Spleen Flashcards
What is the spleen component of?
Reticuloendothelial system
Describe the histology of the spleen. Describe the functions of the different areas
Fibrous capsule which surrounds the pulp There are 2 types of pulp: White pulp (lymphoid follicles) and Red Pulp (splenic cords)
Function of white pulp: this contains 10% macrophages and 25% t cells. It is important in antibody production
Function of red pulp: this is important in filtration and phagocytosis of the damaged and defective RBCs. It is also a reservoir for platelets and synthesis of complement and FVII
How is the red pulp structured to help achieve its function?
It has a fast and a slow circulation. The fast circulation takes 90% of the blood and filters it straight through the arterioles. The slow circulation comprises of splenic cords, which filter the red blood cells exposing them to macrophages and dendritic cells which interact and remove bacterial organelles.
Once filtered, to re-enter the circulation they must push through sinus walls which have narrow and short interendothelial slits
What is splenic sequestration?
This is when RBCs reversibly adhere to the reticular meshwork of the splenic cords leading to an acutely severe drop in haemoglobin.
What can happen with sequestration?
Autotransfusion can occur which suddenly releases trapped RBC leading to increased viscosity. Viscosity can lead to increased risk of stroke
Describe some infectious causes of splenomegaly
Parasites such as Leishmaniasis, Malaria
Bacterial such as Tb, endocarditis
Viral such as EBV HIV
Describe some haematological causes of splenomegaly
Sickle cell leading to splenic sequestration
HbB where there is increased spleen destruction of defective cells
Myeloproliferative disease such as CML and PRV - infiltrate the spleen themselves
In haemolytic anaemia there is increased funcion of the red pulp and increased proliferation of red pulp
What is hypersplenism? What are the features? What does it infer?
Primary or secondary causes Cytopenia Splenomegaly Shortened RBC and platelet survival Leads to pooling of RBCs and platelets
It infers increased function of spleen
What is hyposplenism? What are the causes?
It is decreased splenic function Causes include: Splenectomy SCD - infarcts leading to a small atrophied spleen Thrombosis of the spleen - SLE RA Coeliac disease Congenital absence of the spleen
What are the features of hyposplenism?
Reticulocytosis, lymphocytosis and monocytosis on FBC
Heinz bodies, Howell-Jolly bodies, target cells, spherocytes and nucleated RBCs
What are the indications of a splenectomy?
Severe ITP
Severe HS
Myeloproliferative neoplasms
Thalassemia intermedia
What are the complications of splenectomy?
Transient thrombocytosis
Encapsulated infection susceptibility
Malaria infection
