Session 12 - The Lymphatic System Flashcards
What is the difference between lymph and chyle?
Lymph: The fluid that flows around the lymphatic system and resembles plasma but has lower amounts of proteins
Chyle: The Lymph that arises in the GI tracts. It contains higher concentrations of fats and dissolved lipids. Chylomicrons and fat soluble vitamins. It re-joins the vascular system as normal lymph does
Describe the vessel structure of the lymphatics system
(Blunt ended/blind ended) Capillaries > Trunks > Ducts > Veins (vascular veins as they re-join it).
- They have valves to prevent back flow
- In the limbs, the deep lymphatics pass through muscles where contraction aids lymph movement.
- Ducts and Trunks also contain smooth muscle cells in their walls and contribute to the flow of lymph
- serves as a “filter” as lymph percolates on its way to the vascular system. Trapping antigens, processes antigen and macrophage presents processed antigen to T cell.
- Repository of macrophages, B cells and T cells
How and where is the lymph returned to the vascular system?
- The upper tight quadrant (right arm, right hemisphere of head, upper right quarter of thorax) drains into the RIGHT SUBCLAVIAN VEIN by the right lymphatic duct
- The rest of the body drains into the LEFT SUBCLAVIAN VEIN by the thoracic duct
Describe the structure of lymph node and where are the most clinically important ones are found?
- Have multiple “follicles” that contain immune cells
- Shaped like a kidney
- Each has multiple afferent lymphatic vessels (that enter the convex surface)
- A single efferent lymphatic vessel. That leaves via the concave hilum.
- Each lymph node has a feeding artery and draining vein that also enter and leave via the hilum
Clinically Important locations:
- Neck (cervical), groin (inguinal), armpit (axillae)
Follicular dendritic cells are found within lymph nodes. What are they?
- They are located in the germinal centers
- Antigen antibody complexes adhere to their dendritic processes and retain antigens for months
- These can then stimulate the proliferation of B cells
What is Lymphadenopathy?
This is the swelling of a lymph node die to infection. The germinal centers fill with increasing numbers of lymphocytes causing the lymph nodes to swell.
- Cancers can also metastasise via the lymph nodes which can cause swelling
- Or there can be malignancy of the tissue itself
Name the main organs of the lymphatic system
- Thymus - in the superior mediastinum
- Bone Marrow - Red Bone Marrow
- Spleen - Left side of abdomen
- Tonsils - Oropharynx and Nasopharynx
- Appendix - lower right quadrant of abdomen
- Payer’s Patches - under mucosal membrane of small intestine
What is the thymus?
- Located just inferior and anterior to the heart and between the lungs in the super mediastinum.
- It’s function is to mature none marrow derived stem cells into immunocompetent T cells (“thymic cell education”)
What is the spleen?
- Located inferior to the diaphragm and posterior to stomach
- Similar structure to lymph node separated into white and red pulp
- It filters blood in the same way that lymph nodes filter lymph. Having immune and hemopoietic systems:
Immune Function:
- Antigen presentation by APCs
- Activation and proliferation of B and T lymphocytes, production of antibodies
Hemopoietic Functions:
- Removal and destruction of old, damaged erythrocytes and platelets
- Retrieval of iron
- Erythrocyte storage
What is a splenectomy and what impacts may it have?
- Removal of the spleen. The liver can take over erythrocyte management
- Increases risk of infection by encapsulated bacteria and malaria (spleen good at removing these).
What is splenomegaly?
Enlargement due to response to localised infection (like lymph nodes) and to systemic infection (septicaemia)
- It can enlarge 10x its normal size
What are the tonsils?
- They are located in the oropharynx and nasopharynx
- Prevent pathogen ingress through oral and nasal routes
- Surface epithelia have numerous microfold (M cells) which present antigens to underlying immune cells
What is the vermiform appendix?
- Located inferior to and attached to caecum (ascending colon).
- many M-fold cells in epithelial surface
- functions to prevent pathogen ingress through GI routes
What are payers patches?
- Located inferior to and attached to side of ileum (only 1 side)
- again have many M fold cells on epithelium surface and as such prevent pathogen ingress through digestion
Outline the 4 main functions of the lymphatic system
1) fluid balance - return of interstitial fluid (most but not all, some returns directly into capillaries)
2) Transport of fats and fat-soluble vitamins
3) Defence against invading pathogens and disease
4) Storage and destruction of ages erythrocytes - spleen responsible for this role
