Haematology I Flashcards
what percentage of plasma is water?
92% by weight
what are the 4 proteins found in plasma and what is the overall composition of proteins in plasma
albumins (58%)
globulins (37%)-protective, used to generate colloid oncotic pressure
fibrinogen (4%)
regulatory proteins (1%)
overall percentage= 7% by weight
what other solutes are found in plasma and what is their overall percentage in plasma
electrolytes
nutrients
respiratory gases
waste products
overall= 1% by weight
how many erythrocytes are there in blood per cubic mm
4.2-6.2 million
the average adult has a blood volume of how many litres
5L
blood accounts for approximately what percentage of your weight?
7%
what type of tissue is blood?
specialised form of fluid connective tissue
what are the components of blood
plasma, white blood cells and platelets, and red blood cells
what is the normal range of plasma in blood
approx 55% (normal range= 46-63%)
function of blood
transport – inorganic and organic molecules, formed elements and heat
what does blood transport?
Gases (O2 and CO2)
Nutrients
Excretory products (waste)
Temperature
what allows blood to be defensive
contains antibodies, white blood cells, and clotting factors
hematopoiesis
process of how all blood cells are produced
what is the initial cell responsible for producing all of the blood cells
multipotential hemopoietic stem cell (haemoblast)
what do haemoblasts divide into
common myeloid progenitor and common lymphoid progenitor
what does the common myeloid progenitor divide to produce
other blood cells except lymphocytes
what does the common lymphoid progenitor divide to produce
lymphocytes only
poiesis
production
process of developing an erythrocyte
haemocytoblast -> proerythroblast -> early erythroblast -> late erythroblast -> normoblast -> reticulocyte -> erythrocyte
where is the hameocytoblast found?
only in bone marrow and is able to reproduce due to nucleus
-blast
precursor cell
proerythroblast
-committed cell
pro: at the beginning
erythro- related to rbc
blast: precursor cell
not matured and only in bone marrow
which cells are in the developmental pathway of erythropoiesis
early erythroblast, late erythroblast, normoblast and reticulocyte
what are the 3 phases of the developmental pathway of erythropoiesis
ribosome synthesis
Hb accumulation
Ejection of nucleus
normoblast
rejection of the nucleus
which cell is the first cell to not have a nucleus in erythropoiesis
reticulocyte
what happens to the cells as they mature in erythropoiesis
the nucleus shrinks due to the increased Hb production as well as ribosome synthesis
what protein is needed to stimulate erythropoiesis
erythropoietin (EPO)
erythropoietin
protein that increases the amount of RBCs
-used in sports to increase oxygen production and enhance performance
what 4 other factors are needed for erythropoiesis
iron
vitamins b12 & folic acid (B9)
intrinsic factor -helps body absorb vitamin b12
AAs- needed to make the globin protein of Hb
where does erythropoiesis occur in the foetus
early in yolk sac, then liver & spleen later in bone marrow
where does erythropoiesis occur in an infant
all bone marrow
where does erythropoiesis occur in an adult
only red bone marrow (ribs, vertebrae, skull, upper ends of long bones)
why does erythropoiesis occur in the red bone marrow
perfect environment for rbc production
at what rate does erythropoiesis occur
2 -3 million red blood cells per second
how does the biconcave shape of RBCs help it’s function
thicker outer membrane and thinner membrane allowing for flexibility and can fold in on itself
why are rbcs at more risk of damage
no organelles and main component is Hb therefore can’t repair themselves
what is the life span of rbcs
120 days but damage will leave this to be lower
diameter of rbcs
7.2 um-8.8um
what happens to damaged rbcs
broken down in macrophages in the spleen (mostly), liver, lungs or lymph nodes
what is Hb broken down into
the haem portion (mainly ions) and the globin portion
what happens to the broken down globin
the AAs are recycled to use for other processes
what happens to the iron from broken down Hb
Fe is reused and re-enters circulation, combines with transferrin (transport protein) and stored in the liver as ferritin and goes back into the process of erythropoiesis
what does haem get broken down into
bilirubin and binds withs albumin, transported to the liver and secreted into the bile which is excreted as urobilinogen in urine or stercobilinogen in faeces
why is the erythrocyte breakdown efficient
more products are recycled from the breakdown than excreted
4 steps of erythrocyte homeostasis (negative feedback)
- low oxygen blood level
- kidneys increase production of erythropoietin
- stem cells increase red blood cell production
4.oxygen blood levels return to normal
hypoxia
low levels of oxygen in your body tissues
causes of hypoxia
Increase in exercise
High altitude
Smoking
Bleeding
what is the approx number of Hb molecules per red cell
280 million
where does synthesis of Hb begin
proerythroblast (committed cell)
what percentage of Hb is produced in the erythroblast stage
65%
where is the remaining Hb produced after the erythroblast stage
35% at the reticulocyte stage
functions of Hb
Transports O2 from lungs to tissues
Transport CO2 from tissues to lungs
what volume of Hb is blood
15g/dL of blood
Females 12 - 16g/dL and Males 13.5 - 17.5g/dL
why do men have a higher Hb than females
levels of testosterone affect Hb production, greater muscle mass requires more RBCs due to an increased need for oxygen
which type of Hb makes up most of Hb
HbA
structure of HbA
4 subunits: 2 alpha (α) and 2 beta (β) subunits
each subunit of HbA consists of…
(i) “haem” bound to (ii) long polypeptide chain “globin”
what ion is found in the centre of the haem group of HbA
ferrous iron atom (Fe2+)
iron atom (Fe2+)
reversibly binds with one molecule of oxygen (O2)
Hb functions
Carriage of gases:
Oxygen
Carbon dioxide
Carbon monoxide
H+
3 types of anaemia
- Iron deficiency anaemia
- Megaloblastic anaemia
- Sickle cell anaemia
Anaemia
Haemoglobin concentration in whole blood below the accepted normal range
what is classified as a low level of Hb in blood
Less than13.5g/dL for men
Less than 12.0g/dL for women
anaemia affects what fraction of the population
1/3
causes of anaemia
Decreased RBC production - Lacking in a nutrient that is needed to produce RBCs
Increased RBC destruction – RBCs may be defective in some way and therefore at risk of premature breakdown leading to an increase in RBC destruction
Hidden blood loss or traumatic blood loss due to an injury for example
what is the most common anaemia worldwide
Iron deficiency anaemia
Features of iron deficiency anaemia
Lack of irons leads to cells that are:
Hypochromic (pale colour)
Microcytic (smaller than normal) red blood cells
-decreased mean cell volume
causes of iron deficiency anaemia
pregnancy (increased demand on the mother)
bleeding from GI tract (ulcer, malignancy), malabsorption (reabsorbed iron in the GI tract)
menorrhagia (heavy menstrual flow) malnutrition (dietary)
features of megaloblastic anaemia
Vitamin B12 deficiency or Folate deficiency
Abnormal RBC
Reduced haemoglobin concentration
Macrocytic (larger cells than normal)
Increased mean cell volume (MCV)
signs of megaloblastic anaemia
Macrocytic red blood cells
Hyper segmented neutrophil
Megaloblastic anaemia: Folate deficiency
Folic acid / Folate deficiency
Characteristics similar to Vitamin B12
Macrocytic anaemia
Causes: pregnancy, elderly, dietary deficiency
what is folate and vitamin b12 needed for
healthy cell division, inadequate levels: cells are unable to divide
Megaloblastic anaemia: vitamin B 12 deficiency
Need intrinsic factor (IF) – secreted by stomach for vitamin B12 absorption;
Causes:
Lack of IF – PERNICIOUS ANAEMIA
Crohn’s, coeliac disease (absorption)
Treatment
Vitamin B12 intramuscular injections
why would taking vitamin b12 supplements be inadequate to treat megaloblastic anaemia
Without intrinsic can’t absorb vitamin b12
signs of megaloblastic anaemia
Macrocytic red blood cells
Hyper segmented neutrophil (centre of picture)
formation of sickle cell
Mutation in Hb gene producing Hb s which forms a strange structure within the RBC: when it takes up and gives away oxygen, alters the shape of the RBC
due to this shape, they aren’t as flexible and get stuck in blood vessels causing clots and pains
sickle cell protects against what
malaria
features of sickle cell anaemia
hereditary; African, West Indian
Abnormal haemoglobin structure
sickle shape cells, RBCs get stuck in blood vessels
no cure…..
Thalassaemias
hereditary; Mediterranean, Middle/Far Eastern
Abnormal haemoglobin production - a and b thalassaemias
