Structure and functions of lymph nodes and spleen Flashcards
What are examples of primary/central lymphoid structures?
Bone marrow and thymus
The lymph nodes and spleen are primary/central lymphoid structures. True/false?
False
Lymph nodes and spleen are secondary/peripheral lymphoid structures
Apart from the lymph nodes and spleen, what are some other examples of secondary/peripheral lymphoid structures?
Other secondary lymphoid structures include tonsils/adenoids, Peyer’s patches in intestine
What does the lymphatic system consist of?
Formed by lymphatic vessels and lymph nodes located along their course.
What are the functions of the lymphatic system?
- Lymphatic channels are blind ended vessels that permit passive unidirectional flow of lymphatic fluid - achieved by valves.
- Returns fluid from extracellular connective tissue (lymph) to circulation
- Prevent excessive accumulation of
fluid in tissue (oedema). - Important function in fluid
homeostasis.
- Prevent excessive accumulation of
- As a result, this permits:
- Lymph to pass through lymph
nodes. - Interaction of cells and “molecules”
with cells of immune system -
protective function. - Cell traffic
- Cell trapping
- Lymph to pass through lymph
Features of the lymph nodes?
Encapsulated collections of lymphoid tissue
Ovoid / bean shaped
Usually small (up to 1.5cm) but can become stimulated / enlarged
Distributed along the course of lymphatic vessels
How are the lymph nodes organised?
Often organised into distinct groups:
- Superficial node groups (e.g. in the cervical, axillary and inguinal regions) can be palpated.
- Internal node groups (e.g. mediastinal, para-aortic) can be viewed radiologically.
Groups of nodes drain particular territories
Particular territories drain to specific node groups
How are internal lymph node groups checked?
Internal node groups such as mediastinal and para-aortic are viewed radiologically.
Superficial node groups such as cervical, axillary and inguinal lymph nodes can be palpated on examination.
What is lymphadenopathy?
Enlargement of the lymph nodes.
What are the range of potential causes for lymphadenopathy?
Local inflammation
- Infection (some have typical features e.g TB, Toxoplasma, Cat scratch disease)
- Others e.g. vaccination, dermatopathic
Systemic inflammatory processes
- Infection eg viral infections
- Autoimmune / CT disorders
Malignancy
- Haematological
*Lymphoma / Leukaemia
- Metastatic
Others
- e.g. Sarcoidosis, Kikuchi’s lymphadenitis, Castlemans Disease; IgG4 related disease
What may be the first sign of an underlying malignancy?
Superficial lymphadenopathy
What is Virchow’s node and if this node was enlarged, what could it indicate?
A left supraclavicular lymph node.
It is an important clue for the gastrointestinal (GI) malignancy. It is a sign of advanced disease.
Virchow’s node can also be enlarged in non-GI malignancies like lymphoma, breast, oesophageal, pelvic and testicular cancers.
Enlargement of this node is known as Troiseries sign.
What cell types are located within the lymph nodes?
Lymphocytes
* B cells - associated with follicles and germinal centres.
* T cells - T helper cells, T cytotoxic cells.
* NK cells
Mononuclear phagocytes (macrophages), antigen presenting cells and dendritic cells.
Endothelial cells
What is lymphangitis?
In superficial infections, the presence of lines extending from an inflamed lesion.
What is the sentinel lymph node?
The first lymph node to which cancer cells are most likely to spread.
- There may be more than 1.
- Identified by dye or radioactive isotopes.
- Negative tumour = localised.
- Positive tumour = spread and requires further investigation and treatment.
What does generalised lymphadenopathy suggest?
Suggests an inflammatory/immunological process or widespread malignancy (lymphoma/leukaemia is high on differential diagnosis).
Check FBC (full blood count)
Where is the spleen located?
High in the left upper quadrant of the abdomen.
Is the spleen usually palpable?
Not usually palpable unless substantially enlarged suggesting underlying pathology.
What is the vascular supply for the spleen?
Splenic artery (from coeliac axis) and drained by the splenic vein.
Is a ruptured spleen a medical emergency?
Yes, can rupture due to trauma or having a diseased spleen.
What is the function of the spleen?
Acts as a filter for the blood
- Detects, retains and eliminates unwanted, foreign or damaged material.
- Facilitates immune responses to blood borne antigens.
What is hyposplenism?
Reduced spleen function
What are the causes of hyposplenism?
Splenectomy (most common)
Other causes:
- Coeliac disease
- Sickle cell disease
- Sarcoidosis
- Iatrogenic (non-surgical)
Clinical features of splenic enlargement?
Dragging sensation in LUQ
Discomfort with eating
Pain if infarction
What is hypersplenism?
A triad of:
- Splenomegaly (enlarged spleen)
- Fall in one or more cellular components of blood
- Correction of cytopenias (reduction in mature blood cells) by splenectomy
What are causes of splenomegaly?
Infection
Congestion
Haematological diseases
Inflammatory conditions
Storage diseases
What is the spleen parenchyma?
The functional area of the spleen.
What does the parenchyma of the spleen consist of?
Consists of lymphatic follicles and reticuloendothelial cells, surrounding the arteries (‘white pulp’) and an interspersed network of vascular sinusoids (‘red pulp’).
The ratio of white to red pulp increases with age due to accumulated antigenic exposure and stimulation.
