Dermis structure

Tannage process. Tannage consists in injection of tanning substances into the dermis structure and their interaction with functional groups of protein molecular chains, which results in formation of additional stable cross bonds. Tannage is one of the most important processes for leather manufacture. This stage in the leather industry radically changes dermis... 

Let us consider how the skin is structured to better understand how this tissue performs some of its vital functions. Consider the cross section of the skin sketched in Fig. 1. This illustration shows the readily distinguishable layers of the skin, from the outside of the skin inwards the 10 pm thin, fully differentiated, devitalized outer epidermal layer called the stratum corneum the 100 pm thin live, cellular epidermis and the 1000 pm thin (1 mm thin) dermis. Note that all the thicknesses specified here are representative only, for the actual thickness of each stratum varies severalfold from place to place on the body. Dispersed... 

Collagen fibers are long and thick in the middle dermis but become increasingly fine toward the outer epidermis as well as toward the inner hypodermis. Apart from this structural characteristic, which is common to all animals, the skin of each species has a different and unique morphology that significantly affects its properties (Calnan and Haines 1991). 

The skin consists of two main compartments, the epidermis, a stratified squamous epithelium, and the underlying dermis, a richly vascularized tissue embedded in a connective tissue matrix (Fig. 41.1). The epidermis consists of multiple layers of keratinocytes, which differentiate into the outermost layer, the stratum corneum. This layer contains the hydrophilic structural... 

The dermis provides a base for the epidermis and contains fibroblasts that elaborate proteins, such as collagens and elastin, which are crucial for the skin s structural integrity. In addition, mast cells, enriched in a variety of proinflammatory substances, play an important role in tissue remodeling, wound healing, and fibrosis. 

FIGURE 2.2 A diagram of human skin. Epidermal thickness depends upon body site being thickest on the palms and soles (-1500 pm) and thinnest around the eyes (-10 pm). The stratum corneum is the only layer composed of anucleated, terminally differentiated kerati-nocyte cells called corneocytes. All other epidermal layers contain nucleated keratinocytes. The dermis is composed primarily of the structural proteins collagen and elastin. 

Structurally, the skin consists of the outermost epidermis which is essentially composed of dead squamous cells sloughed off from the underlying dermis (Figure 7.1). The dermis lies on top of subdermal layers, which further down gives access to nerve endings and capillaries of the circulatory system. 

Figure 3.9 The structure of mammalian skin (A) epidermis, (B) dermis, (C) sebaceous gland, (D) capillary, (E) nerve fibers, (F) sweat gland, (G) adipose tissue, (H) hair.

A simple picture of the structure of skin is to consider it as an interwoven mass of protein polymer chains containing channels and voids filled with aqueous matter. These channels in skin dermis are about 10 A in diameter (20). Many substances have been used to simulate skin in drug penetration studies, but they all have the disadvantage that little is known about their inherent structures. General examples illustrative of this fault are the common use of agar gels and cellulose films. 

Dahlback, K., Ljungquist, A., Lofberg, H., Dahlback, B., Engvall, E., and Sakai, L. Y. (1990). Fibrillin immunoreactive fibers constitute a unique network in the human dermis Immunohistochemical comparison of the distributions of fibrillin, vitronectin, amyloid P component, and orcein stainable structures in normal skin and elastosis. / Invest. Dermatol. 94, 284—291. 

Microscopically, the skin is a multilayered organ composed of many histological layers. It is generally subdivided into three layers the epidermis, the dermis, and the hypodermis [1]. The uppermost nonviable layer of the epidermis, the stratum corneum, has been demonstrated to constitute the principal barrier to percutaneous penetration [2,3]. The excellent barrier properties of the stratum corneum can be ascribed to its unique structure and composition. The viable epidermis is situated beneath the stratum corneum and responsible for the generation of the stratum corneum. The dermis is directly adjacent to the epidermis and composed of a matrix of connective tissue, which renders the skin its elasticity and resistance to deformation. The blood vessels that are present in the dermis provide the skin with nutrients and oxygen [1]. The hypodermis or subcutaneous fat tissue is the lowermost layer of the skin. It supports the dermis and epidermis and provides thermal isolation and mechanical protection of the body. 

Structure of skin. Skin is composed of two layers, the epidermis and the dermis, separated by a basement membrane zone. Hypodermis, composed of adipose tissue, sweat glands, and pacinian corpuscles, is not part of the skin.45... 

The dermis can be divided into two layers, the papillary layer adjacent to the epidermis and the deeper reticular layer. Blood vessels and sensory nerve endings are present in this layer. The reticular layer is made up of collagen and elastin lattice. Papillary and reticular layers provide structural and nutritional support.45... 

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