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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?
- Filtration of blood
- Production of antibodies
- Maturation of T cells (correct)
- Storage of immune cells
Which of the following describes the structural characteristics of the thymus gland?
Which of the following describes the structural characteristics of the thymus gland?
- Located exclusively in the abdominal cavity
- Single lobed with a spongy texture
- Surrounded by muscle tissue
- Made up of two lobes with cortex and medulla (correct)
What happens to the thymus gland after puberty?
What happens to the thymus gland after puberty?
- It remains the same size throughout adulthood
- It increases in size and functions more actively
- It decreases in size and is replaced by fibrous tissue (correct)
- It completely ceases functioning
During which phase does positive selection occur within the thymus?
During which phase does positive selection occur within the thymus?
What is a consequence of abnormalities in thymus function?
What is a consequence of abnormalities in thymus function?
Which of the following hormones is NOT associated with the thymus gland?
Which of the following hormones is NOT associated with the thymus gland?
What type of cell does the thymus primarily help mature?
What type of cell does the thymus primarily help mature?
What triggers the migration of thymocytes to the thymus?
What triggers the migration of thymocytes to the thymus?
Flashcards
What is the thymus gland?
What is the thymus gland?
A specialized primary lymphoid organ responsible for the maturation of T lymphocytes (T cells), crucial for cell-mediated immunity.
Where is the thymus gland located?
Where is the thymus gland located?
Located in the upper front part of the chest, behind the sternum and in front of the heart, in a region called the anterior superior mediastinum.
When is the thymus gland most active?
When is the thymus gland most active?
The thymus is most active during childhood and adolescence, reaching its peak size during puberty.
What happens to the thymus gland after puberty?
What happens to the thymus gland after puberty?
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Where do T cells originate?
Where do T cells originate?
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What is the purpose of T cell maturation in the thymus?
What is the purpose of T cell maturation in the thymus?
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What are positive and negative selection in T cell development?
What are positive and negative selection in T cell development?
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What are the consequences of thymus dysfunction?
What are the consequences of thymus dysfunction?
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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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