Human Anatomy and Histology · MU Plovdiv

37. The immune system – definition, classification and principle structure. The thymus and the spleen – position, morphological characteristic, blood supply and nerve supply.

Inside: 9 sections · 6 labelled pictures · 1 table · 29 flashcards · 5 min

Topic 37 of 138 in the MU Plovdiv syllabus for Human Anatomy and Histology (Dental Medicine, Year 1). The free AceMed note covers it in 8 sections, about 617 words (5 min of reading), with 29 flashcards.

In this note

  1. THYMUS
  2. Structure:
  3. Functions:
  4. SPLEEN
  5. Supporting ligamints:
  6. External structure:
  7. Blood Supply:
  8. Internal structure:

THYMUS

  • It is primary lymphatic organ (Produce T & B lymphocytes)
  • Location: ventral part of the superior mediastinum, just behind the Sternum.
  • It contains T-lymphocytes undergoing maturation.
  • The thymus is the largest and most active during the neonatal (newborn) period

During the teenage years it begins to atrophy & involute.

After the age of around fifty, the thymus is almost completely replaced by an adipose tissue

Structure:

  1. Capsule - connective tissue.
  2. Trabeculae - Extensions from the capsule.
  3. Thymic Lobes: right & Left lobes
  4. Cortex: Contains immature T-cells (thymocytes) that undergo maturation & selection processes.
  5. Medulla: Contains mature T cells that have successfully passed through the processes.
  6. Criticomedullary junction: the transition zone between the cortex & medulla.
  1. Thymic (Hassal's) Corpuscles: structures found in the medulla.
  • Their exact function is not fully understood.
  1. Thymic Arteries & veins.

Functions:

  1. Facilitate the maturation of T-cells
  2. Positive & Negative Selections
  • ↳ to detect which T-cells can be send to ..

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