Red blood cells Flashcards
What are the dimensions of a red blood cell?
7.5 micrometer length
2 micrometer thickness
What is the shape of a RBC?
Biconcave disc
What does the shape depend on?
Water content due to presence of aquaporin channels (osmotic effects)
What maintains the RBC shape?
Cytoskeleton, made from ankyrin and spectrin
What shapes are associated with different solutions?
Discocyte shape (isotonic solution ~ 300mOs)
Stomatocyte shape (hypotonic solution ~ 100mOs)
Crenelated echinocyte shape (hypertonic solution ~ 500mOS)
What organelle(s) do RBCs not have?
Nuclei
Mitochondria
What is the benefit of RBC being able to deform?
Squeeze through capillaries
Why do RBC stain pink?
Eosin dye (Hb is a basic protein so binds acid dyes)
Blood has anaomalous…
Viscosity
What happens to blood viscosity as velocity decreases?
Viscosity increases
Why is blood flow low in small vessels?
Adherence of RBCs to each other (rouleaux) and to vessel wall
When is viscosity of blood more visible?
Membrane more rigid
Aged erythrocytes
Inclusions inside cell (e.g. sickle cell)
What happens to cell shape as viscosity increases?
Decreased deformity.
Why is being anucleate beneficial for RBC?
Allows biconvcave shape
Greater SA:V for faster exchange
More deformability to fit through capillaries
Why is being anucleate a disadvantage?
No further protein synthesis or repair, cells have short lifespan, vast replacement, increase risk of neoplasia
Cell is terminally differentiated cannot modify gene expression.
What is normal lifespan of RBC?
120 days
Describe effects of RBC in hypotonic solution
Haemolysis as water enters through aquaporins
What happens in hypertonic medium to RBC?
RBC lose water and become crenated.
Do RBC respire aerobically?
No, they have no mitochondria
How do RBC respire?
Anaerobic glycolysis, with pentose phosphate shunt to prevent oxidative stress (by producing NADPH). Protects cell without DNA.
What sort of environment is RBC, reducing or oxidising?
Reducing
How are RBC destroyed?
Aged RBCs destroyed by marophages in spleen/liver
How are RBCs made?
In bone marrow, nucleated haematopoietic stem cells which can differentiate to progenitor cells then RBC (in response to erythropoietin form kidney)
Describe what happens to haematopoietic stem cells in bone marrow
Can self renew or diff into multipotential stem cell
What accelerates RBC life span?
Abnormal shape e.g. abnormal Hb
Overactive phagocytosis in liver/spleen
What are the 3 different types of anemia?
Microcytic (smaller erythrocytes), normal (sized erythrocytes) and macrocytic (larger erythrocytes)
What causes microcytic anemia?
Still high haematocrit e.g. thalassemia
Low haematocrit e.g. iron deficient anaemia
What causes normal anaemia ?
Haemorrhage, bone marrow disorder
What causes macrocytic anemia?
Vitamine 12 deficiency or folic acid deficiency
Describe the ABO blood system?
2 types of glycoproteins on RBC , type A and B
A and B are codominant, O is recessive (neither A or B antigen expressed).
Blood group determines the antibodies they produce against RBC antigen
e.g. anti A antibody comes across A antigen, RBC agglutinate/congeal
What is the Rh system?
Rh system antigens constitute a group of glycoprotiens aka antigens expressed in most people
People are Rh+ or Rh-
When does a RBC lose its nucleus?
In development
