Skeleton and Muscular Systems

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Skeleton and Muscular Systems

Skeleton System

  • Skull
  • Skull consists of two main parts – cranium and face.
  • Cranium is formed by 8 bones and provides a bony protection for the brain.
  • Face :
  • There are 14 bones which form the skeleton of the face.
  • There are also present 6 ear ossicles into skull.another bone is hyoid, which is horseshoe shaped present in neck between lower jaw and sound box it supports tongue. 
  • Ribs
  • Ribs are 12 pairs (12×2) of bony bars which form the sides of the chest cage. They protect the heart and lungs. 
  • Bone :
  • Bones have cells embedded in a mineralised (calcium) matrix and collagen fibres.
  • The spongy bone of the femur, humerus and sternum contains red marrow in which stem cells reproduce and form the cellular components of the blood and immune system. Yellow marrow at the centre of these bones, is used to store fats. The outer layer of the bones is known as the periosteum.
  • When fractures occur, the pain is carried to the brain by nerves running through the periosteum.
  • Sternum or breastbone :
  • It is a narrow, elongated and flattened structure, present just under the skin in the middle of front of the chest.
  • Joints
  • Synovial joints – movable joints : they are characterised by the presence of a closed space or cavity between the bones.
  • The Kind of joints are classified into six major categories
  • Plane (gliding joint) : present between carpals. Only sliding motion in all directions is allowed.
  • Hinge joint : present between knee point.
  • Pivot joint : present between atlas and axis.
  • Saddle joint : present between carpal and metacarpal.
  • Ball and socket joint : present between humerus and pectoral girdle.

Important points

  • 118 bones are present in both hands and legs, and 206 bones are present in the human body, while during childhood they were 300 bones.  The total number of bones of head- 29
  • Femur is the largest bony and stapes is the smallest bone in the human body.
  • Tendon joins muscle and bone together. Ligaments muscle (made up of yellow fibre) joins bone to bone.

Muscular System

  • Human body has about 639 types of muscles.
  • Striated muscles:
  • Also called skeleton muscles.
  • Each muscle fibre shows dark and light striations and is covered by a sheath, the sarcolemma.
  • Unstriated muscles:
  • These smooth muscles are involuntary muscles.
  • Single unit smooth muscles are present in the urinary bladder and gastrointestinal tract.
  • Multi unit smooth muscles are present in walls of large blood vessels.
  • Cardiac muscles :
  • They are involuntary striated and non fatigued fibres which are found in the wall of the heart where they form myocardium.
  • They generate their own wave of excitation.

Disorders of muscular and skeletal system


  • Myasthenia gravis : autoimmune disorder. It affects muscular transmission.
  • Muscular dystrophy : progressive skeletal muscle weakness, defects in muscle proteins, the death of muscle cells and tissue.
  • Rheumatoid arthritis : inflammation of synovial membrane.
  • Osteoarthritis : degeneration of articular cartilage.
  • Gout : caused by excess formation of uric acid and their deposition in the joints.
  • Osteoporosis : low bone mass, increased fragility and proneness to fracture.

Also Read:

circulatory system

digestive system

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