What is the Musculoskeletal System?

The musculoskeletal system, also called the locomotor system, is an organ system that gives humans and animals the ability to move using their muscular and skeletal systems. It provides stability, form, support, and movement to the body. The skeleton is composed of bones (skeleton), muscles, cartilage, tendons, ligaments, joints, and other connective tissue that supports and binds tissues and organs together. The musculoskeletal system is subdivided into two broad systems, such as the muscular system and the skeletal system.

The given image represents the musculoskeletal system in the human body.
CC BY 4.0 | Image Credits: https://commons.wikimedia.org | OpenStax

Muscular system

The muscular system is an organ system composed of specialized contractile tissue called muscle tissue. This encompasses all of the body's muscles. Muscle tissue is classified into three categories, depending on which all muscles are divided into three groups:

Cardiac muscle

The cardiac muscle is also called the myocardium. In vertebrates, one of the three major muscle types is found only in the heart. Cardiac muscle is similar to skeletal muscle. Cardiac muscle tissue uses involuntary movements to keep your heart pumping. This is one feature that distinguishes it from controllable skeletal muscle tissue. Pacemaker cells are specialized cells that help them achieve this. These are in charge of your heart's contractions. Pacemaker cells get signals from your neurological system that tell them whether to speed up or slow down your heart rate. Your heart's pacemaker cells are linked to other cardiac muscle cells and can send and receive messages. This causes a wave of cardiac muscle contractions, which produces your heartbeat.

Smooth muscle

A smooth muscle is a type of muscle that does not require voluntary control to contract. It is present in the walls of inner organs such as the bladder, gut, stomach, and blood vessels and is made up of spindle-shaped, unstriated cells with only one nucleus.

Skeletal muscle

Skeletal muscle is also known as voluntary muscle. Tendons connect skeletal muscles to bones, and they are responsible for all movements of body parts about one another. Skeletal muscles are long, thin, multinucleated fibers of skeletal muscle that are crossed with a regular pattern of fine red and white lines, giving the muscle its distinct appearance.

The diagrammatic representation of  muscular level of organization shown in this figure.
CC BY 3.0 US | Image Credits: https://courses.lumenlearning.com | Brielle Matson

Functions of the muscular system

  • Many of the muscle helps to move and most of the muscles are attached to bones. This muscle makes the skeleton move.
  • Muscle protects the body and also cover most of the organ inside the body.
  • The muscular system helps the body to keep the internal temperature in a certain range.

The Skeletal system

Bone is the most important part of the skeletal system. The skeletal part of the system is the major storage system for minerals. Minerals such as calcium and phosphorous are stored here. This storage is important because it aids in the regulation of mineral balance in the bloodstream. Calcium is the most abundant mineral in the body and it is important for bone health. The main roles of calcium in the human body are to strengthen the bones and teeth and regulate muscle function. When the fluctuation of minerals is high, minerals are stored in the bone, and when the fluctuation is low, minerals are taken from the bone. The human skeletal system consists of a set of 206 bones that give support and protection to the body. The skeleton is divided into two parts: the axial and appendicular skeletons.

Axial skeleton

Bones such as the skull bones, vertebrae, ribs, and sternum make up the axial skeleton. The organs of the head, neck, and trunk are supported and protected by it.

Appendicular skeleton

The appendicular skeleton is formed by the bones of the pectoral girdle, pelvic girdle, and upper and lower limbs.


Bones are solidified, thick connective tissue structures that are rigid. Bone tissue is made up of a mineralized bone matrix with type 1 collagen fibers scattered throughout the ground material. Osteocytes, osteoblasts, and osteoclasts are three types of specialized bone cells that make up the cellular component of the bones. The bones are divided into two layers, each with its histological appearance and properties.

Compact bone

The hard outer layer of bone is composed of compact bone tissue. This tissue gives bone their smooth, white, and solid appearance.

Spongy bone

It is the bone's deep airy layer. Spongy bone is well-vascularized and has a high metabolic rate. It's most common at the ends of long bones and in the vertebrae.

Types of bones

Bones can be divided based on their shapes; they are:

Long bones

They're tubular, with a larger longitudinal diameter and a smaller transverse diameter. They are mostly made up of compact bone, with spongy bone and bony marrow filling in the gaps.

Short bones

Short bones are roughly cuboid or spherical, with only a thin coating of compact bone encasing the spongy bone.

Flat bones

Flat bones are thin and flat. Sometimes they have a slight curve. Flat bones serve as a point of attachment for muscles or protection for your internal organs.

Sesamoid bones

Sesamoid bones are tiny, spherical bones implanted in muscle tendons at the point where the tendon crosses a joint. The patella is the largest sesamoid bone in the body, but there are other smaller sesamoid bones in hand and foot, usually near the joints.

Irregular bones

The irregular bones are those that, due to their unusual shape, cannot be classified as long, short, flat, or sesamoid. Irregular bones provide a variety of functions in the body, including protecting nerve tissue.


Cartilage is a form of flexible connective tissue that can be found in many different organ systems in the human body. It differs from the bones in several ways. Articular cartilage is found only in the musculoskeletal system. It's a diarthrodial joint's highly specialized connective tissue. Articular cartilage holds the articulating bones together, allowing them to bear weight and glide over one another with minimum friction.


It is the site at which any two or more bone articulated is called a joint. Joints act as a fulcrum for the bones, allowing them to pivot and allow body components to move. Joints can be classified into several types, they are:

Synovial joint

Synovial joints are freely mobile joints in which the bones are separated from one another by a potential space known as the synovial cavity, rather than being in direct contact. The synovial cavity is lined with a synovial membrane that secretes synovial fluid, which nourishes and lubricates the articulating surfaces and reduces friction. Synovial joints include the knee, shoulder, and elbow joints.

Fibrous joint

Fibrous joints are articulations in which the bones are connected by thick fibrous connective tissue. Fibrous joints' bones are securely bound together, allowing the joint to move slightly.

Cartilaginous joints

Cartilaginous joints are articulations that connect the bones with cartilage. The bones have a range of mobility between synovial and fibrous joints. The cartilage joints, synchondrosis, and symphysis are two different forms of cartilage joints.

Functions of the skeletal system

  • The bones give the body its shape and serve as attachment points for muscles, tendons, ligaments, and cartilage.
  • The internal organs are protected by the skeletal system's structural integrity, most especially the brain, which is enclosed by the skull, and the heart and lungs, which are protected by the rib cage.
  • The skeletal system performs a variety of metabolic processes, and the bones store vital minerals like calcium and phosphorus.

Musculoskeletal system disorders

Musculoskeletal disorder is a condition that can affect the muscles, joints, and bones. The musculoskeletal disorder includes osteoarthritis, rheumatoid arthritis, fibromyalgia, bone fractures, and tendinitis. They can affect any major area of the musculoskeletal system, such as the neck, back, shoulders, legs, hips, knees, and feet. Symptoms of the musculoskeletal system can include swelling, stiff joints, and dull aches, etc. Lifestyle, family history, age, and occupations are the risk factors for musculoskeletal system disorders.

Context and Applications

This topic is significant in exams at school, graduate, and post-graduate levels, especially for Bachelors in Biology/Zoology and Masters in Biology/Zoology.

Practice Problems

Question 1: How many cervical vertebrae are in the human spine?

  1. 6
  2. 5
  3. 7
  4. 12

Answer: Option 3 is correct.

The cervical spine is made up of seven bones in the neck that is located above the sacrum. In the chest, the thoracic spine is made up of 12 bones. In the lower back, the lumbar spine is made up of five bones.

Question 2: The _____ ion is essential in muscle contractions.

  1. K
  2. Ca
  3. Mg
  4. Na

Answer: Option 2 is correct.

Explanation: Calcium is necessary for muscular function. Calcium is released into the fiber when the nervous system is stimulated for a contraction.

Question 3: How many bones are there in the average person’s body?

  1. 66
  2. 307
  3. 206
  4. 669

Answer: Option 3 is correct.
Explanation: The adult human skeleton is made up of 206 bones. Bones are made up of connective tissue that is calcium-reinforced, as well as specialized bone cells.

Question 4: Which bone protects the brain?

  1. Cranium
  2. Cerebrum
  3. Cerebellum
  4. Calcium

Answer: Option 1 is correct.
Explanation: Cranium or skull is the bone structure of the head. It supports and protects the face and brain.

Question 5: What makes bone keep strong?

  1. Cartilage
  2. Silica
  3. Ligaments
  4. Calcium and phosphorus.

Answer: Option 4 is correct.

Explanation: The minerals calcium and phosphorus are responsible for bone strength. When mineral fluctuation is high, minerals are stored in the bone, and minerals are taken from the bone.

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