What are the steps involved in primary and secondary cell culture?

There are 5 steps involved in primary cell culture: tissue collection, tissue processing, cell isolation, cell culture, and cell characterization in that order respectively. In the first step, tissue is collected from the target organism, usually by excision or biopsy. In the second step, the collected tissue is processed to isolate primary target cells. Enzymatic digestion, or mechanical disruption may both be involved depending on the cell type. In step three, the primary cells are isolated from the processed tissue using techniques like filtration, or centrifugation. In step four, the isolated primary cells are then placed into a culture with an appropriate growth medium that provides necessary nutrients for cell growth and proliferation. The last step is cell characterization, and primary cells are characterized by analyzing their morphology, chemical properties, and growth rate.    

In secondary cell culture, there are 4 general steps involved: passage, subculture, cell banking, and cell characterization in that order respectively. During passage, primary cells are detached from the cell culture using trypsinization and placed into a new culture at a lower density. This is done to maintain the cell's proliferative capacity. In step two, the process of passage is repeated several times to create a cell line, this is known as subculture. In step 3, the cell line is stored in liquid nitrogen for long term storage. In the last step, the secondary cells are characterized again by analyzing their morphology, chemical properties, and growth rate.