What are the Functions of the Human Skeleton?
The skeleton is a strong, flexible, and bony framework that supports the body and protects the internal organs. The skeleton is a very important part of the human body. Its functions can be grouped conveniently under the headings- support, protection, movement, muscle attachment, etc.
Support:
In land-dwelling vertebrates, rigid skeletal support raises the body from the ground and allows rapid movement. It suspends some of the vital organs, prevents them from crushing each other, and maintains the shape of the body despite vigorous muscular activity.
Situated over the upper part of the ribcage, at the back of the body, are the shoulder blades (scapulae). The collarbones (clavicles) link the scapulae to the breastbone (sternum) and support the shoulders. The upper arm bone which is the humerus bone, fits into a socket in the scapula.
The bones of the arms and shoulder girdle are designed for dexterity, while those of the pelvic girdle and legs are constructed for weight-bearing and walking.
The pelvic girdle also houses and supports the organs of the lower abdomen (liver, kidneys, etc.) It comprises the sacrum, the coccyx, and the two hip bones. Each hipbone is composed of three fused bones - the ilium, the ischium, and the pubis. The ilia are attached to each side of the sacrum, and the two pubic bones are joined at the front of the pelvic girdle. On each side, the ischium unites the ilium with the pubis. The upper leg bone (femur) is socketed into a cavity at the junction of these three bones.
Joined to the strong upper bones of each limb are paired parallel bones - the radius and the ulna in the forearm, the fibula, and the tibia in the lower leg. The wrist and the ankle are composed of several smaller bones: carpals in the wrist and tarsals in the ankle. The framework of the hand is made up of metacarpals, and the foot is composed of metatarsals. The fingers and toes are constructed of bones called phalanges.
Protection:
Some of the delicate and important organs of the body are protected from distortion or injury by several skeletal structures. The 22 bones of the skull (cranium) form a protective vault for the brain and sockets for the eyes, ears, and nose.
Beneath the skull is a total of 34 vertebrae, which make up the backbone and encase the spinal cord. Toward the base of the spine, five vertebrae are fused together to form the sacrum, with the four fused bones of the coccyx beneath them. The 24 curved rib bones are attached to the spine. Out of which, the top 10 rib pairs are attached to the sternum at the front of the body. The ribcage protects the heart, lungs, and the main blood vessels of the body (aorta, vena cava, etc.)
Movement:
Movements of the skeleton are made possible by the joints formed wherever two bones meet. The joints that allow the most freedom of movement are those at the shoulder and the hip. Here, a ball at the end of the limb bone fits into a socket on the girdle. At the knee and the elbow, hinge joints permit the limb to bend in one direction only. The elbow also has a pivot joint enabling the arm to twist. Other mobile joints include the ellipsoid joints between the hand’s phalanges and metacarpals. The saddle joint of the thumb enables it to touch each finger in turn.
Muscle Attachment:
To produce effective movement of any part of the skeleton, the muscles must be attached securely to it at each end. One end of the muscle must be attached to the part of the skeleton to be moved, while the other end is anchored to a part of the skeleton to be held stationary with respect to the moving part.
Muscles that produce movement usually act across joints in such a way that the bones work as levers with a low mechanical advantage. When a muscle contracts, it exerts tension between its two points of attachment. One of these points remains fixed at the origin, while the other end that moves is the point of insertion of the muscle.
Formation of Blood Cells:
Most hollow bones of the human skeleton contain bone marrow. And the marrow towards the two ends of the bone is known as red bone marrow. The red bone marrow produces red blood cells and lymphocytes.
Storage of Fats and Minerals:
The bone marrow contained in the middle part of the bone is known as yellow bone marrow. It acts as a storage of fats and minerals such as calcium and phosphorus.
Respiration:
The breathing process is another application of the skeletal system. Inhalation occurs when the ribs move upwards and outwards as a result of contraction of the intercostal and diaphragm muscles, and exhalation occurs when the ribs move downwards following the relaxed situation of these muscles.
Hearing:
The inner ear has three bones: hammer, anvil, and stirrup. These three bones vibrate when the ear drum receives any sound, creating vibration in the surrounding cochlea, which transmits the signals to the brain.
What Are the Parts of the Skeleton?
The vertebrate skeleton is composed of the axial and the appendicular skeletons.
Axial Skeleton: The axial skeleton consists of the skull, the vertebral column, and the rib cage.
The skull consists of the cranium, with a fixed upper jaw (maxilla) and a movable lower jaw (mandible). Skull bones are spongy to reduce their density.
The vertebral column is made up of individual vertebrae separated by intervertebral discs of cushioning pads.
The ribcage (thorax) is composed of 12 pairs of ribs joined at the back of the thoracic vertebrae. The upper ten pairs are joined by cartilage, at the front, of the breastbone (sternum).
Appendicular Skeleton: The appendicular skeleton is formed by the pelvic and pectoral girdles and the limbs.
The pectoral or shoulder girdle is the portion of the upper extremities to which the upper limbs are attached. It consists of a pair of clavicles or collar bones and a pair of scapulae or shoulder blades at the back. The scapulae are attached to the thoracic vertebrae by muscles and tendons. The clavicles link the scapulae to the sternum. The upper arm bone (humerus) fits into a socket called the glenoid cavity in the scapula. The bones in the shoulder girdle are designed for dexterity. The connection in the girdle is loose and acts as a shock absorber to dissipate the upthrust received by the hands as they work.
The pelvic girdle is the portion of the lower extremities to which the lower limbs are attached. It is made of the sacrum, the coccyx, and the two hip bones. Each hipbone is made up of three fused bones - the ilium, the ischium, and the pubis. These are firmly connected to the sacrum by strong ligaments. The bones of the pelvic girdle are designed for weight-bearing and movement. It is a strong setup that supports the abdominal organs. The fused structure of the pelvic girdle provides the strength to bear the whole body over it and absorb the upthrust transmitted by the legs during walking or running.
Conclusion
The skeleton forms the internal frame with a wide range of functions ranging from protection to hemopoiesis. The bones have a great potential to repair, which has been implemented in certain cases to increase the height of an individual. The bone marrow is one of the important components of the body as it creates the vital cells of the immune system, making the skeletal system responsible for both physical and microbiological protection of the body.
