Introduction into the lymphatic system Flashcards
What is the lymphatic system?
The Lymphatic System is the cleansing system
The lymphatic system acts as a countercurrent system draining from the tissues all waste materials and recycling surplus fluid, salts, proteins, fat and immune cells back to the body.
What does the lymphatic system look like?
Lymphatic capillaries (initial lymphatics):
Blind ended
No smooth muscle
Incontinuous basement membrane
Collecting vessels:
Smooth muscle coverage
Luminal valves
Basement membrane
What moves lymph in the lymph vessels?
What are the purpose of the valves?
Lymph is transported down bigger lymphatic vessels which actually contract so pumping lymph onwards.
Valves ensure lymph flow is in one direction (downstream) to the lymph glands (nodes) and beyond
Describe the process of lymph drainage
Lymph drainage begins with absorption of fluid from the tissues.
Lymph is transported through larger collecting lymphatic vessels to lymph nodes.
Lymph nodes filter the lymph where there is also interaction with the immune system.
After passing through a series of lymph nodes large lymphatic vessels eventually discharge lymph into great veins of the neck .
What is Lymph?
Lymph is interstitial (tissue) fluid containing salts, proteins and cells, originally formed from a plasma ultrafiltrate
What are Lymph Nodes (Glands)?
Lymph glands are filter stations positioned at intervals along the lymph drainage route. They perform two basic functions:
To clean up the lymph before it re-enters the blood stream, by sieving out, trapping and destroying (inorganic) foreign materials
Monitoring the lymph for tell tale signs of (organic) predators e.g. infection, so playing a vital role in our immune system responses
What is the first function of the Lymphatic System?
Is fluid balance (homeostasis) - Clears away the mess the Cardiovascular System leaves behind!’
What is oedema?
When plasma ultrafiltration (lymph load) exceeds lymph drainage for a sufficient period.
Either lymph drainage is insufficient or lymph load (vascular fluid filtration) exceeds lymph drainage capacity
What are the consequences of oedema?
Increased lymph load leads to failure of the lymphatic system and heart failure, venous oedema
Insufficient lymph load can lead to absolute lymphatic failure e.g breast cancer related to lymphoedema and elephantiasis
Sustained increase capillary filtration can lead to exhausting lymph drainage capacity leading absolute lymphatic failure e.g post thrombotic syndrome, longstanding venous hypertension
What is venous oedema?
If oedema persists after treatment of the veins then the lymph drainage is permanently damaged and a state of lymphoedema now exists
What is the second function of the Lymphatic System?
Tissue immunosurveillance
The Lymphatic System houses the immune system and is responsible for tissue immune cell trafficking. A common complication of impaired lymph drainage is infection e.g. cellulitis.
What is the third function of the lymphatic system?
Fat homeostasis
The Lymphatic System is responsible for gut fat absorption and peripheral fat resorption
The Lymphatic System is mainly responsible for the spread of cancer but what does a sentinel lymph node biopsy do?
Is designed to detect the lymphatic spread of cancer and guide treatment.
What is podoconiosis?
Another tropical cause of lymphoedema is podoconiosis. Here lymph vessels become poisoned from silicates in the soil entering the skin and lymph system when children walk barefoot.
What is secondary lymphoedema
Damage to lymph drainage is known as secondary lymphoedema. Primary lymphoedema is when lymphoedema occurs for reasons of of an intrinsic fault in drainage and may be much more common than generally realised.
Understanding the genetic basis of primary lymphoedema is teaching us about the roles of these genes in human biology and diseases.
