PATHOLOGIES Flashcards
Anaemia
Insufficient O2 carrying capacity due to decrease Hb concentrations
Why is there not enough haemoglobin
Bone marrow doesn’t produce enough Hb - hypoproliferation - not enough ingredients or incorrect instructions.
Shortened survival - blood loss, haemolysis
Iron absorption
Absorbed from duodenum.
Regulated by negative feedback of hepcidin - regulates ferroportin receptors on enterocytes, duodenum and proximal jejunum.
Transferred into plasma and bind to transferrin - transport protein.
Absorption depends on hepcidin, activity of ferroportin and type of iron available.
Iron transport and storage
Iron transported from enterocytes to plasma or excess Iron stored as ferritin.
In plasma - attach to transferrin and transported to bone marrow or RBCs.
Where is folate and B12 absrobed from
Folate = duodenum and jejunum B12 = ileum via intrinsic factor
Function of folate and B12
Folate = necessary for synthesis of DNA B12 = co-factor for methylation in DNA and cell metabolism - intracellular conversion to 2 active co-enzymes necessary for homeostasis of methylmalonic acid & homocysteine
Mechanism of absorbing B12
Require intrinsic factors made in parietal cells of stomach
Transcobalamin II and transcobalamin I transport vit B12 to tissues
Pernicious anaemia
Autoimmune disorder - lack intrinsic factor - decrease B12 absorption.
Antibodies against gastric parietal cells or intrinsic factor
Macrocytic anaemia
Low Hb
High MCV
Norm. MCHC
Haemolytic anaemia
Anaemia due to shortened RBC survival
Haemolysis
- Shortened red cell survival
- Bone marrow compensates - increase RBC production
- increase young cells in circulation
Compensated haemolysis
RBC production able to compensate for decrease RBC life span = norm Hb
Incompletely compensated haemolysis
RBC production unable to keep up with decrease RBC life span = decrease Hb
Clinical findings of haemolytic anaemia
Jaundice, pallor/fatigue, splenomegaly
Haemolytic crises - increase anaemia and jaundice with infections.
Aplastic crises - anaemia, reticulocytopenia
Chronic clinical findings of haemolytic anaemia
Gallstones - pigment due to bilirubin
Folate deficiency - increase synthesis for cells, increase demand because more broken down
Haemolytic anaemia - laboratory findings
Increased reticulocyte count Increased unconjugated bilirubin Increased LDH Low serum haptoglobin proteins that binds free haemoglobin Increased urobilinogen Increased urinary haemosiderin Abnormal blood film
Red cell membrane disorders examples
Hereditary spherocytosis
Hereditary elliptocytosis
Red cell enzymopathies examples
G6PD deficiency
PK deficiency
Hereditary spherocytosis
Common haemolytic anaemia - inherited autosomal dominant fashion
defect in protein in vertical interaction between membrane skeleton and lipid bilayer
Decrease membrane deformability - membrane lose shape = RBC spherical
Clinical features of Hereditary spherocytosis
Asymptomatic to severe haemolysis, neonatal jaundice, pigment gallstones.
Decrease eosin-5-maleimide (EMA) binding - binds to band 3
Glucose 6 phosphate deficiency
hereditary, X-linked - protection from oxidative stress
Effects of oxidative stress on Hb and membrane proteins
Hb - denatured Hb - heinz bodies - bind to membrane
Membrane proteins - decrease RBC deformability
Pyruvate kinase deficiency
Autosomal recessive
Required to generate ATP - essential for memrbane cation pumps.
Lose K+ and H2O = dehydrated and rigid
Thalassaemias
Imbalanced alpha and beta chain production - excess unpaired globin chains = unstable.
Precipitate and adamage RBC - ineffective erythropoiesis in bone marrow
Beta thalassaemia major - if transfusion does not occur
Failure to thrive, progressive hepatosplenomegaly, bone arrow expansion - skeletal abnormalities.
Side effects = Iron overload - heart failure, liver cirrhosis, endocrinopathoes
Confirming diagnosis of sickle cell anaemia
Solubility test - expose blood to reducing agent - HbS precipitate = + trait and disease
Electrophoresis
Steps for Primary haemostasis
- Endothelium release small amount of von Willebrand factor
- Collagen exposed to blood – von Willebrand factor binds to it
- Platelets express receptors for both collagen and von Willebrand factor is then active when bound and then express functional fibrinogen receptors – NEEDED for aggregation
Steps for secondary haemostasis
- Platelet is activated
- Tissue factor expressed by many sub-endothelial cells activate coagulation cascade to initiate increase of thrombin
- Factor FVIIa binds to tissue factor – prothrombin into thrombin - Thrombin activates receptors on platelets and endothelium - increase platelet aggregation and initiate release of stored von Willebrand factor from endothelial cells
Steps for amplification stage in blood coagulation
- Thrombin activates 2 cofactors - factor 8a and 5a
- Form Ca2+ dependent complexes on surface of platelets with factor IXa and factor Xa - accelerate production of factor Xa and thrombin = amplification stage
- Increase production of thrombin via tenase and prothrombinase - thrombin converts fibrinogen into fibrin mesh
Steps of fibrinolysis
Plasminogen activated to plasmin by tissue plasminogen activator (t-PA)
Plasmin degrades the fibrin mesh to fibrin degradation products which can be cleared.
What is antithrombin
Serpin = serine protease inhibitor
Activity increases by binding to heparan binding sites on endothelial cells
Protein C
Activated by thrombin + thrombomodulin on endothelial cells = APC
then works with protein S
Protein S
APC cofactor
Help bind to cell surface - APC degrades cofactor FVa and FVIIIa
Molecular basis of Haemophlia
Failure to clot leading to haemorrhage.
Mutation in cogaultion factors - haemophilia A and B
Platelet disorder - von Willebrand disease
Collagen abnormalities - fragile blood vessels and bruising
Molecular basis of thrombophilia
Excessive clotting leading to thrombosis
Inherited = mutation in coagulation factors (DVT)
Acquired = malignancy increase clotting factors (DVT)
Molecular basis of DIC
Whole body clots
Infection - sepsis
Depletion of clotting factors and platelets leading to bleeding
Aneuploid
Chromosome number is not an exact multiple of haploid number
Extra or missing chromosomes - trisomy or monosomy
How does aneuploid chromosomes occur
Error in segregation of pair of homologous chromosomes in meiosis I
Or when there is an error in segregation of chromatids - meiosis II = imbalance of chromosomes in zygote
Trisomy 13
Pataus syndrome
complications of heart abdominal wall and brain
Trisomy 18
Edwards syndromes
complex heart and brain abnormalities
Trisomy 21
Down syndrome
High chance of health problems - congenital heart problems, disorders of digestive tract, visiom and increased risk of leukaemia
Mitotic non-disjunction
Post zygotic non-disjunction - affect only a proportion of cells = mosaicism
Individual has a mixture of cell types
Trisomy rescue/anaphase lag
Mechanism in cell recognise there is a wrong number of chromosomes and throws out one of the chromosomes to become disomic.
Could have both maternal chromosomes - clinical impact
Philadelphia chromosome
Translocation between chromosome 9 and 22.
ABL on chromosome 9 = proto-oncogene
BCR on chromosome 22 = prone to ds DNA breaks.
Exchange material which can trigger oncogene potential in ABL. Can lead to types of leukaemia and myeloma
What occurs in Robertsonian translocation
Involves acrocentric chromosomes
Ds breaks p arm is cut off and lost - q arms stuck together around centromere
Detecting chromosomal abnormalities - what is FISH
Hybridisation - single strand nucleic acid strand binds to new single stranded nucleic acid strand - use metaphase chromosome
Detecting chromosomal abnormalities - steps in FISH
- Fluorescent probe
- Denature probe and target DNA
- Mix probe and target DNA
- Probe binds to target
Steps for array CGH
- Patient and control DNA labelled with fluorescent dyes and applied to microarray
- Patients and control DNA compete to attach or hybridise to the microarray
- The microarray scanner measures the dluorescent signals
- Computer software analyses the data and generates a plot
Looks for microdeletions and duplications