Musculoskeletal System Intro

Lesson Overview

In this lesson, we introduce the musculoskeletal system.


Gain an understanding of the foundational anatomy of the musculoskeletal system.


Explain what is included in the musculoskeletal system and what it does. Define and explain the function of bones, joints and muscles. Name and describe the different types of joints and muscles.


  • The musculoskeletal system gives humans the ability to move using their muscular and skeletal systems.
  • It includes bones, muscles and connective tissue. (While bones and connective tissue are often described separately for learning purposes, expert sources explain that bones are a type of connective tissue.)
  • In addition to enabling body movement, the musculoskeletal system provides form, support and stability, protects vital organs, stores minerals such as calcium, produces red blood cells, moves blood and food, and generates body heat.



  • The skeleton has 206 individual bones.
  • Bones are living tissues that form the body’s structural framework.
  • Bones are defined as “the hard, rigid form of connective tissue constituting most of the skeleton of vertebrates, composed chiefly of calcium salts.” (Medical Dictionary)
  • Bones are comprised of calcium salts, connective tissues, cells and blood vessels.
  • The “axial skeleton” refers to the spine, skull and rib cage.
  • The “appendicular skeleton” refers to the upper and lower extremities.
  • Two particularly relevant areas for Yoga are the shoulder girdle (includes scapula and humerus plus associated joints) and pelvic girdle (includes iliac bones and femur plus SI and hip joints).


  • Bones provide a framework for muscles and other tissues.
  • Bones protect internal organs.
  • Bones enable body movements.
  • Bones store essential minerals such as calcium. And bones store lipids that serve as an energy reservoir.
  • Marrow at the center of large bones produces red blood cells.
  • Various shapes of bones reflect their function.
  • “Long bones provide leverage, flat bones provide protection and a place for broad muscles to attach, and short bones provide for weight bearing functions.” (Ray Long)
  • Bearing weight on bones helps to strengthen them; gravity thus stimulates bone health. Extended weightlessness in space, for example, causes bones and muscles to weaken.

Bones are Alive

The skeletal system is often understood by the layperson as some type of hard, dead, sort of “thing” that is nothing but the framework of our body. In fact, it is a complex, ever-changing system that deals with and reacts to stresses placed on it… Bones are alive. They have a blood supply. They have nerves running in and out them… Bone is yet another varied formation of connective tissue in the body. – David Keil

Yoga Strengthens Bones

Regular practice of Yoga is beneficial for your bones because healthy stresses are applied in a variety of unusual directions. This strengthens bones, which remodel in response to stress by depositing layers of calcium into the bone matrix. – Ray Long



  • Joints are junctions / connecting points between bones.
  • For example, the knee joint is the point of connection between the thigh bone and the shin bone.
  • Joints are also called “articulation.”
  • Joints contain a variety of fibrous connective tissue. Ligaments connect the bones to each other; tendons connect muscle to bone and cartilage covers the ends of bones and provides cushioning. (verywell, Sports Medicine)
  • Some joints move a lot; some very little.
  • The shape of the joints reflects their function.

Types of Joints

  1. Synovial Joints – The most common joints are freely movable joints in the body called synovial joints.
  2. Ball and Socket Joints – This type of joint allows for a wide range of rotation and movement, including rotation.
  3. Condyloid Joints – These joints don’t allow rotation, but are versatile. Examples: jaw and fingers.
  4. Gliding Joints – These joints allow bones to glide around and past each other. Examples: spine, ankles, and wrists.
  5. Hinge Joints – Examples: knees and elbows.
  6. Pivot Joints – These allow bones to pivot or twist around other bones. Examples: neck and elbows
  7. Saddle Joints – Allow side to side and back and forth motion, but don’t fully rotate. Example: Base of thumbs.

More Detail

  • Movable joints are also called synovial joints.
  • Synovial joints have a joint capsule within which synovial fluid is produced to keep the joint moist and healthy.
  • Movement of joints nourishes and helps to keep the joint capsule healthy.
  • A ball and socket joint (such as the hip and shoulder joints) provides the greatest mobility.
  • A hinge joint (such as the knee joint) provides greater stability.
  • An example of applying knowledge of joints in asana: Both the hip and knee joints are involved in Padmasana (Lotus Posture). As a hinge joint, the knee has limited rotational capability. Safe practice of the pose requires the hips (the ball and socket joints) to have adequate range of motion. If they do not, the force may be transferred to the knee which is not designed for such movement, thereby causing injury.

Joints are Relationships

Joints are not things. They are relationships. – Leslie Kaminoff

Part of a Greater Category And Also Unique

Each joint is a world of its own, with its own problems, specific functions, and structures that make it unique, relative to other joints. Each can be classified in one of six categories according to their function, shape, or both. Each joint is in in its own world, but at the same time it lives in a galaxy of joints that exist within the universe of the body. – David Keil 

About Synovial Joints

Synovial joints… are freely movable and need a system that cushions the ends of the bones, allowing them to glide over each other without friction. This system consists of hyaline cartilage, the smooth, whitish covering on the ends of the bones, and the synovial fluid, which fills the space between the cartilage surfaces and facilitates smooth, painless movement between bones. This clear, slightly viscous fluid is also important because it delivers nutrients and oxygen to the hyaline cartilage, which—unlike most body tissues—doesn’t have its own blood supply. Any joint movement helps circulate the synovial fluid, which feeds the cartilage; practicing yoga poses therefore helps keep the cartilage well-nourished. – Julie Gudmestad

See Also



Some definitions we’ve found for “muscles” include:

  • biological units built from various specialized tissues that are integrated to perform a single function
  • a band or bundle of fibrous tissues in a human or animal body that has the ability to contract, producing movement in or maintaining the position of parts of the body
  • provide the force behind movement; composed of layers and layers of fibers
  • voluntary contractile tissue that moves the skeleton, is composed of muscle cells (fibers), layers of connective tissue (fascia) and numerous nerves and blood vessels


  • A muscle is a band or bundle of fibrous tissue that has the ability to contract.
  • Skeletal muscles are composed of muscle cells, fascia, nerves and blood vessels. (Andrew Biel)
  • Muscle is attached to bone by tendons.
  • Please see Connective Tissue for an understanding of the “myofascial approach” vs. “isolated muscle theory” and to get a clear understanding of what a muscle really is.

Three Types of Muscles

Specialists distinguish three types of muscles in the body:

  • Smooth Muscle — muscles that line organs, blood vessels and the digestive tract
  • Cardiac Muscle — specialized muscles within the heart for pushing blood through the arteries and veins
  • Skeletal Muscle — muscles for moving bones

Striated Muscle

Striations are a key attribute to identify skeletal and cardiac muscle types. In contrast to smooth muscle, cardiac and skeletal muscle types possess an internal ultrastructure of highly organized contractile myofilaments.  Actin and myosin myofilaments are stacked and overlapped in regular repeating arrays to form sarcomeres. – McGraw-Hill


  • The main function of the muscular system is movement.
  • Muscles maintain posture and body position. This includes contraction to hold the body still. The muscles responsible for the body’s posture have the greatest endurance of all muscles in the body. (Inner Body)
  • Muscles are responsible for breathing, heart function and much of the circulatory system.
  • Muscles move substances such as blood and food from one part of the body to another.
  • Muscles generate body heat.

Produces Heat

As a result of the high metabolic rate of contracting muscle, our muscular system produces a great deal of waste heat. Many small muscle contractions within the body produce our natural body heat. When we exert ourselves more than normal, the extra muscle contractions lead to a rise in body temperature and eventually to sweating. – Inner Body, Muscular System

See Also