The entire human body is made up of water and a compound of chemical components. Important building blocks are the cells, the so-called spark plugs of the body. A collection of differentiated cells constitutes the tissue, with the cells performing similar tasks to the tissue itself to enable the body’s processes and form the necessary building material for the organs. In general, most of the body’s cells are grouped into tissues, making up, for example, muscle and nerve tissue. In contrast to this are the germ cells. They do not form tissue.
What is tissue?
Generally speaking, tissue is a functional unit composed of cells that makes possible the construction of higher levels of hierarchy, such as that of organs. Especially for cell growth, the overall organization of cells in tissue is significant, because cells in joint activity react differently than the individual cell.
Anatomy and structure
Throughout the organism, there are several types of tissue that can be divided into four main groups. Skin tissue, also called epithelial tissue, occupies the outer and inner surfaces. Supporting or connective tissue holds organs, bones and body parts in place and connects them. Interstitial spaces are filled, including fatty tissue, bone or cartilage. New tissues for blood and free cells are also formed here. Muscle tissue is responsible for active movement and nerve tissue is used to form cells that keep the brain, spinal cord and nerves working. Lymph and blood can also be counted among the basic tissues. Even the organs are composed of intermediate and functional tissues. Different types of tissues usually work together in the construction of organs. Muscle is composed of connective and muscular tissue, skin is composed of connective and epithelial tissue. Different types of tissue are different in cell wall composition, content and shape. In plants, the more tissue types it has, the better adaptation to the environment it shows. Plants consist of two different tissue types. If the embryonic cells are capable of division, we speak of a formative tissue; if the cells are not capable of division, we speak of a permanent tissue. This in turn has a ground tissue consisting of parenchyma, collenchyma (strengthening tissue of living cells and cell walls capable of elongation) and sclerenchyma (strengthening tissue of dead cells and thickened cell walls), a terminal tissue consisting of epidermis and periderm, and a guiding tissue, which in turn is composed of xylem and phloem.
Function and tasks
The study and investigation of tissue is called histology. The exact mechanisms of tissue formation are largely analyzed and are not fully understood. Histology was founded by the anatomist and physiologist Xavier Bichat at the end of the 18th century, who discovered various types of tissue in the human organism and yet was able to describe twenty-one of them without the benefit of a microscope. He himself lived to be only thirty years old and died of tuberculosis. Even today, histology examines tissue samples. They are viewed under a light microscope as microscopic and stained tissue sections. From this, early diagnoses can be made about, for example, benign and malignant tumors or metabolic diseases, which can then be treated in time. Especially in medicine, every removed tissue must be examined. Findings are particularly important when it comes to the malignancy of a tissue change.
Diseases
Pathological changes in tissues are in turn studied by histopathology. The origin of this field can be traced back to Johannes Müller, who wrote in 1838 about structural properties of cancer, among other things. The actual founder was the German physician Rudolf Virchow. Histopathology belongs to the field of pathology and deals with the microscopic, fine-tissue aspect of pathological physical changes. The task is the analysis of tissue samples of the various organs, with the aim of a precise assessment and diagnosis. Here, too, stained tissue sections are used, which are specifically examined by a pathologist for changes. Imaging under the microscope is enhanced by molecular biology and biochemical methods. From this, the appropriate therapy, prognosis and response to drugs can be derived. Human tissue in particular is extremely susceptible to changes and causes various cancers, e.g. skin cancer. It is now possible to create artificial tissue.For example, it has already been possible to grow a human muscle by using muscle precursor cells. Although the cells were already beyond the stem cell stage, they could not yet be called muscle cells. Muscle fibers formed from them. In medicine, researchers are currently trying to rebuild damaged organs. Biological tissue such as skin or cartilage are used in the healing process and can also be artificially grown if the tissue loss is too great. This is done through what is known as TE – tissue engineering, an umbrella term for the production of artificial tissues through the cultivation of human cells, whereby entire organs or parts thereof are reconstructed from human cells. These help to regenerate or completely replace diseased tissue, preserve, renew or simply improve tissue function. In TE, cells taken from the donor organism are multiplied in a laboratory. This can be done as a rush of cells through two- or three-dimensional cell scaffolds, which are then transplanted back into the diseased tissue. This restores a tissue function. The cultivation of the tissue is therefore problematic because it must be ensured that the cells retain their specific functionality. Vessels, for example, must be able to build up a tissue. This has been achieved, for example, by growing differentiated cells in blood vessels, skin and cartilage tissue. Research is also being done with replacement tissue, e.g. from another human or an animal. TE has been successful with tissue from one type of cell, such as the tissue of cartilage.
