Cells and Tissues
Imagine this: if each cell in our body was represented by a one-meter step, we would have to circle the earth over one million times to account for all our cells. It seems absurd, but it’s true. We are each composed of between 50 and 100 trillion cells!
As I continue to report on my study of Human Anatomy and Physiology by Elaine Marieb, I move from chemistry to structural components. Cell theory was developed in the late 1800s and is based on four core elements:
- The cell is the basic unit of living organisms,
- Organisms depend on both individual and combined activities of its cells,
- The activities of cells are dictated by their shape and number of structures they contain, and
- Cells arise from other cells.
Restated, our 50+ trillion cells are the body’s building blocks, they don’t stand alone, they look different and do different things, and they’re self perpetuating. Cells have membranes that allow solutions to move in or out and have specialized organelles, such as mitochondria, which provide the energy for all we do. The nucleus is where our DNA (what makes us us!) lives and cell division happens, without which we would literally be one and done!
As I read through the chapters on cells and tissues, I was once again mesmerized by the intricate nature of our bodies and how narrow a range of conditions must exist for life to prevail. If our chemical and thermal balance (homeostasis) is thrown off, either we come back into balance or we’re history!
After pouring through cell theory and function, the text turns to tissues, which are groups of similar cells that generally perform a common function. You’re no doubt familiar with the four types of tissue: connective (e.g., bones and tendons), muscle (e.g., skeletal and heart), nervous (e.g., our brain, spinal cord, and beacoup nerves throughout), and epithelial (e.g., skin and organ linings). These various tissues interact and depend on each other and their structure directly relates to function. There can’t be rogue players in a healthy body – it’s a total team sport.
The chapter on tissues finishes with something near and dear to all runners — tissue injury and regeneration. We’re all too familiar with inflammation. Lots goes on during this stage as the body responds to intrusions and goes to work to isolate and remove unwanted stuff. Then organization begins, which establishes a new network for blood flow. Finally is regeneration — new tissue forms, sometimes leaving a layer of scar tissue in its path, which we only see if it’s on our skin. Many of us know too well that lingering scar tissue in our hamstrings has a way of haunting us! Some tissues, such as skin, regenerate quickly, while others like muscle and bone take longer. Unfortunately most destroyed brain tissue is lost forever.
The takeaway from this blog post is we are super complicated beasts with many moving pieces that must communicate with each other and work together. And there is good reason why rest may be the best prescription for recovery. The body has work to do and we best give it the time and space to do that!