Thymus, spleen, tonsils Dora Malić Medical English, 2013/14 Mentor: A. Žmegač Horvat
Dec 15, 2015
Thymus, spleen, tonsils
Dora MalićMedical English, 2013/14
Mentor: A. Žmegač Horvat
Thymus
• Anterior superior mediastinum
• Two asymmetrical lobes
• Each lobe composed of lobules
• Lobule – outer cortex and inner medulla
• Two types of cells 1.stromal cells - cortical epithelial cells, thymic
medullary epithelial cells, dendritic cells - selection of functional and self-tolerant T-cell receptors
2.cells of hematopoietic origin – derived from bone marrow hematopoietic stem cells
Function of thymus
• Maturation of T-cells• Migration of hematpoietic progenitor cells from
bone marrow• Thymocytes undergo: 1.positive selection – those with no affinity for
self-MHC on stromal cells are destroyed2.negative selection – those with high affinity for
thymic antigens are destroyed – central tolerance
Involution of thymus
• largest and most active during the neonatal and pre-adolescent periods
Spleen
• Upper left quadrant of the abdomen• Not a vital organ
• Surrounded by afibrous capsule• Composed of red and white pulp
Structure of spleen
• Red pulp 1. sinuses – vessel-like spaces filled with blood2. splenic cords – reticular fibers3. marginal zone bordering on white pulp
• White pulp - nodules - Malpighian corpuscles1. follicles - rich in B-lymphocytes2. periarteriolar lymphoid sheath - T-lymphocytes
Functions of spleen
• Removes old red blood cells from circulation• Reserve of blood• Storage of red blood cells, platelets, and
lymphocytes• Metabolizes hemoglobin• Recycles iron• Part of mononuclear phagocyte system• Active immune response to antigens
Tonsils
• Collections of lymphoid tissue in aerodigestive tract
• Waldayer’s tonsillar ring - adenoid tonsil, two tubal tonsils, two palatine tonsils, lingual tonsil
• First line of defense against ingested or inhaled foreign pathogens
Palatine tonsil
• Non-keratinized stratified squamous• Incompletely encapsulated • Long, branched crypts • Sides of oropharynx - between palatoglossal
and palatopharyngeal arches
• Tonsillectomy
References
• http://en.wikipedia.org/wiki/Tonsil• http://en.wikipedia.org/wiki/Lymph_node• http://www.webmd.com/digestive-disorders/
picture-of-the-spleen• http://en.wikipedia.org/wiki/Thymus