The Song of the Cell: An Exploration of Medicine and the New Human

by Siddhartha Mukherjee

All cells come from cells. The first human cell gives rise to all human tissues. Ipso facto, every cell in the human body can be produced, in principle, from an embryonic cell (or stem cell). Although cells vary widely in their form and function, there are deep physiological similarities that run through them. These physiological similarities can be repurposed by cells for specialized functions. An immune cell uses its molecular apparatus for ingestion to eat microbes; a glial cell uses similar pathways to prune synapses in the brain. Systems of cells with specialized functions, communicating with each other through short- and long-range messages, can achieve powerful physiological functions that individual cells cannot achieve—for example, the healing of wounds, the signaling of metabolic states, sentience, cognition, homeostasis, immunity. The human body functions as a citizenship of cooperating cells. The disintegration of this citizenship tips us from wellness into disease. Cellular physiology is thus the basis for human physiology, and cellular pathology is the basis for human pathology. The processes of decay, repair, and rejuvenation in individual organs are idiosyncratic. Specialized cells in some organs are responsible for consistent repair and rejuvenation (blood rejuvenates through human adulthood, albeit at diminished rates), but other organs lack such cells (nerve cells rarely rejuvenate). The balance between injury/decay and repair/rejuvenation ultimately res...

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