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What structural feature of lymphatic capillaries allows for the uptake of fluid?
Where do antigens become trapped and induce immune responses?
What is the primary function of lymphatic vessels?
Which of the following tissues lack lymphatic vessels?
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What type of lymphatic fluid can be found circulating in lymphatic vessels?
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What is the primary function of the afferent lymphatic vessels in lymph nodes?
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Which part of the lymph node serves as the exit point for efferent lymphatic vessels?
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The reticular tissue in the lymph node is mainly composed of which of the following?
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What is the role of trabeculae within the lymph node?
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Which feature distinguishes the hilum of a lymph node?
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From which embryonic structure does the thymus develop?
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What role do common lymphoid progenitor (CLP) cells play in thymus development?
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At what point is the thymus fully formed and functional?
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What happens to the thymus around the time of puberty?
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Where is the thymus located in relation to other structures?
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What happens to the thymus after puberty?
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Which of the following arteries supply blood to the thymus?
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Which veins drain the thymus?
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What is a common consequence of total splenectomy in adults?
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What may be necessary to treat severe cases of splenomegaly?
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Accessory spleens typically range in size from:
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Post-splenectomy, what is one of the major health risks encountered?
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What describes splenosis?
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What factor promotes lymphangiogenesis in cancer?
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What role does VEGF play in the lymphatic system during cancer progression?
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Where may accessory spleens typically develop?
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What is one potential issue associated with a ruptured spleen repair?
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Which condition most commonly leads to lymphangitis?
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What might cause splenomegaly?
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Which organism is commonly associated with skin-related lymphangitis?
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What is the consequence of targeting the VEGF axis in cancer treatment?
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What can cause lymphangitis besides infectious agents?
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Which of the following is NOT a typical cause of lymphangitis?
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What effect does lymphangiogenesis have on lymph nodes?
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Study Notes
Thymus Development
- Develops bilaterally from the third pharyngeal pouch (endoderm).
- Initial invagination of epithelium grows caudally into the mediastinum, eventually disconnecting.
- Common lymphoid progenitor (CLP) cells from bone marrow invade epithelial rudiment, becoming immunocompetent T cells.
- Fully formed and functional thymus at birth.
- Significant involution around puberty as T-cell maturation decreases and lymphatic tissue replaced by adipose tissue.
- In some infants, the thymus may compress the trachea.
Thymus Anatomy
- Primary lymphoid organ located in the inferior neck and anterior superior mediastinum.
- Flask-shaped lobes posterior to the manubrium, extending anteriorly to the fibrous pericardium.
- Rich arterial supply from anterior intercostal and anterior mediastinal branches of internal thoracic arteries.
- Drains via veins into left brachiocephalic, internal thoracic, and inferior thyroid veins.
- Lymphatic vessels drain into parasternal, brachiocephalic, and tracheobronchial lymph nodes.
Lymphatic Vessels Overview
- Begin as anastomosing lymphatic capillaries, forming plexuses to drain interstitial fluid (ISF) and create lymph.
- Capillaries feature flap valves for fluid uptake and collagen threads for anchorage.
- Lymph transports antigens to lymph nodes (LNs), inducing adaptive immune responses.
- Circulation is unidirectional — from tissues towards the heart.
- Absent in CNS, eyeball, and compact bone.
Lymphatic Capillary Features
- Composed of a single layer of overlapping lymphatic endothelial cells, resembling oak leaves.
- Lack a basement membrane.
Spleen Issues
- Repairing a ruptured spleen can be complicated; splenectomy may be necessary to prevent fatal bleeding.
- Subtotal splenectomy allows for rapid regeneration, while total splenectomy usually presents no severe effects in adults as the liver and bone marrow compensate.
- Post-splenectomy, increased susceptibility to bacterial infections may occur.
- Splenomegaly can be caused by granulocytic leukemia, hypertension, or hemolytic anemias, with potential enlargement up to 10 times normal size.
Accessory Spleens & Splenosis
- Accessory spleens may develop near the splenic hilum, tail of the pancreas, or mesentery; common with typically small size.
- Importance for identification during splenectomy to avoid persistent symptoms.
- Splenosis involves autoimplantation of ectopic splenic tissue following rupture, dispersing into peritoneum or omentum.
Lymphatic Vessel Remodeling
- Occurs in cancer, inflammatory conditions, or injuries, prompting lymphangiogenesis.
- Tumor and immune cells produce VEGF (vascular endothelial growth factor), promoting lymphangiogenesis proximal and distal to draining lymph nodes.
- Facilitates metastasis by allowing primary tumors to spread to secondary sites.
- Targeting the VEGF axis is a strategy in cancer therapy.
Lymphangitis
- Inflammation of lymphatic vessels often following microbial invasion due to skin wounds or abrasions.
- Common causative organisms include Streptococcus pyogenes, Staphylococcus aureus, Pasteurella multocida (dog bites), and Sporothrix schenckii (thorn injuries).
Structure of Lymph Nodes
- Capsules composed of dense connective tissue surround lymph nodes.
- Trabeculae extend from the capsule, forming internal frameworks.
- Reticular tissue, made up of reticular cells and fibers, supports immune functioning within the node.
- Afferent lymphatic vessels bring lymph to the node, entering at various points.
- Efferent lymphatic vessels convey lymph away from the node, exiting at the hilum, which also serves as an entrance for blood vessels and nerves.
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Description
Explore the intricate details of thymus development and its anatomical structure. This quiz delves into the origins, functions, and key aspects of thymic development, particularly its role in T cell differentiation and changes during puberty. Test your knowledge on this essential organ of the lymphatic system.
