Podcast
Questions and Answers
Which anatomical structure drains the right upper arm and right side of the head and thorax?
Which anatomical structure drains the right upper arm and right side of the head and thorax?
How is lymph propelled through the lymphatic system?
How is lymph propelled through the lymphatic system?
What condition is characterized by severe localized edema due to the prevention of normal lymph return to the blood?
What condition is characterized by severe localized edema due to the prevention of normal lymph return to the blood?
Which type of cells mature into either T cells or B cells in the immune system?
Which type of cells mature into either T cells or B cells in the immune system?
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What mechanism increases the flow of lymph in the body?
What mechanism increases the flow of lymph in the body?
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Which area does the thoracic duct drain in the body?
Which area does the thoracic duct drain in the body?
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What is the main function of the lymph nodes in the body?
What is the main function of the lymph nodes in the body?
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What is the role of the cortex region in a lymph node?
What is the role of the cortex region in a lymph node?
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What is the role of the dendritic cells found in lymph nodes?
What is the role of the dendritic cells found in lymph nodes?
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What is the typical size range of lymph nodes?
What is the typical size range of lymph nodes?
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What is the role of the medulla region in a lymph node?
What is the role of the medulla region in a lymph node?
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Where are lymph nodes typically located in the body?
Where are lymph nodes typically located in the body?
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What is the main function of the lymphatic system?
What is the main function of the lymphatic system?
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Which of the following is NOT considered a part of the lymphatic system?
Which of the following is NOT considered a part of the lymphatic system?
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Where are lymphatic capillaries typically absent from?
Where are lymphatic capillaries typically absent from?
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What do lymphatic capillaries help to drain in the CNS?
What do lymphatic capillaries help to drain in the CNS?
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Which of the following can lymphatic capillaries take up that blood capillaries cannot?
Which of the following can lymphatic capillaries take up that blood capillaries cannot?
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How do lymphatic vessels ensure the flow of lymph?
How do lymphatic vessels ensure the flow of lymph?
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What is the main function of the MALT found in the mucosa of various organs?
What is the main function of the MALT found in the mucosa of various organs?
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Which of the following is NOT a type of tonsil in the human body?
Which of the following is NOT a type of tonsil in the human body?
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What is the function of tonsils in the body?
What is the function of tonsils in the body?
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How do tonsillar crypts contribute to the function of tonsils?
How do tonsillar crypts contribute to the function of tonsils?
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Where are Peyer's patches located in the human body?
Where are Peyer's patches located in the human body?
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What is the structural similarity between Peyer's patches and tonsils?
What is the structural similarity between Peyer's patches and tonsils?
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What specialized structures allow lymphatic capillaries to increase permeability?
What specialized structures allow lymphatic capillaries to increase permeability?
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What are lacteals?
What are lacteals?
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Which of the following is NOT a feature of larger lymphatic vessels compared to veins?
Which of the following is NOT a feature of larger lymphatic vessels compared to veins?
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Which of the following is NOT a named lymphatic trunk?
Which of the following is NOT a named lymphatic trunk?
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Where do the collecting lymphatic vessels typically travel in relation to blood vessels?
Where do the collecting lymphatic vessels typically travel in relation to blood vessels?
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What is the function of the internal valves in larger lymphatic vessels?
What is the function of the internal valves in larger lymphatic vessels?
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Study Notes
Lymphatic System Overview
- Lymphatic system returns fluids leaked from blood vessels back to blood
- Consists of three parts: network of lymphatic vessels, lymph, and lymph nodes
Lymph Transport
- Lymph system is a low-pressure system like venous system
- Lymph is propelled by:
- Milking action of skeletal muscle
- Pressure changes in thorax during breathing
- Valves to prevent backflow
- Pulsations of nearby arteries
- Contractions of smooth muscle in walls of lymphatics
- Physical activity increases lymph flow; immobilization of area keeps needed inflammatory material in area for faster healing
Lymphatic Trunks and Ducts
- Lymph is delivered from trunks into one of two large lymphatic ducts
- Right lymphatic duct drains right upper arm and right side of head and thorax
- Thoracic duct drains rest of body
- Each empties lymph into venous circulation at junction of internal jugular and subclavian veins on its own side of body
Clinical Imbalance: Lymphedema
- Severe localized edema caused by anything that prevents normal return of lymph to blood
- Examples: tumors blocking lymphatics or removal of lymphatics during cancer surgery
- Lymphedema may improve if some lymphatic pathways remain and enlarge
Lymphoid Cells and Organs
- Lymphoid cells consist of:
- Immune system cells found in lymphoid tissue
- Supporting cells that form lymphoid tissue structures
- Lymphocytes: cells of the adaptive immune system; mature into one of two main types:
- T cells (T lymphocytes)
- B cells (B lymphocytes)
Lymph Nodes
- Principal secondary lymphoid organs of the body
- Hundreds of nodes are found throughout the body
- Most are embedded deep in connective tissue in clusters along lymphatic vessels
- Some are nearer to body surface in inguinal, axillary, and cervical regions
- Two main functions of lymph nodes:
- Cleansing the lymph: act as lymph "filters"
- Preventing unwanted substances from being delivered to blood
- Immune system activation: offer a place for lymphocytes to become activated and mount an attack against antigens
Structure of a Lymph Node
- Vary in shape and size, but most are bean-shaped
- Small, less than 2.5 cm (~1 inch)
- Surrounded by external fibrous capsule
- Capsule fibers extend inward as trabeculae that divide node into compartments
- Two histologically distinct regions of node:
- Cortex
- Medulla
Cortex
- Superficial area of cortex contains follicles with germinal centers that are heavy with dividing B cells
- Deep cortex houses T cells in transit
- T cells circulate continuously among blood, lymph nodes, and lymph
- Abundant numbers of dendritic cells are closely associated with both T and B cells
- Play a role in activating both lymphocytes
Medulla
Lymphoid Organs and Tissues
- Provide structural basis of immune system by housing phagocytic cells and lymphocytes
- Structures include:
- Spleen
- Thymus
- Tonsils
- Lymph nodes
- Other lymphoid tissues
Distribution and Structure of Lymphatic Vessels
- Lymphatic vessels offer a one-way system, ensuring lymph flows only toward heart
- Lymph vessels (lymphatics) include lymphatic capillaries and larger lymphatic vessels
- Lymphatic capillaries:
- Blind-ended vessels that weave between tissue cells and blood capillaries
- Absent from bones, teeth, and bone marrow
- In CNS, in meninges where they help to drain interstitial fluid and CSF
- Lymphatic capillaries (cont.):
- Similar to blood capillaries, but more permeable
- Can take up larger molecules and particles that blood capillaries cannot
- Example: proteins, cell debris, pathogens, and cancer cells
- Can act as route for pathogens or cancer cells to travel throughout body
MALT (Mucosa-associated Lymphoid Tissue)
- Lymphoid tissues in mucous membranes throughout body
- Protects from pathogens trying to enter body
- Found in mucosa of:
- Respiratory tract
- Genitourinary organs
- Digestive tract
- Largest collections of MALT found in:
- Tonsils
- Peyer's patches
- Appendix
Tonsils
- Simplest lymphoid organs
- Form ring of lymphatic tissue around pharynx; appear as swellings of mucosa
- Named according to location:
- Palatine tonsils
- Lingual tonsil
- Pharyngeal tonsils
- Tubal tonsils
- Tonsils function:
- Gather and remove pathogens in food or air
- Contain follicles with germinal centers and scattered lymphocytes
- Are not fully encapsulated
- Overlying epithelium invaginates, forming tonsillar crypts
- Bacteria or particulate matter enters crypts, where they are trapped and destroyed
- Risky to lure bacteria into tissues, but allows immune cells to become activated and build memory cells against these potential pathogens
Peyer's Patches
- Clusters of lymphoid follicles in wall of distal portion of small intestine
- Also called aggregated lymphoid nodules
- Structurally similar to tonsils
- Location aids in functions:
- Destroy bacteria, preventing them from breaching intestinal wall
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Description
Test your knowledge on the lymphatic system and lymphoid organs and tissues with this quiz. Learn about the network of lymphatic vessels, lymph fluid, and the function of lymph nodes in cleansing lymph. Explore the structural basis of the immune system provided by phagocytic cells and lymphocytes in lymphoid organs and tissues.
