Lymphatic System
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Questions and Answers

What primarily composes the white pulp of the spleen?

  • Connective tissue with adipocytes
  • Vascular tissue with endothelial cells
  • Reticular tissue
  • Lymphoid tissue surrounding a central artery (correct)

    • What is the main function of the marginal zone in the spleen?

  • Storage of platelets
  • Filtering pathogens through reticular fibers
  • Removal of antibodies and lymphocytes from the blood (correct)
  • Production of red blood cells

    • What characterizes the germinal centers of lymphatic nodules in the spleen?

  • Central less-stained area for B-lymphocyte proliferation (correct)
  • Narrow zone of macrophage activity
  • Exclusively populated by plasma cells
  • Site of T-lymphocyte maturation

    • Which of the following statements about red pulp is accurate?

    <p>Consists of splenic cords and venous sinuses</p> Signup and view all the answers

    What defines Peyer's patches in the small intestine?

    <p>Organized lymphatic nodules in the lamina propria</p> Signup and view all the answers

    What is the primary function of the spleen?

    <p>Filtering blood and recycling iron</p> Signup and view all the answers

    Which of the following best describes the structure of lymph nodes?

    <p>They have a distinct cortex and medulla, allowing for efficient filtration.</p> Signup and view all the answers

    What type of lymphatic vessel is primarily responsible for transporting lymph away from lymph nodes?

    <p>Efferent lymphatic vessels</p> Signup and view all the answers

    Which of the following statements about thymocytes is accurate?

    <p>Negative selection is critical for eliminating self-reactive thymocytes.</p> Signup and view all the answers

    What distinguishes medullary sinuses from medullary cords within a lymph node?

    <p>Medullary cords contain lymph and immune cells.</p> Signup and view all the answers

    What is the role of the blood-thymus barrier?

    <p>To protect developing thymocytes from exposure to blood-borne antigens.</p> Signup and view all the answers

    What type of lymphatic tissue is primarily found in the thymus?

    <p>Reticular epithelium</p> Signup and view all the answers

    How does diffuse lymphoid tissue differ from lymphoid nodules?

    <p>Lymphoid nodules have well-defined boundaries, while diffuse tissue does not.</p> Signup and view all the answers

    What tissue type functions primarily as the scaffold in lymphatic organs?

    <p>Stroma</p> Signup and view all the answers

    Which of the following is NOT a function of the thymus?

    <p>Storage of mature B-lymphocytes</p> Signup and view all the answers

    Which characteristic best describes the arrangement of parenchyma in lymphoid organs?

    <p>Diffuse or nodular (follicular)</p> Signup and view all the answers

    What type of cells are included in parenchyma?

    <p>Macrophages and dendritic cells</p> Signup and view all the answers

    What is the primary role of the outer cortex of thymic lobules?

    <p>Maturation of T-lymphocytes</p> Signup and view all the answers

    Which hormone is NOT associated with T-cell maturation in the thymus?

    <p>Calcitonin</p> Signup and view all the answers

    What is the function of epithelioreticular cells in the thymus?

    <p>Form a supportive meshwork for T-cells</p> Signup and view all the answers

    What part of the thymus lobule contains mature T-lymphocytes?

    <p>Medulla</p> Signup and view all the answers

    In which lymphatic organ does the antigen-independent maturation of T-lymphocytes primarily occur?

    <p>Thymus</p> Signup and view all the answers

    Which of the following accurately reflects the structural-functional unit of the thymus?

    <p>Lobule</p> Signup and view all the answers

    What is one of the primary functions of lymph nodes?

    <p>Purify lymph from foreign particles</p> Signup and view all the answers

    Where are high endothelial venules (HEVs) located within a lymph node?

    <p>Paracortex</p> Signup and view all the answers

    Which of the following correctly describes lymphadenopathy?

    <p>Enlargement of a lymph node or nodes</p> Signup and view all the answers

    What type of tissue makes up the stroma of a lymph node?

    <p>Reticular connective tissue</p> Signup and view all the answers

    Which statement is true regarding swollen lymph nodes due to inflammation?

    <p>They are often painful.</p> Signup and view all the answers

    What part of a lymph node contains B-lymphocytes?

    <p>Cortex</p> Signup and view all the answers

    What is the function of the hilum in a lymph node?

    <p>Exit point for veins and efferent lymphatic vessels</p> Signup and view all the answers

    How many lymph nodes are generally found in the human body?

    <p>500-800</p> Signup and view all the answers

    What do the trabeculae of a lymph node connect to?

    <p>Capsule and stroma</p> Signup and view all the answers

    What type of lymphocyte proliferation occurs in lymph nodes?

    <p>Antigen-dependent proliferation</p> Signup and view all the answers

    What is the primary function of thymic hormones produced by epithelioreticular cells in the cortex?

    <p>To transform immature T-lymphocytes into immunocompetent T-cells</p> Signup and view all the answers

    What percentage of T-cells typically die after maturation in the cortex?

    <p>95-98%</p> Signup and view all the answers

    What is the consequence of positive selection during the maturation of T-lymphocytes?

    <p>T-cells that fail to recognize self-MHC die by apoptosis</p> Signup and view all the answers

    Which component is NOT part of the blood-thymus barrier in the cortex?

    <p>Interdigitating cells</p> Signup and view all the answers

    What occurs during acute involution of the thymus?

    <p>Increased lymphocyte death due to stress</p> Signup and view all the answers

    What primarily occupies the medulla of the thymus?

    <p>Mature T-cells</p> Signup and view all the answers

    Which process is crucial for preventing autoimmune diseases in T-cells?

    <p>Apoptosis of self-antigen recognizing T-cells</p> Signup and view all the answers

    What change occurs to the thymus with increasing age?

    <p>It gradually degenerates and is replaced by adipose tissue</p> Signup and view all the answers

    What type of antigens do interdigitating cells present to matured T-cells in the medulla?

    <p>Self-antigens from the body</p> Signup and view all the answers

    What initiates the positive selection process in T-cell development?

    <p>Recognition of self-MHC molecules</p> Signup and view all the answers

    What cellular process occurs in the medulla of the thymus to eliminate potentially autoreactive T-cells?

    <p>Apoptosis</p> Signup and view all the answers

    Which of the following best describes the function of the blood-thymus barrier?

    <p>Prevents immature T-cells from contacting foreign antigens</p> Signup and view all the answers

    What is the role of positive selection in T-cell maturation?

    <p>Allows T-cells to recognize self-MHC molecules</p> Signup and view all the answers

    Which process is characterized by the gradual replacement of thymic tissue with adipose tissue as one ages?

    <p>Involution</p> Signup and view all the answers

    What primarily influences the differentiation of T-cells in the cortex of the thymus?

    <p>Thymic hormones</p> Signup and view all the answers

    What is the main consequence of negative selection during the maturation of T-lymphocytes?

    <p>Removal of self-reactive T-cells</p> Signup and view all the answers

    What primarily occurs to T-cells after they mature in the cortex of the thymus?

    <p>They migrate to secondary lymphoid organs</p> Signup and view all the answers

    Which component of the blood-thymus barrier is NOT present?

    <p>Thymic reticular cells</p> Signup and view all the answers

    What characterizes acute involution of the thymus?

    <p>Increased lymphocyte death during stress</p> Signup and view all the answers

    What primarily composes the cortex of the thymus?

    <p>Immature T-lymphocytes</p> Signup and view all the answers

    What is found in the mantle zone of the lymphatic nodules in the spleen?

    <p>Narrow zone of small lymphocytes</p> Signup and view all the answers

    Which component primarily characterizes red pulp in the spleen?

    <p>Splenic cords and venous sinuses</p> Signup and view all the answers

    What role does the marginal zone serve in the spleen?

    <p>Removal of antibodies and lymphocytes from blood</p> Signup and view all the answers

    What primary structure is located within the white pulp of the spleen?

    <p>Germinal centers</p> Signup and view all the answers

    Where are Peyer's patches primarily located?

    <p>In the lamina propria of the small intestine</p> Signup and view all the answers

    What is the primary role of parenchyma in lymphatic organs?

    <p>Store free cells for immune response</p> Signup and view all the answers

    Which characteristic best describes the function of primary lymphatic organs?

    <p>Generate and mature lymphocyte precursors</p> Signup and view all the answers

    Which structure primarily supports the cells within the thymus?

    <p>Stroma formed by epithelioreticular cells</p> Signup and view all the answers

    What is the primary function of thymic hormones like thymulin and thymopoietin?

    <p>Regulate T-cell maturation and proliferation</p> Signup and view all the answers

    What occurs during the antigen-independent maturation of T-lymphocytes?

    <p>T-cells undergo differentiation without antigen exposure</p> Signup and view all the answers

    Which part of the thymic lobule contains developing T-lymphocytes?

    <p>Cortex</p> Signup and view all the answers

    What distinguishes the outer cortex of the thymus from the inner medulla?

    <p>The outer cortex is the site of T-cell maturation</p> Signup and view all the answers

    What is the main arrangement of cells found in nodular (follicular) parenchyma?

    <p>Concentrated clusters of lymphocytes</p> Signup and view all the answers

    Which of the following locations does NOT contain lymphatic vessels?

    <p>Cornea</p> Signup and view all the answers

    What is the primary function of lymph nodes in the lymphatic system?

    <p>Purification of lymph from foreign particles</p> Signup and view all the answers

    Which part of the lymph node is primarily responsible for housing B-lymphocytes?

    <p>Cortex</p> Signup and view all the answers

    What distinguishes swollen lymph nodes due to inflammation from those caused by a tumor?

    <p>Inflammation usually causes a painful enlargement.</p> Signup and view all the answers

    What is the significant feature of high endothelial venules (HEVs) in lymph nodes?

    <p>They facilitate B and T cell entry into the lymph nodes.</p> Signup and view all the answers

    Which of the following statements about the structure of lymph nodes is accurate?

    <p>Trabeculae connect to the stroma.</p> Signup and view all the answers

    What does lymphadenopathy refer to?

    <p>An enlargement of lymph nodes.</p> Signup and view all the answers

    The paracortex of a lymph node is primarily populated by which type of lymphocytes?

    <p>T-lymphocytes</p> Signup and view all the answers

    What is the role of the medullary cords in a lymph node?

    <p>To form a network leading to the efferent lymphatic vessel.</p> Signup and view all the answers

    Which component of a lymph node allows for the entry of arteries and nerves?

    <p>Hilum</p> Signup and view all the answers

    What is the main function of circulating dendritic cells in relation to naive T-lymphocytes?

    <p>To capture and present antigens for T-lymphocyte differentiation</p> Signup and view all the answers

    Which area of the lymph node is primarily known as the T-zone?

    <p>Inner cortex (paracortex)</p> Signup and view all the answers

    In the spleen, what is the primary role of the red pulp?

    <p>Removal of aged and damaged erythrocytes</p> Signup and view all the answers

    What characterizes a secondary nodule within the outer cortex of a lymph node?

    <p>Formation of a germinal center and active immune response</p> Signup and view all the answers

    Which structure serves as the filtration pathway for lymph entering the lymph node?

    <p>Afferent lymphatics</p> Signup and view all the answers

    Which component of the spleen is primarily involved in the initiation of immune responses?

    <p>White pulp</p> Signup and view all the answers

    Which part of the lymph node has no lymphoid nodules?

    <p>Inner cortex (paracortex)</p> Signup and view all the answers

    What does the subcapsular sinus do in the lymph node?

    <p>Receives lymph from afferent lymphatic vessels</p> Signup and view all the answers

    What happens to lymph as it passes through the medullary sinuses of a lymph node?

    <p>It is filtered and cleansed</p> Signup and view all the answers

    What main constituent does the medullary cords of the lymph node primarily contain?

    <p>B-lymphocytes and plasma cells</p> Signup and view all the answers

    Study Notes

    Functions of the Lymphatic System

    • Maintains fluid balance by returning interstitial fluid to the bloodstream.
    • Filters foreign particles and pathogens through lymph nodes.
    • Transports immune cells, specifically lymphocytes, throughout the body.
    • Absorbs and transports fatty acids and fats from the digestive system via the lacteals.

    Definition and Characteristics of Lymph

    • Lymph is a clear fluid composed of interstitial fluid, proteins, and immune cells.
    • It circulates through the lymphatic system, playing a crucial role in immune function and fluid balance.

    Lymphatic Nodules

    • Primary nodules are sites of lymphocyte development; secondary nodules are where activation occurs in response to antigens.
    • Secondary nodules exhibit germinal centers, indicating active proliferation of B lymphocytes.

    Lymph Nodes

    • Functions: Filter lymph, facilitate an immune response through antigen presentation, and support lymphopoiesis.
    • Location: Distributed throughout the body along lymphatic vessels, with 500–800 nodes arranged in clusters (e.g., neck, axilla, inguinal).

    Structure of Lymph Nodes

    • Capsule: Dense connective tissue that encloses the lymph node.
    • Cortex: Contains lymphoid nodules with B lymphocytes; provides the primary site for immune responses.
    • Medulla: Contains medullary cords and sinuses; facilitates the exit of lymph and immune cells.
    • High Endothelial Venules (HEVs): Specialized venues in paracortex facilitating lymphocyte entry into lymph nodes.

    Structure and Function of Spleen

    • Functions: Filters blood, recycles iron, and supports immune response through lymphocyte activation.
    • Division: White pulp (involved in immune response) and red pulp (involved in blood filtration).
    • Marginal zone: Transitional area between white and red pulp, rich in macrophages.

    Histology of the Spleen

    • White pulp consists of lymphatic sheaths surrounding central arteries: the periarterial lymphatic sheaths (PALS) contain T-lymphocytes.
    • Lymphatic nodules, containing B-lymphocytes, develop germinal centers upon antigen activation.
    • Red pulp comprises venous sinuses and splenic cords, housing various blood cells.

    Thymus Overview

    • Bilobed organ situated in the thoracic cavity, crucial for T lymphocyte maturation.
    • Functions include T lymphocyte development and hormone secretion that regulate immune cell maturation.

    Structure of Thymus

    • Capsule covers the thymus, with septa dividing the tissue into lobules.
    • Each lobule has a dark cortex (immature T cells) and a pale medulla (mature T cells and Hassall's corpuscles).
    • Epithelioreticular cells provide a supportive stroma and secrete important hormones for T cell development.

    T Cell Selection Processes

    • Positive selection: T cells must recognize self-MHC molecules to survive.
    • Negative selection: T cells that strongly bind to self-antigens undergo apoptosis to prevent autoimmunity.

    Blood-Thymus Barrier

    • Exists in the cortex to protect developing T lymphocytes from exposure to foreign antigens.
    • Components include specialized endothelial cells, perivascular connective tissue, and epithelioreticular cells.
    • The thymus enlarges in neonates but involutes with age, reducing in size and being replaced by adipose tissue.
    • Acute involution can occur due to severe stress or disease.

    Lymphatic Vessels

    • Begin as blind-ended capillaries and merge into larger vessels; located throughout the body (excluding specific tissues).
    • Lymphatic capillaries collect interstitial fluid, which is transported to lymph nodes for filtration.

    Tonsils

    • Aggregations of lymphoid tissue located near the oral and nasal cavities; involved in immune responses to inhaled or ingested antigens.
    • Palatine tonsils contain crypts lined by epithelium and associated lymphoid nodules.

    Peyer's Patches

    • Organized lymphatic nodules located in the lamina propria of the ileum, playing a role in immune surveillance in the gastrointestinal tract.
    • Composed of aggregates of lymphatic follicles that respond to intestinal antigens.

    Parenchyma and Stroma

    • Parenchyma consists of functional tissue made up of free cells stored in stroma.
    • Includes lymphocytes (precursors and effectors) and antigen-presenting cells (APCs) like macrophages and dendritic cells.
    • Cell arrangements in lymphoid organs can be diffuse or nodular (follicular).

    Functions of Lymphatic Organs

    • Primary Lymphatic Organs: Include red bone marrow and thymus, generating precursors of lymphocytes (pre-T and B-lymphocytes) and providing a microenvironment for maturation.
    • Secondary Lymphatic Organs: Involved in antigen-dependent proliferation and maturation of T and B-lymphocytes, forming active effector cells for immune response.

    Thymus

    • Bilobed organ located above the heart and below the thyroid gland.

    Functions of Thymus

    • Development of T-lymphocytes from red bone marrow, promoting proliferation and differentiation.
    • Secretion of hormones (thymulin, thymopoietin, thymosin) for T-cell maturation.
    • Hematopoiesis during fetal development.

    Structure of Thymus

    • Contains parenchyma (T-lymphocytes, macrophages, interdigitating cells) and stroma (epithelioreticular cells).
    • Composed of CT capsule, septa, and lobules (functional units); lobules consist of cortex (outer, dark) and medulla (inner, pale).

    Epithelioreticular Cells

    • Form a supportive meshwork in the stroma, allowing tight packing of T-cells.
    • Six types exist, secreting thymosin and thymopoietin, crucial for T-lymphocyte maturation.

    Cortex and Medulla of Thymus

    • Cortex: Contains densely packed immature T-lymphocytes and epithelioreticular cells; differentiation occurs under thymic hormones.
    • Medulla: Fewer T-cells as most enter the bloodstream; self-antigens presented by interdigitating cells, with apoptosis for those recognizing self-antigens preventing autoimmune disease.

    Positive and Negative Selection

    • Positive selection allows survival of lymphocytes recognizing self-MHC molecules.
    • Negative selection eliminates those that recognize self-antigens.

    Blood-Thymus Barrier

    • Exists only in the cortex to prevent immature T cells from contacting foreign antigens.

    Changes of Thymus with Age

    • Larger in neonates, shrinks with aging, replaced progressively by adipose tissue but never entirely disappears.
    • Acute involution may occur due to severe stress or diseases leading to increased lymphocyte death.

    Lymphatic Vessels

    • Begin as blind passages, merging into larger lymphatic trunks; not present in specific areas (e.g., CNS, bone marrow).
    • Filters lymph through lymph nodes, where lymphocytes, macrophages, and dendritic cells cleanse it from antigens.

    Lymph Nodes

    • Peripheral encapsulated lymphoid organs of variable size, typically 10–15 mm, with around 500–800 nodes in various regions.

    Functions of Lymph Nodes

    • Act as immunological filters; present antigens to initiate immune responses and support lymphopoiesis.

    Structure of Lymph Node

    • Composed of dense connective tissue capsule, trabeculae, reticular connective tissue stroma, cortex (B-lymphocytes), and medulla with medullary cords and sinuses.

    High Endothelial Venules (HEVs)

    • Located in paracortex, mainly facilitating entry of B and T cells into lymph nodes; also involved in naive T-lymphocyte programming.

    White and Red Pulp of Spleen

    • White Pulp: Contains periarterial lymphatic sheaths (PALS, T-zone) and lymphatic nodules (B-zone) for immune responses.
    • Red Pulp: Involves removal of old erythrocytes, blood storage, and erythrocyte formation during fetal life.

    Tonsils

    • Aggregates of lymphoid tissue without a capsule, located in the upper digestive tract; combat antigens entering through nasal and oral routes.

    Peyer's Patches

    • Organized lymphatic nodules in the ileum's lamina propria, crucial for immune surveillance in the intestines.

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