Lymphatic System Overview Quiz

Lymphatic System Overview

• The lymphatic system comprises lymphatic vessels and organs
• Primary lymphatic organs include bone marrow and thymus
• Secondary lymphatic organs include spleen, lymph nodes, and mucosa-associated lymphoid tissue (MALT)
• MALT types include bronchus-associated (BALT), gut-associated (GALT), and tonsils (palatine, pharyngeal, and lingual)

Learning Objectives

• Classify lymphatic organs
• Detail lymph node structure
• Describe spleen structure
• Define mucosa-associated lymphoid tissue (MALT)

Lymph Node Structure

• Bean-shaped
• Located along lymphatic vessels
• Can be palpable or non-palpable
• Composed of stroma and parenchyma
• Stroma:
  • Capsule: thick connective tissue, receiving multiple afferent lymphatic vessels that converge to a single efferent lymphatic vessel leaving through hilum.
  • Trabeculae: connective tissue septa dividing the node into compartments
  • Reticular connective tissue
• Parenchyma:
  • Cortex: outer region, with lymphatic nodules (pale-stained central germinal centers surrounded by dark zones of lymphocytes), separated from the capsule by subcapsular sinus
  • Paracortex: deeper part of the cortex, containing T lymphocytes and high endothelial venules (HEVs)
  • Medulla: innermost region, containing medullary cords of branching lymphocytes and medullary sinuses

Spleen Structure

• Large hemolymphatic organ in the left hypochondrium
• Comprised of stroma and parenchyma
• Stroma:
  • Fibromuscular capsule
  • Trabeculae: rich in smooth muscle fibers
  • Reticular connective tissue
• Parenchyma:
  • White pulp (Malpighian bodies): oval/rounded aggregations of lymphocytes surrounding central arterioles. Includes periarteriolar lymphatic sheaths (mainly T lymphocytes), germinal centers (GCs), and marginal zone (mainly B lymphocytes)
  • Red pulp: located between white pulp, with splenic cords (cords of Billroth) containing loose reticular connective tissue, blood cells, plasma cells, reticular cells, and macrophages. Also includes splenic sinusoids supported by reticular tissue, exhibiting discontinuous capillaries

Mucosa-Associated Lymphoid Tissue (MALT)

• Also known as the mucosal immune system
• Present in the lining of common systems (e.g., gastrointestinal (GIT) and respiratory)
• Subdivided into GALT, BALT, and tonsils (palatine, pharyngeal, lingual)
• Besides lymphocytes, also includes plasma cells, dendritic cells, and antigen-presenting cells (APCs)
• Exists in two forms:
  • Diffuse lymphatic tissue (transient): scattered lymphocytes in connective tissue lamina propria, appearing in small nodules, representing temporary response to an infection
  • Lymphatic nodules (permanent): non-capsulated, sharply defined concentrations of lymphocytes, large enough to extend into the submucosa, permanently aggregated in the lamina propria (e.g., tonsils, Peyer's patches, appendix)

Clinical Correlations

• Tonsilitis: acute bacterial inflammation of the palatine tonsils
• Adenoiditis: acute bacterial inflammation of the pharyngeal tonsils
• Appendicitis: acute inflammation of the appendix

Test your knowledge on the lymphatic system with this quiz. Explore the classification of lymphatic organs, the structure of lymph nodes, and the functions of mucosa-associated lymphoid tissue (MALT). Perfect for students studying anatomy and physiology.