Haematology I - Lecture 8 Flashcards
What is the average blood volume of an adult?
5L
What are the main components of blood?
○ 55% = Plasma [normal range 46-63%]
○ 45% = Red blood cells
○ <1% = White blood cells and platelets
What are the components of plasma?
○ Water = 92%
○ Plasma Proteins = 7% (Albumin, globulin, fibrinogen, regulatory proteins)
○ Other Solutes = 1% (Electrolytes, organic nutrients and waste)
What are the main functions of blood?
Transport of:
○ O2 and CO2
○ Nutrients
○ Waste
○ Temperature
○ Hormones
Defenese:
○ Antibodies, WBCs
○ Clotting factors
What is haematopoiesis?
Process by which blood cells are formed from hemocytoblast
What happens during erythropoiesis?
○ Stem cell = hemocytoblast
○ Committed cell = proerythroblast
Phase 1: Ribsome synthesis (decreases)
○ Early erythroblast -> Late erythroblast
Phase 2: Haemoglobin accumulation (increases)
○ Late erythroblast -> Normoblast
Phase 3: Ejection of nucelus
○ Normoblast (ejected nucleus) -> Reticulocyte -> Erythrocyte
What are the requirements for erythropoiesis?
○ Erythropoietin (EPO) = Growth factor
○ Iron
○ Vitamins B12 & folic acid (B9)
○ Intrinsic factor = Absorbs Vitamin B12
○ Amino acids = Used to make globin in haemaglobin
Where does erythropoiesis occur?
○ Foetus: yolk sac, then liver & spleen, later in bone marrow
○ Infant: all bone marrow
○ Adult: red bone marrow (ribs, vertebrae, skull, upper ends of long bones)
Rate: 2-3 million red blood cells per second
What is the structure of a red blood cell?
○ Biconcave disc
○ Highly flexible and readily deformed
○ Contains haemoglobin
○ Average size is 7.2-8.4 um
○ Lifespan ~ 120 days
What cell breaks down aged or damaged RBCs?
○ Macrophage
Which organs are macrophages found?
○ Liver
○ Spleen (main)
○ Lymph node
What is haemaglobin broken down into?
Heme -> bilirubin and iron
Globin -> amino acids
What happens to the broken down iron?
Transferrin (transport protein) stores it in the spleen or stores it as ferritin in the liver
What happens to the broken down bilirubin?
○ Taken to the liver by serum albumin
○ Bilirubin is secreted into the bile
○ Excreted as urine or feces
What happens in erythrocyte homeostasis?
○ Low O2 blood level detected
○ Kidneys increase production of erythropoietin
○ Stem cells increase RBC production
○ O2 blood levels return to normal
What are the causes of hypoxia?
○ Increase in exercise
○ High altitude
○ Smoking
○ Bleeding
How many haemoglobin molecules are there per red blood cell?
~280 million
When does synthesis of haemoglobin begin?
Begins in proerythroblast
○ 65% at erythroblast stage
○ 35% at reticulocyte stage
How much haemoglobin is there in males and females?
○ Females: 12-16g/dL
○ Males: 13.5-17.5g/dL
What is the structure of Haemoglobin adult (HbA)?
○ 4 subunits: 2 alpha and 2 beta
○ Each subunit consists of: Haem bound to long polypeptide chain (globin)
○ Fe2+ in the centre
What is anaemia?
○ Haemoglobin concentration in whole blood below the accepted normal range
○ Less than 13.5g/dL for men and less than 12.0g/dL for women
○ Common problem affecting 1/3 of the world population
What are the causes of anaemia?
○ Decreased RBC production
○ Increased RBC destruction
○ Blood loss
What are the characteristics of iron deficiency anaemia?
○ Most common anaemia
○ Hypochromic (pale RBCs)
○ Microcytic (small) RBCs
○ Decreased mean cell volume
What are the causes of iron deficiency anaemia?
○ Pregnanacy
○ Bleeding from GI tract
○ Malabsorption
○ Menorrhagia
○ Malnutrition
What are the characteristics of megaloblastic anaemia?
○ Abnormal RBC
○ Reduced Haemoglobin concentration
○ Macrocytic (large)
○ Increased mean cell volume
What causes megaloblastic anaemia due to folate deficiency?
Get macrocytic anaemia
○ Pregnancy
○ Elderly
○ Dietary deficiency
What causes megaloblastic anaemia due to Vitamin B12 deficiency?
Unable to absorb vitamin B12
○ Lack of Intrinsic Factor needed to absorb vitamin B12 (pernicious anaemia)
○ Chrohn’s, coeliac disease
What are the characteristics of sickle cell anaemia?
○ Hereditary: African or West Indian descent
○ Abnormal haemoglobin structure
○ Sickle-shaped red blood cells, which can get stuck in blood vessels
What are the characteristics of thalassaemias?
○ Hereditary: Mediterranean, Middle Eastern or Far Eastern descent
○ Abnormal haemoglobin production (alpha and beta thalassaemias)
