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Blood And Components - Topic 5
Describe Blood, Its Composition And Function Of Components:
• Blood is bright red when carrying oxygen and dark red when it is oxygen depleted.
• Blood plays an essential role of transporting materials between body tissues, the lungs, kidneys and GI tract.
• Other roles include buffering changes in pH, heat distribution, delivery of antibodies, WBC’s, hormone control and
maintaining tissue fluid balance.
• Blood plasma is mainly water containing nutrients, gases, hormones, wastes (nitrogenous), proteins (amino acids) and
inorganic ions (electrolytes).
Plasma Proteins • Albumins (60%): Carry molecules through circulation, a blood buffer and major blood protein contributing to plasma
osmotic pressure.
• Globulins 35% (Alpha & Beta): Produced by the liver, most are transport proteins that bind to lipids, metal ions and fat
soluble ions.
• Globulins (Gamma): Antibodies released by plasma cells during the immune response.
• Fibrinogens (5%): Produced by the liver and forms fibrin threads for blood clots.
Define Haematocrit And How This Changes In Health & Disease:
• A haematocrit is the percentage of blood volume that is made up of erythrocytes.
• Normally it is around 45% in men and around 43% in women.
• In anaemia this can drop to 15% and in polycythaemia it can rise to 75%.
• Anaemia - Where blood’s oxygen carrying ability is too low to support normal metabolism and is a sign of a disorder rather
than a disease.
• Polycythemia - The abnormal excess of erythrocytes than increases blood viscosity and volume. The severely impairs
circulation.
Describe The Red Blood Cell And It’s Function:
• Mature erythrocytes are bound by a plasma membrane, lack a nucleus (anucleate) and have no organelles and
mitochondria.
• They are bags of haemoglobin that take up 97% of contents and its function is gas transport.
• It’s small size and biconcave shape provides a huge surface area relative to its volume (30% more SA than spherical cells)
which is ideal for gas exchange.
• Their main role is transporting respiratory gases (oxygen and carbon dioxide) and most oxygen carried in blood is bound to
haemoglobin.
Describe Haemoglobin And It’s Structures And
Function:
• Haemoglobin is made of the red heme pigment
bound to the protein globin.
• Globin consists of four polypeptide chains, two alpha
and two beta, each binding a ringlike heme group.
• Each heme group bears an iron atom in its center.
• A haemoglobin molecule can transport 4 molecules
of oxygen as each iron atom can combine with one
molecule of oxygen.
Describe The Life Cycle Of A Red Blood Cell And The Dietary Requirements For Normal Red Blood Cell Formation
(Haematopoiesis):
• RBC formation in adults occurs in the red bone marrow of the axial skeleton (vertebrae, ribs and sternum) and in the
epiphyses of the humerus and femur.
• Formation in the foetus takes places in the foetal yolk sac, liver and spleen. By the 7th month, red bone marrow is mainly in
the haematopoietic area.
• Haemocytoblasts give rise to all formed elements within blood.
• RBC circulate for around 120 days and we produce and remove around 1-2 million RBC’s per second.
• Worn cell surfaces (glycocalyx) stimulates phagocytosis by macrophages in the spleen and liver to remove these cells.
• The main nutrients and structural materials needed for erythropoiesis are amino acids, lipids and carbohydrates.
• Iron, vitamin B12 and folic acid are also important. Iron is stored within haemoglobin in the liver, spleen and bone marrow.
• Iron is integral to haemoglobin function and crucial to other processes but high plasma iron is toxic so absorption by
intestinal cells is precisely controlled.
• Some iron is stored in protein-iron complexes like ferrin and circulating iron is loosely bound to the transport protein
transferrin.
• RBC breakdown occurs in the spleen and liver. The globin portion is lysed to release amino acids to be reused and the
heme portion are lysed releasing iron and bilirubin.
• Iron - Mainly stored, bound to a protein (reduced toxicity) and reused or excreted.
• Bilirubin - Taken up by the liver, secreted in the bile and by products give the brown colour to faeces.
Define Anemia:
• The insufficient oxygen carrying capacity of blood due to either insufficient RBC’s, haemoglobin or both.
Describe The Different Types Of Anaemia And Their Causes:
Insufficient RBC’s • Hemorrhagic anaemia = Caused by blood loss either sudden or persistent from internal bleeding.
• Haemolytic anaemia = RBC rupture or lyse prematurely is caused by a mismatched blood transfusion, haemoglobin
abnormality and bacterial or parasite infections.
• Aplastic anaemia = Caused by destruction of inhabitation of red marrow by drugs and chemicals, ironising radiation and
viruses. Defects in blood clotting and immunity are also present.
Insufficient Haemoglobin • Dietary iron deficiency causes microcyte production and they are small and pale as they cannot synthesise normal
haemoglobin.
• Pernicious anaemia = An autoimmune disease that often affects the elderly and the immune system destroys cells of the
stomach mucous.
• These cells produce an intrinsic factor that is needed for vitamin B12 to be absorbed.
• Lack of intrinsic factors such as B12 make erythrocytes grow but cannot divide and macrocytes results.
Abnormal Haemoglobin Thalassemias =
• Where one globin chain is absent or faulty and erythrocytes are thin, delicate and haemoglobin deficient.
• Classified according to which haemoglobin chain is affected and where.
Sickle Cell Anaemia =
• Caused by the abnormal haemoglobin (haemoglobin 5-Hbs) and RBC become crescent shaped when they unload oxygen
or when oxygen levels are low like during activities that increase metabolic activities.
• These rupture easily and dam up affecting oxygen delivery.
Define Haemostasis:
• This is the process of preventing blood loss.
• Step One - Vascular spasm: Smooth muscles contract, causing vasoconstriction.