OCR Physiology Practical Revision Semester 1 PDF

PHYSIOLOGY PRACTICAL REVISION Semester One  Determination of Hb concentration in RBCS Hb Content normal range: - In adult male:15-16 gm/dl - In adult female:13-14 gm/dl Sahli’s Method for Hb determination Releases of Hb and reaction with Hcl forming a dark brown acid hematin solut...

PHYSIOLOGY PRACTICAL REVISION Semester One  Determination of Hb concentration in RBCS Hb Content normal range: - In adult male:15-16 gm/dl - In adult female:13-14 gm/dl Sahli’s Method for Hb determination Releases of Hb and reaction with Hcl forming a dark brown acid hematin solution. The greater the hemoglobin content, the darker will be the color of the acid hematin solution. Hb+ HCL Acid hematin (Dark brown in color) Photometric method (Drabkin’s) Drabkin’s Method Principle: Blood is diluted in a solution containing potassium cyanide and potassium ferricyanide (Drabkin) producing cyanmethemoglobin (Yellow in color). potassium ferricyanide + Hb Methemoglobin potassium cyanide cyanmethemoglobin Spectrophotometer: This instrument used to measure the absorbance of any substance at a certain wavelength. Clinical Significance: Hemoglobin content is increased in polycythemia Hemoglobin content is decreased in anemia 1  Hematocrit Value (Hct) Packed cell value(PCV) It is the percentage ratio of the RBCs volume to the total blood volume. Centrifuge is used for the separation of blood components in heparinized capillary tube Measure The percentage volume of RBCs is determined by using special graduated scale(hematocrit chart). Normal PCV values are 45% Clinical Significance: PCV is increased in polycythemia PCV is decreased in anemia 2  RBC’s Count Principle: The blood sample is diluted (usually 200 times) with isotonic solution then the red blood cells will be counted under magnification. Hemocytometer is used to count RBCs under microscope Normal values 5.5 million cells/μl in males 5 million cells/μl in females Clinical Significance RBCs count is increased in polycythemia RBCs count is decreased in anemia Blood Indices RBC indices are part of the complete blood count (CBC) test. They are used to help diagnose the cause of anemia MCV Defines the average size of the red blood cells and is expressed as femtoliters (fl) The normal values for MCV is 80-95 fl. Normocytic: when MCV is (80-95 fl) Microcytic: when MCV < 80 fl Macrocytic: when MVC > 95 fl MCH Quantifies the average amount of hemoglobin per red blood cell. The normal values for MCH are 26-32 picograms (pg) per cell. Erythrocytes with normal MCH are called normochromic. MCH is abnormally low erythrocytes are called hypochromic MCH is abnormally high erythrocytes are called hyperchromic Anemia is classified according to the cause a) Hemorrhagic anemia (Normocytic anemia due to acute bleeding) 3 b) Aplastic anemia (Normocytic anemia due to bone marrow depression) c) Megaloblastic anemia (Macrocytic anemia due to folate or B12 deficiency) d) Anemias due to defective hemoglobin synthesis (Microcytic anemia due to iron deficiency) e) Hemolytic anemia (Normocytic anemia due to excessive destruction of RBCs) WBCs Normal WBCs count is 4000-11000 /mm3 Increased WBCs Decreased WBCs Leukocytosis Leukopenia 4  Blood Groups There are four main blood groups (types of blood) A, B, AB and O. Your blood group is determined by the genes you inherit from your parents. What determines your blood group? The cell membrane of RBCS contains antigens called agglutinogens. These agglutinogens are glycoproteins In the plasma, the antibodies against agglutinogens are normally present. The Rh factor is: an agglutinogen first discovered on the RBCs of Rhesus monkeys and called also D antigen. It is present on the surface of RBCs of 85% of human. And 15% have no D antigen. Individuals having agglutinogen D on the membrane of their RBCs are called Rh positive (Rh +ve) while those who don't have this antigen are called Rh negative (Rh – ve). Antibodies against Rh antigen are called anti-D: They are not present normally in the plasma of Rh –ve individuals , Produced only if exposed to D antigen after receiving Rh +ve blood for the first time. Blood transfusion: If Rh -ve persons is transfused with Rh +ve blood, he will produce agglutinins against Rh factor (anti-D agglutinins). If this person is transfused later with Rh +ve blood, agglutination occurs. 5 Group O is considered as universal donor due to absence of agglutinogens to be attacked. Group AB is a universal recipient due to the absence of antibodies. Blood group Determination Test 6  Hemostatic Test Hemostasis It is the mechanism which limits blood loss when a blood vessel is injured. Hemostasis Involves mechanisms to arrest bleeding as: 1. Local vasoconstriction 2. Formation of platelet plug 3. Blood coagulation Bleeding time It is time needed to stop bleeding from a tiny skin wound without formation of blood clot. This test is a measure of: Presence of adequate number and good function of platelets (Normal Platelets count = 150,000 – 450,000 / mm3) Integrity of blood capillaries and vasoconstriction. Normal range= 1 to 4 mins Clinical conditions characterized by prolonged bleeding time Purpura: It is a bleeding disorder characterized by prolonged bleeding time and subcutaneous petechial hemorrhage due to decrease in platelets count. Prothrombin Time This test is a measure for the extrinsic and common pathway of blood coagulation. Normal range 11-13.5 sec. 7 Prothrombin time is prolonged in: a) Sever liver disease b) Vitamin K deficiency Activated partial thromboplastin time This test is a measure for the intrinsic and common pathway of blood coagulation. Normal range 21-35 sec APTT is prolonged in: a) Sever liver disease. b) Vitamin K deficiency c) Hemophilia A (Factor VIII), Hemophilia B (Factor IX), Hemophilia C (Factor XI) 8