83 Questions
What is the main function of the primary lymphoid organs?
Production and maturation of lymphocytes
Which cell type is primarily responsible for antigen presentation in the lymphoid tissue?
Dendritic cell
Where are the Peyer's patches located in the body?
Small intestine
What is the main function of high endothelial venules (HEVs) in the lymphoid tissue?
Lymphocyte migration
Which structure is responsible for separating the red pulp from the white pulp in the spleen?
Periarteriolar lymphatic sheaths (PALs)
What clinical condition is characterized by the absence or underdevelopment of the thymus gland?
DiGeorge Syndrome
Which type of cells line the splenic sinuses in the red pulp?
Stave cells
Which vessels deliver lymph to the lymph node?
Afferent lymphatic vessels
What is the function of the splenic pulp's red pulp?
Remove defective blood cells
What do trabeculae do in the spleen structure?
Bring blood and nerves
What happens to the central artery when lymphocytes aggregate around it?
It moves to an eccentric position
What is the role of macrophages in the spleen's red pulp?
Destruction of senescent red blood cells
What is the function of the white pulp in the spleen?
Facilitation of immune responses
What do the splenic cords of Billroth contain?
Reticular cells and fibers
Which type of circulation does the splenic artery support?
Open circulation
What is the role of stave cells in the spleen's red pulp?
Selection of healthy red blood cells
What do penicillar arterioles give rise to?
Sheathed capillaries
What is the purpose of the periarterial lymphatic sheath (PALS) in the spleen's white pulp?
Aggregate around antigens to form nodules
Where do B lymphocytes mature?
Bone marrow
Which tissue is NOT included in the secondary (peripheral) lymphatic tissue?
Thymus
What is the site for T lymphocytes maturation?
Thymus
What type of cells are called Thymus Epithelial Cells (TEC) in immunology textbooks?
Type I epithelioreticular cells
Which type of epithelioreticular cells are antigen-presenting cells in the thymus?
Type II epithelioreticular cells
In the thymic medulla, what type of cells form Hassall’s corpuscles?
Type VI epithelioreticular cells
What happens to the thymus after birth?
It gradually involutes and is replaced by fat
What does the blood-thymus barrier protect against?
Blood-borne antigens
What type of selection occurs in the cortex of the thymus?
Positive selection
What happens to non-responsive lymphocytes in the cortex of the thymus?
They are deleted by apoptosis.
What type of selection occurs in the medulla of the thymus?
Negative selection
What percentage of entering lymphocytes emerge as mature T-cells after thymic education?
About 5%
Which cells fail to develop in the given scenario?
Thymic epithelial cells
Where are diffuse lymphatic tissues found?
Lamina propria of the digestive tract and respiratory passages
Which structure contains crypts and may undergo metaplasia due to severe repeated coughing?
Adenoids
What is the function of high endothelial venules (HEVs) in lymph nodes?
To signal T and B lymphocytes to leave circulation and migrate into the lymph node parenchyma
Where are M cells found in the body?
Lamina propria of the intestine
What is the main function of lymphatic nodules/follicles?
To transport antigens to activate lymphocytes
Which structure is a blind pouch connected to the cecum of the large intestine?
Appendix
What type of cells arrive from the blood to diffuse lymphatic tissue?
White blood cells (lymphocytes, macrophages, plasma cells, dendritic cells)
Which type of nodule develops a lightly stained germinal center?
Secondary lymphatic nodule
Where are unencapsulated secondary lymphoid tissues/organs found?
Lamina propria of the digestive tract and respiratory passages
What is the exact function of the appendix?
The exact function remains unclear
What is the role of medullary sinuses in a lymph node?
Spaces between medullary cords
What is the main function of Hassall's corpuscles in the thymic medulla?
Secretion of thymic hormones
Which structure separates the red pulp from the white pulp in the spleen?
Central arteriole
Where are M cells primarily found in the body?
Intestinal mucosa-associated lymphoid tissue (MALT)
What clinical condition is characterized by the absence or underdevelopment of the thymus gland?
DiGeorge Syndrome
What is the role of periarteriolar lymphatic sheaths (PALS) in the spleen's white pulp?
Regulation of T cell activation
What is the function of mucosa-associated lymphoid tissue (MALT) in the body?
Defense against pathogens at mucosal surfaces
Where do B lymphocytes mature?
Bone marrow
Which structure serves as a framework for T cell development?
Epithelioreticular cells
What is the main function of the spleen's red pulp?
Filtration of blood and removal of old or damaged red blood cells
What is the role of the blood-thymus barrier?
To protect against blood-borne antigens
What happens to non-responsive lymphocytes in the cortex of the thymus?
They are removed by phagocytosis
What type of cells are primarily responsible for antigen presentation in the lymphoid tissue?
Macrophages
Where are diffuse lymphatic tissues found?
Intestinal mucosa
What is the function of high endothelial venules (HEVs) in lymph nodes?
Transport of lymphocytes from the bloodstream into the lymph node parenchyma
What clinical condition is characterized by the absence or underdevelopment of the thymus gland?
DiGeorge Syndrome
What is the exact function of the appendix?
Storage of beneficial bacteria
What type of selection occurs in the medulla of the thymus?
Negative selection
Which type of nodule develops a lightly stained germinal center?
Secondary (peripheral) lymphatic tissue
Which of the following is a common feature observed in patients with the absence or underdevelopment of thymic epithelial cells?
Hypoparathyroidism
Where are M cells primarily found in the body?
Small intestine
What is the function of the appendix in the human body?
Immune response to antigens
Which structure is NOT considered part of the secondary lymphatic tissue/organs?
Thymus
What type of cells arrive from the blood to diffuse lymphatic tissue in the lamina propria?
Macrophages
Where are Peyer’s patches primarily located in the body?
Small intestine
What is the main function of high endothelial venules (HEVs) in the lymphoid tissue?
Signal lymphocytes to migrate into tissue
What happens to non-responsive lymphocytes in the cortex of the thymus?
They undergo apoptosis
Where do B lymphocytes primarily mature?
Bone marrow
What happens to the central artery when lymphocytes aggregate around it?
It forms a germinal center.
What type of selection occurs in the medulla of the thymus?
Negative selection
What is the role of stave cells in the spleen's red pulp?
Hematopoiesis
Which structure facilitates immune responses in the spleen?
White pulp
What type of cells are primarily involved in the destruction of senescent red blood cells in the spleen's red pulp?
Macrophages
Which cell type aggregates around the central artery in the splenic pulp of the spleen?
B lymphocytes
In the closed circulation model of blood circulation in the spleen, where do sheathed capillaries open directly?
Into the splenic sinus
What is the main function of the splenic sinuses in the red pulp of the spleen?
Red blood cell destruction
Which type of circulation model is supported by experimental and morphologic evidences for blood circulation in the spleen?
Open circulation
Which structure extends from the capsule and brings blood and nerves to the spleen?
"Trabeculae"
What primarily constitutes the periarterial lymphatic sheath (PALS) in the splenic pulp?
"Lymphocytes"
Which vessels deliver lymph to a lymph node before it sequentially moves through various sinuses?
"Afferent lymphatic vessels"
"Stave cells" are primarily responsible for allowing which type of cells in the splenic cords to enter the sinuses?
Red blood cells
Which type of nodule may associate with periarterial lymphatic sheath (PALS) in the splenic pulp?
Germinal center nodule
Study Notes
- The text discusses the histology of lymphoid tissue, with a focus on recognizing various structures and cell types in primary and secondary lymphoid organs.
- Primary lymphoid tissue includes bone marrow, thymus, and sites where lymphocytes mature.
- Thymus is a primary lymphoid organ where T lymphocytes mature. It contains epithelial reticular cells (erc), which form a cytoplasmic reticulum and serve as a framework for T cell development.
- Young thymus has structural features, including a capsule, trabeculae, and the presence of Hassall's corpuscles.
- Thymus involutes after birth, and the blood-thymus barrier protects against lymph-borne antigens.
- In the thymus, T cell education occurs through positive and negative selection. Positive selection occurs in the cortex, where responsive cells are selected and move to the medulla. Negative selection occurs in the medulla, where self-reactive cells are deleted.
- Secondary lymphoid tissues or organs are the sites where immunocompetent cells interact with antigens and become activated. These include lymphatic nodules, tonsils, and the spleen.
- Lymphatic nodules, or tonsils, are uncapsulated and found in the lamina propria. They contain a diffuse concentration of immune cells, with no germinal center.
- Lymph nodes are capsulated structures and contain a germinal center, which is a sign of an active immune response.
- The spleen is a secondary lymphoid organ that filters the blood and removes old and damaged blood cells. It contains red and white pulp.
- DiGeorge Syndrome is an inherited immunodeficiency caused by the deletion of genes on chromosome 22. It results in the failure of epithelioreticular cells to develop, leading to a lack of T cell precursors and the underdevelopment of the thymus and parathyroid glands.
Test your knowledge on thymic aplasia and DiGeorge syndrome which result in the failure of development of thymic epithelial cells and subsequent inability of T cell precursor differentiation. Learn about the associated symptoms and implications for secondary lymphatic tissues/organs.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
