The Spleen, White Cells, Cytopenia Flashcards
What does the spleen consist of?
Red pulp - sinuses lined by endothelial macrophages and cords
White pulp - similar structure to lymphoid follicles
How does blood enter the spleen?
Via the splenic artery
When blood enters the spleen, what do red cells preferentially pass through?
Red pulp
When blood enters the spleen, what do white cells preferentially pass through?
White pulp
What are the functions of the spleen in adults?
1) Sequestration and phagocytosis - old/abnormal red cells removed by macrophages
2) Blood pooling - platelets and red cells can be rapidly mobilised during bleeding
3) Extramedullary haemopoiesis
4) Immunological function - 25% of T cells and 15% of B cells present in the spleen
Why would the spleen grow?
Overworking red/white pulp Back pressure - portal hypertension in liver disease Extramedullary haemopoiesis Infiltrated by cancer cells Sarcoidosis
What are some causes of hyposplenism?
Splenectomy, sickle cell disease, coeliac disease
What does the blood film of a patient with hyposplenism show?
Howell Jolly bodies (DNA remnants) - purple dots
What are patients with hyposplenism at risk of?
Overwhelming sepsis, particularly from encapsulated organisms (eg pnemococcus, haemophilus influenzae, meningococcus)
What is cytopenia?
Reduction in the number of blood cells
What is leucopenia?
Low white cell count
What is neutropenia?
Low neutrophil count
What is thrombocytopenia?
Low platelet count
What is the term for low red cells, white cells and platelets?
Pancytopenia
What is the term for a high red cell count?
Erythrocytosis
What is the term for a high white cell count?
Leucocytosis
What is the term for a high neutrophil count?
Neutrophilia
What is the term for a high lymphocyte count?
Lymphocytosis
What is the term for a high platelet count?
Thrombocytosis
What is the commonest white cell?
Neutrophil
What hormone controls the production of neutrophils?
G-CSF
What could be used to treat severe neutropenia?
Recombinant G-CSF
What defines neutropenia?
<1.5x10^9/L
Severe if <0.5
Broadly speaking, what could cause neutropenia?
Reduced production, increased removal or use (eg immune destruction, sepsis, splenic pooling)
What things could cause reduced production of neutrophils?
B12/folate deficiency, bone marrow malignancy, aplastic anaemia, radiation, drugs (eg chemotherapy), viral infection, congenital disorders
What do lysosomes in monocytes/macrophages contain?
Lysozyme, complement, interleukins, arachidonic acid,
What things could cause monocytosis?
Chornic inflammatory conditions, chronic infection, carcinoma, leukaemias
What do granules in eosinophils contain?
Arginine, phospholipid, enzymes
What could cause eosinophilia?
Allergic diseases, parasitic infection, skin diseases, hodgkin lymphoma, acute lymphoblastic leukaemia, eosinophilic leukaemia etc
What are the least common, but largest white cells?
Basophils
What are basophils active in?
Allergic reactions and inflammatory conditions
What do the granules in basophils contain?
Histamine, heparin, hyaluronic acid, serotonin
What things could cause basophilia?
Hypersensitivity, UC, RA, CML, mastocytosis
What could cause lymphocytosis?
Viral infections, bacterial infections (especially whooping cough), post splenectomy, smoking, CLL, lymphoma
What is aplastic anaemia?
Pancytopenia with hypocellular bone marrow in the absence of an adnormal infiltrate and with no increase in reticulin (fibrosis)
