Lymphatics Flashcards
Volume of fluids that enters the interstitial space per day and its points of drainage.
20L leaves the arteriolar end per day and then 17L leaves the venular end. As a result, there is 3L unaccounted for that leaves via the lymphatic system. It drains into lymph capillaries which are ‘interlaced’ with blood capillaries.
Lymphatics in the CNS?
For many years it has been thought that waste interstitial fluid in the brain drained into the CSF and was removed that way and that there were no lymphatics as they could cause swelling. However, 2015 research found some lymph vessels in the meninges. Research is ongoing but they certainly are not as prolific as in other parts of the body.
How does fluid move along the lymphatic system?
Lymph vessels, like many veins, have one way valves. Additionally, they run alongside arteries, the pulsation of which moves lymph along. In the limbs, they run through the large skeletal muscle bodies which push lymph along when they contract. These are the major ways but those in the thorax experience a similar effect from pressure changes during ventilation.
Causes of Lymphoedema?
It can either be caused by a congenital lack of lymphatic vessels or by lymphatic vessels that do not work effectively (are not patent). This is known as Primary Lymphoedema. In secondary lymphedema, which occurs often after cancer treatment that damages lymphatics (or even the cancer itself doing this) lymph drainage to a particular region is compromised by tumour material, fibrosis or surgical resection.
Difference between Lymphoedema and Oedema of other causes?
Lymphoedema is a long term condition and represents a mechanical inability of lymph vessels to remove the excess fluid while in normal oedema this issue is caused by issues with starling’s forces etc. Lymphedema is also chronic so fibroblasts start to build up a collagen matrix in the area which means that the odema is non-pitting. Also, it does not go change much throughout the day and is associated with skin changes such as ulceration as skin breaks down due to all of the swelling.
Treatment for Lymphedema
This is a condition that cannot be cured. Quality of life can be maintained by physical therapy (to increase muscle pump effect), compression hosiery and good skin care (such as seen in diabetics to reduce the risk of ulceration).
Elephantiasis/Lymphatic Filariasis
This condition is similar to lymphedema and is caused by filarial worms commonly seen in parts of Africa.
Complications of Chronic Oedema:
- Cellulitis such as that associated with Strep infections (it is difficult to treat as getting Abx into the fluids is difficult).
- Ulceration and skin breakdown owing to swelling.
Types of Lymphatic Tissue
Can be diffuse or nodular.
Diffuse Lymphatics
These fall under the broad definition of Mucosa Associated Lymphatic Tissues (MALT), specifically gut associated and bronchus associated.
Lymphatic Nodules
Lymph nodes occur all over the body, specifically in the tonsils, peyer’s patches in the intestine (esp. in the ileum where there should not be bacteria to cope with reflux of these from the caecum). Finally, there are many lymph nodules in the vermiform appendix for a similar role.
Link between chicken pox and childhood appendicitis?
Some children can have appendicitis after an infection with chickenpox (varicella zoster virus) as it causes the lymph nodules in the appendix to swell. This closes the appendix off and bacteria start to multiply and cause inflamation = appendicitis.
Lymph Node Structure
Afferent lymphatics come in via the convex surface and filter through the germinal centres (in the node’s cortex) which are where the lymphocytes are stored. Efferent lymphatics leave via the hilum which is also where the artery and vein enter.
How do lymphocytes enter the lymph node?
Enter via the feeding artery as they will come from hematopoiesis in the bone marrow.
Folicular dendritic cells in the germinal centres?
The dendrites bind to the antigen-antibody complex and can retain this for long periods of time, allowing for the clonal selection (activation) of memory B cells.
