Skeletal System

• Skeletal system

  The system of bones, associated cartilages and joints of the human body. Together these structures form the human skeleton.
• Skeleton


  The hard framework of the human body around which the entire body is built.
• Joints


  • They make the hard and rigid skeleton allow different types of movements at different locations. If the skeleton were without joints, no movement would have taken place and the significance of the human body would be no more than a stone.
• Components of the human skeleton

  • Bones
  • Cartilages
  • Joints
• Bone


  A tough and rigid form of connective tissue. It is the weight bearing organ of the human body and it is responsible for almost all strength of the human skeleton.
• Types of bones


  • Long bones
  • Short bones
  • Flat bones
  • Irregular bones
  • Sesamoid bones
• Long bones


  • Typically have an elongated shaft and two expanded ends one on either side of the shaft. The shaft is known as diaphysis and the ends are called epiphyses.

  
• Short bones


  • Short in posture and can be of any shape. Most of them are named according to their shape. All the carpal and tarsal bones are included in this category.
• Flat bones


  • Flat in appearance and have two prominent surfaces. They resemble shallow plates and form boundaries of certain body cavities. Examples are scapula, ribs, sternum.
• Irregular bones


  • The shape of these bones is completely irregular and they do not fit into any category of shape. Examples are vertebrae, hip bone and bones in the base of skull.
• Sesamoid bones


  • Not like the other types of bones because they are in the form of nodules embedded in tendons and joint capsules. Examples are patella, pisiform and fabella.
• Types of bone tissue


  • Compact or dense bone
  • Cancellous or spongy bone
• Cartilage


  A form of connective tissue but is not as tough and rigid as bone. The main difference in cartilage and bone is the mineralization factor. Bones are highly mineralized with calcium salts while cartilages are not.
• Types of cartilage


  • Hyaline cartilage
  • Fibrous cartilage
  • Elastic cartilage
• Hyaline cartilage


  • Has very thin fibers having same refractive index as the matrix of the cartilage and thus these fibers are not seen. It is the articular cartilage of long bones, sternum, ribs etc. Its color is bluish white and it is flexible.
• Fibrous cartilage


  • Has numerous white fibers. It is present in the symphysis pubis, and sternoclavicular joint etc. Its color is glistening white and the appearance is opaque.
• Elastic cartilage


  • Has numerous yellow elastic fibers. It is present in the ear pinna, external auditory meatus, eustachian tubes, and epiglottis etc. Its color is yellowish and then appearance is opaque.
• Joints


  Important components of the human skeleton because they make the human skeleton mobile. A joint occurs between "two or more bones", "bone and cartilage" and "cartilage and cartilage".
• Divisions of the human skeleton

  • Axial skeleton
  • Appendicular skeleton
• Axial skeleton


  • Forms the axis of the human body. It consists of skull, vertebral column and thoracic cage.
• Appendicular skeleton


  • The skeleton of appendages of the human body. It consists of shoulder girdle, skeleton of upper limb, pelvic girdle and skeleton of lower limb.
• Functions of the human skeleton

  • Strength, support and shape
  • Protection of delicate organs
  • Leverage for movements
  • Production of red blood cells
• Strength, support and shape

  It gives strength, support and shape to the body. Without a hard and rigid skeletal system, the human body cannot stand upright, and it will become just a bag of soft tissue without any proper shape.
• Protection of delicate organs

  In areas like the rib cage and skull, the skeleton protects inner soft but vital organs like the heart and brain from external shocks. Any damage to these organs can prove fatal, therefore a protective function of the skeleton is very important.
• Leverage for movements


  Bones of the human skeleton in all parts of the body provide attachment to the muscles. These muscles provide motor power for producing movements of body parts. In these movements the parts of the skeleton acts like levers of different types thus producing movements according to the needs of the human body.
• Production of red blood cells

  Bones like the sternum, and heads of tibia have haematopoietic activity (blood cells production). These are the sites of production of new blood cells.