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The Skeletal System

                                          

The skeletal system is made up of bones, tendons, ligaments, and joints.  When you were born, your body was made up of over 300 bones, but as you grow some of these bones begin to fuse, leaving the end result of 206 bones.  These 206 bones form the framework to which soft tissues and organs are attached.  Bones are connected to each other by ligaments, and connected to each muscle by tendons.  These tendons help the bones to perform specific tasks through the force of contractions.  When muscles contract the bones that are attached act as levers and cause movement.  Without your skeletal system and the important role it plays, you would be like a floppy bean bag unable to walk, sit, or stand.

            The skeletal system has five major functions, these include protection, support, movement, storage, and blood cell formation.  Protection occurs in the skeletal system by covering our vital organs such as the heart, brain, and lungs.  Secondly, the skeletal system offers support by providing the shape of the body enabling humans to stand erect instead of falling to the floor.  The third function of the skeletal system is the ability to move.  Our muscles are attached to our bones, therefore when our muscles move our bones move.  The skeletal system also functions in the formation of blood cells.  Most of the blood components are made right in the bone. Lastly, the skeletal system functions as a storage unit for fats and minerals.  This is especially important for the healing process of our bones. 

            The human skeleton is divided into two sections, the axial skeleton and the appendicular skeleton.  The axial skeleton forms the axis or trunk of the body and encompasses all of the upper body bones.  The axial skeleton is made up of 80 of the 206 bones in the human body and functions primarily for protection of our vital organs.  The axial skeleton contains the skull, backbone, and chest.  The skull is the most important structure in the entire skeletal system.  It is made up of 28 bones and houses your brain, as well as provides the framework for your eyes, ears, tongue, nose, and some skin.  The backbone is a flexible structure made up of 26 bones and serves to provide support for the entire upper body, as well as protection of the spinal cord.  Most people believe that all creatures have backbones, but in fact 97% of all creatures on earth do not have backbones.  Just imagine living without a backbone, you could not stand erect and would live life like a jellyfish.  The chest consists of your breastbone or sternum, and ribs, which makes up a total of 25 bones.  The main function of the chest is to provide protection to the lungs and the heart.

            The appendicular skeleton consists of 126 of the 206 bones in the body and serves to attach the limbs to the rest of the body.  The appendicular skeleton contains the upper and lower limbs.  The upper limbs, or arms, contain 64 bones and function to perform work.  The upper limbs are lighter and made to focus on detail.  The lower limbs, or legs, contain 62 bones and structurally serve the same purpose as the upper arms except the lower limbs are stronger and thicker and can support the stress of running or jumping.  These structures are designed primarily for movement and are extremely important in our everyday activities.

            Many people believe that bones are dead material.  This is a huge misconception.  In fact, bones are very much alive.  Bones are made up of tissue that takes on two forms.  These forms include compact or dense bone, and spongy or cancellous bone.  Compact bone is very hard and forms the outer part of all bones.  Spongy bone is contained inside the compact bone, it is lighter than compact bone, and is full of tiny holes throughout.  Bones are also made up of living cells.  These cells help the bone to grow and repair themselves.  Bone cells rely on blood to keep them  alive.  Just like other cells in the body, blood brings the bone food and oxygen and takes away the waste.  Bones are constantly growing and multiplying to repair any breaks.  When you break a bone blood clots form to close up the broken space.  Your body then transfers bone cells to the injured area to bridge the break.  Bones are very important; you can help to keep the skeleton strong by drinking milk and eating other dairy products.  These foods contain calcium which helps the bone to harden and become strong, therefore decreasing the chance for any breaks. 

            The bones of the body can be classified into four types.  These types include  long bones, short bones, flat bones, and irregular bones.  Long bones are defined as bones that are longer than they are wide.  These bones consist of a long shaft with two bulky ends and function primarily as levers.  They are composed mostly of compact bone, but have a large amount of spongy bone at the bulky ends.  Some types of long bones include the upper and lower limbs, for example the humerus, tibia, and femur or thigh bone.  The thigh bone is the longest bone in the human body and is about one quarter of our height.  The second type of bone is known as short bone.  These bones are short and cubed shape, and consist primarily of spongy bone covered by a thin layer of compact bone.  Short bones can be found in the bones of the wrist and ankle.  The next type of bones are called flat bones.  They are thin, flattened, and usually curved in shape.  This type of bone has a broad surface for the protection of organs and the attachment of muscles.  Examples of flat bones include the ribs, and cranial, or skull bones.  Lastly, are the bones known as irregular bones.  These are bones that can not be classified as long, short, or flat.  Irregular bones vary in their shape, size, and surface features, and are composed primarily of spongy bone covered with a thin layer of compact bone.  Examples of irregular bones include vertebrae and a few bones in the skull.  All bones are unique and usually contain holes, depressions, lines, or other markings.  These markings represent passage ways for vessels and nerves, or points of attachment for specific tendons, ligaments, or joints.

            The bones in the body would not move without muscles and joints.  A joint is the place where two bones come together.  These joints provide flexible connections between bones that enable us to move.  There are two main types of joints in the human body.  These include fixed joints and moving joints.  Fixed joints are fixed in place and don’t move at all. An example of a fixed joint are the sutures in the skull.  This joint fuses the bones together in a young child’s head.  The second type of joints are moving joints.  These joints allow you to twist, bend, and move various parts of the body.  There are six types of moveable joints.  These include ball and socket, condyloid, saddle, pivot, and gliding joints.  The ball and socket joint consists of the ball shaped end of one bone fitting into a small cuplike socket of another bone.  This joint allows for the greatest movement in any direction, including rotation.  The ball and socket joint can be found in the hip or shoulder of the human body.  The condyloid joint is an oval shaped joint that fits into the elliptical cavity of another bone, allowing for agular motion, but not rotation.  This joint is found between the fingers and the bones in the palm, as well as between the toes and the bones in the foot.  The third type of moveable joint is known as the saddle joint.  This joint occurs when the touching surfaces of two bones have both concave and convex regions, and the shapes of the bones complement one another.  This type of joint allows for a wide range of motion, but can only be found in the thumb of the human body.  The next moveable joint is known as the pivot joint.  This joint occurs when the rounded surface of one bone fits into the ring of another bone, or tendon allowing for rotation.  Pivot joints can be found in your wrists, neck, and ankles.  Did you know that humans and giraffes have the same number of bones in their neck?  The difference is the vertebrae in a giraffes neck are much longer than in a human neck.  The next  joint is known as the hinge joint.  This is a moveable joint that allows for movement in a single plain.  This joint occurs when the convex projection of one bone fits into the concave depression of another bone.  This joint permits flexion and extension, and can be found in your elbow and knee.  The last moveable joint is known as a gliding joint.  This joint occurs when the flat surface of one bone moves against another allowing sliding or twisting.  The gliding joint can be found in the carpal bones of the wrist and the tarsal bones of the ankle.  Joints play a very important role in the skeletal system.  You have over 230 moveable and semi-moveable joints in your entire body.  Together with your muscles these joints are what keep your body moving.

            In conclusion, the skeletal system gives us the shape we have, and the power to move.  It supports and protects the internal body organs and acts as a storehouse for minerals such as calcium.  The male and female differ slightly in their skeletal systems.  Males have thicker and longer legs and arms, where as females have a wider pelvis and wider space within the pelvis for babies to travel.  Whether male or female, young or old, everyone should take care of their skeletal system with exercise and good nutrition.  Just remember, be kind to your bones and they will treat you right.

 

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