BIOL125 Lecture Notes - Lecture 24: Body Fluid, Aorta, Fibrinogen
8 Jun 2018
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Changes across the lifespan
• 5.19. Age related changes and their consequences in:
o 5.19.1. blood
• Increased: blood viscosity/plasma viscosity
▪ Decreased total water volume in the elderly body -> decrease in plasma
volume and increased plasma viscosity (stickiness/thickness)
▪ Outcomes for body
• Increased viscosity -> increased TPR -> increased workload on
heart and increased damage to blood vessel linings -> increased
thrombosis and plaque formation risk
• Decreased proportion of erythrocytes in blood and decreased haemoglobin
(Hb)
▪ Drop in haematocrit (ratio of volume of erythrocytes to total blood
volume)
• Normal: 39-50% for males and 35-44.5% for females
▪ Hb drops to <13 in males and <12 in females
▪ Outcomes for body
• <34% haematocrit associated with increased mortality
• Decreased Hb associated with increased risk of mortality (1.6% in
males and 2.3% in females)
• Erythrocyte membranes become stiffer/more rigid
▪ Outcomes
• Decreased ability to deform -> reduction in flow through capillary
beds -> reduction in O2 delivery to tissue and decreased removal
of CO2 from tissues
• Anaemia common in elderly
▪ Several potential causes
• Iron deficiency (up to 23% of cases)
• Vitamin B12 or folate deficiencies (up to 14% of cases)
• Chronic disease or inflammation (up to 35% of cases)
• Chronic kidney disease (up to 8%)
• Outcomes
• Impaired functional and cognitive ability
• Symptoms of depression and increased mortality
• Reduction in stem cell numbers in bone marrow -> decreased cell formation
▪ Drop in erythrocyte number -> decreased oxygen carrying capacity of
blood -> decreased energy
▪ Drop in WBC (leucocyte) numbers -> decreased activity of NK cells and
phagocytic cells -> increased risk of infection and delayed inflammatory
response -> increased healing time
▪ Drop in lymphocyte numbers -> reduced specific responses -> increased
risk of more severe infection and delayed healing time
o 5.19.2. the heart
• Reduced cardiac output
▪ Reduced elasticity in fibrous CT in heart -> reduced expansion and recoil
ability
▪ Reduced blood flow into myocardium -> ischaemia, angina and MI
▪ Scar tissue formation -> loss of contractility and potential damage to
signal conduction cells -> arrhythmias
▪ Hypertension -> ventricle hypertrophy and reduced SV
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o 5.19.3. blood vessels
• Clotting changes
▪ Increased change of hypercoagulation due to
• More fibrinogen -> increased haemostatic plug formation risk
• Less movement -> reduced circulation/flow rate -> increasing
thrombosis formation risk
• Dehydration/reduction in total body fluid volume -> viscous blood
-> decreased flow rate and increased cardiac workload
▪ Outcomes
• Increased risk of thrombosis/clot formation -> blocked blood
vessels and increased risk of atherosclerotic plaque formation ->
ischaemic stroke and coronary artery disease or heart attack
(myocardial infarction, MI)
• Arteries: increased endothelial damage from increased BP/MAP
▪ Increased TPR from increased blood viscosity increases BP
▪ Increased BP and TPR from reduced elasticity of arterial walls
▪ Increased BP -> increased risk of atherosclerotic plaque or aneurysm
formation
▪ Hypercoagulability -> increased risk of thrombosis formation
▪ Plaque, smooth muscle infiltration and calcium deposits -> hardening of
arteries and thickening of wall -> less elastic stretch and recoil and
blockage of vessel lumen -> reduced blood flow
find more resources at oneclass.com
find more resources at oneclass.com
