Haemopoiesis , The Spleen And Bone Marrow Flashcards
Define haemopoiesis
Production of blood cells
In an infant , where does haemopoiesis occur mainly ?
Extensive throughout the skeleton as an infant
In an adult , where does haemopoiesis occur ?
It becomes more limited and only occurs :
1) bone marrow of pelvis
2) bone marrow of the sternum
3) bone marrow of the ribs
4) bone marrow of the skull
5) bone marrow of the vertebrae
What is a thine biopsy ?
Method of looking at bone marrow using a needle which extracts liquid bone marrow from specific areas in the body
What do thrombocytes , granulocytes , lymphocytes and monocytes all arise from ?
Multipotent hematopoietic cell
What does the hematopoietic stem cell differentiate into? What two cells
1) common lymphoid progenitor
2) common myeloid progenitor
What is differentiation determined by ?
1) hormones
2) transcription factors
3) interactions with non-haemopoietic cell types eg endothelial cells
What are the two important hormones called that help regulate differentiation of the hematopoietic stem cell ?
1) thrombopoietin
2) erythropoietin
Where is ertpythropoiten secreted from and what is its role ?
Secreted from the kidneys
- it stimulates red blood cell production during periods of stress for example when oxygen levels in the blood is low this is called ‘ hypoxia ‘
Where is thrombipoietin secreted from and what is its function?
Secreted from the liver and the kidneys
- regulates the production of platelets
What are a few characteristics of the hematopoietic stem cell ?
1) capable of self renewal ( they can produce themselves again)
2) they can differentiate into a variety of specialised cells
3)
What are the two sources of hematopoietic stem cells ?
1) bone marrow
2) umbilical cord stem cells
What is the recticuloendothelial system ?( RES)
- part of the immune system and made up of monocytes in blood.
- main organs are the liver and spleen
- role is to remove dead or damaged cells and identify and destroy foreign antigens in blood and tissue
What are monocytes called when they enter the tissue ?
Macrophages
Where are kupffer . Cells found ?
They are found in liver tissue
- they are macrophages
Where are tissue histiocytic found ?
They are found in connective tissue
- they are a type of macrophage
- part of the RES system
Where are microglial found ?
In the central nervous system
- they are a type of macrophage
Where are peritoneal macrophages found ?
- peritoneal cavity
- they are a type of macrophage
Where are red pulp macrophages found ?
In the spleen
Where are langerhans cells found ?
In the skin( epidermis) and mucosa
What are the 4 functions of the spleen ?
1) sequenstration and phagocytosis - the red pulp macrophages remove 120 day old red blood cel,s
2) Blood pooling platelets and red blood cells can be rapidly mobilised during periods of stress eg ( when you are bleeding )
3) they have extramedullary haemopoiesis:pluripotent stem cells proliferate during haematological stress or if marrow fails.
4) immunological function: 25% of T cells and 15% of B cells are present in the white pulp of the spleen
How does blood enter the spleen ?
Via the splenic artery : white cells and plasma preferably pass through the white pulp
- red cells preferentially pass through the red pulp
What is splenomegaly?
Abnormal growth of the spleen
What causes splenomegaly?
1) overwork of the red or white pulp. For example when there is a disorder in red blood cells or bone marrow - the red pulp may work extra hard.
2) Portal hypertension in liver disease ( there is an increase in blood pressure within the portal venous system of the liver )
3) Extramedullary haemopoiesis
4) expanding due to cancer cells ( leukaemia , other cancer metastasis )
5) expanding as infiltrated by other material such as sarcoidosis ( abnormal collecting of inflammatory cells which leads to lumps known as granulomas )
Is it normal for the spleen to be palpable below the costal margin ?
No
What are ttwo major consequences of splenomegaly?
1) more ofyour blood volume would sit the spleen which would decrease blood count.
2) Major risk of rupture if spleen is enlarged and no longer protected by ribcage so they are often advised to not engage in extreme sports
What diseases can cause mild splenomegaly?
- infectious hepatis
- endocarditis
- sarcoidosis
- autoimmune diseases such as AIHA , ITP, SLE