The Skeletal System — Know Your Body


The skeletal system brings to mind, well skeletons, the polished white structure in the corner of the science classroom, or the charred remains of a victim in any episode of that convoluted crime show on late-night television. Needless to say we often associate the skeleton with death and decay, so much so that we often forget that when it is still firmly wrapped in a breathing human, it is very much alive.

What is the Skeletal System Made up of?

The skeletal system is more than just a pile of bones. Although the skeleton is a sturdy frame which the body envelopes, it also contains a network of ligaments, tendons and cartilage which not only connects the bones to each other, but connects the skeleton to muscles. This is not the only network involved, as the bones themselves are being fed by blood vessels and nerves, from the circulatory and nervous systems respectively.

In addition, teeth—which play a vital role in the digestive system—are counted as part of the skeletal system, even though they are made of dentin and enamel, and not bone.

Fun Fact: The hydoxyapatite in teeth makes the tooth enamel the strongest part of the body,

How Many Bones are in the Human Body?

Fresh humans are born with approximately 270 bones and as the humans ripen into adulthood, many of these bones fuse together as the body develops, until the adult has only 206 bones. Variations of the skeleton are not limited to age either.

After puberty, uterus-owners have a flatter, more rounded and a much larger pelvis than their prostate-owning counterparts. This is because the pelvis needs to be larger in order to accommodate pregnancy and facilitate childbirth. Yes, this is where the concept of “child-bearing hips” comes from.

What are Bones Made of?

There are four main materials that make up the bones in your body; the periosteum, compact bone, cancellous bone and marrow.

  • The periosteum is a thin, dense membrane on the outer surface of the bone, this contains the blood vessels and nerves that feed the bone.
  • The compact bone is the hard, smooth and white outer layer.
  • The cancellous bone is a hard layer that looks like sponge, but is still pretty hard.
  • Bone marrow is the inner-most part of the bone, jelly-like in consistency, with blood vessels running through it, marrow is vital in the production of blood cells. It is usually protected by the cancellous bone.

What Does the Skeletal System do?

The skeletal system performs vital functions for the body, including support, protection, movement, calcium storage, endocrine regulation and blood cell production.

The skeletal system consists of the axial skeleton and the appendicular skeleton. The axial skeleton has about 80 bones that make up the vertebral column, the rib cage and the skull. This helps protect the essential organs of the brain and spinal cord, heart and lungs, support the body, and maintain an upright posture.

The appendicular skeleton has 126 bones and contains the upper and lower limbs, and the pectoral and pelvic girdles. They help provide the body with movement, like walking and jumping, and they protect the major reproductive and digestive organs.


Diseases of the Skeletal System

The main conditions associated with the skeletal system are metabolic bone diseases, including osteoporosis and osteomalacia.

Osteoporosis causes bones to lose calcium, become thinner and sometimes disappear completely. It is quite common among the elderly, as bone loss is a natural part of aging, affecting over 3 million people in the UK alone. However, some individuals lose bone density much quicker than usual.

There are several risk factors which increase the risk of developing osteoporosis:

  • Menopause, especially if this occurs before the age of 45.
  • Long-term asthma sufferers who require high-dose oral steroids.
  • Having a low BMI.
  • Heavy smoking.
  • Heavy drinking.
  • Family history of osteoporosis.

Osteomalacia, or rickets in children, is a softening of the bones, causing them to weaken, which can lead to skeletal deformities and bone pain. Children who suffer from rickets are often “bow-legged” and are more likely to fracture their bones.

Other common conditions within the skeletal system are:

  • Arthritis – inflammatory diseases that attack the joints and surrounding structures.
  • Scoliosis – a side to side curve in the back, or spine.
  • Lower back pain, with 90% of people suffering from lumbar pain at some point in their life.

Bone cancer is one of the rarer diseases, with less than one percent of all cancer cases. Unfortunately, primary bone cancer is usually diagnosed in patients under the age of forty. Although leukemia primarily affects blood, it does originate in the marrow of the bone.

The skeletal system has a risk of suffering fractures, breaks and strains.

Liked it? Take a second to support The Nopebook on Patreon!