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Blood: an introduction Mammalian blood consists of cells and cell-like bodies carried about in a fluid called plasma. Blood has three main functions: • transport oxygen and nutrients to cells, and carry waste products from the cells to the organs of excretion • defense against disease (to be covered in “The Search for Better Health” topic),and • regulation of body temperature. Component Plasma

White blood cells

Red blood cells

Platelets

Function • Liquid medium for floating blood cells, antibodies and platelets, • Transports carbon dioxide, food materials, hormones and waste products (urea) in solution. • Transports heat around the body. • 0.02 mm (20µm) diameter, 7000 per mL. • Nucleated cell. • Help destroy bacteria (phagocytes) and fight disease by making antibodies (lymphocytes). • 0.008 mm (8µm) diameter, 5,000,000 per mL. • Disc-shaped cells with no nucleus. • Made in bone marrow (each lasting approx. 120 days) • Contain haemoglobin (pigment which becomes red when combined with oxygen). • Transport oxygen and small amounts of carbon dioxide. • 0.003 mm (3µm) diameter, 250,000 per mL. • Important in blood clotting.


Blood has four main components: Componen Function t Plasma • Liquid medium for floating blood cells, antibodies and platelets, • Transports carbon dioxide, food materials, hormones and waste products (urea) in solution. • Transports heat around the body. White • 0.02 mm (20µm) diameter, 7000 blood cells per mL. • Nucleated cell. • Help destroy bacteria (phagocytes) and fight disease by making antibodies (lymphocytes). Red blood • 0.008 mm (8µm) diameter, cells 5,000,000 per mL. • Disc-shaped cells with no nucleus. • Made in bone marrow (each lasting approx. 120 days) • Contain haemoglobin (pigment which becomes red when combined with oxygen). • Transport oxygen and small amounts of carbon dioxide. Platelets • 0.003 mm (3µm) diameter, 250,000 per mL. • Important in blood clotting. Blood has four main components: Componen Function t Plasma • Liquid medium for floating blood cells, antibodies and platelets, • Transports carbon dioxide, food materials, hormones and waste products (urea) in solution. • Transports heat around the body. White • 0.02 mm (20µm) diameter, 7000 blood cells per mL. • Nucleated cell. • Help destroy bacteria (phagocytes) and fight disease by


Red blood cells

• • • • •

Platelets

• •

making antibodies (lymphocytes). 0.008 mm (8µm) diameter, 5,000,000 per mL. Disc-shaped cells with no nucleus. Made in bone marrow (each lasting approx. 120 days) Contain haemoglobin (pigment which becomes red when combined with oxygen). Transport oxygen and small amounts of carbon dioxide. 0.003 mm (3µm) diameter, 250,000 per mL. Important in blood clotting.


Sample Answers:


2b

perform a first-hand investigation using the light microscope and prepared slides to gather information to estimate the size of red blood cells and draw scales diagrams of each Viewing Blood Cells

Tasks: 1.

Use the bioviewer slides provided to draw scale diagrams of the cellular components of blood. Ensure that you can describe how the light microscope is used to view and estimate the size of cells (ie using mini-grid to determine size of field of view). See page 308-311 of NSW Biology.


Sample Answers:


2.5

outline the need for oxygen in living cells and explain why removal of carbon dioxide from cells is essential Oxygen = good & carbon dioxide = bad, OK?

All living things use the process of respiration to release energy to be used by cells to maintain life processes. Aerobic (oxygenrequiring) respiration is summarized as: glucose + oxygen ďƒ carbon dioxide + water + ENERGY High levels of carbon dioxide are toxic and damage cell metabolism by decreasing pH, which affects enzyme function. High carbon dioxide levels also alter the ability of haemoglobin to bind with oxygen, decreasing the amount of oxygen available for respiration, and thus the amount of energy available for cells. If insufficient oxygen is available, cell death occurs.


2.a

perform a first-hand investigation to demonstrate the effect of dissolved carbon dioxide on the pH of water

EXPERIMENT: The effect of dissolved CO2 on pH Aim: To determine the effect of dissolved CO2 on the pH of water Method: 1.

Obtain 100mL of distilled water in a clean beaker. Use a pH probe to accurately determine the pH.

2.

Blow into the water via a straw for 10 seconds. Record the pH.

3.

Continue blowing into the water and record the pH every 10 seconds until it remains constant.

4.

Record the results in a table and create a graph to show how pH changes with the amount of CO 2 dissolved.

Results:

Conclusion: Write a suitable conclusion for this experiment.


2.1

identify the form(s) in which each of the following is carried in mammalian blood: − carbon dioxide − oxygen − water − salts − lipids − nitrogenous wastes − other products of digestion Blood may carry many substances:

Use a highlighter to summarise the handout provided (“12. Blood” from the Surfing series book) by identifying the substances carried in the blood and the form/s in which they are present. Substance products of digestion Nitrogenous waste Lipids Salt Water Oxygen Carbon dioxide

Form carried in mammalian blood Many products of digestion are soluble and travel dissolved in the plasma, eg amino acids, glucose, vitamins. The nitrogenous waste is ammonia, but as this is toxic most mammals convert this ammonia to urea. The conversion occurs in the liver and the kidneys filter the urea from the blood. Most lipids are not water soluble and only travel in the blood when coated with proteins (becoming lipoproteins) and travel as high-density lipoproteins (HDL) or low-density lipoproteins (LDL). Travels as either positive or negative ions, eg potassium ions. Travels in plasma as water molecules. Combines with haemoglobin to form oxyhaemoglobin in red blood cells. Carbon dioxide travels in different forms in the blood: • around 7% CO2 dissolves directly in the plasma • about 23% combines with haemoglobin forming carbaminohaemoglobin (carbamate) inside the red blood cells • about 70% forms hydrogen carbonate (bicarbonate) ions (HCO 3-) formed in the red blood cells but carried in the plasma


Carbon Dioxide Transport CO2 is much more soluble in blood than oxygen, so about 5 % of CO2 is transported unchanged, dissolved in the plasma. About 10 % of CO2 is transported bound reversibly to haemoglobin (forming carbaminohaemoglobin) and plasma proteins. CO 2 does not bind to iron, as oxygen does, but to amino groups on the polypeptide chains of haemoglobin or plasma proteins. Most CO2, though, is transported as bicarbonate ions, formed in the red blood cells then carried in the plasma. Carbon dioxide enters red blood cells in the tissue capillaries where it combines with water to form carbonic acid (H 2CO3). This reaction is catalysed by the carbonic anhydrase which is found in the red blood cells (this reaction occurs slowly in plasma, which lacks this enzyme). Carbonic acid then dissociates to form bicarbonate ions (HCO3-) and hydrogen ions (H+). The haemoglobin then “picks up” the free H +, allowing haemoglobin to act as a buffer, by “mopping up” excess acid to help maintain the correct pH of the blood. CO2 + H20  H2CO3  HCO3- + H+


Comparing HDL and LDL LDL particles are large with a core that is rich in cholesterol esters. LDL is known as “bad cholesterol” and is the main transporter of cholesterol in the body. When cholesterol levels are high, LDL deposits cholesterol on artery walls, causing atherosclerosis. HDL particles are similar and their protein coat contains a number of different apolipoproteins. HDL is known as “good cholesterol” as it picks up extra cholesterol in the blood and returns it to the liver. Normal levels are:

• Total cholesterol: less than 5.5 mmol/L • LDL: less than 3.5 mmol/L • HDL: greater than 1.0 mmol/L • LDL to HDL ratio: less than 4 • Triglycerides: less than 2.0 mmol/L


2.2

explain the adaptive advantage of haemoglobin Adaptive advantage of Haemoglobin

Haemoglobin is an iron-containing protein that often called a respiratory pigment. That is, haemoglobin is a compound that is responsible for the red colour of blood (a pigment), and it is involved in respiration since it carries oxygen. Left: Adult

haemoglobin – structure can be different in embryonic and fetal development


How does haemoglobin “work”? The structure of haemoglobin allows oxygen to combine loosely (reversibly) to form oxyhaemoglobin, allowing oxygen “pick up” at the lungs and “drop off” at the capillaries: high [O2] in lungs Hb + 4O2

Hb(O2)4 low [O2] in tissues


Increases the oxygen-carrying capacity of blood The presence of haemaglobin increases the oxygen-carrying capacity of the blood. blood Each red blood cell (rbc) can carry more than a billion molecules of oxygen since there are about 280 million haemoglobin molecules in each red blood cell and each is capable of carrying 4 oxygen molecules (since it is composed of 4 subunits). Hemoglobin has an oxygen binding capacity of between 1.36 and 13.7 mL O 2 per gram of haemoglobin, of which there is about 15g per 100mL of blood. The presence of haemoglobin, haemoglobin then, increases the carrying capacity to ~20mL of O2/100mL of blood, blood while blood could carry only about 0.3mL of O2/100mL if it relied only on O2 being dissolved in the plasma, plasma since oxygen is not very soluble in water at standard pressures. Thus, haemoglobin increases oxygen carrying capacity of blood by seventyfold. Ability to bind oxygen increases once the first oxygen binds to it The bonding of oxygen causes the haemoglobin to change slightly in shape, making it easier for each subsequent oxygen molecule to bind with it. This increases the rate and efficiency of oxygen uptake. As a result, a small increase in [O 2] in the lungs can result in a large increase in the oxygen saturation of blood. Capacity to release oxygen increases when carbon dioxide is present Metabolising cells release carbon dioxide, which combines with water to form carbonic acid, which lowers the blood pH. Haemoglobin has a reduced affinity (binding ability) for oxygen at lower pH, so it releases the oxygen in these tissues where it is needed (ie in the tissues where [CO 2] is high, producing a higher acidity).


Capacity to pick up carbon dioxide increases when oxygen has been released This allows some haemoglobin to pick up carbon dioxide for transport back to the lungs. In the lungs, the haemoglobin releases the carbon dioxide in preference for oxygen. Enclosure in red blood cell maintains osmotic balance The fact that haemoglobin is enclosed in a red blood cell is also of advantage because if it were simply dissolved in the plasma, oxygen would upset the osmotic balance of the plasma. All this makes mammals better competitors in their environment Mammals are endotherms and use the heat from internal metabolic process to maintain body temperature . It is therefore an adaptive advantage for mammals to have haemoglobin in their red blood cells to carry more oxygen to release more energy to maintain body temperature, ensure optimal conditions for chemical reactions and for an active life to find food, a mate, and care for offspring i.e. they are better competitors in their environment.


What if we didn’t have haemoglobin? Increased air pressure (e.g. in a hyperbaric chamber) can increase the amount of oxygen that dissolves directly into the plasma. This can be used to temporarily compensate if red blood cells are damaged (eg during treatment for carbon monoxide poisoning), by providing an alternative, but less effective, oxygen delivery route. If 100% oxygen is inspired (breathed in) at 3 atmospheres (ie 3 times normal atmospheric pressure), this should increase the volume of oxygen in solution in the blood to approximately 6mL/100ml of blood. At high altitudes (low air pressure), blood is not able to absorb as much oxygen as at sea level. The human body adapts to what is effectively oxygen deprivation by initially increasing heart rate, breathing rate, then the number of red blood cells (more haemoglobin), then density of capillaries.


Sample Answers:


2.c

analyse information from secondary sources to identify current technologies that allow measurement of oxygen saturation and carbon dioxide concentrations in blood and describe and explain the conditions under which these technologies are used Measuring Blood Gas levels

Blood gas levels may be monitored: • to assess respiratory diseases and other conditions that may affect the lungs eg emphysema or pneumonia • to manage patients receiving oxygen therapy There are different technologies that are able to analyze oxygen and/or carbon dioxide levels in the blood. Each have a different set of advantages and disadvantages, so are utilized in different situations. Summary of Blood Gas Technologies As you read the next few pages, use the information to complete a summary table. Make sure you leave enough space! Arterial Blood Gas Analysis Concentrations of oxygen & carbon dioxide in blood

Measures Situation when used Advantages Disadvantages

• •

Pulse Oximeter Oxygen saturation in blood

• •

Capnometer Carbon dioxide concentrations in respired gas • •


Arterial Blood Gas Analysis (ABG) measures the amount of oxygen and carbon dioxide in the blood by taking a blood sample from an artery (usually in the wrist). This analysis evaluates how effectively the lungs are delivering oxygen and getting rid of carbon dioxide. A blood gas analyser measures the partial pressure of oxygen and carbon dioxide, the oxygen content, oxygen saturation, bicarbonate content, and blood pH. This test is invasive, and there is often a significant time delay between sampling and the availability of results so it is unsuitable for continuous monitoring. A Pulse Oximeter is a non-invasive technique for providing real-time information about oxygen saturation of the blood. A transmission pulse oximeter uses a sensor placed on a thin part of the patient body, and a light of both red and infrared wavelengths is passed from one side to another.

(continued‌)


Bright red oxygenated hemoglobin absorbs more infrared light and allows more red light to pass through, while dark red (or blue, in severe cases) deoxygenated hemoglobin absorbs more red light and allows more infrared light to pass through. The changing ratio of absorbance of red and infrared light gives a measure of oxygenation (oxygen saturation or “sats”), reported as % saturation (acceptable ranges are usually 95-100%).

(continued…)


Pulse oximetry is commonly used during operations using anaesthesia and during the recovery phase to continually monitor patient oxygen saturation in order to determine if additional oxygen is required. The readings can be less accurate, however, if the patient is suffering from vasoconstriction such as that occurring due to cold temperatures or cardiac failure when there is reduced peripheral blood flow.


A capnometer is used to measure the carbon dioxide (CO 2) concentration in an inspired and expired air sample. It does this by measuring the absorption of a beam of infrared light, which is absorbed particularly well by carbon dioxide. It is a non-invasive device that measures the concentrations of respired gases using an infrared beam of light. The amount of light absorbed depends on the number of carbon dioxide molecules present in the air. A capnometer is useful in detecting changes in carbon dioxide concentrations in patients who are haemodynamically stable, but not critically ill. It may be used to monitor air exchange in the lungs of patients on ventilators or under anaesthesia, and it can evaluate the respiratory condition of spontaneously breathing patients.


Sample Answers:


2.4

describe the main changes in the chemical composition of the blood as it moves around the body and identify tissues in which these changes occur Blood Chemistry Changes

The chemical composition of blood changes as it travels around the body, “dropping off” some chemicals and “picking up” others. Location

Chemical that changes concentration

Why the change in concentration occurs


Location Lungs

Chemical that changes concentration Carbon dioxide

Lungs

Oxygen

Villi of small intestine Liver

Glucose and amino acids (building blocks of protein) Glucose

Kidneys

Water

Kidneys

Nitrogenous wastes

Glands

hormones

Why the change in concentration occurs Blood [CO2] decreases as it diffuses into the lungs from the blood returning from respiring cells Blood [O2] increases as it diffuses out of the alveoli in the lungs into the blood to be transported around the body Glucose and amino acids decrease in concentration as they diffuse away from the small intestine in to the blood to be used by cells [Glucose] decreases in the liver when glucose is removed to be stored as glycogen. Glucose concentration increases in the liver when glycogen is converted back into glucose. Water can be removed from blood and reabsorbed back into blood during filtration in the kidneys. Osmoregulation maintains a constant water balance in the body. Urea is formed when excess amino acids cannot be stored and are taken to the liver where they are deaminated. [Urea] increases in the kidneys as it is filtered from the blood and accumulated to be excreted. Endocrine glands secrete hormones directly into the blood, which travel round the body until it reaches the target cell/tissue


When blood flows through capillaries, carbon dioxide diffuses from the tissues into the blood. Some carbon dioxide is dissolved in the blood. A part of CO2 reacts with hemoglobin and other proteins to form carbamino compounds. The remaining carbon dioxide is converted to bicarbonate and hydrogen ions through the action of RBC carbonic anhydrase. Most carbon dioxide is transported through the blood in the form of bicarbonate ions. Carbon dioxide (CO2), the main cellular waste product is carried in blood mainly dissolved in plasma, in equilibrium with bicarbonate (HCO3-) and carbonic acid (H2CO3). 86–90% of CO2 in the body is converted into carbonic acid, which can quickly turn into bicarbonate, the chemical equilibrium being important in the pH buffering of plasma. Blood pH is kept in a narrow range between 7.35 and 7.45. 2d analyse information from secondary sources to identify the products extracted from donated blood and discuss the uses of these products. Uses of Donated Blood Use the worksheet provided (“Products extracted from donated blood”) to get started, then make additional notes using the Redcross Blood Bank website (http://www.donateblood.com.au). Product extracted from blood

Use(s)


Questions: 1.

Identify who is able to donate blood.

2.

Outline the main steps involved in the process of blood donation.

3.

Explain the need to separate donated whole blood into a number of different products.

4.

Construct a pie chart (use Excel) that shows the main groups of patients for whom donated blood is used and the proportion of blood used by each group.


2e

analyse and present information from secondary sources to report on progress in the production of artificial blood and use available evidence to propose reasons why such research is needed Artificial Blood –


ICT task and address the questions below: links on Moodle 1.

What is meant by “artificial blood” and why are blood substitutes often classified as either “volume expanders” or “oxygen therapeutics”?

2.

Create a summary table to identify similarities and differences between artificial blood and real blood.

3.

In the 1960s research began into blood substitutes. Explain why research is needed in this area by identifying the potential uses and benefits of using artificial blood.

4.

Assess a named blood substitute product.

Good websites to start with… http://www.bloodbook.com/substitute.html http://health.howstuffworks.com/artificial-blood.htm


ARTIFICIAL BLOOD: A STUDENT SUMMARY 2e analyse and present information from secondary sources to report on progress in the production of artificial blood and use available evidence to propose reasons why such research is needed. Blood transfusions have been the subject of medical research for centuries. In the early 1900s, successful transfusions were carried out as a better understanding of blood components was developed. Although scientific research into artificial blood started in the 1960s, until the HIV crisis in the 1980s, there was little interest in this research as there did not seem a great need. With the transmission of the virus during transfusions, there was nothing to replace donor blood, so artificial blood became a priority for research. Sensitive screening tests have now been developed for potential infective organisms, such as HIV and hepatitis, making donor blood much safer. There are now available safe and effective blood substitutes for certain applications, although they are still not ready for widespread use. Better blood substitutes are still needed. There is a continuing shortage of donor blood to help the victims of emergencies, civil and international conflicts and natural disasters. Furthermore, there is no guarantee that something similar to the HIV crisis will not occur in the future. Blood substitutes only perform some of the function of biological blood, and are classified by function as: • Volume expanders to increase plasma volume (a loss of only 30% volume can lead to irreversible shock)

• Oxygen carriers No substitutes have yet been developed that can replace other functions – thermoregulation, coagulation and immune defense. Two types of oxygen carriers have been produced: • Perflurochemicals eg Oxycyte – compared with hemoglobin, Oxycyte has been found to be capable of carrying at least five times more oxygen, and the tiny size of the droplets allow them to better deliver oxygen at tissue level; they are cheap to produce and because they are synthetic there is no risk of the material being infected by diseases. Using these chemicals, the amount of oxygen picked up is directly proportional to the amount of oxygen breathed in, thus patients can be given higher levels of oxygen. More research is needed because perflurochemicals must combine with other substance in order to mix in the blood stream. This changes how well the artificial blood can flow through blood vessels. Research has included mixing them with lipids and more recently lecithin. • Haemoglobin-based oxygen carriers eg PolyHeme – made from haemoglobin extracted from red blood cells. Haemoglobin-based oxygen carriers are not contained in a membrane and therefore do not require blood typing and cross-matching of blood. (The membrane of red blood cells contains antigen molecules that determine blood type, A, B, AB & O. In normal blood transfusions


care must be taken to make sure blood types are matched.) More research is needed because haemoglobin must be modified before it can be used. Also, there may be kidney problems associated with its use, as well as the need for an initial supply of haemoglobin. Current blood substitutes do not have the enzymes that prevent haemoglobin from oxidizing. Once haemoglobin is oxidized it cannot carry oxygen. Blood substitutes only stay in circulation for 20-30 hours, compared to red blood cells that remain in circulation for about 100 days which makes them a short-term solution.

Products to replace blood need to be immediately available, safe from disease, able to be stored for a long time (blood from donors must be kept cool and has a shelf-life of 42 days) and be able to be used without blood typing and matching. Such blood substitutes are useful in emergencies, disasters, wars and in countries where there are no blood donor services. Some of these substitutes are nearing the end of their testing phase and may be available to hospitals soon. Others are already in use. For example, an HBOC called Hemopure is currently used in hospitals in South Africa, where the spread of HIV has threatened the blood supply. A PFC-based oxygen carrier called Oxygent is in the late stages of human trials in Europe and North America.


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