effectiveness of the system. These diseases can be difficult to diagnose due to the close relation of the musculoskeletal system to other internal systems. The musculoskeletal system refers to the system having its muscles attached to an internal skeletal system and is necessary for humans to move to a more favorable position.

Skeletal

Front view of a skeleton of an adult human

The Skeletal System serves many important functions; it provides the shape and form for our bodies in addition to supporting, protecting, allowing bodily movement, producing blood for the body, and storing minerals.^[3] The number of bones in the human skeletal system is a controversial topic. Humans are born with about 300 to 350 bones, however, many bones fuse together between birth and maturity. As a result an average adult skeleton consists of 208 bones. The number of bones varies according to the method used to derive the count. While some consider certain structures to be a single bone with multiple parts, others may see it as a single part with multiple bones.^[4] There are five general classifications of bones. These are Long bones, Short bones, Flat bones, Irregular bones, and Sesamoid bones. The human skeleton is composed of both fused and individual bones supported by ligaments, tendons, muscles and cartilage. It is a complex structure with two distinct divisions. These are the axial skeleton and the appendicular skeleton.^[5]

[edit] Function

The Skeletal System serves as a framework for tissues and organs to attach themselves to. This system acts as a protective structure for vital organs. Major examples of this are the brain being protected by the skull and the lungs being protected by the rib cage.

Located in long bones are two distinctions of bone marrow (yellow and red). The yellow marrow has fatty connective tissue and is found in the marrow cavity. During starvation, the body uses the fat in yellow marrow for energy.^[6] The red marrow of some bones is an important site for blood cell production, approximately 2.6 million red blood cells per second in order to replace existing cells that have been destroyed by the liver.^[3] Here all erythrocytes, platelets, and most leukocytes form in adults. From the red marrow, erythrocytes, platelets, and leukocytes migrate to the blood to do their special tasks.

Another function of bones is the storage of certain minerals. Calcium and phosphorus are among the main minerals being stored. The importance of this storage "device" helps to regulate mineral balance in the bloodstream. When the fluctuation of minerals is high, these minerals are stored in bone; when it is low it will be withdrawn from the bone.

 Muscular

Types of muscle and their appearance

There are three types of muscles - cardiac, skeletal, and smooth. Smooth muscles are used to control the flow of substances within the lumens of hollow organs, and are not consciously controlled. Skeletal and cardiac muscles have striations that are visible under a microscope due to the components within their cells. Only skeletal and smooth muscles are part of the musculoskeletal system and only the skeletal muscles can move the body. Cardiac muscles are found in the heart and are used only to circulate blood; like the smooth muscles, these muscles are not under conscious control. Skeletal muscles are attached to bones and arranged in opposing groups around joints.^[7] Muscles are innervated, to communicate nervous energy to,^[8] by nerves, which conduct electrical currents from the central nervous system and cause the muscles to contract.[9]

Diseases of the Musculoskeletal System:

http://bone-muscle.health-cares.net/muscle-diseases.php

Myopathy

Myopathies are diseases of skeletal muscle which are not caused by nerve disorders. These diseases cause the skeletal or voluntary muscles to become weak or wasted. Myopathies are usually degenerative, but they are sometimes caused by drug side effects, chemical poisoning, or a chronic disorder of the immune system .

Chronic fatigue syndrome

Chronic fatigue syndrome (CFS) is an illness characterized by prolonged, debilitating fatigue and multiple nonspecific symptoms such as headaches, recurrent sore throats, muscle and joint pains, memory and concentration difficulties. Chronic fatigue syndrome is a debilitating and complex disorder characterized by profound fatigue of six months.

Fibromyalgia

Fibromyalgia is a debilitating chronic illness characterized by diffuse pain, fatigue, and a wide range of other symptoms. It is a syndrome, not a disease. It is not contagious, and is probably genetic. It affects more women than men, mostly between ages 20 and 50. It is seen in 3-10% of the general population.

Muscular dystrophy

Muscular dystrophy (MD) is a broad term that describes a genetic (inherited) disorder of the muscles. Muscular dystrophy causes the muscles in the body to become very weak. The muscles break down and are replaced with fatty deposits over time. Muscular dystrophy is a genetic disorder that is characterized by muscle wasting and weakening.

Dermatomyositis

Dermatomyositis is one of a group of inflammatory muscle diseases. It is a subtype of inflammatory muscle disease. Dermatomyositis may affect people of any race, age or sex, although it is twice as common in women than in men. Dermatomyositis belongs to a group of conditions called inflammatory myopathies.