L5: Haemapoeisis

Question 1

Define haemopoiesis

Answer 1

Production of blood cells (RBCs, platelets & most WBCs) which occurs in bone marrow

Question 2

For both children & adults, state where bone marrow is commonly found and hence where haemopoiesis takes place

Answer 2

• Children: bone marrow extensive throughout skeleton
• Adults: pelvis, sternum, skull, ribs & vertebrate

Haemopoietic stem cells (hemocytoblasts) can mobilise out of bone marrow into peripheral blood

Question 3

Where does haemopoiesis occur in the early embryo?

Answer 3

Yolk sac and then in the embryonic liver (at 5-8 weeks gestation)

Question 4

State where you would obtain a bone marrow sample from

Answer 4

Right posterior iliac crest

Question 5

State the name for the multipotent heamopoietic stem cell

Answer 5

Hemocytoblast

Question 6

State three ways we can obtain haemopoietic stem cells

Answer 6

• Aspiration of bone marrow (RARE)
• GCSF mobilised stem cells in the peripheral blood (collected by leucopharesis)
• Umbilical cord (at time of normal delivery)

Question 7

Describe the role of the RES (reticuloendothelial system)

Answer 7

Part of immune system which removes dead or damage cells and identifies and destroys foregin antigens in blood & tissue.

Question 8

State the phagocytic cells of RES in:

• Blood
• Tissue (generic)
• Liver
• Connective tissue
• CNS

Answer 8

• Blood= monocytes (differentiate into macrophages when in tissue)
• Tissue (generic) = macrophages
• Liver = kupffer cells (macrophages in liver)
• Connective tissue = hitiocytes (macrophages can therefore be histiocytes)
• CNS: microglial cells

Question 9

State the two maini organs of the RES

Answer 9

• Spleen
• Liver

Question 10

Describe the role of the red pulp of the spleen in the RES

Answer 10

All blood passes through spleen where RES cells dispose of damaged or old cells (in particular RBCs). Hb is removed from RBCs and:

• Globin: degraded into amino acids
• Haem: metabolised into bilirubin which is then conjugated in liver and removed in bile

Question 11

Where is the spleen located?

Answer 11

Left uppper quadrant of abdomen, just beneath diaphragm & posterior to stomach

Question 12

Describe the role of the white pulp & the red pulp in the spleen

Answer 12

White pulp:

• Synthesises antiboides
• Removes anti-body coated bacteria

Red pulp:

• Remvoes old cells
• Metabolises haemoglobin

Question 13

Describe structure of red pulp & white pulp of spleen.

Answer 13

• Red: sinuses lined with endothealil macrophages & cords
• White: simialr to lymphoid follicles

Question 14

How does blood enter the spleen?

Answer 14

Splenic artery

Question 15

State the four main functions of the spleen

Answer 15

• Sequestration & phagocytosis (blood filter)
• Blood pooling (platelets & RBCs can be rapidly mobilised during bleeding)
• Extramedullary haemopoiesis: pluripotent stem cells proliferate during haematological stress or if marrow fails
• Immunological function (contains B & T cells. Important in removing encapsulated bacteria)

Question 16

What passes through red & white pulp of spleen?

Answer 16

• Red: RBC
• White: WBC & plasma

Question 17

Define splenomegaly and sate some common causes:

Answer 17

Splenomegaly= enlargement of the spleen (NEVER NORMAL)

Causes:

• Back pressure (in liver disease, liver becomes fibrotic so hard to allow blood to flow through vessels in liver. Leads to increased pressure in vessels and increased pressure in spleen “portal hypertension”)
• Overworking red or white pulp
• Extramedullary haemopoiesis
• Presence of abnormal cells
• Contains other material that shoudln’t be there (e.g. in sarcoidosis you have increased gramulomas in spleen)

Question 18

What advice should be given to patients with splenomegaly (particularly those who are active) and why?

Answer 18

Avoid dangerous activities which may involve trauma to spleen as since it is enlarged it is no longer protected by ribcage. Trauma to spleen could cause rupture leading to internal haemorrhage/haematoma.

Question 19

Describe how you would examine the spleen for splenomegaly

Answer 19

Palpate below costal margin starting in the right iliac fossa. Should feel splen edge move towards you on inspiration. Measure, in cm, from costal margin to mid clavicular line.

Question 20

Give two example conditions for if splenomegaly is:

• Massive
• Moderate
• Mild

Answer 20

• Massive: malaria, chronic myeloid leukaemia
• Moderate: infections (e.g. malaria) & liver cirrhosis
• Mild: endocardititis & infectious hepatitis

Question 21

Define hyposplenism and state what is it associated with

Answer 21

Hyposplenism= reduced function of spleen

Associated with increased risk of sepsis

Question 22

Describe what would be seen on a blood film of someone with hyposplenism and why

Answer 22

Howell-Jolly bodies (nuclear fragments/clusters of DNA) in circulating erythrocytes. During erythropoiesis, erythroblasts usually expel nuclei but sometimes this fails; normall, such cells would be removed by spleen but they are not due to reduced function of spleen (hyposplenism).

Question 23

State two possible consequences of splenomegaly

Answer 23

• Rupture leading to haematoma
• Infarction of spleen due to compression of blood vessels as it enlarges

Question 24

State two causes of hyposplenism

Answer 24

• Splenectomy
• Diseases that destroy spleen (e.g. sickle cell or coeliac)

Question 25

# Define hypersplenism When does it occur?

Answer 25

Overactivity of spleen Occurs when there is pooling of blood in an enlarged spleen which leads to overactivity and low blood counts

Question 27

State some functions of RBCs

Answer 27

* Deliver oxygen to tissues (and remove CO₂) * Carry Hb * Maintain osmotic equilibrium

Question 28

On what chromosomes are globin genes found on?

Answer 28

* Alpha = 16 * Gamma & beta = 11

Question 29

Define cytopenia

Answer 29

Reductioon in number of blood cells

Question 30

Define anaemia

Answer 30

Low RBC count

Question 31

Define leucopenia

Answer 31

Low WBC count

Question 32

Define neutropenia

Answer 32

Low neutrophil count

Question 33

Define thrombocytopenia

Answer 33

Low platelet count

Question 34

Define pancytopenia

Answer 34

Low RBC, WBC & platelet count

Question 35

Define cytosis (or philia)

Answer 35

Increase in number of blood cells

Question 36

Define erythrocytosis

Answer 36

High RBC count

Question 37

Define leucocytosis

Answer 37

High WBC count

Question 38

Define neutrophilia

Answer 38

High neutrophil count

Question 39

Define lymphocytosis

Answer 39

High lymphocyte count

Question 40

Define thrombocytosis

Answer 40

High platelet count

Question 41

Once neutrophils are mature, how long do they circulate in blood for?

Answer 41

1-4 days

Question 42

What hormone controls neutrophil production & action and state 4 ways in which it controls both production & action

Answer 42

G-CSF (granulocyte colony stimulating factor) * Increases production of neutrophils * Decreases time to release mature blood cells from bone marrow * Enhance chemotaxis * Enhance phagocytosis

Question 43

If a patient has severe neutropenia (e.g. in sepsis or after chemotherapy) what can we give to correct this?

Answer 43

Recombinant G-CSF *NOTE: if have neutropneic sepsis must give Iv antibiotics immediately*

Question 44

State some risk factors for neutropenia and some possible consequences

Answer 44

**Risk factors:** * Sepsis (increases removal) * Splenic pooling * Viral infection * Infiltration of bone marrow * Aplastic anaemia **Consequences:** * Infections can be life threatening * Mucosal ulceration

Question 45

State some risk factors and possible consequences of neutrophilia

Answer 45

**Risk factors:** * Drugs (e.g. steroids) * Myeloproliferative diseases * Increased cytokines **Consequences:** * Tissue damage * Inflammation * Cancer * Acute haemorrhage

Question 46

State the role of monocytes

Answer 46

Respon to inflammation & antigenic stimuli and migrate to tissues where they then differentiate into macrophages and remove foregin orgnanims by phagocytosis or pinocytosis

Question 47

Define monocytosis and state some possible causes

Answer 47

Monocytosis= increased monocyte count Causes: chronic inflammatory conditions *(e.g. Crohn's)*, chronic infectioni *(e.g. TB)*, myeloproliferative disorders or carcinomas

Question 48

Describe role of eosinophils

Answer 48

Deal with some parasitic infections and act as a mediator of allergic responses & hypersensitivity. Migrate to epithelial surfaces and phagocytose

Question 49

Define eosinophilia and state some posible causes

Answer 49

Increase in eosinophil cell count Causes: * Allergic disease (e.g. asthma) * Hodgkins lymphoma

Question 50

Describe role of basophils

Answer 50

Involved in allergic reactions & inflammatory conditions. Contain dense granules of: * Heparin: anticoagulant * Histamine: vasodilation * Serotonin: * Hyaluronic acid:

Question 51

Define basophilia and state some causes

Answer 51

Basophilia: increase in basophil cell count Causes: * Ulcerative colitis * Rheumatoid arthritis * Myeloproliferative disorders

Question 52

Define lymphocytosis and state some possible causes

Answer 52

Increase in lymphocyte cell count Causes: * Viral or bacterial infection * Stress * **Post splenectomy**

Question 53

Why does jauncie occur?

Answer 53

High bilirubin in blood Occur due to excess breakdown of RBC or impaired liver function which means that not all bilirubin can be conjuaged to make it more soluble and then excreted by kidneys or used in bile.

Question 54

Define panmyelosis

Answer 54

High RBC, WBC & platelet count