Flashcards in The Lymphatic System Deck (24):
Which cells does the lymphatic system consist of?
– Lymphocytes (B cells, T cells and Natural Killer (NK) cells)
– Supporting cells, in particular follicular dendritic cells and macrophages
Where can lymphatic vessels be found?
- Lymphatics tend to lie adjacent to arteries and veins
- Like veins, lymphatic vessels are arranged into superficial and
deep (deep to the deep fascia). Flow is superficial to deep.
- In the limbs the deep lymphatics pass through muscles. Muscle contraction within the deep compartments is critical to lymph
Which lymphatics contain smooth muscle in their walls and why?
- Larger lymphatics, in the abdomen or thorax for example contain smooth muscle in their walls.
- Contraction of this smooth muscle is an important contributor to lymph flow at these sites
What helps to propel the lymph fluid?
- Skeletal muscle movement
- Pressure changes in the thorax during breathing
- Pulsations of adjacent arteries
What tissues are involved with the lymphatic system?
– Diffuse, mucosal associated lymphatic tissue (MALT), this includes gut-associated lymphatic tissue (GALT) and bronchus-associated lymphatic tissue (BALT)
– Lymphatic nodules which include Tonsils, Peyer’s patches and the
Name three major organisms of the lymphatic system
– Lymph nodes
What is a Peyer's patch?
Peyer's patches are small masses of lymphatic tissue found throughout the ileum region of the small intestine. Also known as aggregated lymphoid nodules, they form an important part of the immune system by monitoring intestinal bacteria populations and preventing the growth of pathogenic bacteria in the intestines
How can chicken pox lead to appendicitis?
During chicken pox lymphatic nodule tissues on the vermiform appendix become really inflamed. These block off the appendix so that the contents cant get out, leading to infection and appendicitis.
What is the function of a lymph node?
• Serve as filters as lymph percolates on its way to the vascular
What is the difference between an afferent and an efferent lymphatic?
Each node has:
- afferent lymphatic vessels that enter via the convex surface
- efferent lymphatics that leave via the hilum
How do the lymph node feeding artery and draining vein enter and leave?
Each lymph node has a feeding artery and draining vein that enter and leave via the hilum
What is the function of a follicular dendritic cell?
• Antigen antibody complexes adhere to their dendritic processes and the cell can retain antigen for months
• Follicular dendritic cells cause proliferation of B cells, in particular
memory B cells
Where are follicular dendritic cells located?
Located in the germinal centres
Explain the importance of antigen presenting cells
Unlike B cells, T cells fail to recognize antigens in the absence of antigen presentation
What is the bodies first response to an antigen?
- Inflammatory response.
- Mediated mainly by neutrophils and/or macrophages.
- Degradation of the antigen may lead to presentation of a portion of
the antigen to elicit a specific immune response
The specific immune response is composed of which two immune responses?
- Humoral (within the body fluid)
- Cell mediated
What is humoral immunity?
Humoral immunity is B lymphocyte mediated and involves antibody production by B lymphocytes that transform into plasma cells that synthetise and secrete a specific antibody
What is cell-mediated immunity?
Cell-mediated immunity is T cell mediated. T cells need antigen
presenting cells (macrophages, B lymphocytes) to recognise antigen.
When is cell-mediated immunity particularly important?
Cell-mediated immunity is important in defence against:
– viral, fungal and mycobacterial infections
– tumour cells
– transplant rejection
What is lymphadenopathy?
- Enlarged lymph nodes
- As lymph nodes fight infection the germinal centres fill with
increasing numbers of lymphocytes causing the lymph nodes to swell
- Can also cause some pain
- Cancers can metastasise to lymph nodes vie the afferent lymphatics
- Lymphoma often presents with lymphadenopathy
What is the spleen?
- Largest lymph organ
- Very rich blood supply
- The spleen filters blood in the same way that lymph nodes filter
- It has functions in both the immune and haemopoietic systems
Explain the spleens role in the immune system
– Antigen presentation by APCs
– Activation and proliferation of B and T lymphocytes, production of
– Removal of macromolecular antigen from blood (macrophages do this)
The spleen may enlarge as a result of infection.
Describe the haemopoietic functions of the spleen.
– Removal and destruction of old, damaged and abnormal erythrocytes and platelets
– Retrieval of iron from erythrocyte haemoglobin