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Chapter 9.docx

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York University
Kinesiology & Health Science
KINE 2011
Olivier Birot

Chapter 9: The Blood Blood Generalities - Represents about 8% of total body weight - Average volume: o 5 L in women o 5.5 L in men - Blood = plasma (liquid portion) + cells (3 types suspended in the plasma) o Erythrocytes red blood cells O 2CO t2ansport 99% of blood cells o Leukocytes white blood cells Immune systems mobile defense units o Platelets cell fragments Important in hemostasis - Blood composition: o Plasma - 55% (men), 58% (women) o Haematocrit or packed cell volume: Buffy coat (platelets + leukocytes) - less than 1% Erythrocytes - 45% (men), 42% (women) 1000 RBCs for every 1 WBC Plasma - 91% water o Transport medium, absorbs and distributes heat - 6-8% proteins do not settle in the blood/stay in the plasma o Prevent excessive loss of plasma from the capillaries, maintain plasma volume Are dispersed evenly throughout the plasma as a colloid o Responsible for plasmas capacity to buffer changes in pH o Each plasma protein performs a different task: Albumins (58%) contribute most to the colloid osmotic pressure because they are the most abundant of the plasma proteins Bind to substances that are poorly soluble in plasma so that they can be transported in it Globulins (38%) there are 3 subclasses: Alpha (), beta (), gamma () o /: Bind to substances that are poorly soluble in plasma (water-insoluble) so that they can be transported in it highly specific Are factors in the blood-clotting process o : inactive precursor molecules; are activated as needed by specific regulatory inputs o : immunoglobulins; antibodies crucial to the bodys defence mechanism Fibrinogens (4%) key factor in blood clotting Inactive precursor for the fibrin meshwork of a clot - 2% other solutes o Ions Roles: membrane excitability, osmotic distribution of fluid between ECF and cells (ICF), buffers pH changes o Nutrients, waste products, dissolved gases (O and2CO ), re2ulatory substances (hormones) Merely being transported by the blood CO i2 the blood plays a role in acid-base balance Is carried in the blood in three ways: - o 70-80% is converted to HCO by ca3bonic anhydrase (in erythrocytes) in RBCs by the reaction: CO +2H O 2 H CO 2 + 3CO + 3- o 5-10% is dissolved in the plasma o 5-10% is bound to haemoglobin (in erythrocytes) as carbamino compounds Binds near N terminus, separate from Fe where O 2 binds Erythrocytes - Red blood cells - Main function: O transport in the blood 2 o Also transports CO and2H ions in the blood (to a lesser extent) o Structure is well suited to this (flat, disc-shaped cells indented in the middle on both sides) Biconcave discs Provides larger surface area for diffusion of O 2cross the membrane Thinness of cell enables O to diffuse rapidly between the exterior 2 and innermost regions of the cell Flexible membrane can deform as they squeeze single file through a capillary Allows RBCs to travel through narrow capillaries without rupturing in the process Most important anatomic feature that enables O tra2sport haemoglobin Found only in RBCs Is a pigment (naturally coloured) that contains iron o Appears reddish when oxygenated (arteries) o Appears bluish when deoxygenated (veins) Consists of 2 parts o Globin portion protein composed of 4 highly folded polypeptide chains (2 alpha, 2 beta) quaternary protein structure o Heme groups 4 iron-containing nonprotein groups, each of which is bound to one of the polypeptides Each of the 4 iron molecules can combine reversibly with one O 2olecule (up to 4 O2/hemoglobin) Primary role carry O 2 o Also combines with: CO 2 transports this from tissue cells back to the lungs Acidic H ion portion of ionized carbonic acid buffers this acid so that it minimally alters the pH of the blood CO not normally in the blood; if inhaled it preferentially occupies the O 2binding sites on haemoglobin; causes CO poisoning Nitric oxide binds to haemoglobin in the lungs, is released at the tissues where it relaxes local arterioles; ensures O2-rich blood can makes its vital rounds, stabilizes blood pressure There are up to 250 million haemoglobins/RBC - Contain no nucleus, organelles or ribosomes (to make more room for haemoglobin) o Cant participate in any respiratory processes that require a mitochondria - Key erythrocyte enzymes: o Glycolytic enzymes Necessary for generating energy to fuel active transport mechanisms involved in maintaining proper ionic concentrations within a cell Rely on glycolysis for ATP format
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