Learn more: http://www.khanacademy.org/video?v=uY2ZOsCnXIA
Understanding the structure of a muscle cell

Length: 16 minutes

Role of Phagocytes in Innate or Nonspecific Immunity

Length: 8 minutes

Types of immune responses: Innate and Adaptive. Humoral vs. Cell-Mediated

Length: 14 minutes

B Lymphocytes (B cells)