Haemapoesis Flashcards
What is haempoiesis?
It is the production of blood cells and it occurs in the bone marrow.
How it Bone marrow distributed?
In infants bone marrow is widely distributed but in adulthood, bone marrow is in the Pelvis, Sternum, Skull, Ribs, Vertebrae
How is haemopoiesis controlled?
It is controlled by hormones.
What types of blood cell are there?
What are some characteristics of haemopoietic stem cells?
- It has the greatest power of self renewal compared to any other adult tissue.
- It can renew itself and can differentiate to a variety of specialised cells depending on the different stimuli.
- It can mobilise out of the bone marrow into circulating blood
- It can undergo apoptosis.
What are the sources of HPSC?
Used to used aspiration of bone marrow (be put under anaesthetic and suck 2L out of bone marrow using a needle). Rarely done anymore.
Now, GCSF mobilised stem cells in the peripheral blood (collected by leucopharesis) - This is when you stimulate stem cells to go into the blood and collect the stem cells by using an aphoresis machine. This method is what happens if donating stem cells to a siblign or as a voluntary donor.
Umbilical cord stem cells. These are donated by people wo have just had a baby and are usually used for children.
What is therReticuloendothelial system?
The RES is a network in blood and tissues which is part of the immune system containing phagocytic cells:
- Monocytes
- Macrophages
- Kuffper cells
- Tissue Histiocytes
- Microglial cells in the CNS.
Cells of the RES can identify and mount an appropriate immune response to foreign antigens.
The main organs are the liver and the spleen.
All blood passes through thr speen, the RE cells in the spleen can dispose of blood cells, in particular damaged or old red cells.
Extracellular fluid travels via lymphatics to the lymph nodes.
What does the spleen consist of?
Red pulp - sinuses lined by endothelial macrophages and cords
White pulp - similar to the structure of lymphoid follicles
White cells and plasma preferentially pass through white pulm whereas red cells preferentially pass throguh red pulp.
Blood supply of spleen?
- The spleen gets its bloos via the splenic artery that splits into multiple arterioles.
- Blood then leaves through venules joining splenic vein, into superior mesinteric vein then into the portal vein.
- Remember: The portal vein takes blood from splenic vein.
What are the functions of spleen in adults?
Sequestration and phagocytosis - old / abnormal red cells removed by macrophages.
Blood pooling - platelets and red cells can be repaidly mobilised during bleeding
Extramedually haemopoisis - (make blood outside bone marrow) - pluripotent stem cells proliferate during haematological stress or if marrow fails (eg myelofibrosis)
Immunological function - 25% of T cells and 15% of B cells are present in the speen. There are even more during infection.
How do you meaure the size of the spleen?
- It is never normal to palpate the spleen below the costal margin.
- Start to palpate in the right iliac fossa or will miss massive spenomegaly.
- You feel the spleen edge move towards your hand on inspiration.
- Feel for the spenic notch.
- Measure in cm from the costal magin to the mid clavicular line.
Why would the spleen grow?
- Back pressure (portal hypertension in liver disease)
- Over working red pulp
- Over working white pulp
- Reverting to what it used to do (extramedullary haemopoisis.)
- Extending as infiltrated by cels which shouldn’t be there.
- Eg cancer cells of blood origin (Leukeimia) or other cancer metastasis
- Expanding as infiltrated by other material.
- Eg Gauchers disease or sarcoidosis.
What can cause massive splenomegaly?
Chronic myeloid leukaemia, myelofibrosis, maleria, schistosomiasis
Wha could cause moderate splenomegaly?
Massive + lymphoma, leukemias, myeloproliferative disorders, liver cirrhosis with portsl hypertension, infections such as glandualr fever causes by Epstein Barr virus.
What could cause mild splenomegaly?
Massive + Moderate + Infections such as infectious hepatisis, endocarditis, infiltrative disorder such as sarcoidosis, autoimmune diseases.
What is hyperslenism?
Low blood counts can occur due to pooling of blood in the enlarged spleen.
What kinds of things should people with spleenomegaly avoid?
Contact sports eg Rugby, Cycling (because of handlebars), Gardening.
What are the complications of splenomegaly?
- Infections - hear splenic rub if listen with stephescope.
- Rupture causes haematoma.
What is hyposlenism?
Lack of functioning splenic tissue.
What are the causes of hyposplenism?
- Splenectomy
- Sickle cell disease in older children and adults (due to multiple infarcts then fibrosis)
- Coeliac disease.
A blood film woudl reveal Howell Jolly bodies (DNA remianants).
What is the structure of an erythrocyte cell membrane?
The erythrocyte cell membrane is a lipid bilayer that contains proteins such as spectrin, Ankyrin, Band 3 and protein 4.2. These proteins facilitate vertical interactions with the cytoskeleton of the cell which are essential for maintaining the red cell’s biconcave shape and deformability.
Gene mutations in these membrane associated proteins can result in diseases such as hereditary spherocytosis which cause the red cells to lose their biconcave shape.
How does neutrophil maturation occur?
- Myeloblast
- Promyelocyte
- Myelocyte
- Metamyelocyte
- Band
- Neutrophil
