Spleen, WBCs, Cytopenia and Endocrine Control of Appetite Flashcards
What are the 2 types of tissue in the spleen and where does the blood go when it enters?
Red pulp, consisting of sinuses lined by endothelial macrophages and cords.
White pulp, with a similar structure to lymphoid follicles.
Blood enters via the splenic artery with WBCs and plasma preferentially passing through the white pulp and RBCs through the red pulp.
In children, the spleen is haematopoietic, what are its functions in an adult? (4-5)
Sequestration and phagocytosis - old/abnormal RBCs removed by macrophages.
Blood pooling, so platelets and RBCs can be rapidly mobilised during bleeding.
Extramedullary haemopoiesis - pluripotent stem cells proliferate and differentiate during haematological stress/if BM fails (myelofibrosis).
Immunological function - holds 25% T cells and 15% B cells. It’s needed to remove encapsulated bacteria and malaria.
What are you doing when looking for splenomegaly?
You can’t normally palmate the spleen below the costal margin, but you must start at the right iliac fossa (RIF), then edge up and to the left. Feel for splenic notch and measure in cm from the costal margin in the mid clavicular line.
Why might the spleen grow?
Back pressure (portal hypertension - liver disease),
Overworking red pulp (haemolytic anaemia),
Or white pulp (infection),
Reverting to extramedullary haemopoiesis,
Expanding as infiltrated by inappropriate cells (cancer cells of blood origin/metastases),
Or infiltrated by other material (Gaucher’s disease, sarcoidosis).
Aside from size, how may splenomegaly appear different on a scan?
It may be haemogenous or have attenuation (spots seen on a CT).
Spleen enlargement may be massive, moderate or mild, name some conditions that can cause each.
Massive: chronic myeloid leukaemia, myelofibrosis, chronic malaria, Schistosomiasis.
Moderate: as above and lymphoproliferative or myeloproliferative disorders,liver cirrhosis with portal hypertension, infections like Glandular fever caused by EBV.
Mild: as above and infections e.g. Hepatitis, endocarditis or infiltrative disorders e.g. Sarcoidosis or some autoimmune.
What is hypersplenism?
Pancytopenia or thrombocytopenia occurring due to a pooling of blood in an enlarged spleen.
(Also risk of rupture since no longer protected by rib cage, so avoid dangerous activities).
List some complications of hypersplenism.
Rupture leading to haematoma, infarction (repetitive) - functionally asplenic/hyposplenic e.g. Sickle cell.
What is hyposplenism and what may cause it?
Lack of functioning spleen tissue caused by a splenectomy, Sickle cell (older children/adults - multiple infarcts –> fibrosis), Coeliac disease.
What can cause patients to have Howell Jolly bodies seen on their blood filmand what are they?
Howell Jolly bodies are DNA remnants which look on a blood film like small purple dots. They appear when a patient has hyposplenism.
What are patients with hyposplenism at risk of?
Patients are at risk of overwhelming sepsis, particularly from encapsulated organisms, e.g. Pneumococcus, Haemophilius influenzae and Meningococcus.
Also, cytopenia - a reduction in the number of blood cells: anaemia, leukopenia, neutropenia, thrombocytopenia.
What is the opposite of cytopenia?
Cytosis/philia - increase in the number of blood cells with various forms: erythrocytosis, leukocytosis, neutrophilia, lymphocytosis and thrombocytosis.
Neutrophils are ___ responder phagocytes, the commonest ____ and an essential part of the ________ immune system. There maturation is controlled by the ________ hormone, which _________ production and decreases the time to release mature cells from the ______ _________ - they enhance chemotaxis, phagocytosis and killing of ___________.
1st WBC Innate G-CSF Bone marrow Pathogens
Describe the pathway that produces neutrophils (from a myeloblast).
Myeloblast –> promyelocyte –> myelocyte –> metamyelocyte –> band (non lobed) –> neutrophil.
In which situations may recombinant G-CSF be administered?
If there is severe neutropenia and sepsis after chemotherapy (readily prescribed and can be self-injected).
List some causes of neutrophilia (including one haematological cause).
Acute inflammation, tissue damage, cancer, drugs (e.g. Steroids), infection (bacterial), acute haemorrhage, cytokines (G-CSF), smoking, metabolic/endocrine disorders and (haematological) myeloproliferative disorders, where the bone marrow overproduces.
Neutropenia is < 1.5 x10(9)/L and is severe if < 0.5 x10(9)/L. What are the 4 different ways it can come about?
Reduced production of neutrophils, increased destruction/use, benign neutropenia (Afro-Caribbean) or cyclic neutropenia.
In what way might neutropenia be caused by increased removal/use?
Immune destruction, sepsis or splenic pooling.
What could be the underlying cause of neutropenia by decreased production?
B12/folate deficiency, infiltration of bone marrow (malignancy/fibrosis), aplastic anaemia (empty bone marrow), radiation, drugs, viral infection or congenital disorders.
What are the consequences of neutropenia?
Severe bacterial/fungal infection, mucosal ulceration e.g. Painful mouth ulcers.
Neutropenic sepsis is a medical emergency and IV antibiotics must be administered immediately.
Monocytes respond to _________ and antigenic stimuli. They migrate to _______ where they become macrophages and their lysosomes contain ________, _______ proteins, IL, __________ acid and CSF. They can perform phagocytosis and ____________.
Inflammation Tissues Lysozyme Complement Arachiodonic Pinocytosis
What are the causes of monocytosis?
Chronic inflammatory conditions, chronic infection (TB), carcinoma and (haematological) myeloproliferative disorders/leukaemias.
Eosinophils have a lifespan of __ to ___ days and spend 3 to 8 ___ in circulation. They deal with some __________, mediate __________ responses and migrate to __________ surfaces. Their granules contain _______, phospholipids and _______. Also, they phagocytose ___________-__________ complexes and mediate _____________ reactions (drugs/asthma/skin inflammation).
8 to 12 Hours Parasites Allergic Epithelial Arginine Enzymes Antibody-antigen Hypersensitivity
What are some causes of eosinophilia?
Allergic disease (eczema, hay fever etc), drug hypersensitivity (penicillin), Chaurg Strauss, parasitic infection, skin diseases. Haematological causes: Hodgkin lymphoma, acute lymphoblastic leukaemia, acute myeloid leukaemia, myeloproliferative conditions, eosinophilic leukaemias and idiopathic hypereosinophilic syndrome.
Which granulocyte am I describing?
The least common but the biggest, black berry looking, active in allergic and inflammatory conditions. Has dense granules containing histamine, heparin, hyaluronic acid and serotonin.
Basophils.
What may cause basophilia?
From reactive (immediate hypersensitivity reactions, Ulcerative colitis or Rheumatoid Arthritis - unusual) or myeloproliferative causes.
Lymphocytes originate in the bone marrow, what are the B and T cells involved in?
B cells are involved in humoral immunity, with antibody/immunoglobulin forming cells.
T cells are involved in cellular immunity, with CD4+ helper cells, CD8+ cells and natural killer cells - cell mediated cytotoxicity.
Lymphocytosis can be reactive or lymphoproliferative (malignant); list some causes.
Reactive: viral infection, bacterial infection (especially Whooping cough), stress related (MI-cardiac arrest), post-splenectomy or smoking.
Lymphoproliferative: chronic lymphocytic leukaemia (CLL - B cells), T or NK cell leukaemias are less common or lymphoma (cells spill out of infiltrated bone marrow).
Pancytopenia can be caused by increased removal, what may underlie this?
Immune destruction (rare), splenic pooling, haemophagocytosis in bone marrow (rare).
Pancytopenia can be caused by reduced production, what may underlie this?
B12/folate deficiency, bone marrow infiltration, marrow fibrosis, idiopathic immune aplastic anaemia, radiation, drugs, viruses, congenital bone marrow failure (Falconi’s anaemia - may have double digit) - lose 50:50 fat to cells in bone marrow.
