2
1 Methods Describing the Interaction of Laser Radiation with Biological Tissues
1.2 The Structure and Optical Properties of Biological
Tissues
From the point of view of controlling the optical parameters of tissues the fibrous
tissues (sclera eyes, dermis of skin, dura, etc.) are of the most interest makes. Fibrous
tissue make up approximately 50% of body weight. Loose connective tissue of fatty
tissue, dens, tendons and intermuscular fascial layers, derma of skin and an intraorganic stroma of parenchymatous organs, neuroglia and peritoneum are all connecting
fabrics or fibrotic thanks to the existing characteristics of fibrillar structures [1]. All
varieties of fibrous tissue in spite of their morphological differences, are built an
common, with the same principles, which mainly include the following [1]: (a) the
connective tissue contains cells, but compared to other tissues there are fewer. As a
result, the amount of intercellular substance is larger than the cellular elements; (b)
the connective tissue is characterized by the presence of fibrous (fibrous) structures
- collagen, elastin and reticular fibers, which are the main structural elements of the
fibrous tissue, and surrounded by intercellular substance; (c) the connective tissue is
rich with the intercellular substance when has a very difficult chemical composition.
The characteristic component of the structure in fibrous tissue (tendons, cartilage,
the dermis of the skin, eye sclera, etc.) are the collagen fibers. They carry protective functions. For collagen, the specific amino-acid structure and a unique spatial
location of polypeptide chains is a characteristic. As opposed to other proteins, large
number of amino acids are contained in collagen: glycine, proline, hydroxyproline,
lysine, oksilizin. Collagen makes up 25–30% of the total protein in adult, or 6% of
total body weight [2]. The molecule of collagen consists of three polypeptide chains
forming structure of a threefold spiral. The length of the collagen molecule is 280
nm, the diameter of 1.4–1.5 nm [3].
The Structure and Optical Properties of the Skin
Human skin is an example of a multicomponent turbid biological medium and it is
very difficult to describe the construction of the models. Optical characteristics of
such complex environment as a whole depend on many factors. To correctly build
the model of the skin and the description of optical properties one needs to get some
understanding in the biological features of the structure of skin (see Fig. 1.1).
Skin consists of two main layers [4]. The external layer is the multilayered flat
keratinized epithelium - epidermis. The average thickness of the epidermis, of which
there is relatively little change in thickness, is approximately 100 µm [5]. Epidermis
consists of two various layers of cells: an external, corneal layer of dry acaryocytes
(Stratum corneum) and inside cellular layers, i.e. actual epidermis from which, after
modification, there are superficial cells: (Living epidermis) [6]. The main type of cells
in this epitelialny continuum is the epidermalny cell, most often called keratinotsity,
so called because the family of fibrous proteins is keratins. The epidermis unites
subpopulation of migrating cells of treelike types: melanocytes and melanosomes
are pigment-producing melanin; Langerhans cells, considered as monokletki derived
from bone marrow, and Merkel cells, considered as derivatives of keratinocytes [2].
1 Methods Describing the Interaction of Laser Radiation with Biological Tissues
1.2 The Structure and Optical Properties of Biological
Tissues
From the point of view of controlling the optical parameters of tissues the fibrous
tissues (sclera eyes, dermis of skin, dura, etc.) are of the most interest makes. Fibrous
tissue make up approximately 50% of body weight. Loose connective tissue of fatty
tissue, dens, tendons and intermuscular fascial layers, derma of skin and an intraorganic stroma of parenchymatous organs, neuroglia and peritoneum are all connecting
fabrics or fibrotic thanks to the existing characteristics of fibrillar structures [1]. All
varieties of fibrous tissue in spite of their morphological differences, are built an
common, with the same principles, which mainly include the following [1]: (a) the
connective tissue contains cells, but compared to other tissues there are fewer. As a
result, the amount of intercellular substance is larger than the cellular elements; (b)
the connective tissue is characterized by the presence of fibrous (fibrous) structures
- collagen, elastin and reticular fibers, which are the main structural elements of the
fibrous tissue, and surrounded by intercellular substance; (c) the connective tissue is
rich with the intercellular substance when has a very difficult chemical composition.
The characteristic component of the structure in fibrous tissue (tendons, cartilage,
the dermis of the skin, eye sclera, etc.) are the collagen fibers. They carry protective functions. For collagen, the specific amino-acid structure and a unique spatial
location of polypeptide chains is a characteristic. As opposed to other proteins, large
number of amino acids are contained in collagen: glycine, proline, hydroxyproline,
lysine, oksilizin. Collagen makes up 25–30% of the total protein in adult, or 6% of
total body weight [2]. The molecule of collagen consists of three polypeptide chains
forming structure of a threefold spiral. The length of the collagen molecule is 280
nm, the diameter of 1.4–1.5 nm [3].
The Structure and Optical Properties of the Skin
Human skin is an example of a multicomponent turbid biological medium and it is
very difficult to describe the construction of the models. Optical characteristics of
such complex environment as a whole depend on many factors. To correctly build
the model of the skin and the description of optical properties one needs to get some
understanding in the biological features of the structure of skin (see Fig. 1.1).
Skin consists of two main layers [4]. The external layer is the multilayered flat
keratinized epithelium - epidermis. The average thickness of the epidermis, of which
there is relatively little change in thickness, is approximately 100 µm [5]. Epidermis
consists of two various layers of cells: an external, corneal layer of dry acaryocytes
(Stratum corneum) and inside cellular layers, i.e. actual epidermis from which, after
modification, there are superficial cells: (Living epidermis) [6]. The main type of cells
in this epitelialny continuum is the epidermalny cell, most often called keratinotsity,
so called because the family of fibrous proteins is keratins. The epidermis unites
subpopulation of migrating cells of treelike types: melanocytes and melanosomes
are pigment-producing melanin; Langerhans cells, considered as monokletki derived
from bone marrow, and Merkel cells, considered as derivatives of keratinocytes [2].