Skeletal System

Human anatomy > Skeletal System

The skeletal system acts as a strong foundation for the body. It allows the body to stand erect, sit and perform all bodily functions that need movement. The skeleton provides an anchor for muscles, tendons and ligaments. There are more bones during childhood because some of them have not fused yet, like the fontanels in babies. When a person matures, some bones fuse together and become 206.

Skeletal System

Functions of the Skeletal System

  • Protects the vital organs of the body by forming an outer covering around most of the major organs.
  • Provides osteocalcin, which is responsible in carbohydrate and lipid homeostasis.
  • Provides the framework in which the body could perform its bodily movements through the support of its ligaments and tendons.
  • Responsible in the storage of calcium deposits, which the body needs for growth and development.

Bones grow and lengthen because of osteocytes, osteoblasts and osteoclasts.  These are the bone cells responsible for bone development.


Majority of bone cells are osteocytes. These mature bone cells ensure that the calcium components of the bones are sufficient.  The appropriate amount of calcium makes the bone strong and not easily breakable.


These cells are responsible in reshaping the bones.  Osteoblasts have minerals like zinc, copper and tissue collagen, which help in proper bone development.  They are also called young bone cells, which later become mature bone cells or osteocytes.


Osteoclasts are responsible for bone resorption; hence, together with osteoblasts, they are responsible for bone growth and natural development. Growth factor interleukin 6 (IL-6), parathormone (PTH) and calcitonin are substances that regulate osteoclasts.  Parathormone or parathyroid hormone is produced by the parathyroid hormone and is responsible for the regulation of calcium concentration in the blood. Calcium is needed in proper bone development. Calcitonin is secreted by the thyroid gland, which has the same function as PTH.  IL-6, on the other hand, helps also in the regulation of osteoclasts.

The skeletal system is also composed of ligaments, joints, periosteum, and bursa.  Aside from these, the bone is composed of the diaphysis and epiphysis.  The diaphyses contain the yellow bone marrow, while the epiphyses are the ends of long bones.  Up to the age of 18 to 21, the bone lengthens and people grow in height; but once the epiphyses meet, height increase usually stops.  This is why it is important to nurture the bone’s growth while still young.  As a person ages, calcium reabsorption decreases and bones also no longer grow.   

Two General Types of Bones According to location


These are bones belonging usually to the lower part of the body.  They make movements of the upper and lower limbs possible. These include the pectoral girdle, the leg and feet bones.


The bones that are found in the upper portion of the body are responsible in the movement of the arms and the trunk going upwards.  These include the vertebral column, the trunk, the arm, and hand bones.

Disease Conditions Associated with Bones

Osteoporosis is the most common bone condition which people suffer from. It is weak bone formation because of the inability of the body or bone to retain calcium. The vital nutrients needed by the body for bone formation are not also properly maintained.

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