haematology

what are the main functions of blood ?

transport, regulation, protection

what is the avg. volume of blood in an adult ?

4.5 - 5.5L

what is the pH of blood

alkaline - pH 7.4

what causes blood to appear bright red or darker ?

oxygen

bright red = oxygenates

darker = deoxygenated

what are the 2 main components of blood ?

plasma and cellular components

what are the 3 main cellular components of blood ?

platelets, leukocytes, erythrocytes

composition of plasma

90% water 10% solutes (eg. albumin, fibrinogen, globulins)

what % of blood do erythrocytes make up ?

45

what is unique about mature erythrocytes

anucleated, no organelles

what is the avg. lifespan of erythrocytes ?

120 days - high turnover rate

what protein do erythrocytes contain and what is its function ?

Hb - binds and transports oxygen

how many oxygen molecules can one Hb reversibly bind ?

4

why don’t erythrocytes use the oxygen they carry ?

generate ATP anaerobically

how many g of Hb per 100ml of blood ?

13 - 18

how and where are erythrocytes produced ?

haematopoiesis in red bone marrow - axial skeleton, girdles, proximal femur/humerus

what stimulates erythrocyte production ?

demand for oxygen - regulated by erythropoietin

what differentiates leukocytes (WBCs) from other blood cells ?

only “true cells” with nuclei and organelles

diapedesis

process by which leukocytes leave blood vessels to reach tissues

leukocytes account for what % of blood volume ?

1

mnemonic for leukocytes abundance

never let monkeys eat bananas

Neutrophils > Lymphocytes > Monocytes > Eosinophils > Basophils

which leukocytes are granulocytes ?

neutrophils, eosinophils, basophils

which leukocytes are agranulocytes ?

lymphocytes and monocytes

how and where are leukocytes produced ?

leukopoiesis in bone marrow

where do lymphocytes mature ?

thymus, bone marrow

what is the lifespan of leukocytes

granulocytes < 9 days

lymphocytes - hours to decades

monocytes - several months

neutrophil

eosinophil

basophil

lymphocyte

monocyte

T lymphocyte

directly responds to tumour and virus infected cells

B lymphocyte

produce specific antibodies against antigens

once leaving the bloodstream monocytes become…

macrophages

all leukocytes originate from…

early myeloid or lymphoid progenitors

what are platelets derived from ?

budding off megakaryocytes

lifespan of platelets

10 days

what do platelet granules contain ?

calcium - important for clotting

what is the primary function of platelets ?

initiate clotting at sites of vessel injury

platelet

haemostasis

localised multistep process to stop bleeding

what are the key steps in haemostasis ?

starts with platelet plug

ends with fibrin blood clot

what triggers the coagulation cascade ?

intrinsic (contact) or extrinsic (tissue factor) pathways

the intrinsic and extrinsic pathways converge to form

common coagulation pathway

outline the common coagulation pathway

factor X converted to Xa (active form)

prothrombin (factor II) converted to thrombin (IIa)

converts fibrinogen (factor I) to fibrin monomers

factor XIIIa cross links to form soft fibrin clot

what guides neutrophils to site of infection ?

chemotaxis

what is extravasation ?

adhesive interaction between neutrophils and capillary walls

what leukocytes originate from myeloid progenitors ?

neutrophils, monocytes, eosinophils, basophils

what leukocyte originates from lymphoid progenitors ?

lymphocytes

what is erythrocytosis

persistently elevated Hb and RBC count

Hb thresholds for erythrocytosis

> 185g/L in males

165 in females

4 types of erythrocytosis

relative - plasma conc.

apparent - raised haematocrit

idiopathic - no clear mechanism

absolute - congenital or acquired

what is anaemia ?

low RBCs / Hb

reduced oxygen carrying capacity

what Hb levels indicate anaemia ?

< 130 g/L in males

120 in non pregnant females

what is haemorrhagic anaemia ?

significant loss of RBCs leading to decreased haemoglobin

but normal erythropoiesis

acute haemorrhagic anaemia

sudden and often traumatic eg. stab wound

chronic haemorrhagic anaemia

slow / over long period of time eg. internal bleed

causes of decreased erythrocyte production

iron/B12 deficiency

renal failure

bone marrow failure

drugs

haemolytic anaemia

premature RBC destruction

causes of haemolytic anaemia

• allo and auto immune responses

• haemolytic uraemic syndrome

• prolonged mechanical trauma

jaundice is caused by

buildup of bilirubin in blood

what causes WBC disorders ?

oncogenic mutations

cause disregulation of WBC production and function

examples of WBC disorders

leukaemia, lymphoma, multiple myeloma, MDS

leukaemia

accumulation of abnormal WBCs in blood or bone marrow

lymphoid or myeloid lineage

lymphoma

malignancy of lymphoid origin

restricted to lymphoid organs

acute vs chronic leukaemia

acute - rapid progression, accumulation of ‘blast cells’, children

chronic - slower, mature but dysfunctional

blast cells

immature blood cells that are precursors to mature blood cells

general symptoms of leukaemia

fatigue, weight loss, infections, bruising, enlarged lymph nodes

leukaemia treatments

chemotherapy, radiotherapy, bone marrow/stem cell transplant

what happens in hypercoagulable states ?

increased clotting risk (e.g. DVT, thrombosis)

what happens in hypocoagulable states ?

increased bleeding tendency

clot breakdown by fibrinolysis

haemophilia

inherited bleeding disorder due to missing clotting factors

haemophilia A is a deficiency of

factor VIII

haemophilia B is a deficiency of

factor XI

who is more commonly affected by haemophilia ?

males - X linked recessive

treatment for haemophilia A and B

Octacog alfa (A)

Nonacog alfa (B)

desmopressin

recombinant proteins