Session 12 ILOs - The Lymphatic system

Question 1

List the components of lymphatic system, where in the body they are and where lymphatics are not found

Answer 1

Thymus: in the mediastinum

Bone Marrow: red bone marrow of bones

Tonsils: oropharynx and nasopharynx

Appendix: lower right quadrant of abdomen

Payer’s Patches: under muscoal membrane of the small intestine

Spleen: posterior to stomach (left side of abdomen)

Lymphatics are NOT found in the brain/CNS - cerebrospinal fluid is thought to fulfil the role of lymph in the CNS

Question 2

Describe the role the lymphatic system in the presentation of foreign bodies to the immune system

Answer 2

The lymphatic system presents forge in bodies through:

Lymph nodes - contain multiple follicles containing immune cells (including T cells) which can present antigens. Specifically, antigen presenting cells (APCs) which includes B lymphocytes, which allow them to be recognised by the T cells.

Question 3

Describe the role of sentinel lymph nodes in metastatic cancer

Answer 3

Sentinel lymph nodes are the lymph nodes closest to the cancer tumour - first node to receive lymph from an area of a primary tumour

The cancer sends out protein vesicles which interact with myeloid cells and because them to have an effect, (e.g. making matrix) which means the cancer cell has the right environment to grow when it does metastasise

Therefore you can test this node to see whether the cancer has spread, used in the following cancers:

1. Malignant melanoma
2. Breast cancer
3. Endometrial cancer

Question 4

Explain the function of the tonsils, thymus, lymph nodes, the spleen and vermiform appendix

Answer 4

Tonsils: protect the oropharynx and nasopharynx AND aural route from pathogens (line of defence at openings)

Thymus: allow T cells to mature into immunocompetent T lymphocytes (from bone marrow derived stem cells)

Lymph nodes: contain all of the immune cells

Spleen: filters blood - haemopoietic and immune functions
Haemopoietic - removal and destruction of RBC and platelets and RBC storage
Immune - antigen presentation by APC and activation and proliferation of B and T cells and production of antibodies

Vermiform appendix: prevents pathogen ingress through GI routes and ileum

Question 5

Outline how fluid (lymph) travels through the lymphatic system and give examples of what happens when lymph does not move as expected

Answer 5

Lymph travels through the lymphatic system, through lymphatic vessels which have valves to ensure unidirectional flow of lymph. Lymph enters the lymphatic vessels from the interstitial fluid through small gaps.

Tissue fluid -> lymphatic capillary -> vessel -> node (filtration) -> trunk -> duct -> vein

Muscle contraction assists lymph movement and larger lymphatic vessels contain smooth muscle which is under autonomic control.

If valves are damaged, then lymph cannot return back and there is fluid accumulation

Question 6

Describe the difference between primary and secondary lymphoedema

Answer 6

Primary lymphoedema is generally hereditary and is there from birth (3 types with differing onset, Milroy’s disease, Meige’s disease and Tarda)

Secondary lymphoedema is usually caused by a medical intervention (e.g. removing excess lymph nodes accidentally) or sometimes by parasites or infections