You cells are the smallest unit of your body and are responsible for the most fundamental processes in life, such as breathing, moving and reproducing.
Every tissue in your body is made up of groups of cells with specialized functions, linked by intricate systems of communication; there are more than 200 different types of cells in the body. The final structure of the body, although very complex, is generated by a limited repertoire of cell activities. Most cells grow, divide and die while performing functions that are particular to their tissue type, such as the contraction of muscle cells.
In the vast majority of cases, you cells contain structural elements called organelles, which are involved in each cell’s metabolism and life cycle. This includes the uptake of nutrients, cell division and the synthesis of proteins.
Living cells in the body have a finite life. In many tissues, this means cells must be replaced regularly.
This is the term used to describe replacing injured or dead cells. The rate, at which this occurs, if at all, is variable between tissue types. For example, the lining cells of the esophagus have a rapid turnover, whereas the nerve cells that transmit signals in the brain and the spinal cord cannot replicate themselves at all. Other cells only divide when stimulated by injury or disease.
Scarring occurs following injury when the tissue cells cannot be replaced with functionally identical cells and instead fibrous tissue cells multiply in their place. Damaged tissues are vulnerable during the repair process and, when scar tissue forms, there may be contraction of the wound as can be found with skin injuries.
Massage should be avoided until the healing process is complete. In the case of skin wounds, applying force across the healing wound can damage scar fibers and interrupt healing, leading to a permanent scar. Once healing is complete, massage can help to soften scar tissue.
A tissue is a collection of similar cells. Each cell type has a set of distinctive characteristics relating to its specific function.
All cells in the body derive from the single fertilized egg, which multiplies rapidly into a cluster of genetically identical daughter cells. Early on in the development of the embryo, however, the cells that are a product of that single egg cell’s reproduction begin to specialize, some becoming nerve cells, some muscles cells, and some blood cells and so on. The process by which cells acquire distinctive feature is called cell differentiation.
The main features of cells include:
Structural variations
Cells may be many shapes depending on their specific function, including cuboidal, flattened, branched, round, oval, spindle-shaped, star-shaped, columnar or disc-shaped.
Extracellular material
Cells may be closely packed or spread out due to the presence of extracellular material, such as fibers, gel or fluid.
Ability to divide
Not all cells can divide once differentiated; for example, red blood and verve cells.
Excitability
Some cells react by moving or by generating electrical activity in response to changes outside the cell. Muscle and nerve cells are good examples of this behavior.
Producing proteins
Most cells make proteins, but the repertoire of chemicals can be restricted and specific; for example, only certain cells situated in the pancreas are responsible for producing insulin.
Every cell is covered in a membrane, which is a barrier between the inside and outside of the cell. Some molecules pass through it, while others have either restricted or no access. By determining which chemicals are allowed in and out of the cell, the cell controls its internal environment and can communicate with other cells.
Oils are absorbed and used by the skin cells because they are lipid-soluble, so are able to penetrate and enter the phospholipid layer
