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Questions and Answers
What are the two overlapping systems of the Lymphatic System?
What are the two overlapping systems of the Lymphatic System?
What fluid is absorbed by the lymphatic system?
What fluid is absorbed by the lymphatic system?
Lymph
Lymphatic capillaries are less permeable than blood capillaries.
Lymphatic capillaries are less permeable than blood capillaries.
False
What structures form the basis of the immune system?
What structures form the basis of the immune system?
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Which of the following is NOT a type of lymphatic vessel?
Which of the following is NOT a type of lymphatic vessel?
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What is the role of macrophages in lymphoid tissues?
What is the role of macrophages in lymphoid tissues?
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The specialized lymphatic capillaries that absorb fat in the small intestine are called ______.
The specialized lymphatic capillaries that absorb fat in the small intestine are called ______.
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What are the two major functions of lymphoid tissues?
What are the two major functions of lymphoid tissues?
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Which lymphatic duct drains lymph from the right upper limb and right side of the head?
Which lymphatic duct drains lymph from the right upper limb and right side of the head?
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Study Notes
Lymphatic System Overview
- The lymphatic system and lymphoid tissues/organs work together to maintain cardiac function and protect the body from infection.
- The lymphatic system returns leaked fluids from the vasculature back to circulation.
- Lymph is a fluid transported via lymphatic vessels.
- Lymph nodes cleanse lymph as it passes through.
- The lymphoid tissues/organs are the structural basis of the immune system, including the spleen, thymus, and tonsils.
Lymphatic Vessels
- Fluid is pushed out of circulation by hydrostatic and colloid osmotic pressures at capillary beds.
- About 3 liters of fluid daily become interstitial fluid.
- Lymphatic vessels absorb this fluid and return it to the circulatory system, maintaining blood volume.
- Absorbed fluid is called lymph.
Lymphatic Capillaries
- Lymphatic capillaries weave between cells and blood capillaries in loose connective tissue of the body.
- They are exceptionally permeable.
- Adjacent cells overlap, forming minivalves.
- When interstitial fluid volume increases, the valves are pushed open to allow fluid entry.
- Specialized lymphatic capillaries called lacteals absorb fat in the small intestine.
Larger Lymphatic Vessels
- Vessels have the same three tunics as veins but have thinner walls with more anastomoses (connections between branches).
- Trunks drain large areas of the body, named according to the region they drain.
- Lymphatic ducts: Right lymphatic duct drains the right upper limb and right side of the head and thorax.
- Thoracic duct drains the rest of the body.
- Both ducts empty into the junction of the internal jugular vein and subclavian vein.
Lymph Transport
- Lymphatics have no pump mechanism; movement relies on low-pressure conduits.
- Mechanisms contributing to lymph movement include skeletal muscle movements, pressure changes in the thorax during breathing, valves preventing backflow, nearby artery pulsation, and smooth muscle contractions in lymph vessels.
- Lymph movement is sporadic and slow.
Lymphoid Cells
- Immune system cells are found in lymphoid tissues, providing support and structure.
- Lymphocytes (T cells and B cells) are the main warriors of the immune system.
- Macrophages, dendritic cells, and reticular cells also play vital roles.
- Lymphocytes perform antigen presentation; the dendritic cells are superior to macrophages in antigen presentation.
- Lymphoid cells form a network called stroma, supporting other cell types in lymphoid organs.
Lymphoid Tissues & Organs
- Lymphoid tissues have two major functions: proliferation sites for lymphocytes and surveillance vantage points for lymphocytes and macrophages.
- Lymphoid tissues are organized as diffuse lymphoid tissue (loose arrangement) and lymphoid follicles (nodules).
- Lymphoid organs are virtually all organs, including tonsils, thymus, spleen, Peyer's patches, and appendix.
- The lymphatic tissues and organs help protect the organism from infection.
Lymph Nodes
- Hundreds of lymph nodes cluster around lymphatic vessels.
- Two basic functions: filtration, and immune activation (lymphocyte activation).
- Lymph nodes contain macrophages and lymphocytes.
- External capsule, trabeculae, cortex, medulla, sinuses, and vessels (afferent and efferent) are key structural elements.
Additional Lymphoid Organs (Thymus, Spleen, and MALT)
- Thymus: Site of T-lymphocyte maturation, activity decreases with age; stroma is epithelial cells not reticular fibers.
- Spleen: Largest lymphoid organ; erythrocyte graveyard, removing old/defective erythrocytes and platelets; storage of platelets and monocytes; possible fetal erythrocyte production.
- MALT (Mucosa-Associated Lymphoid Tissue): Includes tonsils, Peyer's patches, and appendix; they capture and remove pathogens in different body regions.
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Description
Explore the critical roles of the lymphatic system in maintaining fluid balance and immune defense. This quiz covers lymphatic vessels, capillaries, and the functions of lymphoid tissues and organs. Test your knowledge on this essential body system and its components.
