The body’s natural healing takes place at all levels - from organs, to tissues, to individual cells.
An organism is an individual living system, like your brother, an oak tree, or an amoeba. In other words, an organism is a life form.
All organisms have these things in common. They can all:
- React to stimuli (things that happen to them)
- Grow
- Reproduce
Though they’re all similar in those ways, organisms vary wildly in their complexity. They can have anywhere from one cell (like bacteria) to many billions of cells divided into specialized tissues and organs (like us!).
An organ is a group of tissues that perform a function, as well as the associated blood vessels and extracellular matrix. A group of organs is called a system. For example, the heart, together with all the blood vessels in the body, is part of the cardiovascular system.
The heart is made up of a main tissue called the myocardium. It also has connective tissues, nerves, and blood vessels. The bone also contains several different types of tissues: compact bone, spongy bone, and bone marrow.
A tissue is a group of connected cells that perform the same function. The four main types of tissue are:
Epithelium tissue - layers of cells that line surfaces in the body. Examples include the skin and the inner lining of the gut.
Connective tissue – it connects other tissues. This is the tissue that contains the extracellular matrix. Examples include bone and blood.
Muscle tissue – muscles are what cause our bodies to move: either through the world spatially, such as walking, or in the body internally, like the beat of your heart or the peristaltic movements of your esophagus.
Nervous tissue – nervous tissue makes up the brain, spinal cord and nervous system.
Within a tissue, the cells may not be identical, but they still work together. For example, nervous tissue includes neurons, oligodendrocytes, astrocytes, and even more kinds of cells!
The extracellular matrix (ECM) is the structure surrounding and supporting cells within tissues. The ECM is like a natural scaffold for the cells. It’s made up of fibers and proteins that the cells themselves produce.
The ECM is what gives the tissue its shape. Bones are solid because their ECM is solid. Blood is liquid for the same reason. It’s not the cells themselves – cells are always soft, pliable sacs.
The cells and the ECM are intimately connected. The ECM’s composition changes depending on what the cells release into the environment. This change affects how the cells themselves behave. In particular, the ECM can contain growth factors that tell young cells what they’re supposed to be when they grow up.
As you can see, the ECM is as crucial to tissue growth and healing as the cells themselves! This natural scaffold is imitated in regenerative medicine, as scaffolds give stem cells a structure to grow on.
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