Constituents of the Blood
Dr K K Hampton
University of Sheffield
Blood has two phases
• 1) Cellular component
Red cells
White cells
Platelets
• 2) Fluid component
Plasma
Blood
• Cellular = 45%
• Plasma = 55%
Haematocrit 0.45
• In anaemia cellular component decreased
acute anaemia = bleeding, also loose plasma
haematocrit 0.45, Hb low
• chronic anaemia: only loose cells, plasma
compensates
haematocrit 20%, Hb low
Blood
• In Polycythaemia
cells > plasma
haematocrit > 50%
Causes:
Blood
• In Polycythaemia
cells > plasma
haematocrit > 50%
Causes: Erythropoietin
Hypoxia (leading to elevated Epo)
Haematopoiesis
(formation of the blood cells)
• Red cells, white cells and platelets in
circulation are mature cells, with finite life
span
red cell = 120 days (make 2 million/sec)
white cell = 6 hours
platelet 7-10 days
red cells and platelets anucleate
Haematopoiesis
• Precursor cells of mature cells are in the
bone marrow
Adult = axial skeleton
Child = all bones
In utero = yolk sac, then liver and spleen
• Precursor cells are not found in blood
Haematopoiesis
• Most primitive cells = stem cells
Pluripotent: can replicate and differentiate
into RBC, WBC and platelets
(stem cells vital for marrow transplantation)
• In bone marrow primitive cells proliferate
and differentiate into mature cells
Haematopoiesis
• Hormonal growth factors stimulate cells to
proliferate and differentiate
• Epo = red cells
• G-CSF = white cells
• Tpo = platelets
Red Cells
• Simple cells, no nucleus, no mitochondria
• Membrane to enclose Haemoglobin
• Enzymes of glycolysis
• Haemoglobin to carry oxygen
Have a lot of them 4 X 1012/l
Have 5 litres of blood
Haemoglobin
• Carries oxygen from lungs to tissues
• Consists of protein, haem, ferrous 2+ ion
• Allows oxygen to combine Reversibly with iron in
an aqueous environment
• Haemoglobin is a tetramer of 2 alpha and 2 beta
chains
White cells
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•
•
•
Neutrophils
Monocytes (macrophages)
Basophils
Eosinophils
• Lymphocytes
Neutrophils
• Phagocytose bacteria and foreign material
increased in bacterial infections
• Inflammatory cells, release pyrogens that
increase temperature
• Made in bone marrow from primitive cells
called myeloblasts
Lymphocytes
• Immune cells
B cells (bone marrow) = 1 make antibodies
2 memory cells
T cells helper cells
• Lack = immunodeficiency
HIV virus infects CD4 T cells
• Make in bone marrow from lymphoblasts
Platelets
• Small cytoplasmic anucleate cells that block up
holes in blood vessels
• Determine the bleeding time
• Circulate in inactive state
• Bind to damaged blood vessel and
adhere
change shape
degranulate
aggregate into platelet plug = haemostatic
Platelets
• Made in bone marrow from cells called
megakaryocytes
Polyploid cells, cytoplasm buds off to
become platelets
Platelet number
• Normal = 140 – 400 X 109/l
• Reduced = thrombocytopenia
> 80 = increased bleeding
> 20 = spontaneous bleeding
• Increased = thrombocytosis
Arterial and venous thrombosis
Plasma proteins
• Soluble and in plasma component
•
•
•
•
Albumin
Carrier proteins for nutrients, hormones
Immunoglobulins
Coagulation proteins
Albumin
•
•
•
•
Major protein in the plasma
Produced in liver
Determines oncotic pressure
Keeps intravascular fluid in that space
Lack of albumin results in oedema
Liver disease
Nephrotic syndrome
Immunoglobulins
• Produced by plasma cells = differentiated B
lymphocytes
• Several classes, IgG, IgM, IgA, IgE
• Produced in response to non-self protein antigens
• Production of antibodies basis of immunity and
vaccination
Coagulation proteins
• Series of proteins (enzymes) that circulate
in inactive form
• Function is to make blood clot
• Convert soluble fibrinogen into insoluble
fibrin polymer
Overactivity = thrombosis
Failure = bleeding