Detailed Notes on Lymphatic System and Lymphoid Organs

Lymphatic Capillaries and Lacteals

  • Capillaries in the lymphatic system have one-way valves, ensuring lymph flows into the system but not back into tissues.
  • Lacteals are lymphatic vessels in the small intestine that absorb fats. They are not related to milk production.
  • Lacteals transport absorbed fats into the lymphatic system, which then returns them to the bloodstream for use by the body.

Lymphatic Vessels and Nodes

  • Lymph nodes are located throughout the body, including the neck (cervical nodes), armpits (axillary nodes), and groin (inguinal nodes).
  • Lymph nodes are named after the area they drain.
  • Lymphatic vessels drain tissues and eventually empty into the subclavian veins, which lead to the vena cava.
  • The vena cava is the largest vein that returns blood to the right side of the heart.
  • There are two main lymphatic ducts that drain into the blood system: the right lymphatic duct and the thoracic duct.
  • The right lymphatic duct drains the right side of the head, neck, right arm, and part of the thorax.
  • The thoracic duct drains the rest of the body, including the left side of the head and neck, left arm, thorax, abdomen, and lower extremities.

Lymph Nodes as Filters

  • Lymph nodes filter lymph, removing disease-causing agents, white blood cells, and bacteria.
  • Lymph nodes sterilize or kill pathogens, allowing the body to eliminate them.
  • Analogy: Lymph nodes act like oil filters in cars, removing sludge and waste products to keep the system clean.
  • Analogy: Lymph nodes are similar to filters in fish tanks, removing feces, dead food particles, and dead fish particles.
  • Analogy: Brita filters and refrigerator filters also function similarly by removing impurities.

Lymphatic Drainage and Clinical Implications

  • After filtration, lymph drains back towards the heart.
  • The right lymphatic duct drains into the right subclavian vein, which empties into the vena cava and the right atrium.
  • The thoracic duct drains into the left subclavian vein, which also empties into the vena cava and the right atrium.
  • Blood pressure should not be taken on a limb after breast removal or lymph node dissection because it can damage lymphatic vessels and cause lymphedema.
  • Breast cancer treatment often involves removing lymph nodes, disrupting lymphatic drainage and leading to swelling (lymphedema) in the arm.
  • Edema in the legs can also be caused by faulty lymphatic drainage due to damaged lymph vessels or clogged lymph nodes.
  • Wearing TED hose can help facilitate lymph drainage and prevent fluid buildup.

Lymphatic System Mechanics

  • Lymphatic vessels, like veins, have valves to prevent backflow.
  • Lymph movement relies on muscle contraction, breathing, and gravity.
  • Lymphatic vessels have minimal peristalsis to aid lymph movement.
  • Elevating a body part helps facilitate lymph flow back to the heart.
  • RICE (Rest, Ice, Compression, Elevation) is a common treatment for swelling.
  • PRICE (Protection, Rest, Ice, Compression, Elevation) is a variation of RICE
  • Blood pressure does not influence lymphatic movement.

Characteristics of Lymphatic Vessels

  • Lymphatic vessels have thin walls.
  • They are blind-ended, originating in tissues.
  • They contract to propel lymph (peristalsis).
  • They do not take lymph to the tissues; they drain lymph from the tissues.

Lymph Node Structure and Location

  • Lymph nodes filter lymph, removing pathogens and waste.
  • Lymph nodes are found in clusters, including cervical (neck), axillary (underarm), tracheobronchial (around trachea and bronchi), mesenteric (around intestines), femoral, and inguinal (groin) regions.

Lymphoid Organs

  • Lymphoid organs include the tonsils, thymus, and spleen.

Tonsils

  • Tonsils are located in the back of the throat.
  • Palatine tonsils are near the uvula.
  • Pharyngeal tonsils, or adenoids, are located in the pharynx.
  • Tonsils filter pathogens and can become inflamed during infections, such as strep throat.
  • White pustules on the tonsils indicate infection.

Thymus

  • The thymus is located in the chest, below the thyroid.
  • It is most active in childhood, producing thymosin and T lymphocytes for immunity.
  • The thymus shrinks and becomes less active after puberty.
  • Kids have an active thymus to combat new diseases, while adults have developed immunity to many diseases.

Spleen

  • The spleen is a lymphatic organ that filters blood, not part of the digestive system.
  • It cleanses blood by removing pathogens and old red blood cells.
  • The spleen contains phagocytes that engulf pathogens and digest them.
  • The spleen destroys old red blood cells.
  • In the womb, the spleen makes red blood cells for the fetus.
  • The spleen stores extra blood for emergencies.
  • People without a spleen (splenectomy) are more susceptible to getting sick.
  • Ruptured spleens require removal and do not repair themselves.
  • Individuals without a spleen are considered immunocompromised and need protection from infections.

Additional Notes

  • COVID-19 and Mask Wearing
    • Wearing masks can help protect against infectious diseases, especially for those who are immunocompromised or lack a spleen.
    • The presenter shared personal experiences with COVID-19 and the importance of mask-wearing.
  • The lecture includes anecdotes and personal experiences to illustrate concepts.