Histology of the Immune System

Questions and Answers

What is the primary outcome of the process of apoptosis during T cell maturation?

Promotion of autoimmune diseases

Increased proliferation of T cells

Enhanced rearrangement of TCR genes

Removal of T cells that react to self-antigens (correct)

Which of the following is NOT part of the maturation process of T cells in the thymus?

Rearrangement of TCR genes

Production of antibodies (correct)

Acquisition of surface receptors

Enforcement of self-tolerance

What are the cells associated with the cortex of the thymus responsible for?

Generating red blood cells

Supporting thymocytes maturation (correct)

Producing antibodies

Facilitating digestion in the lymphatic system

Which part of the thymus contains fewer and larger, more mature lymphocytes?

Medulla Signup and view all the answers

What is the significance of self-tolerance in T cell maturation?

It prevents T cells from attacking the body's own components. Signup and view all the answers

What percentage of immature T-lymphocytes survive the maturation process?

2% Signup and view all the answers

What role do secondary lymphoid organs play in the life of mature T cells?

They facilitate T cell recirculation in quest for antigens. Signup and view all the answers

Which of the following best describes the cortex of the thymus?

It is the outer layer with dark staining due to thymocytes. Signup and view all the answers

What is the primary function of Hassall’s corpuscles in the thymus?

To regulate CD4+ regulatory T cell development Signup and view all the answers

Which chromosomal defect is associated with DiGeorge syndrome?

Chromosome 22 recombination error Signup and view all the answers

What consequences arise from the failure of the thymus to develop properly in DiGeorge syndrome?

Selective T cell deficiency and immunodeficiency Signup and view all the answers

What is one major pathological feature associated with Hassall’s corpuscles?

Persistence of anterior mediastinal mass Signup and view all the answers

Which of the following statements about the thymus is correct?

The size of the thymus decreases very slowly after puberty Signup and view all the answers

What type of epithelium lines the palatine tonsils?

Stratified Squamous Epithelium Signup and view all the answers

What structure forms at the entrance of the oropharynx?

Waldeyer’s Ring Signup and view all the answers

Which artery provides blood supply to the tonsils?

Tonsillar branch of the facial artery Signup and view all the answers

During which developmental stage does the spleen begin hematopoiesis?

4 - 8 months Signup and view all the answers

What occurs to the tonsils during late puberty?

Progressive Atrophy Signup and view all the answers

What type of lymphocytes primarily enter the spleen?

T and B lymphocytes Signup and view all the answers

What is the primary role of the tonsils in the immune system?

To encounter antigens from the mouth and nose Signup and view all the answers

What is one of the primary functions of the spleen regarding iron?

Recycling iron to the bone marrow Signup and view all the answers

What is a notable feature of the tonsillar crypts?

They have pits that are openings Signup and view all the answers

What structures are formed by the entry of lymphocytes into the spleen?

White and red splenic pulp Signup and view all the answers

What type of lymph node drains lymphatic fluid from the tonsils?

Tonsillar or jugulodigastric Node Signup and view all the answers

What is a potential complication during tonsillectomy related to venous drainage?

Troublesome hemorrhage Signup and view all the answers

From which embryonic layer does the stroma and capsule of the spleen develop?

Mesoderm Signup and view all the answers

What is the primary function of the thymus?

Production of T lymphocytes Signup and view all the answers

During which week does the endoderm of the third pouch begin to proliferate to form the thymus?

4th week Signup and view all the answers

Which type of cells migrate from the bone marrow to the thymus for maturation?

Prothymocytes Signup and view all the answers

What is the term for the process by which the thymus involutes over time?

Adipogenesis Signup and view all the answers

What hormone do Hassal's corpuscles secrete during T cell maturation?

Thymosin Signup and view all the answers

What anatomical structure is located anteriorly to the mediastinum?

Thymus Signup and view all the answers

Which type of tissue forms the connective structure of the thymic lobes?

Neural crest derived tissue Signup and view all the answers

At what stage does maturation of T lymphocytes predominantly begin?

Embryonic stage Signup and view all the answers

Study Notes

Palatine Tonsils

Develop from endoderm of the second pharyngeal pouch by the 5th week of gestation, forming epithelium and tonsillar crypts.
Mesodermal origin provides the stroma of the palatine tonsil.
Lymphatic nodules start forming by the 20th week of gestation.
Comprised of several types: tubal (pair), pharyngeal, and lingual tonsils.
Openings called pits connect to tonsillar crypts; lined by stratified squamous epithelium.
Function as lymphoid tissues encountering antigens in the posterior oral cavity and nasopharynx.
Experience progressive atrophy during late puberty.
Blood supplied by the tonsillar branch of the facial artery; venous drainage through the paratonsillar vein, affecting surgical procedures like tonsillectomy.
Drain lymph to the jugulodigastric node near the jaw.
Form part of Waldeyer's ring, a protective lymphatic tissue aggregation at the oropharynx entrance.

Thymus

Originates from mesoderm of the dorsal mesentery by 5 weeks, serving as the primary site for T-cell maturation.
Major functions include the maturation of T lymphocytes and the secretion of thymosin and thymopoeitin.
Structurally encapsulated with trabeculae defining multiple lobules; contains a cortex and medulla that differ in staining characteristics due to cellular composition.
Thymic cortex features densely packed thymocytes associated with thymic epithelial cells; the medulla houses fewer, larger, and more mature lymphocytes.
Mature T cells migrate to secondary lymphoid organs to eventually recirculate and manage immune responses.

T Cell Maturation Process

Involves proliferation and rearrangement of T-cell receptor (TCR) genes, ultimately acquiring surface receptors.
Selection processes occur within the thymus to achieve MHC restriction and self-tolerance, with about 98% of immature T cells undergoing apoptosis.
Loss of self-reactive T cells helps prevent autoimmune disorders.

Spleen

Forms during 5 weeks with a mesoderm origin that builds stroma and capsule.
Functions as a site of hematopoiesis between 4 to 8 months gestation.
Main roles include antibody production, activated lymphocyte formation, and recycling of iron to the bone marrow.
Located in the upper left quadrant of the abdomen, measuring approximately 12 x 7 x 3 cm, with size variations post-puberty.

Hassall's Corpuscles

Characteristic of the thymic medulla, formed by type VI epithelioreticular cells.
Secrete cytokines regulating dendritic cells' functions, contributing to the development of CD4+ regulatory T cells.
Important for the removal of apoptotic thymocytes.

DiGeorge Syndrome

Rare congenital disorder often linked to a deletion in chromosome 22 affecting the development of the thymus.
Results in selective T-cell deficiency leading to severe immunodeficiency and recurrent opportunistic infections.
Associated malformations include those of the heart, esophagus, great vessels, and parathyroid glands, with high infant mortality rates.

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Description

This quiz covers the histological aspects of the immune system with a focus on the palatine tonsils. It explores the embryonic development of the tonsils, including the endoderm and mesoderm contributions. Dive into the structure and function of lymphoid organs with this informative quiz.