Lymph Vessels

1. Structure: lymph capillaries similar to blood capillaries in structure; lymphatics similar to veins but are thinner walled, have more valves, and have lymph nodes in certain places along their course.
2. Names: largest lymphatic known as thoracic duct; drains lymph from entire body, except upper right quadrant, into the left subclavian vein (where it joins the internal jugular); right lymphatic ducts drain lymph from the upper right quadrant into the right subclavian vein.
3. Functions
   
   1. lymphatics returned fluid and protein to blood from interstitial fluid; about 60% of fluid filters out of blood capillaries returned to circulation via lymphatics rather than by osmosis into venous ends of capillaries; about 50% of total blood proteins leaked out of capillaries per day; the only way these large molecules can return to blood is via lymphatics.
   2. Adequate lymph return is essential for maintaining homeostasis of blood proteins and therefore of blood volume
   3. Interference with the return of proteins to the blood results in edema caused by the loss of protein and changes in colloid osmotic pressure.

   Lymph Nodes

   1. Structure: lymphatic tissue, separated into compartments by fibrous partitions; afferent lymphatic vessels enter each node; one (usually) efferent vessel drains lymph out of node
   2. Location: usually in clusters, some of the more important groups, from nursing viewpoint, are
      1. Submental and submaxillary groups in floor of mouth; lymph from nose, lips, and teeth drains through these nodes.
      2. Superficial cervical nodes in neck, along sternocleidomastoid muscle; lymph from head and neck drains through these nodes.
      3. Superficial cubital nodes at bend of elbow; lymph from hand and forearm drains through these nodes.
      4. Axillary nodes in armpit; lymph from arm and upper part of the chest wall, including the breast, drains through these nodes (may be removed during mastectomy for carcinoma)
      5. 5. Inguinal nodes in groin; lymph from the leg and external genitals drains through these nodes.
   3. Function
      1. Help defend the body against injurious substances (notably, bacteria and tumor cells) by filtering them out of lymph and thereby preventing their entrance into bloodstream; leukocytes in lymph nodes destroy many of these substances by phagocytosis and antibody action.
      2. Lymphatic tissue of lymph nodes carries on the process of hemopoiesis, specifically, it forms T and B lymphocytes

Lymph

1. Definition: fluid in lymphatics
2. B. Source: interstitial fluid that has entered the lymphatic capillaries
   1. Interstitial fluid is the fluid in the microscopic tissue spaces.
   2. Interstitial fluid is formed by plasma filtering out of the blood capillaries into the tissue spaces.