ABC Flashcards
Erythrocytes: basic properties (3)
- Structure
- Lifespan
- Clearance by ….
- Biconcave disc shape, anucleate
- 90 -120 days
- Reticuloendothelial system (spleen)
Erythrocytes: function
- Transport of O2 and CO2 around the body
Platelets (thrombocytes): function
- Blood coagulation upon vasculature injury
- Release granules and activate clotting cascade
Platelet structure:
- Surface coated with glycoproteins for adhesion/aggregation
Platelets: interactions
1. Platelet-platelet
2. Platelet-endothelium
- bind to fibrinogen for platelet-platelet adhesion
- bind to von WIllibrand Factor (vWF) for platelet endothelium adhesion
Myeloid cells:
- definiton
- Types
- Blood cells that originate from progenitor cells born in bone marrow
- Monocytes, granulocytes, erythrocytes, megakaryocytes
Monocytes: definition
- Undifferentiated leukocytes that differentiate into:
1. Macrophages
2. Dendritic cells
Granulocytes:
- Definition
- Types (4)
- Cells characterised by specific granules in their cytoplasm
1. Neutrophils
2. Eosinophils
3. Basophils
4. Mast cells
Neutrophils: role
- Phagocytose, degranulate and release NETs to kill bacteria and fungi
Neutrophils: development
- Location
- Requires …..
- Mature in bone marrow prior to circulation
- G-csf for proliferation/differentiation
Neutrophils: basic properties
- Structure
- Lifespan
- Clearance
- Multi-lobed nucleus (1-5), granular cytoplasm
- 6-10 hours
- Reticuloendothelial system (spleen)
Types pf phagocytes: (3)
- Monocyte/macrophage
- Neutrophils
- Dendritic cells
Monocytes: basic properties
- Size
- Functions
- Lifespan
- Largest leucocyte
- Diverse subsets and functions
- 1-2 days
Monocyte development:
- Requires (2)
- Shares common progenitor with ….
- Develops into …..
- GM-CSF, M-CSF
- granulocytes
- Macrophages and dendritic cells in tissue
Monocytes: function
- Differentiate into macrophages and dendritic cells
Eosinophils: function
- Target larger parasites and modulate allergic reactions
Basophils: function
- Release histamines for inflammatory responses and ALLERGIC REACTIONS
Mast cell: function
- Release histamines and serotonin to modulate allergic reactions and INFLAMMATORY RESPONSE
Lymphoid cells:
- blood cells that arise from progenitor cells born in the bone marrow but must migrate to the lymphatic organs to differentiate
- B & T -lymphocytes
B-lymphocyte function: (2)
- function in the humoral immunity component of the adaptive immune system
- Produce plasma cells that produce antibodies
T-lymphocytes:
- Function
- Subsets (2)
- Function in the adaptive immune response
- Cytotoxic T cells and Helper T cells
Normal blood cell production: start point
- Multipotent hematopoietic stem cell
Blood cell production: myeloid pathway start
- Multipotent hematopoietic stem cell -> Common myeloid progenitor
Myeloid production: Megakaryocyte
- Route
- Via
- Common myeloid progenitor -> Megakaryocyte
- Via Thrombopoietin (TPO) prod. by liver
Myeloid production: Erythrocyte
- Via
- Erythropoietin (EPO) prod. by kidneys
Myeloid production: granulocytes
Myeloblast -> granulocytes
- Via granulocyte colony stimulating factor (G-CSF)
What does the full blood count (FBC) measure?: (4)
- RBC’s
- WBC’s
- WBC differentiation
- Platelets
Reticulocyte count: definition
- The number of developing RBC’s
Relevancy of reticulocyte count in differential diagnosis of anaemia: (2)
- Increased RC: Reduced RBC survival (haemolysis or bleeding)
- Reduced RC: problem with production
Blood film definition:
- Snapshot of the cells that are present in the blood at the time that the sample is obtained
Blood film diagnostic uses: (2)
- Assess red cell, platelet and white cell (numbers, size, colour and morphology)
- View any abnormal cells
Haemostasis: blood vessel wall
- Endothelial cell role
- Contains negative regulators to reduce haemostasis
Negative regulators in endothelial cells:
- Soluble mediator
p
Soluble mediators:
- Prostacyclin
Negative regulators in endothelial cells:
- Surface mediators (3)
E
T
H
Surface mediators
- Endothelial protein C receptor
- Thrombomodulin
- Heparens
Haemostasis: blood vessel wall
- Sub-endothelial cells
- Have activators that enhance haemostasis
Sub- endothelial cell activators for haemostasis: (3)
- Collagen
- Tissue factor
- Von Willebrand Factor (VWF)
Role of platelets in haemostasis:
Adhere …
Activate ….
Support …..
- Adhere to sub-endothelial proteins after vascular damage
- Activate and aggregate other platelets
- Support activation of coagulation factors
Role of VWF in haemostasis:
- Binds platelet surface proteins to mediate platelet adhesion
Role of coagulation factors in haemostasis:
- Series of plasma proteins which convert prothrombin to thrombin
Roles of fibrinogen in hameostasis:
- Binds…..
- Polymerised …..
- Binds platelet surface integrins to mediate platelet aggregation
- Polymerised to thrombin to form fibrin clot
Cell based model of haemostasis:
- all the components of haemostasis interact in a regulated way to generate clot only at the site of vascular injury
Thrombin:
- Definition
- Role
- An activated coagulation factor that is the main effector of haemostasis
- Thrombin polymerises fibrinogen to FIBRIN and fully activates PLATELETS
Haemostasis - step 1: trigger
(2)
- Collagen and tissue factor exposed
- Von Willebrand Factor (vWF) binds collagen
Hameostasis - step 2: Primary Haemostasis
(2)
- Platelets adhere to vWF-collagen
- Platelets activate and aggregate
Haemostasis - step 3: Thrombin generation
- Tissue factor initiates rapid thrombin generation on activated platelets
Hameostasis - step 4: consolidation
- Thrombin converts fibrinogen to fibrin and completes platelet activation
- Stable fibrin-platelet clot is formed
Regulation of haemostasis: clot formation
1. vWF adhesivity is regulated by …….
ADAMTS 13
Regulation of haemostasis: clot formation
2. Thrombin is regulated by ……. (2)
- Antithrombin
- Activated protein c system
Regulation of haemostasis: fibrinolysis
- Thrombin converts enzyme plasminogen to plasmin
- Plasmin cleaves fibrin to degradation products (D-dimer)
Core laboratory tests of haemostasis: (4)
- Platelet count + blood screen
- Coagulation screen (PT + APTT)
- Fibrinogen level
- D Dimer level
PT + APTT tests principles: (3)
- Add activator (phospholipid+Ca2+) to anticoagulated blood
- Incubate at 37*C
- Measure time to fibrin clot formation
Indications of prolonged PT or APTT: (3)
- Reduced levels of coagulation factors (bleeding disorders)
- Reduced function of coagulation factors (anticoagulant drugs)
- Laboratory artefact (human error)
Isolate prolonged PT?:
- Factor VII issue (extrinsic pathway)
Isolated prolonged APPT?:
- Issues with factors VIII, IX, XI (intrinsic pathway)
Long PT and APTT?:
- Multiple factor defects; II, V, X, fibrinogen (common pathway)
What does high fibrinogen levels indicate?:
- Acute phase response, pregnancy
What do low fibrinogen levels indicate?:
A
L
M
- Acquired bleeding disorders
- Liver disease
- Massive transfusion
What does an elevated D-dimer level indicate?:
D I C
V
Multiple
- Disseminated intravascular coagulation
- Venous thrombosis
- Pregnancy, liver/kidney disease, sepsis
Point-of-care tests of haemostasis:
- Example
- Importance
- Thromboelastometry
- Quick and easy to perform and interpret, useful in urgent clinical settings
Virchow’s triad:
- Hypercoagulability
- Endothelial injury
- Venous stasis
Risk factors for VTE: physiological factors (4)
- Dehydration
- Obesity
- Pregnancy
- Old age
Risk factors for VTE: other factors (3)
- Medical comorbidities
- Significant reduction in mobility
- Vascular access and devices
Risk factors for VTE: medications (3)
- Hormone replacement therapy
- Some cancer treatments
- Oestrogen-containing contraceptives
Risk factors for VTE: hospital/surgery (3)
- Surgery with general anaesthetic + time > 90mins
- Critical care admission
- Hospital admission
DVT signs and symptoms:
L
S
T
D
P O
- Leg pain
- Swelling
- Tenderness
- Discolouration
- Pitting oedema
VTE ‘atypical’ presentations:
B L S
A
D
P
- Bilateral leg swelling
- Asymptomatic
- Death
- Pyrexia of unknown origin
Diagnosis: DVT^1,2: (2)
- Confirmatory test:
1. Venous ultrasonography
2. MRV or CTV for VTE at unusual sites
Diagnosis: PE^2-4:
- Confirmatory tests:
1. CT pulmonary angiogram
2. Ventilation-perfusion scan
D-dimer test for VTE:
- Use
- False negatives if. …..
- Increased levels in VTE and other diseases/conditions
- False negative: patient on anticoagulants, take blood before starting anticoagulants
Screening thrombophilia to see if it is….. (2)
- Inherited thrombophilia
- Acquired thrombophilia: screening for antiphospholipid syndrome
Antiphospholipid syndrome:
- Description
- Associations
- Autoimmune, acquired prothrombotic condition
- Associated with systemic lupus erythematosus (SLE)
Antiphospholipid syndrome: clinical features
A T
V T
M T
P L
L R
T
- Arterial thrombosis
- VTE
- Microvascular thrombosis
- Pregnancy loss
- Livedo reticularis (red-blue rash)
- Thrombocytopenia