Haem 1 - Physiology of blood cells and haematological terminology Flashcards
Describe the physiology of the blood cells?
1) All blood cells originate in the bone marrow
2) They derived from multipotent haemopoietic stem cells
3) The multipotent haemopoietic stem cell gives rise to the myeloid stem cell and the lymphoid stem cell, from which red cells, granulocytes, monocytes and platelets are derived
Draw the stem cell hierarchy
See diagram
What are the essential characteristics of stem cells?
Ability to self renew and produce mature progeny - divides into two cells. Another stem cell and another cell capable of differentiating to mature progeny.
As a result it can preserve the bone marrows ability to constantly reproduce it’s self.
Describe the physiology of the red blood cells?
myeloid stem cell –> proerythroblast –> erythroblasts –> erythrocytes
Blasts - indicate that it is a precursor: large nuclei, small amount of cytoplasm. Cytoplasm changes from dark blue to pink.
Life span of 120 days, O2 transport with some CO2 transport, destroyed in the spleen by phagocytic cells
What is the process of producing red blood cells?
Erythropoiesis - requires erythropoietin produced from the kidneys in response to hypoxia. Erythropoietin can also be made in the liver.
Process:
1) Hypoxia is detected by the kidneys
2) Increase in erythropoietin synthesis
3) Increase bone marrow activity
4) Increase in RBC production
Where is erythropoietin synthesised?
Kidney - juxtatubular interstitial cells (90%)
Liver (10%)
Describe the physiology of the white blood cells?
Multipotent haematopoietic stem cells can give rise to myeloblasts which give rise to granulocytes and monocytes. For the differentiation of these cell lineages you need cytokines: G-CSF, M-CSF, GM-CSF and various interleukins
CSF - colony stimulating factor
G - granuloyte
M - macrophage
Describe neutrophils
Survives 7-10 hours in circulation before migrating into tissues.
Main function: defence against infection - phagocytoses microorganisms
Describe eosinophils
Spends less time in circulation compared to neutrophils
Main function: defence against parasitic infection
Two lobed nucleus
Describe basophils
Main function: allergic response
Can’t see nucleus because of the many dark blue spots
Describe monocytes
They spend several days in circulation
Main function: Migrate into tissue where they develop into macrophages and other specialised cells with phagocytic function
Large cells with kidney bean shaped nucleus
They store and release iron
Describe platelets
Megakaryocyte –> platelets
They survive in the circulation for about 10 days
Main function: haemostasis - they contribute a phospholipid that promotes blood coagulation
Describe lymphocytes
The lymphoid stem cells gives rise B, T and NK cells.
They circulate to lymph nodes and other tissues and then back into the blood stream.
Intravascular life span is very variable
Define anisocytosis
Red cells show more variation in size than is normal
Define poikilocytosis
Red cells show more variation in shape that is normal. There lots of different shapes: Spherocytes Irregularly contracted cells Sickle cells Target cells Elliptocytes Fragments
Define macrocytosis and macrocyte
Red cells are larger than normal
A red cell that is larger than normal
There are 3 different types of macrocytes - round, oval and polychromatic macrocytes
Define microcytosis and microcyte
Red cells are smaller than normal
A red cell that is smaller than normal
Define microcytic, normocytic and macrocytic
Microcytic - anaemia with small red cells
Normocytic - anaemia with normal size red cells
Macrocytic - anaemia with large red cells
Use lymphocytes as a reference to determine whether the cells are bigger or smaller than normal. Normally a red cell is a bit smaller than a lymphocyte
Define hypochromia
The cells have a larger area of central pallor than normal. Normal red blood cells have about one third of the diameter that is pale.
This larger area of central pallor means that there is a lower haemoglobin content and concentration and a flatter cell. Cells are hypochromic.
Hypochromia and microcytosis often go together
Define hyperchromia
The cells lack central pallor - thicker than normal or shape is abnormal. Cells showing hyperchromia can be described as hyperchromatic or hyperchromic. There are two important types of hyperchromia:
Spherocytes - approximately spherical in shape with a round regular outline and lack of central pallor. This is caused by the loss of cell membranes without the loss of an equivalent amount of cytoplasm. Hereditary sperocytosis
Irregularly contracted cells - irregular outline but smaller than normal cells, they have lost central pallor. Caused by oxidant damage to the cell membrane and to the haemoglobin.
Define polychromasia
Increased blue tinge to the cytoplasm of a red cell - indicates the red cell is young
What are reticulocytes?
They are RBC that are slightly younger than the proper mature cells. They can be detected with reticulocyte stain - methylene blue.
Describe target cells
Cells with an accumulation of haemoglobin in the centre of the area of central pallor - occur in obstructive jaundice, liver disease, haemoglobinopathies and hyposplenism.
Describe elliptocytes
They are elliptical in shape - occur in hereditary elliptocytosis and in iron deficiency. See diagram
Describe sickle cells
Sickle or crescent shaped
Result from the polymerization of haemoglobin S when it it present in a high concentration
Describe fragments
Fragments or schistocytes are small pieces of RBC indicating it has fragmented.
Describe Rouleaux
Stacks of red cells that resemble a pile of coin. It results from alterations in plasma proteins - increased so are pushing the cells together
Describe agglutinates
Red cell agglutinates differ from rouleaux in that are irregular clumps, rather than tidy stacks - result from antibodies on the surface of the cell
Describe a Howell-jolly body
This is a nuclear remnant in a red cell - commonly caused by lack of splenic function
Define the more terminology section
See notes
Describe an atypical lymphocyte
An atypical lymphocyte is an abnormal lymphocyte, used to describe the type of lymphocytes seen in infectious mononucleosis (glandular fever) See notes
What is Left shift?
This means that there is an increase in non-segmented neutrophils or that there are neutrophil precursors in the blood.
If there are lots of band form neutrophils = left shift. This means you are fighting an infection because the bone marrow is producing lots of lymphocytes. Raised cytokines and inflammation
What is toxic granulation?
Heavy granulation of neutrophils resulting from infection, inflammation and tissue necrosis. This is also a normal feature of pregnancy.
What is a hypersegmented neutrophil?
This is a neutrophil that has an increase in the average number of neutrophil lobes or segments. Results from a lack of vitamin B12 or folic acid.
