Thymus Gland Overview

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Questions and Answers

What is the primary function of the thymus gland?

  • Maturation of T cells for the immune response (correct)
  • Filtration of blood and immune response regulation
  • Secretion of digestive enzymes
  • Production of hormones that stimulate bone growth

Where is the thymus gland located?

  • In the upper front part of the chest, behind the sternum (correct)
  • Near the lungs, in the mediastinum
  • Above the kidneys, in the lower back region
  • In the abdominal cavity, behind the stomach

What occurs during the positive selection of T cells in the thymus?

  • T cells undergo apoptosis if they do not bind to MHC (correct)
  • T cells are activated only in the presence of pathogens
  • T cells are induced to migrate back to the bone marrow
  • T cells learn to recognize antigens found in body tissues

What is the consequence of congenital problems in the thymus development?

<p>Development of severe immunodeficiency (B)</p> Signup and view all the answers

What hormones and cytokines attract thymocytes to the thymus?

<p>Thymulin, thymopoietin, and thymosins (C)</p> Signup and view all the answers

Which of the following describes a condition associated with thymus dysfunction?

<p>Autoimmune polyendocrine syndrome type 1 (B)</p> Signup and view all the answers

What happens to the thymus gland after puberty?

<p>It decreases in size and is replaced by fibrous tissue (D)</p> Signup and view all the answers

Which process occurs in the medulla of the thymus?

<p>Negative selection of T cells (B)</p> Signup and view all the answers

Flashcards

Thymus gland

A specialized primary lymphoid organ of the immune system, located in the chest, responsible for T cell maturation.

T cells (T lymphocytes)

A type of white blood cell that develops in the thymus, playing a crucial role in cell-mediated immunity.

T cell maturation

The process of selecting and developing T cells that can recognize and attack pathogens, while eliminating those that react with the body's own tissues.

Negative selection (T cell maturation)

The process of eliminating T cells that react to the body's own tissues, preventing autoimmune diseases.

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Positive selection (T cell maturation)

The process of selecting T cells that can recognize and respond to specific foreign antigens.

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Thymus involution

The state of the thymus being largest and most active during childhood, gradually decreasing in size as we age.

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Congenital thymus defects

A condition where the thymus fails to develop properly, leading to a deficiency in T cells and increased susceptibility to infections.

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Thymus dysfunction

A condition caused by abnormal thymus function, resulting in reduced T cells and autoimmune diseases like myasthenia gravis.

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Study Notes

Thymus Gland Objectives

  • Definition and location
  • Function of the thymus gland
  • Dysfunction of the thymus gland

Thymus Gland Structure and Location

  • The thymus gland is a primary lymphoid organ in the immune system
  • Located in the upper front part of the chest
  • Located in the anterior superior mediastinum
  • Behind the sternum and in front of the heart
  • Composed of two lobes
  • Each lobe has a central medulla and an outer cortex
  • Surrounded by a capsule

Thymus Gland Function

  • Most active during neonatal and pre-adolescent periods
  • At birth, it is 4-6 cm long, 2.5-5 cm wide, and 1 cm thick
  • Grows until puberty then shrinks (involution)
  • Replaced by fibrous tissue
  • Continues T cell development throughout adult life
  • T cells mature within the thymus
  • T cells are part of cell-mediated immunity
  • T cells start as hematopoietic precursors from bone marrow
  • Migrate to thymus, called thymocytes
  • Attracted to the thymus by hormones and cytokines (e.g., thymosin, thymopoietin)

T Cell Maturation Process

  • Maturation process ensures T cells react against antigens (positive selection) but not body tissues (negative selection)
  • T cell receptors bind to the major histocompatibility complex (MHC)
  • The MHC presents antigen to the T cell receptor
  • If the T cell receptor matches the antigen, the T cell becomes active
  • Positive selection in the cortex and negative selection in the medulla of the thymus
  • Successful T cells leave the thymus, regulated by sphingosine-1-phosphate
  • Further maturation occurs in peripheral lymphoid organs

Dysfunction and Abnormalities

  • Congenital problems with thymus development can lead to immunodeficiency.
  • Thymus abnormalities can cause a decrease in T cells
  • Can result in autoimmune diseases, like autoimmune polyendocrine syndrome type 1 and myasthenia gravis

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