When I first think of the word “skin”, I think of human skin, and how vital skin is to our survival. According to the Stanford Children’s Health website, skin serves as a protective shield against heat, light, injury, and infection for the human body. It regulates body temperature, stores fat and water, prevents water loss, and acts as barrier between us and the environment. When I think of the word “bark”, and how it relates to “skin”, I think how bark is the skin of trees, and how it is as equally vital to their survival. According to the U.S. Department of Agriculture’s website, the tree’s outer bark is its protection from the outside world. Similar to how human skin heals and regenerates, bark continually renewed from within and prevents moisture from escaping in dry air.
Comparing human skin and tree bark makes one reflect on how humans and tree are both organisms on this earth how nature has evolved us to use similar methods for survival. Both of our species has a place on this planet, so it is important for us to recognize the importance of deforestation and how it effects our ecosystem.
Layers of human skin
The epidermis is the thin outer layer of the skin. It consists of 3 types of cells:
- Squamous cells. The outermost layer is continuously shed is called the stratum corneum.
- Basal cells. Basal cells are found just under the squamous cells, at the base of the epidermis.
- Melanocytes. Melanocytes are also found at the base of the epidermis and make melanin. This gives the skin its color.
The dermis is the middle layer of the skin. The dermis contains the following:
- Blood vessels
- Lymph vessels
- Hair follicles
- Sweat glands
- Collagen bundles
- Fibroblasts
- Nerves
- Sebaceous glands
The dermis is held together by a protein called collagen. This layergives skin flexibility and strength. The dermis also contains pain and touch receptors.
The subcutaneous fat layer is the deepest layer of skin. It consists of a network of collagen and fat cells. It helps conserve the body’s heat and protects the body from injury by acting as a shock absorber.
Layers of tree bark
The outer bark is the tree’s protection from the outside world. Continually renewed from within, it helps keep out moisture in the rain, and prevents the tree from losing moisture when the air is dry. It insulates against cold and heat and wards off insect enemies.
The inner bark, or “phloem”, is pipeline through which food is passed to the rest of the tree. It lives for only a short time, then dies and turns to cork to become part of the protective outer bark.
The cambium cell layer is the growing part of the trunk. It annually produces new bark and new wood in response to hormones that pass down through the phloem with food from the leaves. These hormones, called “auxins”, stimulate growth in cells. Auxins are produced by leaf buds at the ends of branches as soon as they start growing in spring.
Sapwood is the tree’s pipeline for water moving up to the leaves. Sapwood is new wood. As newer rings of sapwood are laid down, inner cells lose their vitality and turn to heartwood.
Heartwood is the central, supporting pillar of the tree. Although dead, it will not decay or lose strength while the outer layers are intact. A composite of hollow, needlelike cellulose fibers bound together by a chemical glue called lignin, it is in many ways as strong as steel. A piece 12” long and 1” by 2” in cross section set vertically can support a weight of twenty tons!
Experimental making
I juxtaposed two close-up images of a tree and human to show the similarities of the patterns are created on both tree and human skin.
So how to dig into this topic – where to find/make meaning? I am curious if you came across any uses/applications for bark (human and non-human) and what kind of a system might encompass bark (or an aspect of bark) aside from it’s factual role in the physiology of a tree.
When reading Rene Croteau’s The analogy of skin in architecture revisited and the Eyes of the Skin art exhibition, I thought of how your topic “bark” might fit into the analysis. These two readings both mentioned the concept of “layers,” “layering” being a crucial part of the skin, which is also like what you pointed out in your analysis of human skin. But when drawing a comparison between architecture and skin, I can see how trees can be analyzed like that as well. I am curious about the function of bark as for the whole tree, and their play in Eastern medicine. I believe trees die soon once they lose their bark, so I’m also curious if there are sustainable ways for us to utilize the bark without killing a tree that took decades to grow.