Skeletal System

Our bones form the basis of our overall structure. Within the human body are 206 bones which are arranged in a perfect order to allow for a variety of different movements and postures. They are held together by cartilage and ligaments, and these structures together form the skeletal system. In this article we shall take a closer look at this system.

Classification

The skeletal system is divided into 2 main types – the axial skeleton and the appendicular skeleton.

Axial Skeleton

The axial skeleton refers to the vertebra, the rib cage and the skull. The bones are joined together by numerous ligaments and tissues. The axial skeleton is responsible for maintaining the upright posture of the body, and bears a significant amount of body weight as well. It forms a path for the weight to be transmitted through the skeleton, and as a result, is prone to weight related damage. In addition to these bones, the axial skeleton also consists of tiny ossicles that are located within the middle ear

The skull houses the brain surrounded by cerebrospinal fluid, and also consists of a number of blood vessels and nerves. The vertebrae not only maintain posture, they also protect the spinal cord and the nerves that emerge from them.

Appendicular skeleton

On the other hand, the appendicular skeleton consists of the bones that form the upper and lower limb, along with the pelvis, pelvic girdle and pectoral girdle. The bones are utilized for a variety of movements and also provide protection to organs.

The shoulder girdle is the part of the appendicular skeleton that attaches the upper limb to the trunk.  In addition to the humerus forming a part of the shoulder joint, the girdle is also formed by the scapula (wing bone on the back) and the clavicle (collar bone).

The upper limb consists of bones of the arm i.e the humerus, forearm (radius and ulna) and the bones of the wrist and the hand. Similarly, the lower limb consists of the femur, tibia, fibula and the bones of the ankle and the foot. The pelvic girdle consists of the two hip bones that are joined to each other at the front and through the sacrum at the back.

It is clear from the above discussion that the skeletal system is a fairly complex structure that consists of a large number of bones that are arranged in close proximity and relationship to each other to perform a variety of different movements and functions.

Below is a video that explains the skeletal system in a bit more detail:

In the next section, we shall briefly discuss the function of the skeletal system.

Functions of the skeletal system

Below are listed the important functions of the skeletal system:

1. Movement – The bones of the skeletal system are joined together by ligaments, muscles and joint tissue so as to produce a variety of different fluid movements. The joints are of different types, and have variable range of movements. For example, the shoulder joint is a ball and socket joint that can move in a number of different directions, while the elbow joint is a pivot joint that bears limited movement.

2. Protection of underlying tissues – The bones that form the skeletal system protects the vital organs within the body that are essential for human survival. The skull protects the brain, the vertebrae protect the spinal cord, the rib cage and sternum protects the heart and the pelvic girdle protects the uterus (in women) and the bladder. Some bones help stabilize neighboring structures – for example the clavicle and the scapula help stabilize the shoulder joint in conjunction with the rotator cuff muscles.

3. Support – Our skeleton is responsible for the shape of our body. It provides support to the muscles and surrounding tissues, and any breakage or fracture can result in a change in the shape of the skeletal structure temporarily, till it heals.

4. Production of blood cells – Within the skeletal structure s present bone marrow. The bone marrow is responsible for the production of red blood cells, white blood cells and platelets. These cells are essential for a number of different functions that includes oxygen transport to vital organs.

5. Endocrine function – It may be surprising to hear that the cells within the bone release a compound called osteocalcin – a hormone that helps control secretion of insulin and the sensitivity of the body to insulin.

6. Mineral storage – The bones are composed of calcium, and hence form an area of storage of calcium.

Below is another video that explains the structure and function of the skeletal system :

Diseases of the skeletal system
One of the most common conditions that affect the bones is called osteoporosis. This is a clinical condition characterized by thinning of the bones due to a reduction in their calcium and mineral composition.

Osteoporosis is a disease often seen in women after menopause who choose not to have hormone replacement therapy, and is also seen in elderly patients. The thinned bones are brittle and can be subject to fracturing easily. Osteoporosis is also seen in individuals suffering from chronic lung disorders, primarily due to long term use of steroids.

Osteoarthritis is also another clinical condition that affects the skeletal system, though it is primarily a disease of the joints. In this condition, patients develop degeneration of the bone which is usually age related, though it can be seen in people who subject their bones and joints to constant trauma (such as athletes). X-ray tests are diagnostic and treatment often involves physical therapy with pain relief and mineral supplementation combined with bone protection.

The skeletal system is a complex arrangement of over 200 bones that provides protection to internal organs and a variety of other functions as discussed above. Diseases can also effect the skeletal system and can have an impact on overall health. The accompanying videos will give you a good idea regarding the arrangements of bones and how they function.

Further reading about the Skeletal System

Inner Body

Biology at About

 

 

Skull Anterior View

Skull Anterior View

Skull Anterior View

1. Frontal Bone
2. Supra-Orbital Foramen
3. Orbit (Orbital Cavity)
4. Superior Orbital Fissure
5. Inferior Orbital Fissure
6. Zygomatic Bone
7. Infra-Orbital Foramen
8. Maxilla
9. Mandible
10. Mental Foramen
11. Incisive Fossa
12. Symphysis
13. Vomer
14. Inferior Nasal Concha
15. Middle Nasal Concha
16. Perpendicular Plate of Ethmoid
17. Nasal Bone
18. Lacrimal Bone