Lecture 14 - Haemopoiesis Flashcards
What is haemopoeisis?
Differentiation of bone marrow cells to cells of the blood
Structure linked to function of red blood cells
- biconcave shape to increase surface area fro diffusion of gases
- no nucleus/minimal organelles to maximalist oxygen holding capabilities
- no mitochondria to ensure oxygen is not used by erythrocytes
- haemoglobin (made from iron) to increase affinity of oxygen binding
What is erythropoiesis?
The process in which red blood cells are formed from a myeloid progenitor
Stages of erythropoiesis
- Erythroblasts start of with large nucleus , prominent nucleoli and large amounts of RNA
- gradually nucleus shrinks and is removed along with majority of RNA
- RBCs are formed
What are reticulocytes ?
- final step before mature erythrocyte
- small RNA present to help make haemoglobin
- normally removed in 1-2 days
What is high amount of reticulocytes in the blood be an indicator of?
A body recovering from blood loss
How will the body stimulate more red blood cell production ?
- kidney senses tissue hypoxia (low levels of oxygen )
- low oxygen means low levels of red blood cells
- kidney increases secretion of erythropoietin
What is erythropoietin ?
- glycoprotein(hormone) produced by kidney to increase levels of red blood cells
- produced by kidneys in response to tissue hypoxia
- acts yo stop programmed cell death of erythrocytes progenitors (myeloid)
- made in the liver during fetal and kidney by birth
What are granulocytes?
- sub group of WBC’s that fight infections and inflammation
- act to mediate inflammatory reactions in the body
- act by releasing cytokines, interleukins, leukotrienes which recruit various other immune cells
3 types of granulocytes
- neutrophils (12-15 micrometer )
- basophils (11-14 micrometer )
- eosinophil (10-12 micrometers )
Key features of neutrophils
- multilobed nucleus
- 3 types of granules
- most abundant type of granulocytes
Function of a neutrophil
- granules contains lysosomes, matrix metalloproteinases (MMPs)
- phagocytose
- antigen presents and signals
- Neutrophil extracellular traps (NET) ; capture multiple pathogens
- Respiratory burst; production of free radicals
Role of G-CSF ?
Granulocyte - colony stimulating factor
- secreted by multiple immune cells and endothelial cells
- released in response to inflammation
- acts on the bone marrow to increase the number of circulating neutrophils
- increase the speed at which neutrophils mature as well as the numbers
Structure of basophils
- bilobed nucleus
- purple granules (stained due to basic dye )
- granules contains histamine and heparin(blood thinner)
Role of basophils
- Release histamine to trigger inflammation
- mediates hypersensitive reactions
Structure of eosinophils
- 2 nuclear lobes
- spheric granules - acid loving granules
Role of eosinophils
- phagocytose pathogens
- fight parasitic worms and have a role in inflammation
-granules contains
>(antihelminthic) anti parasite proteins such as major basic protein and eosinophilic cationic protein
>cell components destroying enzymes
What does granulopoeisis entail ?
All 3 granulocytes go through the maturation process of nuclear condensation and lobulation and formation /increased number of granules
Structure of macrophage (in tissues )/monocytes (in blood)
Largest of all mature blood cells
Unilobular horseshoe shaped nucleus
Function of macrophages
- first line of defence
- phagocytose pathogens, cell debris and senescent cells
- presents foreign antigens
What is thrombopoieis ?
Formation of platelets (thrombocytes)
Structure of platelets (thrombocytes)
- 2 to 3 micro metre in size
- biconvex shape
- no nucleus , just cytoplasm
- contains vast amount of proteins and clotting factors
- have special receptors on surface which cause platelet aggregation
Function of platelets ( thrombocytes)
To stop bleeding and ,editable haemostasis
How is thrombopoesis regulated ?
Unregulated by thrombopoietin from the liver
How are platelets(thrombocytes) eventually formed from thrombopoiesis ?
Megakaryocyte breaks down which eventually forms 2000-3000 platelets
What is Lymphopoiesis ?
Formation of B lymphocyte, T lymphocyte and natural killer cell
Function of B cells
- revolves around production of antibodies
- activates T cells
- play a part in humoral adaptive immunity
Where does maturation occur for B lymphocytes ?
In the bone marrow
Intestines
Spleen
Lymph nodes
Function of T lymphocytes
- kill virus infected cells , neoplastic cells and transplanted tissue
- carries out cell mediated immunity
- activates B cells to make antibodies using IL 4
Structure of T lymphocytes
-large nucleus with small rim of cytoplasm
Microscopically indistinguishable from B cells
Where to T cells mature ?
In the bone marrow or fetal liver then migrate to thymus to mature
What is plasma ?
- supporting medium for all circulating blood cells
- made up of 92% water , 8%. Protein and ions
> proteins include albumin, clotting factors and hormones, cytokines, antibodies
