Chapter 2: In The Lab

Transcription

1 Handbook of Anatomy and Physiology 75 Chapter 2: In The Lab The Metric System and Measurement Introduction The metric system is the world standard for measurement. Not only is it used by scientists throughout the world, but most nations have adopted it as their standard of measurement. All of the measurements done in this course will use the metric system. The table below shows the standard unit of length, weight, volume, and temperature in the metric system. It also shows the English equivalent. Metric English Length meter inches Weight gram ounces Volume liter quarts Temperature degree (Centigrade) 1.8 degrees Fahrenheit Vocabulary for Chapter 2: SI Units Meter Gram Liter Kilo Deci Centi Milli Micro Nano Mass Volume Temperature Density Monocular Light Microscope Binocular Light Microscope Scale/balance Beaker Flask Test tube Pipette Graduate Cylinder Ruler Meters, grams, and liters (see the table above) form the basis for larger or smaller units. The units are named using these prefixes: Kilo = 1000 Deci = 1/10 Centi = 1/100 Milli = 1/1,000 Micro = 1/1,000,000 Nano = 1/1,000,000,000

2 Anatomy Curriculum Guide Page 76 of 16 The table below shows how meters are related to five other measures of length. Unit Length kilometer (km) 1,000 m (1 X 10 3 m) meter (m) 1 m centimeter (cm) 0.01 m (1 X 10-2 m) millimeter (mm) m (1 X 10-3 m) micrometer (um) m (1 X 10-6 m) nanometer (nm) m (1 X 10-9 m) Notice that each of the units in the table above are related to meters by a multiple of 10. The photograph below shows the end of a meter stick. The 90 cm mark can be seen in the center of the photograph. One meter = 100 cm. Notice that each centimeter is divided into 10 mm.

3 Anatomy Curriculum Guide Page 77 of 16 The tables below show similar units based on grams (weight) and liters (volume). Unit Weight metric ton (t) 1,000 kg or 1,000,000 g (1 X 10 6 g) Kilogram (kg) 1,000 g (1 X 10 3 g) gram (g) 1 gram milligram (mg) g (1 X 10-3 g) microgram (ug) g (1 X 10-6 g) nanogram (ng) g (1 X 10-9 g) Unit Volume kiloliter (kl) 1,000 liters (1 X 10 3 l) liter (l) 1 liter milliliter (ml) liter (1 X 10-3 l), 1cm 3 microliter (ul) liter (1 X 10-6 l) Notice in the table above that one milliliter (ml) equals one cubic centimeter (1 ml = 1 cc or cm 3 ).

4 Anatomy Curriculum Guide Page 78 of 16 Metric Conversions Exponents The table below shows how numbers can be written using exponents. For example, a second way to write the number 1,000 is 1 X = = 1 X = 1 X ,000 = 1 X = 1 X = 1 X 10-3 Examples 256 = 2.56 X = X = 5.5 X 10-2 Exponents are useful when writing numbers that are very large or very small. For example the number 1,930,000,000,000,000,000 is easier to write as 1.93 X Decimal Point Metric conversions are done by moving the decimal point. When converting a large unit such as meters to a smaller unit such as millimeters, the decimal point is moved to the right. When converting smaller units to larger units, the decimal point is moved to the left. You must subtract the exponents in order to determine how many places to move the decimal point. Larger (move decimal point to the left) 10 3 m kilometer (km), kilogram (kg), kiloliter (kl) 10 0 m meter (m),gram (g), liter (l) 10-2 centimeter (cm) 10-3 millimeter (mm), milligram (mg), milliliter (ml) 10-6 micrometer (µm), microgram (µg), microliter (µl) 10-9 nanometer (nm) Smaller (move decimal point to the right)

5 Anatomy Curriculum Guide Page 79 of 16 Examples Convert 2.6 cm to µm. This problem is solved by subtracting the exponents. The exponent for cm is -2; the exponent for µm is -6. Subtract the two numbers: (-2 - (-6) = 4). Therefore, to convert 2.6 cm to µm, you must move the decimal point 4 places to the right. 2.6 cm = µm Convert 57 µm to cm. The exponent for µm is -6. The exponent for cm is -2. You must subtract these two number to determine how many places to move the decimal point (-2) = -4. The negative sign indicates that you must move the decimal point 4 places to the left. 57 µm = cm. Rounding and Significant Digits It is often desirable to round numbers. For most purposes in this laboratory course, numbers should be rounded to 3 significant digits. Some examples below illustrate this concept. The number 35,832,487 can be rounded to 35,800,000. We use the three digits that are furthest to the left; the rest become zeros. The number 35,852,487 becomes 35,900,000. If the number to the right of the 3rd digit is 5 or greater, the 3rd digit is rounded up. If it is less than 5, it is rounded down. The number becomes The number becomes Examples The table below shows the number rounded to several different significant digits. Number of significant digits Number

6 Anatomy Curriculum Guide Page 80 of 16 The table below shows the number rounded to several different significant digits. Number of significant digits Rounded Number Laboratory Exercise Record your answers to the questions below on the separate answer sheet. Do not use scientific notation (exponents) or fractions in your answers to the questions below. Write all of the zeros. Length Measurement of Length I) Measure the width of this page using a small plastic ruler. Record your measurement in 1. millimeters, centimeters, and meters. 2. Record your answers on the answer sheet. II) Use a meter stick to measure the width of the laboratory table in 1. millimeters, centimeters, and meters. Which unit of measurement (kilometer, meter, centimeter, millimeter, micrometer, or nanometer) would be most appropriate for measuring the width of this room?

7 Anatomy Curriculum Guide Page 81 of 16 Conversions of Length Perform the following conversions. 1) 1 m = cm. 2) 1 cm = m. 3) 3.57 mm = um. 4) 452 cm = mm. 5) 0.04 um = mm 6) 37.6 nm = mm 7) 52 nm = µm 8) 4.3 m = µm 9) 4206 mm = cm 10) 18) mm = nm 11) 19) 4.8 cm = µm Use the following information to perform the calculations below. Metric to English: 1 meter = inches = feet English to Metric: 1 inch = meters; 1 foot = meters inches = m Round your answer to the nearest m feet, 3 inches = m Round your answer to the nearest 0.01 m. [Hint: First, convert 12 ft. 3 inches to feet. It is not 12.3 feet.]

8 Anatomy Curriculum Guide Page 82 of 16 Mass Measurement of Mass The laboratory scale shown below has a sensitivity of g. Due to its sensitivity, moving air will cause it to fluctuate. The glass chamber surrounding the weighing pan prevents air currents from interfering with the weight. The scale in the photograph to the left has a sensitivity of 0.01 g. The scale can be set to zero by pressing the zero (tare) button on the lower left part of the scale. Place a small beaker on the pan of the scale and zero it by pressing down on the zero (tare) button located on the front of the scale. Place a penny in the beaker to obtain its weight. 14. How much does the penny weigh in grams? Remove the beaker from the scale and weigh the penny without using the beaker. You must first zero the scale before weighing the penny.

9 Anatomy Curriculum Guide Page 83 of 16 Conversions of Weight Perform the following conversions g = mg mg = g g = kg Use the following information to perform the calculations below. Metric to English: 1 g = ounces = pounds English to Metric: 1 ounce = grams; 1 pound = grams pounds = kg Round your answer to the nearest 0.01 kg oz = g Round your answer to the nearest 0.01 g.

10 Anatomy Curriculum Guide Page 84 of 16 Volume Measurement of Volume Obtain a 10 ml graduated cylinder (shown below) and fill it about half full with water. Hold the graduated cylinder in a vertical position at eye level and read the number of milliliters of water that are in the cylinder. Be sure to read the water at the bottom of the meniscus. The arrow points to the bottom of the meniscus in the photograph below. What is the volume of water in the cylinder? Use a 50 or 100 ml graduated cylinder to determine the amount of liquid that a test tube can hold (it's volume). How did you determine the volume of the test tube?

11 Anatomy Curriculum Guide Page 85 of 16 Conversions of Volume ml = liters µl = liters l = ml ml = µl Sometimes volume is measured using cubic centimeters (abbreviated cc or cm 3 ). One cubic centimeter equals one milliliter (1cc = 1ml) ml = cc (or cm 3 ) Use the following information to perform the calculations below. Metric to English: 1 liter = quarts = gallons English to Metric: 1 quart = liters; 1 gallon = liters quarts = liters Round your answer to the nearest 0.01 liter gallons = liters Round your answer to the nearest 0.01 liter. Temperature Measurement of Temperature The following temperature measurements should be done in Centigrade (Celsius). 27. Measure and record the temperature of the air in the laboratory room. 28. Measure and record the temperature of ice water. 29. Measure and record the temperature of boiling water.

12 Anatomy Curriculum Guide Page 86 of 16 Conversions of Temperature The temperature in Fahrenheit can be converted to Centigrade (Celsius) using the formula: C = 5/9( F - 32) For example, to convert 60 F to C, subtract 32 (=28), multiply it by 5 (=140) and divide it by 9 (=15.56). The steps listed above are performed in reverse order to convert Centigrade to Fahrenheit. The equation is below: F = (9/5 C) + 32 For example, 20 C is converted to F by multiplying it by 9 (= 180), dividing it by 5 (= 36), and adding 32 (=68) F = C For this one, use the formula C = 5/9( F - 32). Round your answer to the nearest 0.1. (Note- If you do not have a calculator, use the one on the computer. Click Start, Programs, Accessories, Calculator) C = F For this one, use the formula F = ( 9/5 C) + 32

13 Anatomy Curriculum Guide Page 87 of 16 Introduction to the Light Microscope 1. Examine your microscope. Familiarize yourself with the parts of the microscope. The magnification written on the ocular lens (eyepiece) is The magnification written on: the scanning objective (this is the first and largest number written on it) x the low power objective is x the high power objective is x 2. The total magnification using the lenses can be determined by multiplying the objective lens with the ocular lens. What is the total magnification of an item viewed with the: LOW power objective. The HIGH POWER The SCANNING 3. Examine the diaphragm (underneath the stage). The numbers on the edge of it range from ONE to 4. Look into the eyepiece, twist it left and right. Notice the line inside that moves as you twist. (Some microscopes do not have this, see if you can find one that does in the room). What do you think this is for? 5. Place the slide of the "letter e" on the stage so that the letter is over the hole and is right side up. Use the scanning objective to view the letter and use the coarse knob to focus. Repeat on the low power objective. Finally, switch to high power. Remember at this point, you should only use the FINE adjustment knob. Draw the "e" as it appears at each magnification. Drawings should be drawn to scale and you should note the orientation of the e in the viewing field (is it upside down or right side up?)

14 Anatomy Curriculum Guide Page 88 of Choose 2 specimens from the box of fixed specimens". Use the circles below to sketch your specimens under SCANNING and LOW power. You may practice focusing with the high power, but you do not need to sketch it. Label your specimens from the name written on the slide. Specimen 1 Specimen 2 Scanning Low Power

15 Anatomy Curriculum Guide Page 89 of Answer true or false to each of the statements On high power, you should use the coarse adjustment knob. The diaphragm determines how much light shines on the specimen. The low power objective has a greater magnification than the scanning objective. The fine focus knob moves the stage up and down. Images viewed in the microscope will appear upside down. If a slide is thick, only parts of the specimen may come into focus. The type of microscope you are using is a scanning microscope. For viewing, microscope slides should be placed on the objective. In order to switch from low to high power, you must rotate the revolving nosepiece. The total magnification of a microscope is determined by adding the ocular lens power to the objective lens power.

16 Anatomy Curriculum Guide Page 90 of 16 Sweetness! Dear Lord! exclaimed the nurse as she read off the patient s lab report. Get the Doctor immediately she blurts out panickedly! Your pager goes off. You dial the number. This is Doctor (your name here) and I just got a page. You listen to the nurse. Oh really! I'll be right there! When you arrive at the nurses station she hands you the report. You immediately look over the numbers and rush towards the patient's room. You burst in to find Mr. Sewell, calmly resting in his bed, watching the ballgame on ESPN. A quick battery of evaluations leads you to the conclusion that Mr. Sewell is not in any distress. So you look at the lab report again. Na K Cl CO 2 O meq/l meq/l meq/l mm Hg mm Hg Uric Acid Creatine(CK) Glucose ph Hematocrit % mg/dl units/l mg/dl This blood report was just taken this morning. As a matter of fact, you had drawn the blood when you checked up on him this morning on your way to another surgery. You were in a hurry and didn t spend much time with Mr. Sewell, but he had seemed to be doing fine. He had wanted to know if he could get the IV out today. Said he was tired of his left arm being used for a pincushion. But otherwise he was in good spirits. Mr. Sewell had a cholecystectomy just yesterday. 1) What is abnormal about the report? 2) Can these readings be explained physiologically? 3) What should you do next? Use the values at to analyze values. Directions: Analyze the report, answer the questions and your results to Mr. Sewell in the proper format.