BL 23 Flashcards
Learn the major lymph nodes, lymph tissues and lymph organs
Remember that bone marrow is part of this system!
Organisation of the lymph system, what are the main components of it?
- Lymph
- Lymphatic vessels
- Lymphoid tissues and organs
- Cells contained within the tissues and organs
Description of lymph (what does it contain, it’s pH etc)
A thin fluid that resembles plasma (pH 7.4)
• Lower amounts of protein in lymph compared to plasma
What is chyle?
- Lymph that arises in the GI tract
- White, cloudy substance
- Contains fats and dissolved lipids – Chylomicrons and fat soluble vitamins
How much lymph is produced each day?
Approximately 3-5 litres produced (recycled) each day
Describe lymphatic capillaries structure
- Overlapping endothelial cells. The overlapping endothelial cells have gaps between them (don’t have tight junctions)
- they are blunt ended
- sit in and around blood capillaries in capillary beds
- Fluid enters from capillary bed into the lymph
- Collagen reticular fibres hold the lymph capillaries together (also called anchoring fibres)
- Valves ensure uni-direction of flow
How does lymph move through the lymph capillaries, lymph trunks and lymph ducts? Which direction does lymp flow in the body?
• Direction of lymph flow: Like veins, lymphatic vessels are arranged into superficial and deep (deep to the deep fascia) - Flow is superficial to deep
• Lymphatic vessels tend to lie adjacent to cardiovascular vessels (capillaries, arteries and veins). Pulsations of adjacent ateries also help properl lymph along.
• In the limbs, the deep lymphatics pass through muscles where contraction aids lymph movement
• Larger lymphatic vessels (ducts and trunks), contain smooth muscle cells in their walls e.g. in the abdomen or thorax
- Contraction of smooth muscle is an important contributor to lymph flow at these sites
Does increasing physical activity increase or decrease flow of lymph?
Increases it
Are they are lymphatic vessels in the CNS?
No, there are no lymphatics in the CNS
What is the process called that helps move lymph along the lymph vessels?
Lymphangion compression by local veins and arteries propels the lymph
How does lymph enter the lymph capillary?
- The fluid accumulates in the interstitial space inside tissues after leaking out through the cardiovascular capillaries
- This increases the pressure in the interstitial space.
- The fluid enters the lymphatic capillaries by leaking through the minivalves located in the junctions of the endothelium
Draw out a small mindmap showing how the lymph system links to the cardiovascular system and the ‘progression of lymp vessels’
Comparison of lymphatic capillary to veins
- Low pressure system
- Valves present
- (BUT) no cells (normally)
pic is taken at at 45 degree angle so can see the lymphatic valve. Also can see the vein full of cells
Do lymphatic trunks and ducts still have valves?
Yes they do, the valves are fibrocartilaginous!
What is the cisterna chyli?
The cisterna chyli receives the lymphatic drainage in the abdomen, just posterior to the aorta. It passes through the aortic hiatus of the diaphragm, where it continues as the thoracic duct.
When lymphatic capillaries join together they become…
…trunks
How much ducts are in the body and what are their names?
2 ducts in the body:
Right lymphatic duct
Thoracic duct
What is the role of the lymph ducts?
A lymphatic vessel that empties lymph into one of the subclavian veins
How is lymph drained? (all details including ducts, viens, regions of the body etc)
- Upper right quadrant (above the ambivilus) drained by the right lymphatic duct into the right subclavian vein/internal jugular vein
- Rest of the body: drained by the thoracic duct into the left subclavian vein/internal jugular vein
Capilliaries -> ____ -> ____ -> ____ -> ____
Where else does lymph pass through? (filtering component)
Lymph nodes
How many lymph nodes are in the body?
600-700
Which lymph nodes are the most clinically important?
- Axillae (armpits)
- Neck (cervical)
- Groin (Inguinal)
Lymph node structure (basic structure)
- Shaped like a kidney
- Each node has multiple afferent lymphatic vessels - that enter via the convex surface
- A single efferent lymphatic vessel - that leaves via the concave hilum (concave surface is called the hilum)
(lots of lymph capillaries enter the node, only one lymph trunk leaves the node) - Each lymph node has a feeding artery and draining vein that also enter and leave via the hilum (node’s own blood supply)
- Capsule: this is the browny/yellow colour in the diagram, it is made of connective tissue. It’s extensions are called trabeculae
- Cortex is split into two: out cortex and inner cortex (inner cortex is also called the paracortex)
- Inner portion is called the medulla
Lymph node structure cont. (more detail of the cortex)
- Lymphatic Follicle: In outer cortex of the lymphatic follicle, B lymphocytes are in the lymphatic follicle. Macrophages and follicular dendritic cells are also present in the outer cortex (reticular cells also present).
Actively dividing B-lymphocytes are in the centre of the follicle, they undergo mitotic division and the follicle becomes large. The outer part of the lymphatic follicle is not stimulate B cells. As the B cells in the centre of the follicle are dividing, they have loose structure of chromatin so the centre appears lighter under the microscope, the B cells on the outside which aren’t proliferating are in resting phase, there chromatin is condensed. - Germinal centre - this is the actively dividing B cells in the centre of the lymphatic follicle.
- Inner cortex: T cells. Macrophages and dendritic cells are also present in the inner cortex.
Blood flow is in the germinal centres, as the way the lymphocytes reach the germinal centres is through blood vessels - Medulla is the innermost layer of the lymph node and contains large blood vessels, sinuses, and medullary cords. The medullary cords contain antibody-secreting plasma cells, B-cells, and macrophages.
Journey of lymph through the lymph node
Afferent lymphatics -> subcapsular sinuses -> trabecular sinuses -> medullary sinuses -> efferent lymphatics
- Afferent lymphatics: carry lymph to the lymph node from peripheral tissues. The afferent lymphatics penetrate the capsule of the lymph node on the side opposite the hilum
- The afferent vessels deliver lymp to the subcapsular space, a meshwork of reticular fibres, macrophages and dendritic cells. Dendritic cells are important for initiation of the immune response.
- Lymph next flows into the outer cortex, which contains B cells within germinal centres that resemble those of lymphoid nodules
4, Lymph then flows through lymph sinuses in the deep cortex, which is dominated by T cells
- Lymph continues into the medullary sinus at the core of the lymph node. This region contains B cells and plasma cells.
- Efferent lymphatics have the lymph node at the hilium. These vessels collect lymph from the medullary sinus and carry it toward the venous circulation.
Journey of lymph through lymph node… (diagram to show this)
What connective tissue in lymph nodes?
- Reticulin (collagen 3) (in the capsule and it’s extensions)
How do the immune cells interact in the lymph node?
- Dendritix cell is bringing the bacterium to the macrophage cell
- It presents the bactera to the macrophage that engulfs it
- The macrophage then engulfs the pathogen and produces the antigen-antibody complex
- The dendritic cell present the antigen, whilst T cells come in and are activated
- Activated T cells are passed through the septum into the B cell zone
- This leads to B cells secreting plasma cells
- The plasma cells leave through the efferent lymphatic vessels and start making antibodies
Antibodies then find the bacterium and destroy it
What is the role of follicular dendritic cells?
Follicular dendritic cells cause proliferation of B cells and B memory cells
What type of white blood cell needs antigens to be presented to it?
- T lymphocytes do not recognise antigens (they need to be presented to the antigen)
- B lymphocytes do recognise antigens
How do macrophages, T lymphocytes and B lymphocytes all interact?
APC - means antigen presenting cells
- APC (e.g. the macrophage) interact with T cells
- T cells are presented to the antigen
- T cells then put antigens on their surface
- The specific B cell will recognise it
- The B cell makes an antibody against this antigen
- Antibody interacts with the pathogen
Big difference between B cells and T cells (where they attack)
B cells attack outside the cells
T cells attack inside the cells
Where does lymphadenopathy occur?
• Lymphadenopathy can occur in all the nodal regions or affect lymphatic organs
Thymus - location
- superior mediastinum
- is fully formed and functional at birth
- involutes after puberty by late teens, is mostly fat
- gradually gets smaller as we age and turns into adipose tissue
Thymus - the type of fibres, diagram
- Capsule and septa made mainly of reticulin/reticular fibres in fairly dense ECM
- Changes in the thymus associated with myasthenia gravis – leads to Myasthenia crisis - inability to swallow because of weakened muscles
- in the diagram - can see germinal centres etc
Spleen - Location
Largest lymphatic organ, very rich blood supply!
- Inferior to diaphragm
- Posterior to stomach is fully formed and functional at birth
Functions of the spleen - Haemopoietic function
- Removal and destruction of old, damaged and abnormal erythrocytes and platelets
- Retrieval of iron from erythrocyte haemoglobin
- Erythrocyte storage - after erythrocytes are formed in the bone marrow, can then come and stay in the red pulp
RED PULP - around the outside (cortex)
Splenomegaly
Enlargement of the spleen
- Enlarges in response to localised infection (just like lymph nodes)
- Enlarges in response to systemic infection (glandular fever, malaria, septicaemia)
- Can enlarge to 10x its normal size
What does a ruptured spleen look like?
Top left picture, shows ruptured spleen and lots of blood
Tonsils - location
- Oropharynx (oral cavity) and nasopharynx (nasal cavity)
- Fully formed and functional at birth
- Affected mostly in childhood
- Together constitute Waldeyer’s ring
What do swollen palatine tonsils look like?
What do swollen lingual tonsils look like?
What do swollen adrenoids look like?
Image taken with a tube up through the nose
Vemiform appendix - Location
• Inferior to and attached to caecum (ascending colon) (initial part of the ascending colon)
Vemiform appendix - Structure
Nodules reside inferior to surface invaginations (crypts)
Many M-fold cells in epithelial surface
C in pic is referring to crypts
What does an INFLAMMED appendix look like?
Peyer’s patches - Structure
Nodules reside inferior to surface domes
Many M-fold cells in epithelial surface
Clinical correlates - cancer and lymphoedema (brief explaination of both)… for one of them, need to talk about the sentinel lymph node
More detail for all later
• Sentinel lymph nodes:
- First node to receive lymph from area of a primary tumour
• Primary lymphoedema
- Usually congenital
• Secondary lymphoedema
- Usually medical intervention or immobility
- Occasionally parasite or infections
How does cancer metastasise? (spread over the body)
- Through newly produced vasculature (angiogenesis and vasculogenesis)
- Through interstitial space (through interstitum)
- Through lymph
How does the cancer ‘prepare’ the lymph, so the lymph can then ‘support’ it when it arrives?
- Tumour cells send out protein vesciles which interact with myeloid cells in the lymph nodes
- this makes the lymph node starting making matrix etc, it does this so when the cancer cell does move, it has the environment in which it can grow. Cancer cells therefore interact with lymphocytes to create a new tumour site
Sentinel lymph nodes in cancer detection
First set of lymph nodes that swell
• Axilla or pectoral in breast cancer – frozen section whilst in theatre (‘old hat’)
• Presence of malignant epithelial cells - mastectomy (this is an operation to remove the breast)
An example where sentinel lymph nodes are used in cancer detection
- Inject a blue dye into the tumour
- The blue dye is able to move through to the nearest lymph node
- When it gets into the lymph node, we use fluorography
- Blue dye is where the cancer cells are
- Surgeons will then go in and remove the lymph node and everywhere with the blue dye as possible
*Therefore, the primary tumour and sentinel lymph nodes are removed. Must leave some lymph nodes behind to drain this area.
Pic of cellulitic, primary - tarda and secondary - filariasis
Cellulitis - infection within the lymphatic system
Second pic - can see necrosis due to poor blood supply
Lymphoedema - Treatments
Lympha Press system - messaging the limb, moving the lymph fluid away from periphery back into the body
Improvement of symptoms - but no known cure
