Lecture Notes on the Spleen and Lymphatic System

Introduction to the Spleen

• The spleen is located on the left side of the body, opposite the liver.
• It has a unique shape, being compressed by surrounding organs:
  • Gastric Impression: Stomach
  • Colic Impression: Colon
  • Renal Impression: Kidney
• The spleen is a solid organ with a hilum where blood vessels and lymphatics enter and exit.
• Size: About 5 inches long.

Structure of the Spleen

• Stroma: Includes the capsule, trabeculae, fibers, and fibroblasts.
• Parenchyma: Composed of white pulp and red pulp.
  • White Pulp: Lymphatic tissue around branches of the splenic artery.
  • Red Pulp: Contains venous sinuses filled with blood and splenic tissue.
    • Stores platelets and removes old or defective red blood cells.
    • Contains red blood cells, macrophages, lymphocytes, plasma cells, and granulocytes.
    • Involved in blood cell production during the second trimester of pregnancy.

Clinical Aspects of the Spleen

• Highly susceptible to rupture from abdominal trauma due to a rich blood supply.
• Splenectomy is often preferred over repair to prevent internal bleeding.
  • Post-splenectomy, reduced immunity necessitates lifelong prophylactic antibiotics.

Lymphatic Tissue and Organs

• Lymphatic tissue without a capsule is found throughout mucous membranes as MALT (Mucosa-Associated Lymphoid Tissue).
• Most lymphatic tissue is located in the GI tract.
• Peyer's Patches: Lymphatic tissue clusters in the ileum, part of the small intestine.
  • Located at the junction of the small intestine and colon.

The Appendix

• Found in the cecum at the start of the colon.
• Can become inflamed (appendicitis) and pose a risk if ruptured.

Tonsils

• Five tonsils: Two palatine, one lingual, and adenoids (pharyngeal tonsils).
• Tonsillitis involves inflammation and infection of the tonsils.

Learning Goals

• Differentiate between primary and secondary lymphatic organs.
• Define terms: stroma, parenchyma, capsule, trabecula, cortex, medulla, hilum, efferent, afferent, metastasis, red pulp, and white pulp.
• Describe the functions of the thymus, spleen, and lymph nodes.
• List and describe the five tonsils.
• List different types of MALT tissue.
• Describe the structure and function of lymph nodes, the thymus, and the spleen.
• Explain why a splenectomy is often preferred over repair.
• Discuss why the thymus is larger in children than in adults.
• Discuss features of lymph nodes that make them ideal for detecting cancer spread.