Lymphatics and the Spleen Flashcards
What tissues make up the reticuloendothelial system?
Monocyte/Macrophage system = Mononuclear phagocytic system
What is the purpose of the reticuloendothelial system?
It is a network of phagocytic cells that forms part of the immune system (humoural and cell mediated immunity)
What is the purpose of the lymphatic system?
Immune functions (lymphoid cell actions)
Lymphatic fluid (involved in circulation)
What determines what macrophages are called?
Their location
What are macrophages located in tissue called?
Histiocytes
What are macrophages in the CNS called?
Microglia
What are sinus histiocytes?
Lymph node macrophages
Where are lymph nodes located?
They are typically clustered in regions around joints
Basic principles of lymphatic system:
Lymph nodes cluster in regions
Lymph fluid is resorbed interstitial fluid and white blood cells
Lymphatics are similar to capillaries in structure
Lymphatics generally follow veins and fluid is returned to CVS through veins in a generally predictable pathway (Right lymphatic duct draining into right sublavian vein and thoracic duct into left subclavian vein)
Lymph nodes:
Filter lymph
Receive antigen from circulating cells
Stimulate B cells to produce antibodies
What blood vessels do lymphatics typically follow?
Veins
What blood vessels are lymph vessels structurally similar to?
Capillaries
What is the name of the lymph vessel that drains lymph from the abdomen?
Cysterna Chyli
Where are efferent vessels of lymph nodes located?
At the hilum
Where are afferent vessels of lymph nodes located?
They enter at various points of the capsule
What are the structures of the lymph node cortex?
in the cortex:
Follicles (B cells and Dendritic cells located here)
Mantle and Marginal zones
What are the types of follicles in a lymph node?
Primary (Quiescent)
Secondary (Active, have germinal centers)
What are the structures of the lymph node medulla?
Cords (plasma cells and mature B cells accumulate here where they are matured and able to be released via efferent vessels)
Sinuses
Where in the lymph nodes are T cells located?
In the paracortex
Where are mantle and marginal zones located?
Around follicles within cortex.
What are the types of diseases of lymph nodes? Which ones are most important?
MIDNIGHT
Metabolic
*Inflammatory
Degenerative
- Neoplastic
- Infectious
Genetic/congenital
Haemodynamic
Trauma
What is lymphadenopathy?
Multiplication of cells within the node (lymphatic malignancy)
Draining of an increased number of cells
Infiltration of cells from outside the node such as malignant cells
What is reactive lymphadenitis?
Inflammation of the lymph nodes
What are the changes seen in acute lymphadenitis?
Short time-course and tender nodes
Follicular hyperplasia (B cells) [bacterial infection and some autoimmune disorders]
Paracortical hyperplasia (T cells) [viral infections including glandular fever or shingles]
Sinus histiocytosis [nodes draining chronic infections, abscesses, or cancers]
What are the features of a chronic lymphadenitis?
Longer time-course; non-tender
Often non-specific
Can reflect a condition that is chronic (chronic infection for example)
Can also occur idiopathically or in immune mediated disorders
What are the types of neoplastic disorders that can affect the lymph nodes?
Primary (haematolymphoid)
Secondary (Metastases)
What are lymph nodes used for with cancer patients?
They provide diagnostic and prognostic information (they are useful for staging via the TNM method)
Where is the spleen located?
Left upper quadrant and size of fist just under ribcage.
What is the shape and size of the spleen?
Fist sized and shaped (12cm long and 150 - 200 grams)
What surrounds the spleen?
Flexible, fibroelastic capsule
What are the relations of the spleen?
Anteriorly (posterior wall of the stomach)
Posteriorly: Left part of the diaphragm
Inferiorly: Splenic flexure of left colon
Medially: Left kidney
Hilum is usually in contact with tail of the pancreas
How is spleen connected to the stomach and the kidney?
Connected to greater curve of the stomach by the gastrosplenic ligament and to the left kidney by the splenorenal ligament
Where does the spleen get its blood supply and how is that important in clinical practice?
The splenic artery goes over the tail of the pancreas to supply the spleen and so removal of the pancreas often means the spleen must also be removed.
What are the 4 major functions of the spleen?
Filtering the blood (removing damaged RBCs and bacterial particles via red pulp macrophages)
Antibody production (in the white pulp there is presentation of antigens to T lymphocytes)
Haematopoiesis (Compensatory in settings where increased haematopoiesis is needed and important for foetal haematopoiesis)
Sequestration of blood (in cases of splenomegaly can store a huge amount of blood and platelets to release them when the time is right)
What are the 2 functionally and histologically distinct parts of the spleen?
White pulp: Lymphoid aggregates and macrophages
Red pulp: Sinusoids and cords of Billroth.
What makes up the red pulp?
Sinuses which build up to a major sinus and cords of Billroth.
What makes up the white pulp?
Lymphoid aggregates and macrophages
What are the types of diseases the spleen can encounter?
Congenital (accessory spleen [common] or hypoplasia/aplasia [uncommon])
Acquired (splenomegaly, trauma, infarct, neoplasms)
What are the causes of splenomegaly?
Passive enlargement
Secondary to infection or inflammation
Hypersplenism [overactive spleen leading to cytopaenias of RBCs and platelets]
Growth disorders and tumours [neoplasms, amyloidosis, sarcoidosis]
Malaria most common cause
Sickle cell disease
What kind of neoplasms affect the spleen?
Leukemia
Myeloma
Lymphoma
Also haemangioma/angiosarcoma
What are accessory spleens and where are they typically located?
Functional extra spleens located within mesentery. If a patient has hypersplenism then this accessory spleen must also be removed.
What happens as a result of hypersplenism?
Overactive spleen
Peripheral cytopaenia
Primary (idiopathic)
Secondary to infection, alcohol, portal hypertension, systemic inflammatory disorders
