Tissue layers basement membrane

Airway cross-sections have the nominal anatomy shown in Fig. 5.16. Airway surface liquid (AST), primarily composed of mucus gel and water, surrounds the airway lumen with a thickness thought to vary from 5 to 10 mm. AST lies on the apical surface of airway epithelial cells (mostly columnar ciliated epithelium). This layer of cells, roughly two to three cells thick in proximal airways and eventually thinning to a single cell thickness in distal airways, rests along a basement membrane on its basal surface. Connective tissue (collagen fibers, basement membranes, elastin, and water) lies between the basement membrane and airway smooth muscle. Edema occurs when the volume of water within the connective tissue increases considerably. Interspersed within the smooth muscle are respiratory supply vessels (capillaries, arteriovenous anastomoses), nerves, and lymphatic vessels. 

The innermost layer of an artery, which consists of loose connective tissue covered by a monolayer of endothelium that resides on a basement membrane. In human arteries, the intima often contains resident smooth muscle cells even early in life. Atherosclerotic plaques form in the intima. 

The lens is an avascular transparent tissue enveloped in the lens capsule, a basement membrane composed of type IV collagen (Harding and Crabbe, 1984). The single layer of epithelial cells under the anterior portion of the capsule divide throughout life, accumulate crystaUin... 

The tracheo-bronchial epithelium forms the interface between the conducting airways and inspired air. As described above, the epithelium is layered upon a connective tissue substratum consisting of a basement membrane, lamina propria, and submucosa [6], The submucosa contains elastic fibres, a muscularis mucosa, connective tissues and seromucous glands. Lymphatics are also located in the bronchial walls [2],... 

Microscopically, the cornea shows a rather simple and multilayered structure that can be divided into six layers the epithelium, basement membrane, Bowman s layer, stroma, Descemet s membrane, and endothelium. The corneal tissue consists of three different cell types epithelial cells, keratocytes (corneal fibroblasts), and endothelial cells. The outermost corneal surface is covered with the preocular tear film, which is functionally associated with the cornea. The epithelial surface must be kept moist and smooth, a role played by the tear film in conjunction with a spreading function of the eyelids during blinking motions. Furthermore, the tear film provides a protection against infectious agents that may gain access into the eye. 

The oral mucosa is anatomically divided into three tissue layers (Fig. 1) [10] the epithelium, the basement membrane, and the connective tissues. 

The basement membrane (BM) is a continuous layer of extracellular materials, forming a boundary between the basal layer of the epithelium and the connective tissues of the lamina propria and the submucosa. It can be subdivided into the lamina lucida,... 

Because the mucus layer or the underlying cells may serve as either final accumulation sites of toxic gases or layers through which the gases diffuse en route to the blood, we need simplified models of these layers. Altshuler et al. have developed for these layers the only available model that can be used in a comprehensive system for calculating tissue doses of inhaled irritants. It assumes that the basement membrane of the tracheobronchial region is covered with three discrete layers an inner layer of variable thickness that contains the basal, goblet, and ciliated cells a 7-Mm middle layer composed of waterlike or serous fluid and a 7-Mm outer layer of viscous mucus. Recent work by E. S. Boatman and D. Luchtel (personal communication) in rabbits supports the concept of a continuous fluid layer however, airways smaller than 1 mm in diameter do not show separate mucus and serous-fluid layers. 

Beneath die basement membrane of the epidermis is the dermis, a thick, tough, collagen-rich connective tissue. Blood vessels and nerve endings are found in this layer, as are roots of hairs and oil and sweat glands.1 ... 

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 reticular layer of basement membrane in a tissue such as the skin contains a variety of matrix structures. Strands of basement membrane may project down to type I collagen fibers. Anchoring fibers, banded fibers composed of type VII collagen, extend into the basement mem-... 

All of these structures have an epithelial lining that lies at the interface as well as extracellular matrix including basement membranes and loose connective tissue that supports the cellular layers (Table 3.2). These tissues are similar in their general structure they all have an inner cellular layer, supportive connective tissue, and an outer cellular layer. It is important to be familiar with the structure of these tissues to be able to analyze how external and internal mechanical forces are transduced at both the macroscopic and microscopic level into and out of cells. The effect of mechanical loading on these tissues is complex, but as discussed above, with increased frictional forces on the epidermis, the surface layer of skin actually increases the thickness of the epidermis. 

The pleura and peritoneum are composed of a thin mesothelial cell lining that rests on a basement membrane and a thin layer of connective tissue that contains endothelium and smooth muscle cells (peritoneum) and fibroblasts (Figure 3.6). These cell linings are continuous with internal tissues that he beneath and also contract when the tension is released but not as much as cornea or skin. 

The boundary between the epidermis and dermis is a basement membrane (see Figure 3.9) it can be described by four planes proceeding from the basal epidermal side to the dermal side (a) the border of the basal ker-atinocyte (b) the lamina lucida, an electron lucent layer that lies beneath the epidermis (c) the lamina densa, an electron dense layer also known as the basal lamina and (d) the reticular lamina or subepidermal zone consisting of connective tissue immediately below the epidermis. The mechanical continuity at the epidermal-dermal junction, as well as between keratinocytes, is key to normal transfer of internal and external mechanical forces between the epidermis and dermis. 

The epithelia are a diverse group of tissues, which, with rare exceptions, line all body surfaces, cavities and glands. They consist of one or more layers of cells, separated by a minute quantity of intercellular material. All epithelia are supported by a basement membrane of variable thickness, which separates the epithelium from underlying connective tissues. 

In common with all epithelial interfaces (see Section 1.3.2), the epithelium of the oral cavity is supported by a basement membrane, which separates the epithelium from the underlying connective tissue layer (the lamina propria) (Figure 7.1). Oral epithelium is broadly similar to stratified squamous epithelia found elsewhere in the body, for example the skin (see Section 8.2.1), in that cells are produced by mitosis in the basal layer of the epithelium and these proliferating cells push existing cells towards the surface. The phases of this dynamic process are represented in four morphological layers ... 

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