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Biology Homework Help: Artificial Skin
Artificial SkinThe skin produced in vitro is in fact only the epidermis portion of skin; when the epidermis is applied to the burnt area, it leads to the regeneration of dermis (the remaining parts of skin) underneath. But improvements in the techniques have permitted the reconstitution of virtually complete skin (both epidermis and dermis), called living skin equivalent (LSE); this technology employs a collagen matrix as a support for growth of the tissue. According to homework help service the skin explants used for obtaining artificial skin may be either obtained from the patient concerned or from the foreskin (loose skin from the tip of penis) of newborn babies. Skin cells of new-borns grow more vigorously than adult skin; the use of a synthetic polymer called PGA allows the newborn skin to grow without scars. Artificial skin from newborn skin explants is used to cover the wound till the patient’s skin is cultured and artificial skin is obtained for grafting.
The production of artificial skin, in simple terms, is as follows and is essentially cell and not organ culture. The bulk (Ca 90%) of epidermis is constituted by cells called keratinocytes which produce the dead cells (corneocytes) making up the outermost cornified layers of skin. The keratinocytes are dissociated by treating the skin explant with trypsin. These cells are cultured in vessels the bottom of which is covered with irradiated 3T3 fibroblast cell line; this is because certain products from fibroblast cells facilitate the proliferation of keratinocytes. Keratinocytes grow to form colonies, which are again dissociated into single cells and cultured in the same manner. According to studydaddy.com/homeworks-answers the process is repeated till a confluent sheet of pure epithelium is formed; this sheet is detached from the culture vessels, cleaned and used for grafting. The explant for preparing artificial skin for the graft must come from the patient himself to avoid rejection. A 3 cm2 skin explant can yield about 1.7 m2 artificial skin in 3-4 weeks representing a 5000-fold increase. In about 5 years after grafting of the artificial skin, all the essential components of skin are regenerated. Artificial skin grafts have been used to successfully repair several type of skin defects, including chronic skin ulcers.
Animal Tissue Culture
The term tissue culture refers to the culture of whole organs, tissue fragments as well as dispersed cells on a suitable nutrient medium. It can be divided into (1) organ culture and (2) cell culture mainly on the basis of whether the tissue organisation is retained or not. In organ cultures whole embryonic organs or small tissue fragments are cultured in vitro in such a manner that they retain their tissue architecture. In contrast, cell cultures are obtained either by enzymatic or mechanical dispersed of tissues into individual cells or by spontaneous migration of cells from an explants; they are maintained as attached monolayers or as cell suspensions.
Freshly isolated cell cultures are called primary cultures; they are usually heterogeneous and slow growing, but are more representative of the tissue of their origin both in cell type and properties. According to studydaddy once a primary culture is subcultured, it given rise to cell lines which may either die after several subcultures (such cell lines are known as finite cell lines) or may continue to grow indefinitely (these are called continuous cell lines). Usually normal tissues give rise to finite cell lines, while tumours give rise to continuous cell lines. But there are several examples of continuous cell lines which were derived from normal tissues and are themselves non-tumorigenic, e.g. MDCK dog kidney, 3T3 fibroblasts etc. The evolution of continuous cell lines from primary cultures is supposed to involve a mutation which alters their properties as compared to those of finite lines.
The beginning of animal tissue culture can be traced to 1880 when Arnold showed that leucocytes can divide outside the body. Later in 1903, Jolly studied the behaviour of animal tissue explants immersed in serum. Lymph or ascites fluid. In 1907, Harrison cultured frog tadpole spinal cord in a lymph drop hanging from a cover slip into the cavity on microscopic slide; this is regarded as the turning point. Subsequently in 1913, Carrel developed a complicated methodology for maintaining cultures free from contamination, especially by bacteria. Subsequently, suitable culture media were developed and the techniques of cell culture were refined. More resources:
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