The Skeletal System

The human body is composed of a symphony of different systems, organs and tissues types.  It takes all of them for the body to function the way God designed it to.  Remove any one of these systems and the body dies.  One of those important systems is the skeletal system.

The number of bones in the human body varies from 206 to 300.  At birth, one starts out with 270 to 300 bones depending on the source of information.  As the child grows older, a number of bones fuse together, reducing the overall number.  By the time the child becomes adult, the number of bones has been fused down to only 206.  The diagram below labels a number of those bones for you.

During the development and growth of the unborn child, the bones that make up the skeleton are formed by two different processes:

  • Endochronal Ossification – The early skeleton starts out as pliable cartilage.  As the unborn child develops, some of the cartilage begins to harden into bone.  This is known as endochronal ossification.  Many of the supporting bones such as the femur and humerus are formed this way.
  • Intramembranous Ossification – Instead using cartilage tissue, Intramembranous ossification involves a type of connective tissue known as mesenchyme and is the process used to form the bones of the skull.  The mesenchyme connective tissue forms a layer over the developing brain and then slowly begins to ossify or harden.  At birth, this layer of bone is still somewhat pliable, allowing the baby’s head to fit through the birth canal.  The ossification of the skull bones continues through childhood and is completed in early adulthood.  A forensic pathologist can often determine the approximate age of a skull by the degree of fusion of the skull bones.

The skeleton is divided into two sections:

  • Axial Skeleton – The axial skeleton consists of the vertebral column, rib cage, sternum and skull.  Its main function is the protection of the brain, heart and lungs.
  • Appendicular Skeleton – The appendicular skeleton consists of the shoulder and pelvic girdles along with the arm and leg bones.  The main function of the appendicular skeleton is the protection of the digestive organs along with the excretory and reproductive organs, as well as locomotion of the body.

The bones that make up the skeleton are divided into five groups:

  • Long Bones – Bones that are longer than they are wide are classified as long bones.  This includes the bones of the arms and legs
  • Short Bones – Bones that are as wide as they are long are classified as short bones.  This includes the carpals and tarsals.
  • Flat Bones – Bones that are flat in shape are classified as flat bones.  They primarily provide protection to internal organs.  The skull, scapula and pelvic bones are flat bones.
  • Irregular Bones – Bones that have an irregular shape are classified as irregular bones.  This includes the vertebrae and lower jawbone.
  • Sesamoid Bones – Bones that are smaller and located in joints are classified at sesamoid bones.  This includes the patella or knee cap.

Bend your knee or elbow, raise one leg off the ground, turn your head from one side and then the other and then watch your fingers as they bend to grasp something.  All of these movements are made possible by the joints where two or more bones meet.  If damage occurs to some of these joints, everyday tasks can become extremely painful and even impossible.  There are three main types of joint in the human body:

  • Synovial Joints – Synovial joints are those that have a fairly free range of motion such as the knee, elbow, shoulder and hip.
  • Cartilaginous Joints – Cartilaginous joints have a restricted range of motion such as the discs between the vertebrae.
  • Fibrous Joints – Fibrous joints are fixed and cannot move such as the joints between the bones in the skull.

If you have ever watched the news or any of the police or forensic programs, you will have heard that sometimes the sex of human skeletal remains can be determined by the bones.  The forensic examiner will examine the pelvis, shoulder blade, jawbone and eyebrow ridges.  The most notable difference they will find is the pelvic girdle.  A woman will have a rounder and flatter pelvis than a man.  This is to allow the baby as much room as possible during birth.  Less telling are the other differences.  In general a woman has a rounder shoulder blade than men; men will have a squarer shaped jawbone and thicker eyebrow ridges than a woman.

Many people think the sole purpose of our skeleton is to support our bodies so it can stand up.  While that may be an important function of the skeletal system, it is not the only function.  The various functions of our skeletons include:

  • Support and Shape – The skeleton is the framework that supports and shapes the human body much like the steel girders and beams that support and shape a building.
  • Protection of Vital Organs – In vital areas like the head, chest and pelvic areas, the skeleton offers protection to the soft internal organs.  I’m sure all of us have bumped our heads at one time or another.  Imagine if you will what would have happened had you not had your skull to protect the brain from being damaged.
  • Muscle Attachment & Movement – The movement of the body is accomplished by a sophisticated system of muscles and tendons that attach to the various bones along with different types of joints connecting the bones together.
  • Manufacturing of Red Blood Cells – Red blood cells are produced in the inner marrow of the bones.
  • Storage of Minerals – The bones both calcium and iron that can be drawn out and used when necessary.  If a pregnant woman does not take in a sufficient amount of calcium on a regular basis, her body will draw the calcium from her bones in order to ossify the bones in her unborn child.  This is one of the leading causes of osteoporosis in women.
  • Endocrine production – The bones produce a hormone known as osteocalcin which helps regulate the storage and deposition of fat and glucose in the body.
  • Manufacturing of Stem Cells – The bones produce stem cells that are eventually turned into red and white blood cells and platelets.  These stems cells can also be used in research instead of using embryonic stem cells.

There is one other unique feature that involves a group of flat bones – the ribs.  In Genesis 2:21-22 it states:

So the LORD God caused a deep sleep to fall upon the man, and while he slept took one of his ribs and closed up its place with flesh. And the rib that the LORD God had taken from the man he made into a woman and brought her to the man.

For centuries people believed that men had one less rib than women because of the verse in Genesis 2.  However, that is not the case because men and women have the same number of ribs.  But what makes this verse in Genesis 2 so interesting is a little known fact outside the medical profession.  Unlike other bones, the rib bone can be carefully removed from the protective lining that surrounds it.  If the protective sheath is not damaged, it will grow a new rib in the place of the missing one.  Surgeons with this knowledge have successfully removed rib bones from people and used them to rebuilt severely damaged jawbones.  The rib is the only bone known to have this regenerative property.

The skeletal system is marvelously designed for multiple purposes and functions. Without it we would look and act like a quivering mass of flesh, kind of like an octopus on dry land.  Like building a house on a firm foundation, God made our bodies with a firm skeletal foundation.

Additional Resources

Fearfully & Wonderfully Made (DVD)

When does life begin?

Take a journey from conception to birth with Dr. David Menton, former professor of anatomy at the prestigious Washington University School of Medicine in St. Louis. Dr. Menton provides both a biblical and scientific answer to the question of when life begins.

Taken from one of Dr. Menton’s lectures, this video will reveal the wondrous design of the womb along with the numerous miracles involved along every step of the development of the unborn child.

Following the tragic starvation induced death of Terry Schiavo, Dr. Menton clearly shows the value and sanctity of human life.

With grace and sensitivity Dr. Menton concludes with a salvation message and explanation of the second birth process as described in John 3.

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