Lymphatic channels

Lymph Node Metastases Tumor ceils often metastasize through lymphatic channels (Abe and Taneichi, 1972 Knapp and Friedman,... 

Simply stated, lymphangitis is an inflammation of a lymphatic channel. Lymphangitis begins when a local skin infection is not contained. The infection spreads into the lymphatic channel and is carried to the regional lymph nodes. Most cases are attributed to GAS. 

Absorption via Lymphatic Channels. Some lipophilic chemicals dissolved in lipids may be absorbed through the lymphatics. 

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. 

Drainage of interstitial fluid IgG into lymphatics depends on the concentration gradient and occurs passively via convection [l].The leg lymph fluid of humans contains less than 25% of the amount of IgG found in plasma [65], Other specialized lymphatic channels drain peritoneal, pleural, or pericardial cavities. Lymphatic drainage enters lymph nodes via the subcapsular sinus, and the lymph fluid IgG is available for reticuloendothelial clearance of IgG (subcapsular sinus, perivascular or parenchymal macrophages, perivascular or parenchymal dendritic cells, sinusoidal endothelium) as detailed next. 

After spore uptake into phagolysosomes by tissue macrophages, the bacilli are transported via lymphatic channels to local and regional lymph rtodes. 

FIGURE 31.2. Spore uptake in inhalational anthrax disease. The steps involving spore deposition into a pulmonary alveolus, margination of alveolar macrophages out of capillaries into the alveolar space, spore uptake, and entry into lymphatic channels are illustrated. Illustrations are copyright protected and printed with permission by Alexandre M. Katos. 

Macrophages and dendritic cells marginate out of lymphatic channels and blood capillaries to engulf spores colonizing the intestinal epithelium. 

In general, the California encephalitis subgroup viruses spread from the site of inoculation to skeletal muscles, which is the major site of replication. The virus then spreads to the lymphatic channels, thus spreading to additional skeletal muscles and cardiac muscles. Ultimately, the virus ends up in the CNS, where viral replication can occur in neurons and glial cells. Due to considerable neuronal necrosis, death can... 

Local invasion through the basement membrane and into the surrounding stroma is enabled by increased production of proteases by tumor cells themselves (Duffy, 1996), or by their ability to induce such a response in host stromal cells (Basset et al., 1990 Ahmad et al., 1997). Thin-walled vessels, such as newly forming capillaries or lymphatic channels, offer very little resistance to penetration by tumor cells and provide the most common pathways for tumor cell entry into the circulation. 

Acute lymphangitis is an inflammation involving the subcutaneous lymphatic channels. Lymphangitis usually occurs secondary to punctme wounds, infected blisters, or other skin lesions. Most infections are caused by S. pyogenes. 

Cultures of the affected lesions often yield negative results because the infection resides within the lymphatic channels. 

Four major tissue layers, from the lumen outward, form the large intestine the mucosa, submucosa, muscularis externa, and serosa (Fig. 127-3). Embedded in the submucosa and muscularis externa is a rich lymphatic capillary system. Lymphatic channels do not extend into the mucosa. The muscularis externa consists of circular smooth... 

Lymphangitis—An inflammation involving the subcutaneous lymphatic channels. 

FIGURE 19.30 Immunohistochemical stain for D2-40 demonstrates selective staining of lymphatic endothelium (A) compared to CD31, which stains both lymphatic and vascular endothelium (B). A side-by-side comparison of lymphatic channel and breast duct shows intense reactivity of lymphatic endothelium but somewhat "smudgy" weak staining around the duct (C). 

The pitfalls of interpretation of lymphatic channels in paraffin-embedded breast tissue are well known. Retraction artifacts, ducts with misplaced epithelium, and artifactual displacement of cells commonly complicate the interpretation of biopsy samples. A recently available antibody, D2-40, shows high sensitivity and specificity for normal lymphatic channels in a variety of tissues. 493 D2-40 stains the lymphatic endothelium crisply and intensely but does not stain the normal vascular endothelium (Fig. 19.30).It is highly sensitive and specific in identifying lymphatic space invasion. 

FIGURE 61.3 Tracing of a typical lymphatic channel (bottom panel) in rat spinotrapezius muscle after injection with a micropipette of a carbon contrast suspension. All lymphatics are of the initial type and are closely associated with the arcade arterioles. Few lymphatics follow the path of the arcade venules, or their side branches, the collecting venules or the transverse arterioles. (From Skalak et al., 1986. In A.R. Hargens (Ed.) Tissue Nutrition and Viabilityy pp. 243-262, Springer-Verlag, New York. With permission.)... 

The lumen cross section of initial lymphatics is highly irregular in contrast to the overall circular cross section of coUecting lymphatics (Figure 61.4). Luminal cross sections of initial lymphatics are partially or completely coUapsed and may frequently span around the arcade arteriole. In fact, we have documented cases in which the arcade arteriole is completely surrounded by an initial lymphatic channel, highhghting the fact that the activity of the lymphatics is closely linked to that of the arterioles [Ikomi and Schmid-Schonbein, 1995]. 

FIGURE 61.4 Histological cross sections of lymphatics (LYM) in rat skeletal muscle before (a) and after (b) con traction of the paired arcade arterioles (ART). The lymphatic channel is of the initial type with a single attenuated endothelial layer (curved arrows). Note, that in the dilated arteriole, the lymphatic is essentially compressed (a) while the lymphatic is expanded after arteriolar contraction (b) which is noticeable by the folded endothelial cells in the arteriolar lumen. In both cases, the lumen cross-sectional shape of the initial lymphatic channels is highly irregular. All lymphatics in skeletal muscle have these characteristic features. (From Skalak T.C., Schmid-Schonbein G.W., and Zweifach B.W. 1984. Microvasc. Res. 28 95.)... 

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