Blood cells Flashcards
Average diameter of RBC
7.2 um
Shape of RBC, and how it is achieved
S_o_a_ocyte
E_h_n_cyte
R_u_e_u_
Three types, dependant on water content:
- Discocyte (biconcave disk)
- Stomatocyte (more swollen
- Echinocyte
Deformability maintained by specialised cytoskeleton:
-e.g. spectrin, ankyrin and band 3 anchoring proteins
Stack end-to-end forming Rouleaux
Contents of RBC
No nucleus, no mitochondria
Lots of Hb each with 4 haem groups which can each carry one O2
Enzymes for glucose metabolism
Ions
Why is it important that RBCs are deformable, and what physical property does this give to blood?
So they can fit into capillaries
Visco-elasticity so hard to find artificial substitutes:
-viscosity increases with decreased velocity due to their stacking into Rouleaux
Normal turnover time of RBC
120 days
Where and how are old/defective RBCs cleared?
In the spleen via phagocytosis by macrophages
Destruction gives off iron and waste products:
- iron is transferred by transferrin to the bone marrow
- waste products dealt with by the liver
What different types of anaemia are there and what can cause each of them?
Two types:
- microcytic (where there is a low average RBC size) caused by iron deficiency l - accompanied by low haematocrit
- macrocytic (where there is a high average RBC size) caused by vitamin B12 and/or folic acid deficiency
Define haematocrit
% of RBC in blood
What is EPO?
Erythropoietin - stimulated by hypoxia or increased O2 demand by tissues
Stimulates synthesis of more RBCs
Where is endogenous EPO made and what can exogenous EPO be used to treat?
Endogenous EPO synthesised and released by kidneys
Exogenous EPO used to treat anaemia, kidney diseases and chemotherapy side effects, for example
Describe the appearance and size of a neutrophil
Multi-lobed nucleus
Granulocyte - lysosomes and toxic granules containing strong oxidisers
10um
When and from where does neutrophil number increase?
Acute bacterial infection
Mobilised from reserves and increased production from myeloid progenitors
Describe their pathway to sites of acute inflammation
Adhere to vascular endothelium
Transmigrate via diapedesis through capillary walls
What do neutrophils leave behind after carrying out phagocytic activity?
Pus - a fluid containing dead neutrophils, liquefied tissue and cellular debris
Which white blood cells belong to the granulocyte family?
Neutrophils
Eosinophils
Basophils
Describe appearance of eosinophils
Stain pink due to presence of cationic proteins within large ovoid granules
Bigger than neutrophils
What is characteristic of eosinophil plasma membranes?
IgE receptors for recognising allergens or certain antigens
When does eosinophil number increase?
Chronic allergic conditions and tropical parasitic infection
What do basophils secrete on activation?
Histamine
Interleukins/cytokines
Is a macrophage a blood cell?
No - but a monocyte is…
Define monocyte
A blood cell that can give rise to a macrophage after migrating into a tissue
What are the roles of macrophages?
Tissue dependant, but generally they:
- phagocytose, and kill organisms
- remove tissue debris (by secreting enzymes) for repair
- involved in tissue homeostasis and remodelling (e.g. phagocytose apoptotic bodies)
Key points of Till & McCullogh 1963 experiment showing the presence of haematopoietic stem cells
Heavily irradiated mice
Injected bone marrow cells, and observed small nodules later dubbed ‘spleen colonies’ in spleen, number of which was proportional to the amount of bone marrow cells injected
Around 10,000 bone marrow cells had to be injected before a nodule formed
Each nodule spawned red cells, white cells and platelets
Hypothesised that each nodule was formed from one stem cell
What two main divisions arise from haematopoietic stem cells, and give examples for each?
Common myeloid progenitors - granulocytes, red blood cells, mast cells, monocytes
Common lymphoid progenitors - lymphocytes
