Lymphoid Organs and Immune System Overview

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Questions and Answers

Which characteristic is exclusive to Hodgkin's lymphoma compared to Non-Hodgkin's lymphoma?

Malignancy of lymph nodes (correct)

Being the 5th most common cancer

Rapid metastasis of lymphocytes

Unknown etiology

What is the primary function of the spleen related to blood cells?

Cleansing the blood of aged cells and platelets, along with debris. (correct)

Storing new white blood cells.

Initiating lymphocyte proliferation and response.

Producing new red blood cells.

Where do the lymphatic collecting vessels primarily drain in the head and neck?

Thoracic duct

Axillary nodes

Inguinal nodes

Cervical nodes (correct)

What physiological change occurs in lymph nodes after antigen stimulation?

More than 20-fold increase in the flow rate. Signup and view all the answers

Which of the following is typically NOT a function associated with the spleen?

Storage of new white blood cells Signup and view all the answers

Which of the following best describes the primary function of mucosa-associated lymphatic tissue (MALT)?

To protect the digestive and respiratory systems from foreign matter. Signup and view all the answers

What is a key function of Peyer's patches and the appendix?

To generate 'memory' lymphocytes and prevent bacteria from breaching the intestinal wall. Signup and view all the answers

What is the primary role of the tonsils within the human body?

To prevent pathogens in the respiratory and digestive tracts from penetrating mucous membranes. Signup and view all the answers

Which type of immune cells are predominantly found in the lamina propria according to the content?

Activated CD4+ T cells Signup and view all the answers

Which of the following is NOT a type of tonsil?

Gastric tonsils Signup and view all the answers

Which of the following accurately describes the maturation process of T cells?

They migrate from the bone marrow and mature in the thymus, developing antigen receptors on their plasma membrane. Signup and view all the answers

What is the primary role of T cells, specifically in relation to B cell activity?

To destroy cells and stimulate B cells and also have the ability to check for the presence of MHC. Signup and view all the answers

What is the role of MHC molecules in the immune system?

To present antigens to T cells, which is vital for immune response. Signup and view all the answers

Which of the following is a key component of the lymphatic system's structure?

A network of lymphatic vessels, lymph fluid, and lymphoid tissues and organs. Signup and view all the answers

Where are the MHC-II molecules primarily found?

Exclusively on antigen-presenting cells (APCs). Signup and view all the answers

Which of the following locations does NOT contain lymphatic capillaries?

Teeth Signup and view all the answers

What is the primary function of lacteals?

Absorbing digested fats and delivering them to the blood Signup and view all the answers

What is the direction of flow in the lymphatic system?

From the tissues to the heart Signup and view all the answers

If the lymphatic system is blocked or surgically removed, what condition might a person develop?

Edema Signup and view all the answers

What is a characteristic of the minivalves in lymphatic capillaries?

They only allow fluid to enter the capillaries. Signup and view all the answers

What substances, besides excess tissue fluid, can lymphatic capillaries pick up?

Bacteria, viruses, proteins, and electrolytes Signup and view all the answers

In which region of the body are the axillary lymph nodes located?

Armpit Signup and view all the answers

What is the role of the high endothelial venules (HEV) in the lymphatic system?

They are present in lymph nodes and Peyer's patches, and function in lymphocyte trafficking. Signup and view all the answers

What is the primary function of the lymphatic system regarding interstitial fluid?

To return interstitial fluid and leaked plasma proteins back to the blood. Signup and view all the answers

How does fluid move through the lymphatic system?

Through the activity of skeletal muscles and pulsations of nearby arteries. Signup and view all the answers

What makes lymphatic capillaries highly permeable?

Endothelial cells overlap to form one-way minivalves. Signup and view all the answers

What is the role of lymph nodes in the lymphatic system?

To filter lymph fluid for antigens and bacteria. Signup and view all the answers

Where does the lymph fluid return to the circulatory system?

Into the subclavian veins. Signup and view all the answers

What is characteristic about the movement of lymph fluid in the lymphatic system?

It is a one-way system always moving towards the heart. Signup and view all the answers

Which of the following is NOT a component that can enter the lymphatic system?

Red blood cells Signup and view all the answers

What is the hilum of a lymph node?

The region where efferent lymphatic vessels exit. Signup and view all the answers

What is the primary function of the red pulp in the spleen?

Filtering blood and removing worn-out red blood cells Signup and view all the answers

Which of the following is a unique characteristic of the thymus compared to other lymphoid organs?

It functions solely in T lymphocyte maturation without directly fighting antigens Signup and view all the answers

What type of cells primarily populate the white pulp of the spleen?

Lymphocytes on reticular fibers Signup and view all the answers

Which hormones are secreted by the thymus?

Thymosin and thymopoeitin Signup and view all the answers

What are Hassall’s corpuscles and where are they found?

Aggregations of epithelial cells in the thymus medulla Signup and view all the answers

Which area of the thymus contains a high density of lymphocytes and scattered macrophages?

The cortex Signup and view all the answers

What do Langerhans cells residing in the skin do after capturing antigens?

They migrate to the dermal area Signup and view all the answers

What type of cells are found in the Intraepithelial lymphocytes (IEL) of the skin?

TCD8+ cells Signup and view all the answers

Study Notes

Lymphoid Organs and System

Lymphoid tissues are categorized as primary, secondary, and tertiary
Primary lymphoid organs (Thymus, bone marrow, yolk sac, liver, and spleen) are where lymphocytes develop and mature.
Secondary lymphoid organs (lymph nodes, spleen, tonsils, payer's patches, appendix) are where immune responses occur.
Tertiary lymphoid organs refer to sites where immune responses occur anywhere.
Lymphocytes include T cells (80% of circulating lymphocytes), B cells (10-15% of circulating lymphocytes), and natural killer (NK) cells (5-10% of circulating lymphocytes)
T cells are further categorized, including cytotoxic, regulatory, and memory cells, each with distinct functions in the immune system. T cells, in general, attack foreign and faulty cells.
B cells differentiate into plasma cells to produce antibodies to target pathogens.
NK cells are part of the immune system's surveillance mechanism, attacking and destroying infected or cancerous cells.
Different cell types express distinct cell surface receptors (e.g., CD3+, CD4+, CD8+, CD19+, CD20+, CD16+, CD56+, CD14+, CD11c+)
The process of producing naïve lymphocytes (in mice, 1-3 months) is under equilibration, involving lymphocyte death via apoptosis for homeostasis.
Lymphoid tissues include lymph nodes, spleen, thymus, payer's patches, tonsils, and bone marrow and appendix.
Lymphatic capillaries are similar to blood capillaries but are very permeable and have valves preventing backflow.
Lymph nodes filter lymph, removing antigens, bacteria, and other debris; B and some T cells mature in these nodes.

Lymph

Lymph is the fluid that moves via the lymphatic vessels
Lymph transport relies on skeletal muscle activity and pulsating arteries.
About 3 liters of lymph enter the bloodstream per 24 hours.

Lymphatic System

The lymphatic system is a one-way system from the tissues to the heart
It collects excess tissue fluid and leaked proteins in the body.
Edema occurs if the system is blocked or surgically removed
Lymphatic vessels are present in most areas of the body where blood capillaries occur.
The lymphatic system is part of the immune system, helping to return interstitial fluid, protein, and other fluid elements from the tissues to the bloodstream.

Lymph Node Anatomy

Lymph nodes contain follicles with germinal centers
Lymph nodes are not fully encapsulated.
Epithelial tissue invaginates to form tonsillar crypts, trapping and destroying bacteria and particulate matter.
Lymphocytes congregate in the lymph node.

What is in the lymphatic system?

Lymph nodes are part of the lymphatic system, filtering lymph fluid for antigens, bacteria, and other foreign substances.
Lymph nodes are a common site for certain cancers, such as Hodgkin's lymphoma (lymph node malignancy) and Non-Hodgkin's lymphoma.
The multiplication and metastasis of lymphocytes, part of the lymphatic system, are involved in immune responses.

Lymphatic Capillaries

Lymphatic capillaries are very permeable, taking up cell debris, pathogens, and cancer cells.
Endothelial cells overlap to form one-way minivalves, preventing collapse.

Lymphocyte Recirculation

Lymphocyte homing is a selective process for specific tissues, not general.
It is antigen-dependent.
Naive T cell migration differs from effector and memory T cell migration.
Cell migration is controlled by adhesion molecules (selectins, integrins, super Igs).

Immune System in Skin

The immune system in skin involves Langerhans cells, intraepidermal lymphocytes (IEL), and perivascular macrophages.

MALT

Mucosa-associated lymphatic tissue (MALT) protects digestive and respiratory systems from foreign matter.
MALT includes Peyer's patches, tonsils, and appendix.

Aggregates of Lymphoid Follicles

Peyer's patches and appendix are aggregates of lymphoid follicles in the small intestine.
They destroy bacteria, preventing them from breaching the intestinal wall, and generate memory lymphocytes.

Tonsils

Tonsils are simplistic lymphoid organs that form a ring in the pharynx.
Tonsils include palatine, lingual, pharyngeal, and tubal tonsils.
Tonsils prevent pathogens from penetrating the mucous membrane in the respiratory and gastrointestinal tracts by having a high antibody response and tolerance in T cells.

Spleen

The spleen is the largest lymphoid organ.
It's served by splenic artery and vein, entering and exiting at the hilus.
The spleen is the site of lymphocyte proliferation and response.
It cleanses the blood of aged cells, platelets, foreign matter, bacteria, viruses, and debris.
It stores breakdown products of red blood cells (e.g., iron).
Erythropoiesis occurs in the fetus.

Structure of the Spleen

The spleen is divided into white pulp (lymphocytes around central arteries) and red pulp (venous sinuses and cords).
White pulp is involved in immune functions, while red pulp disposes of worn-out red blood cells and pathogens.

Thymus

Thymus is located on top of the heart.
It secretes thymosin and thymopoietin, causing T-lymphocytes to function against pathogens.
It is most active during childhood and often replaced by fibrous and fatty tissue in adulthood.
It is important for T cell maturation.
The thymus has distinct cortex and medulla regions containing lymphocytes and macrophages. Thymic Hassal's corpuscles are in the medulla and involved in regulatory T cell development.

Other

High endothelial venules (HEV) are specific to lymph nodes and Peyer's patches.
Naive T-cells express L-selectin, and activated T cells express other ligands allowing for entry into the lymph nodes.

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Description

Explore the essential components of the lymphoid system, including the differentiation between primary, secondary, and tertiary lymphoid organs. Understand the roles of various lymphocytes, including T cells, B cells, and NK cells, in the immune response. This quiz will deepen your knowledge of how the immune system operates and the function of each lymphoid organ.