Lymphatic system Flashcards
What is Lymph?
is a coagulable fluid
similar to plasma
contains white blood cells (lymphocytes) and lipids (chyle)
- only called lymph when in lymph vessels
General role of lymphatic system (clinical significance)
- Drains fluid from tissue spaces, thus prevents oedema
- Absorbs and transports fatty acids from small intestine
- Part of the body’s defence mechanism
It has a clinically important role as the pathway for the spread of:
- Infective material (infection)
- Neoplastic cells (cancer)
Location of the lymph system
•Location: the nodes and vessels cover the entire body but in the deeper regions are more closely associated (run alongside) with
arterial vasculature, e.g. aorta
viscera, e.g. small intestine
Movement pathway of lymph
what is the role of lymph capillaries with respect to interstitial fluid
drains excess interstitial fluid into capillaries which then leads to vessels
Features of Lymph. Capillaries
- Form plexuses of vessels in tissue space
- 10 – 50 microns in diameter (larger than blood capillaries)
- Single layer of endothelial cells
- Large pores in wall
- Arranged so that flow is only allowed one direction
- Lymphatic capillaries in the small intestine, that carry lipids, are called lacteals
- Lymph in lacteals is called chyle
Afferent lymph vessels
• Lymphatic capillaries join to form lymphatic afferent vessels
- These transport lymph towards lymphatic nodes
- Just like veins, these vessels contain valves to prevent backflow
- Vessels possess a three-layered wall; endothelium, tunica media, tunica adventitia
How does lymph move through the system?
Movement of lymph from tissue spaces and within
lymphatic capillaries/vessels:
- Filtration pressure in tissue spaces
- Contraction of neighbouring skeletal muscles
- Respiratory movements
- Contraction of lymphatic vessel walls
Describe the appearance of lymph nodes
- Nodes are oval bodies located along lymphatic vessels
- Approx 600 small (1 – 25 mm), located superficial or deep these nodes span the entire body
- Clusters of nodes are found in well defined topographical sites
Lymph node gross anatomy
• Structure:
Confer shape in both health and disease
CT capsule (plus underlying subcapsular sinus)
Trabeculae (partition the cortical region)
Supporting reticular fibres
• Parenchima (function):
Particulate matter filtered (e.g. bacteria)
Immune cell response
Cortex: Outer – B cells + macrophages; Inner – T cells
Medulla: B cells + macrophages
Flow through the node
Afferent lymph vessels
↓
subcapsular sinus
↓
Trabecular sinus
↓
cortex
↓
Medulla
↓
Efferent lymph vessels
Lymph node chains: different types and why do they form chains
- Lymph nodes often aggregate into clusters, interconnected by chains of lymph vessels
• Primary nodes – first node or group within chain.
Also known as outlying or peripheral
• Terminal nodes – last node or group within chain
Chain of nodes so it makes it more likely to pick up an infection earlier
Deep Lymph nodes characteristics
• Lymph nodes are closely located to either
Vasculature (vessels, although primarily arteries)
Viscera (organs)
• Node nomenclature is often taken from neighbouring structure
Examples:
- Aortic nodes (close to aorta)
- Tracheal nodes (close to trachea)
- Pulmonary nodes (in the lungs)
Deep LNs Proximity to vasculature
- Majority of node cluster around major vessels
- Lymph plexus often surround arteries
DLN proximity to Viscera
• Need to be specific when identifying the location of deep nodes close to or within viscera (note: L = Left)
e.g. lungs
Lymph movements - the last steps
