Veins, elastic tissue

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. 

Blood vessels include capillaries, arterioles, arteries, and veins. Each of these structures is composed of three layers the intima, media, and adventitia (Figure 3.12). For example, in elastic arteries the wall consists of an intimal layer containing endothelial cells and connective tissue a media containing smooth muscle cells, collagen, and elastic fibers and an adventitia containing collagen fibers, nerves, and blood vessels. In cross-section,... 

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.

AVM Cerebral hemispheres brainstem cerebellum Veins and arteries with often poorly formed elastic membrane gliotic brain tissue... 

Hayreh (66) has argued that since the lamina cribrosa comprises a firm rather than elastic band of collagen tissue, an incision in one aspect should not relax the tissue and allow decompression of the central retinal vein. He has also commented that as the thrombosis is often posterior to the lamina cribrosa, decompression at... 

In case of circulatory disorders, pressure exerted by elastic biomateiial cumulates with the tissues specific one, resultant obtained being opposed to voious l dro/static pressure, with effect in limiting vascular walls extensibility. Simultaneously with veins caliber decrease, an increase of circulation speed takes place. 

Venous flow is a complex interaction between the compliant structures (veins and surrounding tissues) and the flow of blood. Since venous blood pressure is low, transmural pressure can become negative, thereby resulting in blood flow through a partially collapsed tube. Early studies with a thin-walled elastic tube revealed the relevant experimental evidence (Conrad, 1969). The steady flow rate (Q) through a given length of a uniform collapsible tube depends on two pressure differences... 

The venous sinuses are spaces within dural layers that convey venous blood from veins within the cranium to the systemic venous circulation (Fig. 103-4). Venous sinuses are devoid of the elastic and muscle tissue found in all other veins and therefore have no elasticity and muscular contraction to enhance drainage. Circulation is dependent on motion. During the inhalation phase, the sinuses change from "V"-shaped to ovoid, with a resultant Increase In capacity. During this phase, the tributary veins increase drainage into the sinuses. 

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