Organisation Of Lymph Flashcards
What is the difference between the immune system and the lymphatic system?
Immune system is a network collective of cells, proteins, tissues and organs of the body working together to protect the body from infectious microorganisms.
Lymphatic system is the collection of secondary lymphoid organs, fluids and vessels of the immune system
What is the difference between primary and secondary lymphoid organs?
Primary - they generate lymphocytes e.g., bone marrow and thymus
Secondary - do not generate lymphocytes, e,g., lymph nodes as a site of maturation of lymphocytes
What does the lymphatic system do?
It drains tissue fluid from the extracellular compartment and processes tissue fluid through lymph nodes. It then returns tissue fluid back to the systemic circulation through venous channels.
Where is the lymphatic system absent?
(Debatably the CNS), eyeball, inner ear, cartilage, bone and avascular planes
How is lymph formed?
When hydrostatic pressure is greater than oncotic pressure, tissue fluid leaves the capillaries at the arterial end. 90% of it returns on the venous end, but 10% passes through the tissues into the lymphatic system.
What is tissue fluid?
Interstitial fluid
Occupies the extracellular compartment of the body
Composition of lymph
96% water, 4% solutes
Rate of production and flow of lymph
Production at rest: 3-4 litres of lymph a day
Flow rate of 120ml/hour: 100ml through thoracic duct and 20ml through right lymphatic duct
Importance of the lymphatic system
- Assists capillaries in the return of plasma fluid and proteins that leak into extracellular space back to circulatory system
- Absorbs and transports fats from digestive system
- Fluid balance of the body
- Cell volume regulation
- immunological functions of the body
Clinical importance of the lymphatic system
- major constituent of immune system
- conduit for spread of infections, malignant diseases (secondary tumours) and a site for primary tumours
- blockage of lymph circulation leads to lymphoedema
- primary site for infections
Structure of the lymph node
Kidney shaped, capsule cortex and medulla
Lymph enters though afferent channels, percolates through sinuses and leaves through efferent channels (which have valves)
What are in lymph nodes?
Phagocytes and macrophages to clean up lymph
General drainage of lymph
Lymphatic channels start as microscopic channels, gradually becoming vessels, which will drain into superficial then deep nodes, and collect to become trunks, and then either the right lymphatic duct or thoracic duct. Ducts drain into the venous system (by subclavian veins), returning it into the circulatory system, becoming a constituent of blood.
What does the right lymphatic duct drain?
Drains lymph from upper right quadrant of the body - right side of head, neck, thorax and upper limb
Where does the right lymphatic duct enter the venous system?
Enters the venous system at the right venous angle - point of union of the right subclavian vein and internal jugular vein
What does the thoracic duct drain?
Drains lymph from the rest of the body - left side and bottom right.
Where does the thoracic duct enter the venous system?
Enters venous system as the left venous angle - point of union of left subclavian vein and left internal jugular vein
How are superficial and deep nodes separated?
Investing layer of fascia in the neck
What are regional and terminal lymph nodes?
Regional drain specific anatomical regions of the body and can be superficial or deep. Terminal lymph nodes are the point of confluence of lymph drainage from many regional lymph nodes and are always deep. Lymph drains from regional nodes into terminal nodes (then trunks then ducts)
How are superficial lymph nodes arranged?
An outer circle: forming a collar around the lower margins of the head from chin to occiput bilaterally
An inner circle: within the outer circle surrounding the upper airway passages and part of the tonsillar system of the head. For the Walder’s ring of lymphatic tissues.
Where are deep lymph nodes found?
Within deep fascia, beneath SCM, found in carotid sheath
Surround IJV
How does lymph drain into superficial nodes?
Power system with no energy (no pump). Superficial tissues into superficial nodes then deep nodes.
How does lymph drain into deep nodes?
Deep tissues can drain lymph directly into terminal lymph nodes or into regional first then terminal nodes.
What are deep nodes further divided into?
Superior deep lymph nodes and inferior deep lymph nodes
(Basically above or below SCM) omohyoid is the anatomical boundary.
