Skeletal System

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Skeletal System

• Bones - the organs of the skeletal system.

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2 Divisions

• The human skeleton has two divisions
• Axial skeleton Consist of the skull, vertebrate
  column, and the rib cage
• The Appendicular Skeleton - Consist the bones of
  the arms and legs, shoulder, and the pelvic
  girdle .
• The Skeleton of Humans is composed of a special
  connective tissue called BONE
• There are 206 bones in the human body

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Meet BONES
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Functions of the Skeletal System

• support - it forms the body's framework to
  support the muscles and organs.
• protection - the skeletal systems protects by
• 1) forming the bony cavities around organs,
• the thoracic cavity protects the heart and lungs
• the cranial cavity protects the brain.
• 2) the yellow marrow in bones produces white
  blood cells which protect against invading
  microorganisms.
• movement - bones form joints which provide levers
  for movement such as walking, lifting, etc.
• hematopoiesis (blood cell production) - the red
  marrow produces red blood cells.
• mineral storage and homeostasis - the skeleton
  forms a reservoir of minerals, especially
  calcium, for maintenance of homeostasis.

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2 Basic types of bone tissue

• 1. Compact bone - dense, smooth. Contains few
  spaces. Covers spongy bone tissue. Provides
  protection and support and helps long bones
  resist stress of weight.
• 2. Spongy bone - composed of small needle-like
  pieces and open spaces filled with red marrow.
  Makes up most of short, flat and irregular shaped
  bones and most of the epiphysis of long bones.
• Bones are classified by their shape
• 1. Long bones (humerus, femur)2. Flat bones
  (skull)3. Short bones (fingers)4. Irregular
  bones (vertebrae)

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Joints

• JOINTS WHERE TWO BONES MEET
• Cartilage is responsible for keeping bones far
  enough apart so they do not rub against each
  other as they move. At the same time, joints hold
  the bones in place.
• Joints work by attaching muscles which work in in
  pairs - ANTOGONISTIC MUSCLES - flexors
  extensors
• Muscles attach to bone via connective tissue
  called TENDONS
• Bones attach to bones via connective tissue
  called LIGAMENTS

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There are two kinds of joints

• IMMOVABLE JOINT
• THEY ARE OFTEN CALLED FIXED JOINTS, AND ALLOW NO
  MOVEMENT BETWEEN BONES.
• These joints are interlocked and held together by
  Connective Tissue, or they are fused together.
• The places where the bones of the SKULL meet
  (SUTURE) meet are examples of immovable joints.
• Immovable joints are located in bones of the
  skulls and the ribs
• 2. MOVABLE JOINTS
• MOST OF THE JOINTS OF THE BODY ARE FREELY
  MOVABLE JOINTS.
• In Freely Movable Joints, the ends of the bones
  are covered with a layer of Cartilage that
  provides a smooth surface at the joint. Joints
  are a place where two or more bones come
  together.
• Examples are the ball-and-socket, pivot, hinge,
  and gliding

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Moveable JointsBall-and-socket joint

• Ball-and-socket joints allow the greatest range
  of motion. They can be found in the shoulder
  where the top of the arm bone fits into the deep,
  bowl-like socket of the scapula (shoulder blade).
  
• This joint allows you to swing your arm freely in
  a circle, your hips also have ball-and-socket
  joints

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Moveable JointsHinge joint

• Permits a back-and-forth motion.
• The Knee enables your leg to flex and extend.
• The Elbow, which allows you to move your forearm
  toward and away from your body.

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Moveable JointsPivot Joint

• A pivot joint allows one bone to rotate around
  another
• A pivot joint can be found in the top of your
  neck, which gives you limited ability to turn
  your head from side to side

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Moveable JointsGliding Joint

• A gliding joint allows one bone to slide over
  another bone
• The joint located in your wrist is an example of
  a gliding joint this joint enables you to bend
  and flex your wrist, as well as make limited
  side-to-side motions.

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Joint Activity

• What types of joints are involved in the
  following activities
• 1. Move your arm in a circle
• 2. Push open a door
• 3. Lift a book off the table
• 4. Kneel down
• 5. Wave your hand
• 6. Twist your head from side to side

• Answers
• 1. Arm ball-and-socket joint
• 2. Door hinge joint (elbow)
• 3. Book Gliding joint (wrist)
• 4. Kneeling hinge joint (knee)
• 5. Hand gliding joint (wrist)
• 6. Head Pivot joint (neck)