Session 6: Haemopoiesis and blood counts

Question 1

Explain what haemopoiesis is, and some important hormomes in the 5 major lineage pathways

Answer 1

Production of blood cells, occurs in blood marrow (pelvis, skull etc). Decreases in adulthood.
1. Erythropoietin: secreted by kidney for erythrocyte synthesis
2. Thrombopoietin: produced by liver and kidney, regulates platelet synthesis

Question 2

What is a haemopoietic stem cell

Answer 2

Capable of self renewal than other adult tissie, can differentiate into a variety of cells.
Extramedullary hematopoiesis: formation of blood cells outside bone marrow, colonizes other tissues. Can derive these cells from umbilical cord

Question 3

What does the rectoendothelial system(RES) do ?

Answer 3

Part of the immune system and made up of monocytes and phagocytic cells.
Function: removes dead or damaged cells, identifies and destroys antigens in blood.
Main organs of system: spleen and liver
In spleen: disposes damaged or old blood cells

Question 4

What are the red and white pulp in the spleen?

Answer 4

Red pulp: sinuses lined by endothelial macrophages and cords, contains more RBC
White pulp: similar structure to lymphoid follicles, part of immune system, consists of WBC

Question 5

Wha are the 4 functions of the spleen?

Answer 5

1. Phagocytosis: old/ abnormal RBC cells removed
2. Blood pooling: mobilises platelets and RBC when bleeding
3. Extramedullary haemopoiesis: stem cells proliferate during haematological stress or if marrow disfunctions
4. Immunological function: 25% of T and 15% of B cells are in present in spleen. T cells identify foreign bodies while B cells make antibodies.

Question 6

Describe splenomegaly

Answer 6

An enlarged spleen. Due to:
1. Portal hypertension( blood pools in spleen due to liver cirrhosis through hepatic portal vein)
2. red or white pulps overwork and increases in size
3. Expanding as infiltrated by cells due to cancer
4. Due to extramedullary haemopoiesis
Note:hypersplenism(overactive spleen) can lead to low blood counts as cells pool in spleen instead of blood.

Question 7

What are some causes of splenomegaly?

Answer 7

Malaria, Leukaemia, Liver cirrhosis with portal hypertension, infectious hepatitis.

Question 8

What are the causes of hyposplenism?

Answer 8

Lack of functiing splenic tissue.
Causes: splenectomy( removal due to cancer etc), hashimoto’s disease, rhematoid arthritis, sickle cell disease.
Patients with this dease are at risk of sepsis from bacteria as it is harder for macrophages in spleen to filter and phagocytose bacteria.

Question 9

State the function and structure of erythrocytes

Answer 9

Function: delivers O2 to tissues, carries haem and maintains it in reduced state, maintains osmotic equilibrium, produces energy

Question 10

How does the spleen regulate RBC?

Answer 10

1. Changes to plasma membrane cause cells to become less deformable and more fragile.
2. Spleen recognises cells as abnormal and removes them from circulation.
3. Haemolytic anaemia caused: rate of destruction of RBC is greater than production

Question 11

Explain the degradation of haem, and how it may lead to jaundice

Answer 11

1. Old RBC are engulfed by macrophages
2. Iron in haemoglobin is recycled
3. Unconjucated bilirubin transported in blood bound to albumin, taken to liver.
4. Excess bilirubin in blood from haemolytic anaemia can cause jaundice.
5. Bilirubin is secreted as bile in duodenum from the liver into SI.
   Brown colour of faeces comes from stercobilin, yellow colour of urine comes from urobilin

Question 12

Describe the function of neutrophils

Answer 12

First responder phagocyte, commone WBC, invades tissues.
Maturation of neutrophil is controlled by hormone G-CSF, which: increases production of neutrophils, speeds up release of mature cells from BM, enhances phagocytosis.
G-CSF adminsitered after chemotherapy when patient has severe neutropenia.

Question 13

What is netrophilia?

Answer 13

Increase in ciculating netrophils( marginated pool not counted, only released during haemorrage).
Causes: infection, inflammation, cancer etc.

Question 14

What is neutropenia?

Answer 14

Reduced production of neutrophils or increased usage.
Reduced production: Viral infection, drugs( chemotherapy-inhibits blood cell production), vit B/folate deficiency- insufficient DNA synthesis.
Increased usage: immune destruction( antibodies destroy neutrophils), sepsis( neutrophils migrate into tissues, marrow unable to synthesise neutrophils to maintain circulatory numbers), splenic pooling
Consequences: serious bacterial and fungal infection
Neutropenic sepsis: present with high or low temperature. Adminster intravenous antibiotics immediately.

Question 15

State the function of monocytes

Answer 15

Differentiate into macrophages or dendritic cells. Phagocytose and remove cellular debris. Antigen presenting role to lymphocytes, important in defending against bacterial infections like TB.

Question 16

What are causes of monocytosis?

Answer 16

Increased number of monocytes
1. Bacterial infection eg TB
2. Inflammatory conditions eg rheumatoid arthritis
3. Carcinoma:epithelial tissue cancer
4. Leukaemia

Question 17

State the function of eosinophils

Answer 17

Responsible for immune response against parasites. Phagoctyosis of antigen and antibody complex. Inappropriate activation responsible for tisue damage and inflammation eg Asthma

Question 18

What are the causes of eosinophilia?

Answer 18

Increased level of eosinophiles
Causes: allergic diseases, infection, drug hypersensitivity, leukaemia

Question 19

State the definition of basophils

Answer 19

Looks like blackberries, active in allergic reactions and inflammatory conditions, contains histamines, serotonin.

Question 20

What are some causes of basophilia

Answer 20

Increased level of basophils
Causes: rheumatoid arthritis( inflammation), immediate hypersensivity( when body makes exaggerated/ inappropriate responses to antigens)

Question 21

State the function of lymphocytes

Answer 21

Originates in bone marrow. Consists of:
1. B cells- creates antibodies, attacks invaders outside cells
2. T cells- cellular immunity, attacks infected cells
3. Natural killer cells

Question 22

What are the causes of lyphocytosis?

Answer 22

Increased lymphocytes in bood.
Reactive:
1. Infections- bacterial eg whooping cough and viral
2. MI
3. Post splenectomy: lymphocytes are often found in spleen
Lymphoproliferative: excess lymphocytes are produced
1. leukaemia
2. Lymphoma( cells spill out of BM)

Question 23

Explain the concept of a normal range

Answer 23

Normal range only includes 95% of health poplulation. Always use +- 2.5% to get nomal range, and pay attention to significant increase or decrease in values

Question 24

Explain the significance of recticuloctye count

Answer 24

Measurement of number of young erythrocytes, indentified using size and RNA content.
High levels due to: haemolytic anaemia, blood loss, response to iron/ vit b12/folate replacement
Low levels due to: bone marrow failure

Question 25

Define the following RBC terminology: Microcytic, Macrocytic, Anisocytosis, Hypochromic, Hyperchromic, Dimorphism, Polychromatic

Answer 25

Microcytic: small RBC Macrocytic: large RBC Anisocytosis: increased variation in size Hypochromic: pale, less Hb Hyperchromic: Dense, more Hb in given volume Dimorphism: two distinct populations of RBC, after transfusion Polychromatic: recticulocytes

Question 26

Define the following RBC terms regarding their shape: Poikilocytosis, Spherocytosis, Elliptocytosis, Irregularyl contracted cells, Echinocytes, Schistocytes, Sickle cells, Target cells, Bister cells

Answer 26

Poikilocytosis: Abnormally shaped RBC Spherocytosis: spherical RBC Elliptocytosis: elliptical RBC Irregularyl contracted cells: small dense RBC but not as regular as spheres Echinocytes: spiculated cells thin spines on surface) Schistocytes: red cell fragments Sickle cells: crescent or sickle shaped cells Target cells: RBC with dark area in middle Blister cells: empty pocket at the edge of red cell, consistent consistent with G6PD deficiency

Question 27

Name the 7 red cell parameters of a FBC

Answer 27

1. Packed cell volume/ Haematocrit: proportion of blood made up of RBC, used to assess polycythaemia( excess RBC) 2. Haemoglobin: concentration of haemoglobin in blood, can vary due to bleeding or dehydration 3. Red cell count: number of RBC in given volume of blood, used to assess anaemia and erythrocytosis( high conc of RBC in blood) 4. Mean cell volume: most important in determining cause of anaemia. High value= megaloblastic anaemia( abnormally large RBC made by BM due to vit B/folate def), liver disease, haemolitic anaemia(RBC destruction>production), hypothyroidism Low value= Iron deficiency anaemia, thalassaemia 5. Red cell distribution width: variation in size of RBC, increased range signifies growth, increased in recently treateed iron deficiency, normal in thallasaemia trait 6. Mean cell haemoglobin: average measure of Hb in each RBC, used in assessment of anaemia. Low level in iron deficiency, thalassaemia, high levels in macrocytic anaemia(abnormally large RBC produced by BM) 7. Reticulocyte count: measurement of number of young erythrocytes. High levels= haemoytic anaemia, response to vit B12/folate /iron replacement, recent blood loss. Low levels: haemanitic def(def in neccessary vitamins and minerals for normal erythropoiesis), BM failure

Question 28

Describe the difference in appearance between normal blood, anaemic blood and polycythemic blood

Answer 28

Anaemia: more plasma, same buffy coat, less haemocrit Polycythemia: less plasma, same buffy coat, more hematocrit Plasma: water, hormones, nutrients etc Buffy coat: WBC, platelets Hematocrit: RBC