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Metabolism, Endocrinology and Haematology > Haemopoiesis, the Spleen and Bone Marrow > Flashcards

Haemopoiesis, the Spleen and Bone Marrow Flashcards

1
Q

What is haemopoiesis

A

Process by which blood cells are formed

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2
Q

Where does haemopoiesis take place

A

In the bone marrow, mainly in pelvis, sternum, skull, ribs and vertebrae

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3
Q

What cell is in the bone marrow that differentiates into blood cells

A

Haemopoietic stem cell (multipotential)

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4
Q

What are the five main lineage pathways arising from haemopoietic stem cells

A

Thrombopoiesis

Granulopoiesis

Monocytopoiesis

Lymphopoiesis

Erythropoiesis

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5
Q

What is thrombopoiesis

A

Production of platelets - platelets are membrane bound fragments which bud off from megakaryocytes

Megakaryocyte formation is driven by thrombopoietin (TPO)

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6
Q

What are the cells produced by granulopoiesis

A

Granulocytes - basophils, neutrophils and eosinophils

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7
Q

What is granulopoiesis

A

Production of granulocytes from myeloblast cells

Myeloblast cells airse from common myeloid progenitor cells

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8
Q

What is the function of neutrophils

A

Migrate to areas of inflammation by chemotaxis where they phagocytose invading microbe and destroy them by respiratory burst

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9
Q

What is the function of eosinophils

A

Phagocytose microbes and are associated with immune response to multicellular parasites

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10
Q

What is the function of basophils

A

Role similar to eosinophils in parasitic infections and allergy

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11
Q

What is monocytopoiesis

A

Production of monocytes from myeloblast cells

Myeloblast cells airse from common myeloid progenitor

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12
Q

What is lymphopoiesis

A

Production of B and T lymphocytes from small lymphocytes which arise from common lymphoid progenitors

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13
Q

How do B lymphocytes develop

A

Start development in foetal liver and bone marrow

During development, immunoglobulin genes rearrange to allow production of antibodies with wide range of specificities

Final maturation of B-cells requires exposure to antigen in lymph nodes

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14
Q

How do T lymphocytes develop

A

T-lymphocyte progenitors arise from foetal liver and migrate to thymus gland early in gestation

Immature T-cells undergo rearrangement of T-cell receptor genes resulting in ability to produce wide range of T-cell receptors

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15
Q

What is erythropoiesis

A

Process by which erythrocytes are produced in the bone marrow

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16
Q

What hormone drives erythropoiesis and where is it produced

A

Erythropoietin

Produced by the kidneys

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17
Q

What factors cause an increased erythropoietin production

A

Hypoxia caused by:

Decreased RBC count

Decreased Hb

Decreased oxygen availability

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18
Q

What is the function of erythropoietin

A

Inhibit apoptosis of CFU-E (colony-forming units of erythroid cell line) progenitor cells

Allow these cells to develop, proliferate and differentiate

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19
Q

How do erythrocytes develop

A

Nucleated erythroblasts extrude their nuclei and most organelle forming reticulocytes

Reticulocytes are released into circulation where they extrude remaining organelle to form erythrocytes

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20
Q

What proteins are found in the erythrocyte cell membrane

A

Spectrin

Ankyrin

Band 3

Protein 4.2

21
Q

What is the function of the proteins found in the RBC membrane

A

Facilitate vertical interactions with cell cytoskeleton and are essential in maintaining the RBCs biconcave shape and deformability

22
Q

What disease is associated with a mutation in RBC membrane proteins

A

Hereditary spherocytosis

23
Q

What is the spleen split into and what cells go into the different parts

A

Red pulp - sinuses lined by endothelial macrophages and cords. RBCs pass through red pulp

White pulp - structure similar to lyphoid follicles. White cells and plasma passes through here

24
Q

What is the spleen’s functions

A

Sequestration and phagocytosis

Blood pooling

Extremedullary haemopoiesis

Immunological functions - antibody synthesis, removal of antibody-coated bacteria

Red pulp removes old RBCs and metabolises Hb

25
Q

What causes splenomegaly

A

Haemolytic anaemia

Infiltration by leukaemias and lymphomas

Accumulation of waste products of metabolism

Infections like malaria, schistosomiasis, HIV, glandular fever due to EBV

Chronic myeloid leukaemia

Myelofibrosis

Liver cirrhosis with portal hypertension

Myeloproliferative disorders

26
Q

What is generally the aetiology behind splenomegaly

A

Typically due to increased workload

27
Q

What risks are there with hyposplenism or having a splenectomy

A

Overwhelming sepsis

Infection by encapsulated bacteria

28
Q

What are the causes of hyposplenism

A

Underlying disease causing destruction of spleen tissue - sickle-cell disease, coeliac disease

Splenectomy

29
Q

What would you seen in the blood film of a patient with hyposplenism and why

A

Howell-Jolly bodies - DNA remnants in circulating erythrocytes

These are present as they are not removed due to the hyposplenism

30
Q

What is the RES

A

The reticuloendothelial system

A network of cell located throughout the body and is part of a larger immune system

Role is to remove dead or damaged cells and identify and destroy foreign antigens in the blood

31
Q

What function does the spleen have in the RES

A

Filters blood to remove damaged and old cells from circulation

Hb is removed from senescent erythrocytes and recylced with the globin portion being degraded to amino acids and haem portion metabolised to bilirubin

32
Q

Describe the process by which bilirubin is removed from the body

A

Bilirubin is conjugated in the liver and secreted in bile

Bacteria in colon deconjugate and metabolise bilirubin into urobilinogen which is oxidised to form urobilin and stercobilin

Small amount of urobilinogen is reabsorbed and processed by kidneys to give yellow colour

33
Q

What is the term for a low number of blood cells

A

Cytopenia

34
Q

What is the term for a low number of red cells

A

Anaemia

35
Q

What is the term for a low number of white cells

A

Leucopenia

36
Q

What is the term for a low number of neutrophils

A

Neutropenia

37
Q

What is the term for a low number of platelets

A

Thrombocytopenia

38
Q

What is the term for a low number of RBCs, WBCs and platelets

A

Pancytopenia

39
Q

What endings denote an increase in the number of cells

A

…cytosis or …philia

40
Q

What is hypersplenism

A

Low blood count due to pooling of blood in an enlarged spleen

41
Q

What controls neutrophil development and what does it do

A

G-CSF hormone which causes:

  • Increased neutrophil production
  • Decreased time to release mature neutrophils
  • Enhanced chemotaxis
  • Enhanced phagocytosis and pathogen destruction
42
Q

What are the causes of neutrophilia

A

Actue inflammation

Haemorrhage

Smoking

Cancer

Tissue damage

Drugs

Cytokines

Metabolic/endocrine disorders

Myeloproliferative diseases

43
Q

What are the causes of neutropenia

A

Increased removal/use - splenic pooling, sepsis, immune destruction

Benign ethnic neutropenia

Cyclic netropenia

Reduced production - B12/folate deficiency, infiltration of bone marrow by malignancy/fibrosis, aplastic anaemia, drugs, viral infections, congenital disorders

44
Q

What are the potential consequences of neutropenia

A

Severe bacterial/fungal infection

Mucosal ulceration

Neutropenic sepsis

45
Q

What are the causes of monocytosis

A

Chronic inflammatory conditions

Chronic infections

Carcinoma

Myeloproliferative disorders

46
Q

What are the causes of eosinophilia

A

Allergic diseases

Drug hypersensitivity

Parasite infection

Acute lymphoblastic leukaemia, acute myeloid leukaemia, eosinophilic leukaemia

Hodgkin lymphoma

Myeloproliferative disorders

47
Q

What are the causes of basophilia

A

Immediate hypersensitivity reactions

RA

Ulcerative colitis

Myeloproliferative disorders - systemic mastocytosis

48
Q

What are the causes of lymphocytosis

A

Viral infections (especially in children)

Bacterail infections

Stress related

Post splenectomy

Smoking

Lymphoproliferative disorders - chronic lymphocyte leukaemia, lymphoma

Metabolism, Endocrinology and Haematology (27 decks)

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