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Blood Histology Notes

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Blood Histology Notes – Aarohi Pathak BLOOD :  Many functions of blood : 1. Transport of: dissolved gases (O2 & CO2), nutrients (to the tissues and organs), metabolic wastes (away from the tissues and the organs), hormones ( from the endocrine system to the tissues that have the receptors) 2. Stabilization of : the pH and the composition of the interstitial fluid (fluid between the different tissues) and also body temperature (heat is lost or expose to the surface of the body by blood warming and temp. is maintained) 3. preventions of fluid lost (during a cut, blood clotting happens so that the fluid is not lost from the body) 4. defence against pathogens & diseases (white blood cells fight infections)  blood is composed of plasma (55%) and formed elements (45% which are majority RBC and WBC, Platelets..) PLASMA:  mostly water (92%), because it transports anything that dissolved in it, such as proteins, sugar, ions, the formed elements (suspended within the water) and also heat  the next most abundant component is plasma proteins (7%) which are broken down into different classes that have different structures and responsibilities  the most abundant plasma protein found is albumins that transport hydrophobic molecules  the next abundant plasma protein is globulins which not only serves the purpose of transport of hydrophobic molecules as well as serves the purpose of being antibodies, help to fight pathogens (immunoglobulins)  92% and 7% but 1% is left which is other solutes which include (electrolytes, organic nutrients, organic wastes) Formed Elements : RBCs  another name for red-blood cells is erythrocytes  Hematocrit = means the volume % of the formed elements but since RBC are what forms majority of the formed elements it is then described as % of erythrocytes  If you increase the hematocrit the greater the percentage of volume of erythorocytes which increase oxygen carrying capacity which is beneficial for endurance  This is why runner’s train in higher altitudes because there is lower oxygen concentration in air therefore higher hematocrit  Blood has an interesting shape which has a functional implication (described as biconcave disc)  From the above shape it has three functional implications : 1. increases the SA to V ratio - this means that the cytoplasm has closer to the surrounding plasma, facilitates gas transfer 2. form “rouleaux” - it allows more efficient transport of RBCs in small vessels (like stacking plates) and it dissembles in a large vessels spontaneously 3. increase flexibility - BRCs are 8 micron in diameter but some vessels that they pass through are smaller diameter so what to do? … it is able to fold in half so it can pass through small capillaries  under microscope : homogenously pick, it has no nucleus, endoplasmic reticulum, ribosomes, mitochondria. It is largely just cytoskeleton which maintain the biconcave shape of the blood and cytoplasm  its life span is typically just 120 days and there after are eliminated in the spleen  RBC’s cytoplasm is 2/3 water and 1/3 protein (95% of this protein is Hemoglobin) Hemoglobin (Hb) :  Hemoglobin is a tetramer which means it has 4 globular protein subunits. Each of these subunit is referred to as globin.  Each of these subunits contain a heme molecule and at the core of these molecules is a single ion of iron  The iron associates weakly with o2, therefore we can say that each hemoglobin molecules carries 4 oxygen.  You may wonder why associates weakly ? .. because you also want it to be released when it is needed  Co2 also binds to hemoglobin but no to the iron but the amino acid of globin subunits  Therefore we can say this is a non-competitive relationship between the o2 and co2 because they don’t bind to the same binding sites  With the co2, Hb only carries around 23% of co2 transported to the lungs.  Where is the rest? …. The rest is actually turned into bicarbonate ions in the RBCs and then goes into the plasma which helps the plasma to act as a buffer. Blood Groups :  Blood groups simply represent the presence or absence of certain antigens (genetically determined, differs person to person) that are found on the surface of RBC membrane ( ie. A+)  The reason why its important to know the blood type before giving it to them because it will prevent cross-reaction  Cross-reaction can cause two things : 1. agglutination (clumping) – the donated blood and the blood within your body will react together which results in clumping which can now block small capillaries, can cause death 2. hemolysis (cell rupture)  ABO group : antibodies against the antigens that are circulating in the plasma without the prior exposure to the missing antigens (ie. Blood group A would have anti-B)  The positive or the negative comes from Rh Group. Rh+ antigen has no antibodies however and this is the difference between the ABO and the Rh group is that Rh- antigen only develops the antibodies after it have been exposed to Rh+ Diapedesis :  Dia meaning to cross, therefore Diapedesis means the process in which the WBCs move from the blood into the tissue spaces  This occurs at a high rate when
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