Elastic connective tissue

Figure 9.17 Routes of parenteral medication, showing the tissues penetrated by intramuscular, intravenous, subcutaneous and intradermal injections the needles, with bevel up, penetrate the epidermis (cuticle) consisting of stratified epithelium with an outer horny layer, the corium (dermis or true skin) consisting of tough connective tissue, elastic fibres, lymphatic and blood vessels, and nerves, the subcutaneous tissue tela subcutanea) consisting of loose connective tissue containing blood and lymphatic vessels, nerves, and fat-forming cells, the fascia (a thin sheet of fibrous connective tissue), and the veins, arteries and muscle.

Proteins can be classified by the functions just discussed. They can also be classified into two major types, fibrous and globular, on the basis of their structural shape. Fibrous proteins are made up of long rod-shaped or stringlike molecules that can intertwine with one another and form strong fibers. They are water-insoluble and are usually found as major components of connective tissue, elastic tissue, hair, and skin. Examples are collagen, elastin, and keratin (see > Figure 9.4). 

Those proteins which form long chains bound together in a parallel fashion are called fibrous proteins. They are the proteins of connective tissue, elastic tissue, and hair, or specifically collagen, elastin, and keratin. Fibrous proteins are not very digestible. 

Another noteworthy anatomical feature of the arteries is the presence of elastic connective tissue. When the heart contracts and ejects the blood, a portion of the stroke volume flows toward the capillaries. However, much of the stroke volume ejected during systole is retained in the distensible arteries. When the heart relaxes, the arteries recoil and exert pressure on the blood within them, forcing this "stored" blood to flow forward. In this way, a steady flow of blood toward the capillaries is maintained throughout the entire cardiac cycle. 

Due to the significant amount of elastic connective tissue and smooth muscle in their walls, arteries tend to recoil rather powerfully, which keeps the pressure within them high. In contrast, veins contain less elastic connective tissue and smooth muscle so the tendency to recoil is significantly less and the pressure remains low. 

Describe the role of elastic connective tissues in elastic recoil of the lungs as well as in lung compliance... 

Submucosa. The submucosa is a thick middle layer of connective tissue. This tissue provides the digestive tract wall with its distensibility and elasticity as nutrient materials move through the system. 

Bone is an extremely dense connective tissue that, in various shapes, constitutes the skeleton. Although it is one of the hardest structures in the body, bone maintains a degree of elasticity owing to its structure and composition. It possesses a hierarchical structure and, as most of the tissues, is nanostructured in fact, it is a nanoscaled composite of collagen (organic extracellular matrix) and hydroxycarbonate apatite, (HCA, bone mineral). This nanostructure is in intimate contact with the bone cells (several microns in size), which result (at the macroscopic level) in the bone tissue. Figure 12.2 shows the bone hierarchical ordering from the bone to the crystalline structure of HCA. 

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],... 

Muscles are attached to bone by tendons tough, strong strands of connective tissue which transmit the force from muscle to bone. In addition, because of their elastic properties, they convert some kinetic energy into potential energy which is then used during the next stroke. This reduces the amount of ATP and hence the amount of fuel required to power running (Box 13.1). 

Pulmonary arteriole Elastic connective tissue Lymphatic... 

The pleural tissue is a typical connective tissue that consists mostly of matrix the fibrous proteins (collagen, elastin), and mucopolysaccharides, and a few scattered mesothelial cells, capillaries, venules, and ducts. Anatomists have defined several layers (Fig. 3.4) for each of the pleura. Layers 3 and 5 in Fig. 3.4 contain an abundance of fibrous protein, especially elastin. Both the interstitial (Layer 4) and mesothelial (1 and 2) layers contain capillaries of the vascular system and lymphatic channels. The matrix (ground substance) gives the pleura structural integrity and is responsible for its mechanical properties such as elasticity and distensibility. 

Function and location of elastin Cause of Marfan syn drome Elastin is a connective tissue protein with rubber-like properties. Elastic fibers composed of elastin and glycoprotein microfibrils, such as fibrillin, are found in the lungs, the walls of large arteries, and elastic ligaments. [Note Mutations in the fibrillin gene are responsible for Marfan syndrome]... 

According to Loeper et al., who have studied the role of silicon in human and experimental atherosclerosis6 7 silicon has a protective function for the artery by decreasing the atheromatous deposits and by conserving the integrity of the elastic tissue and the connective tissue. 

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