Blood Flashcards
What are the functions of blood?
- Transport
* Defence
Main components of blood seen when separated by centrifugation
•Plasma (extracellular fluid)
Contains dissolved substances, occupies 55% of volume
•Cells
WBC’s -for immune defence - & Platelets - for haemostasis
RBC’s which occupy 45% of volume
Describe the features of RBC’s (erythrocytes)
Bi-concave discs
Diameter ~ 7microm
Full of Hb for O2 carriage
No nucleus (extruded b4 released into blood)
Normal count: 4-6X10^12/L
Life span of about 120 days, then destroyed in spleen & liver
Continuous production (0.8% total per day)
Describe the features of WBC’s (leucocytes)
WBC count normal range: 4-11X10^9/L
Leucopenia: decrease in number
Leucocytosis: increase in number
Contains a nuclei
Main role in immune defence against microorganisms, other foreign cells & molecules
3 main kinds:
Granulocytes
Monocytes
Lymphocytes
How can you show all the main cell types in the blood?
Smear out blood of a glass plate, then you stain it with a standard
(Like Haemotoxicilin & Eosin stain)
Describe the features of Granulocytes
Main part of WBC’s
All have multi-lobed nucleus, and granular cytoplasm
Innate/unspecific IR
The 3 types of Granulocytes?
Main type is the Neutrophil:
•short-lived ‘front line’ defence against microorganisms
•role in inflammatory response to injury. To do this, they have 3 characteristics
•# in circulation increases rapidly in response to infection
•main constituent of ‘pus’ at sites of infection
•highly motile & phagocytic, with granules (inc lysosomes) containing a variety of enzymes & inflammatory mediators
Rare type is Eosinophil:
•red-stained granules
•functions poorly understood, but are involved in defence against parasitic infections and in some allergic conditions
•1-6% of WBC
Rare type is Basophil:
•blue-stained granules, which contains histamine & Vaso-active mediators
•circulating precursors of tissue ‘mast’ cells, involved in some allergic/hypersensitivity responses
•<1% of WBC
Describe the features of Monocytes
•They are the largest of the WBC
•2-10% of WBC
•highly motile phagocytes
•relatively long lifespan
•Monocytes spend bread period in blood before migrating out into tissues where they become macrophages
(circulating precursors of tissue macrophages)
functions (as macrophage):
>destruction of damaged tissue
>release cytokines
>assist specific immune response by acting as ‘antigen presenters’ to lymphocytes
Know how the antigen-presenting cell links to T-lymphocyte
Macrophage takes up some patho-organisms, where antigens are infested and broken down. Fragments will bound to MHC II on surface
APC then ‘presents’ the antigen fragment to t-cell. Then the T-lymphocyte that’s highly specific (thru mutagenesis) to the protein being presented binds to this, and activated the T cell
T cell then divides and carries out immune response
Features of Lymphocytes
Lymphocytes are responsible for specific immune response to ‘foreign’ cells & molecules.
- characteristic round nucleus, relatively small diameter and pale, non-granular cytoplasm
- long lifespan (bc primary role is in immune defence)
3 kinds with different functions
•B-lymphocytes- antibody producers, ‘memory’ cells
•T-lymphocytes. helper & suppressor - regulate immune response
Cytotoxic - Kill some virus-infected & malignant cells
•NK cells - kill viruses & rumour cells
Features of platelets (thrombocytes)
- 150-400X10^9/L
- tiny fragments of cells with ‘sticky’ membrane
•important role in haemostasis (arrest of bleeding):
> Aggregate to from temporary ‘plug’ as immediate response to damage of vessel wall
Plug promotes clot formation by acting as surface for assembly of clotting proteins
Secrete factors involved in vascular replace
How do the motile cells escape from the blood into the tissues?
Neutrophil squeeze though the lining of the blood vessel into the surrounding tissue
It follows chemotaxic gradient
>to move to the site of inflammation/invasion
What are the 4 ways blood cells are analysed
Know the values for clinical blood parameters
1) Haematocrit
Fraction/% of volume which is RBC’s
Normal value ~ 45%
Low values may be due to few RBC’s and/or smaller sizes of rbc (=anaemia)
2) Haemoglobin content
Normal value ~ 150g/L
Importance is that Hb is the O2 carrier (~1.3mls O2 carried per g Hb)
Reduction caused by: decreased # RBC, decreased size of RBC, decreased [Hb] per RBC. Result —> Anaemia —> poor tissue oxygenation
Increase is rare…
3) RBC parameters
RBC count: 4-6X10^12/L. Increased = polycythaemia. Decreased = one of causes of Anaemia
•from count & PCV, mean RBC V (~90fL)
•from count & [Hb], mean RBC Hb content (~30pg)
•from PCV & [Hb], mean RBC Hb conc
(~30g/dL)
