Haemopoisis, The spleen, And Bone Marrow. Flashcards
Understand and explain the basis of haemopoeisis
Haemopoiesis is the process by which blood cells are formed. In the early embryo, this process begins in the vasculature of the yolk sac before shifting to the embryonic liver. Shortly after birth, the sole site of haemopoiesis is in bone marrow. The main sites of haemopoisis in adult marrow are the pelvis, sternum, skull, ribs and vertebrae.
What are the five major lineage pathways arising from the haemopoietic stem cells in bone marrow
Thrombopoiesis - Results in the formation of platelets (thrombocytes)
Granulopoiesis - The granulocytes (basophils, neutrophils, and eosinophils), arise from myeloblast cells which in turn arise from common myeloid progenitor cells.
Monocytopoiesis - Monocytes circulate in blood for 1-3 days before moving into tissues where they differentiate into macrophages or dendritic cells
Lymphopoiesis - Although B and T lymphocytes are found in the bloodstream, they principally belong to the lymphatic system
Erythropoiesis - Process by which red blood cells (erythrocytes) are produced in the bone marrow.
Describe the function of the main blood cell types
Describe the role of the spleen
The spleen is located in the upper left quadrant of the abdomen and consists of red pulp and white pulp. Blood enters the spleen through the splenic artery with white cells and plasma.
The role of the spleen is essentially a blood filter. The red pulp removes old red cells and metabolises the haemoglobin whilst the white pulp synthesises antibodies and removes antibody-coated bacteria and blood cells
What causes Splenomegaly and what is its clinical significance
Splenomegaly is enlargement of the spleen, and it is typically associated with an increased workload e.g., haemolytic anaemia where an increased number of defective red blood cells are removed from circulation.
Some infectious diseases are also characterised by splenomegaly most notably malaria, schistosomiasis, HIV and glandular fever.
What is hypersplenism and what is its clinical significance
Hypersplenism is used to describe reduced splenic function and is associated with an increased risk of overwhelming sepsis. Causes include underlying diseases which destroy spleen tissue such as sickle cell and coeliac disease as well as splenectomy which may be required due to a splenic rupture.
What is the reticuloendothelial system
It is a network of cells located throughout the body and part of the larger immune system. Role is to remove dead or damaged cells and identify and destroy foreign antigens in blood and tissue. Cells that make up this system are phagocytic and include monocytes in blood and different types of macrophages in various tissue.
Explain the concepts of a normal range
How is a laboratory test able to determine what values are normal or abnormal
Normal range only includes 95% of the population. 2.5% above and below the range indicate abnormal results. Significant fall in values is also a cause for concern.
Explain the significance of the reticulocyte count
Reticulocytes are immature red blood cells. They are counted using special stains or fluorescent dyes which bind to rRNA, (it’s not present in mature red blood cells). The reticulocyte count is a very useful test in evaluating different kinds of anaemia
Explain the meaning and possible clinical significance of the terms that are frequently used to describe abnormalities in a blood count or film (Increase)
Erythrocytosis/Polycythaemia - Increase in red blood cells
Leucocytosis - Increase in white blood cells
Lymphocytosis - Increase in lymphocytes
Monocytosis - Increase in monocytes
Neutrophilia - Increase in Neutrophils
Eosinophilia - Increase in Eosinophils
Thrombocytosis/Thrombocythemia - Increase in platelets
Panmyelosis - Increase in all blood cell types.
Explain the meaning and possible clinical significance of the terms that are frequently used to describe abnormalities in a blood count or film (Decrease)
Anaemia - Decrease of red blood cells
Leucopenia - Decrease in lymphocytes
Lymphocytopenia - Decrease in lymphocytes
Monocytopenia - Decrease in monocytes
Eosinopenia - Low Eosinophil count
Basopenia - Low basophil count
Thrombocytopenia - Decrease in platelet count
Pancytopenia - decrease in all blood cell types
Display an understanding of how a FBC is analysed
The full blood count (FBC) sample must ne:
- k-EDTA anticoagulated
- Chelated calcium ions
- Stops blood coagulation
The FBC is an automated test that provides greater accuracy and includes essential parameters such as:
- Red cells (Indices, RCC, haemoglobin)
- Platelets (Count and size)
- White cells (Count, full differential)
Understand the terms used to describe blood cell parameters and appearance
