- Provides an important immune mechanism for the body.
- Is involved in the metastasis of cancer cells.
- Provides a route for transporting fat and large protein molecules absorbed from the intestine to the thoracic duct.
Lymphatic vessels
- Serve as one-way drainage toward the heart and return lymph to the bloodstream through the thoracic duct (the largest lymphatic vessel) or the right lymphatic duct
- Are not generally visible in dissections but are the major route by which carcinoma metastasizes.
- Function to absorb large protein molecules and transport them to the bloodstream because the molecules cannot pass through the walls of the blood capillaries back into the blood.
- Carry lymphocytes from lymphatic tissues to the bloodstream.
- Have valves, which are constricted at the sites of valves, showing a beaded appearance.
- Are absent in the brain, spinal cord, eyeballs, bone marrow, splenic pulp, hyaline cartilage, nails, and hair.
Lymphatic capillaries
- Begin blindly in most tissues, collect tissue fluid, and join to form large collecting vessels that pass to regional lymph nodes.
- Absorb lymph from tissue spaces and transport it back to the venous system.
- Are called lacteals in the villi of the small intestine, where they absorb emulsified fat.
Lymph nodes
- Are organized collections of lymphatic tissue permeated by lymph channels.
- Produce lymphocytes and plasma cells and filter the lymph.
- Trap bacteria drained from an infected area and contain reticuloendothelial cells and phagocytic cells (macrophages) that ingest these bacteria.
- Are hard and often palpable when there is a metastasis and are enlarged and tender during infection.
Lymph
- Is a clear, watery fluid that is collected from the intercellular spaces.
- Contains no cells until lymphocytes are added in its passage through the lymph nodes. Its constituents are similar to those of blood plasma (e.g., proteins, fats,lymphocytes).
- Often contains fat droplets (called chyle ) when it comes from intestinal organs.
- Is filtered by passing through several lymph nodes before entering the venous system.
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