In this lab exercise, we will draw a small blood sample from a finger (not the arm). We will examine the
different components of blood as well as look at some of the basic diagnostic tests commonly used in
hematology.
Working safely with blood
In this lab exercise, we will be working with human blood (your own or that of your lab partners). If you
are not comfortable with drawing blood, if you know you are sick, if you have history of fainting, if you
consider yourself at risk for transmitting a blood born disease, etc., then please do not use your own
blood. Work to safely support your peers in your laboratory group.
While it is unlikely that someone in this class carries an infectious agent in their blood (bacteria, viruses),
it is a universal practice in all laboratories to assume that every blood, tissue, or fluid sample is tainted
with something harmful. As a result, we will follow the following safety protocols:
a) Always wear disposable gloves whenever you are handling blood or any materials that
have come into contact with blood (even if it is your own).
b) Any object which has (or may have) come into contact with blood must be disposed of in
appropriate receptacles. These are never discarded in the trash.
c) Any surface which has (or may have) been contaminated with blood or another body fluid
must be disinfected.
d) Even though you have been wearing gloves, wash your hands before leaving the lab.
Disinfecting solutions supplied by the Biology department are available in the lab for your use.
Microscope slides, gloves, lancets, paper towels, etc. must be placed in designated “biohazard”
receptacles. Your laboratory instructor will discuss these precautions with you.
A. BLOOD PLASMA:
It is important to understand some of plasma’s properties, even though it is not the major focus of this
lab. Plasma makes up approximately 55-60% of our blood volume and is nearly 95% water. The
remaining 5% of plasma consists of ions (also called electrolytes), many different proteins, antibodies,
hormones, nutrients, waste products, and clotting factors. When fresh blood is allowed to settle, the
formed elements sink to the bottom and a yellow-tan (straw colored) fluid rises to the top. This yellow
fluid is the blood plasma.
Since plasma is 95% water, it is a major reservoir for water in our bodies and it is considered one of the
major “fluid compartments” in the human body. When we become dehydrated our tissues pull water
from our plasma and our overall blood volume drops. If we are over-hydrated, the extra fluid volume is
added to the plasma where it can eventually be removed by the kidneys and excreted in the urine. In
addition to acting as a reservoir for water, plasma also plays an important role in maintaining the pH, or
acid/base, balance of the body. Plasma contains buffer molecules which allow the blood and most other
tissues of the body to maintain a relatively constant pH of approximately 7.4. Plasma also plays an
important role in maintaining body temperature near 98.6
o
F since water has a great capacity to absorb
and release heat. As a result, on a hot day plasma supplies the water in sweat that helps cool our bodies.
On a cold day, delivery of warm plasma from our body’s core to our extremities helps keep them warm
when we are outside enjoying the Minnesota winter! We will discuss more about the plasma when we
study our hematocrits later on in lab