L2-Structure of RBCs in erythropoiesis Flashcards
What are erythrocytes
No nucleus blood elements that contain hemoglobin and some enzymes
What is the function of erythrocytes
Responsible for the transport of oxygen and carbon dioxide to and from the tissues of the body
How are blood cells destroyed
They display on their surface a group of oligosaccharides and these blood cells are destroyed by macrophages of the spleen bone marrow and liver
What are the structure adaptations of Ethrythrocytes to their function
▪️Shape:biconcave disc like this shape provides the cell with a large surface area relative to its volume thus enhancing its capability for gaseous exchange
▪️They expel all cell organelles including the nucleus to provide more space for hemoglobin during stages of development in bone marrow
▪️Packed with Hb which is concentrated at the periphery of the erythrocytes to facilitate gaseous exchange
Describe the cell membrane of the erythrocyte
Its molecular structure provides erythrocytes with a high degree of flexibility that can tolerate shearing forces with maintaining structural and functional integrity
Describe the molecular structure of the cell membrane
▪️Transmembrane proteins principally glycophorin a (responsible for MNS blood groups) and Rh factor
▪️Ion channels which transport Cl- and HCO3
▪️A network of cytoskeleton(mainly sceptrin tetramers,actin and adducin)
Is attached to the cytoplasmic aspect of the Red blood cell plasmalemma through anchoring peripheral proteins such as ankyrin and other transmembrane proteins
This cytoskeleton network helps to maintain the biconcave disc shape of the erythrocyte
Describe hereditary spherocytosis
Caused by synthesis of an abnormal spectrin
Abnormally shaped blood cells
More fragile and transport less O2 compared to normal cells
More over these erythrocytes are preferentially destroyed in the spleen leading to anemia
What determines the blood group of an individual
The extra cellular surface of red blood plasmalemma has specific inherited carbohydrate chains that act as antigens
Where does postnatal hemopoiesis occur
In the bone marrow
What happens during hemopoiesis
Stem cells under go multiple cell divisions and differentiate through several intermediate stages eventually giving rise to the mature blood cells
Where do all blood cells arise from
Pluripotential hemopoietic stem cells
What are the two types of multipotential hemopoietic stem cells
▪️Colony forming units lymphocytes cells
▪️colony forming units ,granulocyte, erythrocyte, monocyte, megakaryocyte cells
What are these two populations of MHSCs is responsible for
Formation of various progenitor cells
Where are stem cells in the cell cycle and how can they be driven to the G1
They are in the G0 and can be driven to the G1 by various growth factors and cytokines
Define the progenitor cells
Resemble small lymphocytes
All unipotential (committed to forming a single line such as eosinophils)
their mitotic activity and differentiation are controlled by specific hemopoietic factors
