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Questions and Answers
What is the primary function of the thymus gland?
What is the primary function of the thymus gland?
Which of the following describes the structural characteristics of the thymus gland?
Which of the following describes the structural characteristics of the thymus gland?
What happens to the thymus gland after puberty?
What happens to the thymus gland after puberty?
During which phase does positive selection occur within the thymus?
During which phase does positive selection occur within the thymus?
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What is a consequence of abnormalities in thymus function?
What is a consequence of abnormalities in thymus function?
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Which of the following hormones is NOT associated with the thymus gland?
Which of the following hormones is NOT associated with the thymus gland?
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What type of cell does the thymus primarily help mature?
What type of cell does the thymus primarily help mature?
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What triggers the migration of thymocytes to the thymus?
What triggers the migration of thymocytes to the thymus?
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Study Notes
Thymus Gland Definition and Location
- The thymus gland is a primary lymphoid organ in the immune system
- Situated in the upper front part of the chest
- Located in the anterior superior mediastinum
- Positioned behind the sternum and in front of the heart
Thymus Gland Structure
- Composed of two lobes
- Each lobe has a central medulla and an outer cortex
- Surrounded by a capsule
Thymus Gland Size and Activity
- At birth, roughly 4-6 cm long, 2.5-5 cm wide, and 1 cm thick
- Largest and most active during neonatal and pre-adolescent periods
- Increases in size until puberty, then gradually shrinks (involution) and replaces with fibrous tissue
- Some T cell development continues throughout adulthood
Thymus Gland Function (Maturation)
- Site where T lymphocytes (T cells) mature.
- Crucial part of cell-mediated immunity
- T Cells originate as hematopoietic precursors from bone marrow, migrate to thymus, termed thymocytes.
- Maturation involves positive and negative selection:
- Positive selection: Ensures T cells react to antigens
- Negative selection: Ensures T cells do not react to body tissue antigens
- Attracted by hormones (e.g., thymulin, thymopoietin, thymosins), released by cells in the thymus.
- Mature T cells leave the thymus, guided by sphingosine-1-phosphate, for maturation in peripheral lymphoid organs.
- MHC (major histocompatibility complex) crucial in T-cell development
- MHC presents antigens to receptors on T- cells
- T-cells become active if the presented antigen matches the specific T-cell receptor
- T cell receptors bind to the MHC on body cells
Dysfunction and Associated Conditions
- Congenital problems with thymus development can lead to immunodeficiency.
- Abnormalities of the thymus can result in a reduced number of T cells.
- Certain autoimmune diseases (e.g., autoimmune polyendocrine syndrome type 1, myasthenia gravis) may be linked to thymus abnormalities.
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Description
Explore the thymus gland, a vital organ in the immune system, located in the anterior superior mediastinum. Learn about its structure, size, activity, and crucial role in T cell maturation, particularly during early childhood and beyond.
