14 : Support & Movement in Humans and Animals

• There are three types of skeletons - exoskeleton, endoskeleton, hydrostatic skeleton
• Exoskeleton is found in insects and crabs
• Exoskeleton support and protect body organs and enable these animals to move
• Hydrostatic skeleton is found on animals with soft tissues such as earthworms
• Hydrostatic skeleton maintain a rigid body shape
• Endoskeleton maintains body shape, support soft body tissues and protect internal organs from injury
• Axial skeleton comprises the skull, vertebral column, ribs and sternum (breastbone)
• Appendicular skeleton includes the pectoral girdle, pelvic girdle, upper and lower limbs
• Lumbar vertebrae are the biggest and strongest vertebrae
• Caudal vertebrae are four bones fused together to form a triangular structure which is pointed at one end
• Sacral vertebrae are five vertebrae fused together to form a triangular bone
• Thoracic vertebrae possess a long spinous process
• Spinous and transverse processes serve as attachment sites for muscle and ligaments
• Lumbar vertebrae possess a short spinous process
• Lumbar vertebrae possess a large centrum to bear the weight of the lower back of the body
• Atlas vertebra is the first cervical vertebra
• Axial vertebra is the second cervical vertebra
• Freely movable joints allow free movements
• Capsule is the fibrous tissue that encloses and provides protection to the joint
• Cartilage serves as a cushion to the joint, absorbs shocks and reduces friction between bone ends
• Cartilage protects the bone from wearing out
• Synovial membrane secretes synovial fluid into the synovial cavity
• Synovial fluid serves as lubricant that reduces the friction between the ends of bones
• Ball-and-socket joint allows rotational movement in all directions (360 degrees)
• Hinge joint allows the movement of bones in one plane (180 degrees)
• Arm straightening

  • Triceps contracts
  • Biceps relaxes
  • Pull force is transmitted to the ulna
  • Ulna is pulled downwards
• Arm bending

  • Biceps contracts
  • Triceps relaxes
  • Pull force is transmitted to the radius
  • Radius is pulled upwards
• Describe the first step of leg movement.

  • The right calf muscle contracts - heel is lifted
  • Ball of the foot pushes against the ground

  
• Describe the second step of leg movement

  • Biceps femoris contracts - foot is bended at the knee joint
  • Right leg is lifted
• Describe the third step of leg movement

  • Right leg leaves the ground
  • Body weight is supported by left leg that is on the ground
  • Quadriceps femoris contracts to straighten the leg