Skeletal System

(not anatomically correct)

      Bones, obviously, are the body's framework and support system.  They provide a "case" for the organs of the body, allow movement with muscles, store essential minerals, and allow blood cell formation. Though bones are often thought of as perfectly smooth rounded pieces they're really not.  There are various bulges, depressions, and holes that allow muscles and tendons to attach and join.

        Bones and cartilage are everywhere in the body.  There are three types of cartilage Hyaline, Elastic, and Fibrocartilage.  Hyaline cartilage is biggest portion of of skeletal cartilage.  It not only supports but is  resilient and flexible.  It can also be seen in articular, costal, respiratory, and nasal cartilage.  Elastic cartilage is quite similar to hyaline but is seen more in the epiglottis and ear areas.  Finally Fibrocartilage, this cartilage contains collagen fibers and is thus one of the strongest types of cartilage.  This type of cartilage is found in the knee as well as the intervertebral discs.  In order to create cartilage it must go through 3 phases, Appositional, Interstitial, and calcification.

             The bones of the body are classified into many sections.  Axial are the bones of the skull, vertebra, and ribs.  Appendicular, like the name implies, make up the appendages-arms and legs.  They are then classified by shape.  Long Bones are obviously longer than they are wide.  There are then short bones that can be cube shaped these can be found in the wrist and ankle areas.  Flat Bones are tin and...flat, and occasionally curved.  Lastly Irregular bones, which are basically everything that can't fit into any of the other categories.  These bones are oddly shaped and complicated.  

        There are many, many markings on the the bones which include: Tuberosity which is a rounded projection, Crest a narrow ridge of bone, Trochanter a large blunt irregular surface, and Line a ridge of bone.  Tubercle is a small rounded area, Epicondyle is the raised area above the condyle, a Spine is a sharp area, and Process is obvious prominence.  The Head is a bony expansion carried on a narrow neck, a Facet is a smooth flat area, a Condyle is a rounded projection, a Ramus is an arm like bar of bone.  The Meatus is a canal, Sinus is a basic cavity, Fossa is a basin like depression, a Groove is a furrow, a Fissure is narrow slit, and the Foramen is a round opening in bone.

               Bones are also classified with textures such as compact bone which is the dense outer layer, and spongy bone which is honeycomb like.  Bones are then classified into structures such as long bones that consist of diaphysis and an epiphysis, diaphysis is a shaft that forms the axis of bones.  Epiphyses are the expansions of long bones the inside is spongy and the joint surface is covered with articular cartilage.  The epiphyseal line separates these two sections.  The structure of short, flat, and irregular bones is, on the other hand, quite different.  They are thin sections of periosteum covered in compact bone on the outer section with endosteum, on the opposite side is spongey bone.  These bones do not have diaphysis or epiphyses and contain marrow between the trabeculae.  The microscopic strucure of the compact bone is the aversion system or the structural unit.  The Lamella is the weight bearing column, and the Haversian is the central canal that contains blood vessels and nerves.  Volkmann's canal are channels lying at right angles to the central canal connecting blood and nerve supply.  Osteocytes are mature bone cells and Launae are tiny cavities that hold the osteocytes.  And Canaliculi are hairlike canals that connect lacunae to the central canal.  Hydroxyapatites are mineral salts that make up more than half of the bone mass.  Since it's a salt it's mainly calcium phosphates which is thus responsible for the hardness of bones.  

          Bone development begins in embryos and doesn't stop until early adulthood, the process of of bone formation is called Osteogensis and Ossification.  Ossification forms most flat bones, the skull and clavicles.  This process is located mainly in the center of the fibrous connective tissues membranes.  The bone matrix is set within the fibrous membrane.  The woven bone and periosteum forms and the collar bone of compact bone forms and red marrow appears. Long bone's growth zone is when the cartilage cells undergo mitosis this results in the separation of epiphysis and diaphysis.  It then undergoes the transformation where old cells enlarge and the matrix becomes calcified.  The Cartilage cells then die and the matrix begins to deteriorate.  The Osteogenic zone is when new bone forms after the deterioration of the matrix.  Bone growth is most active during youth and adolescence.  The epiphyseal plate or growth plate is quite active.  When the person is fully grown the growth plate closes, or seals.


Spiral Fracture

           Obviously the stress we put our bodies under is tremendous.  Our bones are put to the test on a daily basis, some far more than others.  Which is why our bones simply give out under such stress.  Breaking bones isn't uncommon and they come in a whole array of forms.  Breaks can range anywhere from a tiny, but still painful, hairline fracture, to a compound fracture, which is most severe...and revolting.  Bone breaks are classified by the position of the bone after break, the completeness of the break, the orientation of the bone in comparison to the long axis, and if the bone penetrates the skin (compound).  Within these classifications there are more condensed classifications as to what type of break it is.  For example there is displaced and non-displaced also known as a dislocation, where the bone slips out of its typical position.  Complete and incomplete where the bone is either broken all the way through or not.  Linear where the bone breaks parallel to the axis of the bone, and Transverse where it is perpendicular to the axis.  Compound fractures penetrate the skin and Simple does not.  Typical types of fractures are Comminuted where the bone breaks into several pieces, ew!  A spiral fracture where it twists throughout the bone.  My dance teacher suffered this type of fracture just before she was to go to London to dance with the Royal Danish Ballet,  it's tragic, I don't know how she could have taken it so well, her career as a dancer slipping away so quickly...Anywho,  Depressed fractures are sections where the bone is pressed inward.  A compression is where the bone is entirely crushed, again ew!  Epiphyseal is where the epiphysis seperates from the diaphysis.  Greenstick is a partial break where the bone breaks some of the way through but not all the way, these are particularly common in children because their bone are so pliable.  A bone heals itself by first forming hematoma at the break this causes swelling.  Fibrocartilaginous then begins forming then granulation tissue forms finally capillaries begin to grow through again phagocytic cells begin cleaning.  All of this is typically done while the bone is supported/structured by a cast or splint of some sort in order the help the bone heal properly.

         Bone breakage is caused not only by serious amounts of force are placed on the bone but also an inadequate diet causing weakness in bones, this is called Osteomalacia.  Rickets are deformations in the bones, commonly seen in children.  Osteoporosis is when the bones become incredibly fragile and brittle.  This is caused when bone reabsorbing outpaces bone deposit.  Osteoporosis is most commonly seen in postmenopausal women.
       Bones can also believe it or not, bruise.  Bruising is caused similar to breaking where a huge amount of force is placed on a certain area.  Bruising typically occurs withing the marrow or withing the structures of the joints.  Several years ago when I was still competing in gymnastics I was warming up as I did every day.  We were going back and forth across the floor.  Our last warm up before we went to our events was a simple round-off, back handspring, back tuck.  When I came down out of my tuck I landed a bit funny, like I rolled out of it on my heels.  I felt an immediate sharp pain.  I have a fairly high tolerance for pain so I thought I would be able to just walk it off.  I tried rolling my ankle, thinking that maybe I just needed to pop it.  When I tried walking again the pain persisted.  I didn't want to be hurt I wanted to keep working out, but the pain in my heel was persistent.  So I was forced to condition on bars for the rest of the night.  I went home and lazed about.  When I needed to get up I forgot about my foot and tried bounding off of the couch, not my best idea, the sharp pain pierced through my heel again.  I lay on the floor a moment holding my foot, this is so stupid I thought.  Before too long I was taken to the doctor's office to have it looked at.  After quite a bit squeezing and poking and a couple of X-Rays the doctors concluded that I had damaged my growth plate.  They were unsure of what exactly I had done because the pain seemed to be right on my growth plates; and growth plates, until they are sealed, cannot be seen on an X-Ray.  It was most likely that I had either bruised it or received a hair line fracture.  They ended up suiting me up with a clunky boot for the next 3 weeks, not what I wanted.  After some of the injuries I've seen however, I should consider myself lucky.  I thought about adding a video here but then I thought, breaking bones is rather horrific, and I really have no intention of screening videos of people breaking themselves.  So I'm going to leave it up to you, the reader, to explore the world of these graphic examples on your own time.