IB DP Biology: HL复习笔记11.2.4 Skills: The Human Elbow & Sarcomeres

• The human elbow is an articulated synovial joint which means that it is a junction where two moving bones meet encapsulated in synovial fluid
• It consists of several components which can be labelled on a diagram and annotated with descriptions of each structure in the following way:

The human elbow joint

• An accurate drawing of the sarcomere is a good way to demonstrate the relative movement of the muscle fibres during muscle contraction
• It also allows us to understand the visible bands seen in the images of muscle tissue in micrographs
• Some important considerations are as follows:
  • Z-lines mark either end of a sarcomere
  • Actin must be adjoined clearly to the z-lines and is thinner than the myosin
  • Myosin should be shown with the crossheads visible and should be thicker than actin
  • Light bands (around the z line) and dark bands (where the 2 filament types overlap) should be labelled

The sarcomere