Recent Question/Assignment Just need to do the highlighted three short answer question and references not required. BIOL2044 Human Physiology 2: Body Systems Blood/immunity practical/workshop: Blood typing and haematocrit Learning objectives At the end of this session and the accompanying lectures, students should be able to: • Define haematocrit and explain the factors that regulate erythrocyte production. • Explain the physiological basis of the ABO and RhD blood groups. • Describe the principles of blood typing, and explain why blood typing is important in blood transfusions. Pre-practical preparation Before coming to the practical please read these practical notes and the recommended sections of the prescribed textbook (Silverthorn’s Human Physiology 7th edition: pg 535 – 47 [elements of blood] and 801 – 802 [blood group and typing]). Based on your readings, please complete the tables below. Table 1: Pre-practical preparation for Activity 1 & 2. Provide a brief (1 – 2 sentences) description for each of the following. Term Definition erythrocyte leukocyte haemoglobin haematopoiesis erythropoietin haematocrit mean corpuscular volume antigen antibody agglutination Table 2: Pre-practical preparation for Activity 2. Complete the table, identifying the red blood cell antigens and plasma antibodies that will be present in each of the ABO blood groups ABO blood group RBC antigens Plasma antibodies A B AB O Practical class learning activities There are two main learning activities: the first focuses on factors that regulate red blood cell production, whilst the second explores blood groups and blood typing. For each task, work through the questions and activities in order, asking the teaching staff for assistance where necessary. Activity 1 – Blood and blood cell production Background Blood is approximately 8% of body weight. The average volume of blood in healthy adult males is 5-6 L, which is more than that seen in healthy adult females (4-5 L). Whole blood consists of two components – a fluid part, called plasma (~55% by volume), and a solid part, called the formed elements (~45% by volume). These formed elements are the living blood cells (eg. erythrocytes or red blood cells [RBC], leukocytes or white blood cells [WBC], and platelets) suspended in the plasma. The leukocytes are further subdivided into granulocytes (basophils, neutrophils, eosinophils), lymphocytes and monocytes. Blood is transported around the body by the circulatory system. The main blood vessels responsible for carrying blood around the body are the arteries (which generally carry oxygenated blood) and veins (which generally carry deoxygenated blood). The normal pH range of blood is 7.35 – 7.45. Some of the major functions of blood include: (1) Distribution of oxygen and nutrients to all cells; (2) Removal of excretory wastes from cells; (3) Regulation of body temperature, pH and fluid volume; and (4) Protection (eg. blood clotting, antibodies). Erythrocytes are anucleate (lacking a nucleus) and have a concave shape that allows them to travel freely through the circulatory system. The main protein found in these cells is haemoglobin that carries O2 and CO2 around the body. Haemoglobin is composed of two parts – haem (~4% weight comprised of iron and porphyrin) and globin (a protein that comprises ~96% of haemoglobin weight). The formation of blood cells is called haematopoiesis and occurs in the bone marrow. All formed elements in the blood originate from a progenitor haematopoietic stem cell. The process of erythrocyte (RBC) formation is called erythropoiesis. The production of RBCs is primarily regulated by the hormone erythropoietin. The synthesis and release of erythropoietin is stimulated by hypoxia (low oxygen levels). Anaemias can can be characterised by low haemoglobin concentration, red cell count, and haematocrit, may represent acute or chronic blood loss, excessive haemolysis, or deficient blood production. The haematocrit is a measurement of the concentration of erythrocytes in the total volume of blood. It is expressed as the percentage of erythrocytes in the total blood volume and may also be called the packed cell volume (PCV). Learning activities & discussion questions 1. What does haematocrit measure? a) What sort of situations would lead to an increase in haematocrit? b) What sort of situations would lead to a decrease in haematocrit? 2. Janet is a healthy 42 year old female who has been on a 2 month holiday in Nepal, where she trekked to Everest base camp. Two days after her return, she is sent for a complete blood count. Identify what sort of changes you would expect to see in each of the following parameters, and explain your reasoning. o Haematocrit o RBC count o WBC count o Mean corpuscular volume 3. Scientists have developed a synthetic version of erythropoietin using recombinant DNA technology, and this product is currently in clinical use. a) What is erythropoietin? b) What clinical conditions might be treated with erythropoietin? 4. In sports, erythropoietin is banned by the World Anti-Doping Agency because it is a performance-enhancing drug. a) How would erythropoietin enhance sporting performance? b) What type of athletes would be most likely to see performance-enhancing effects with erythropoietin? c) Misuse of erythropoietin increases the risk of heart disease, stroke, and pulmonary embolism. Why is this the case? Activity 2 – Blood groups and blood typing Background Red blood cells have a range of different cell surface markers or antigens. There are over 30 different groups of RBC antigens, and the presence or absence of these different antigens are what determines an individual’s blood group. Two important groups of antigens are the ABO blood group antigens and the Rhesus (Rh) antigens. The ABO antigens are based on two cell surface antigens found on erythrocytes, A and B. These antigens are genetically inherited, so an individual may have antigen A, antigen B, both antigens (blood group AB), or neither antigen (blood group O). The plasma can also contain antibodies (or agglutinins) to the antigens found on the erythrocytes. These antibodies will be formed against the ABO antigens that are NOT present on a person’s RBCs. If these antibodies come into contact with their corresponding antigen, they can cause agglutination and destruction of the RBCs. Blood typing is therefore critical for blood transfusions, to ensure that transfusion reactions do not occur. In blood typing for ABO groups, antisera containing anti-A and anti-B antibodies are added to blood samples. If the RBCs in the blood sample contain the corresponding antigen, agglutination of the cells will visible. Another important system is the Rhesus system (Rh). There are many different Rh group antigens, however the RhD antigen is what we are usually referring to when we talk about an individual being ‘Rh-positive’ or ‘Rh-negative’. Unlike the ABO system, there is no pre-formed Anti-D antibody found in the blood. However, a RhD-negative person can make Anti-D antibodies following exposure to RhDpositive blood. Differences in the Rh D antigen status between mother and child can lead to hemolytic disease of the newborn. This condition can occur when a pregnant RhD- female has a baby which has inherited RhD+ blood from its father. If the mother has been previously exposed to RhD+ blood (such as during a previous pregnancy with a RhD+ foetus), this can activate the mothers immune system and lead to the formation of RhD antibodies in the mother. If the mother has a subsequent pregnancy with a RhD+ foetus, the maternal RhD antibodies can attack the developing foetus. The mothers antibodies bind to the foetal erythrocytes and haemolyse them. In some cases this can cause the death of the foetus depending on the intensity of the immune response. RhD- mothers who have had an RhD+ pregnancy are given an injection of the drug Rho-GAM after delivery. This prevents the mother from making antibodies against RhD+ blood, thereby preventing an immune attack against a future RhD+ foetus. 1. Look at the images provided in the practical class. For each example: o Identify the RBC antigens and antibodies that will be present in the blood sample o Identify the blood group of that individual Sample Blood group RBC antigens Antibodies 1 2 3 4 2. What would happen if a person with type O blood receives a whole blood transfusion from a type B donor? 3. What would happen if a person with type AB blood receives a transfusion of red blood cells from a type B donor? 4. Blood donors with O negative type blood are sometimes referred to as ‘universal donors’. Why is this? 5. What determines whether an individual is RhD-positive or RhD-negative? 6. Why is the Rh status of both mother and child particularly important in pregnant women? 7. Looking back at your answers to question 1, identify which blood groups each person could donate blood to, and which blood groups they could receive blood from. Sample Blood group Could donate to Could receive from 1 2 3 4 To help you with this there is an online blood typing game to reinforce your understanding of blood groups and blood typing. Select ‘quick game – random patients’ if you do not want to register. http://bit.ly/2oHUrwM Questions for online practical submission SAQ 1. Nick Jones is an RMIT student who is taking a ‘gap year’, and spends 6 months living at altidtude in the Andes in South America. Whilst living in the Andes, his haematocrit increases. Explain why his haematocrit has increased, and the physiological mechanisms that are responsible this increase in haematocrit. (2 marks) SAQ 2. Jane Smith is a RhD-negative mother who is 28 weeks into her second pregnancy with a RhD-positive foetus. Jane has her blood tested as part of her routine ante-natal care, and is found to have antibodies to RhD. Explain the most likely reason for why Jane Smith has antibodies to RhD in her blood. (1 mark) SAQ 3. The following table shows the blood typing observations for two different patients. For each patient, identify their blood group (both ABO and RhD), and briefly explain your reasoning for each patient. (2 marks) Patient Anti-A Anti-B Anti-D Patient Jones Agglutination No agglutination Agglutination Patient Smith Agglutination Agglutination No agglutination Let’s block ads! (Why?)
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