Lecture 29 – The Science of Blood

Congratulations on remaining steadfast during our lengthy discussion on the skeletal system.  I hope you feel comfortable with the knowledge you have obtained.  We are all at varying levels, so even if this was a review for you I hope it was enjoyable.

Hematology is the science of blood.  There are many issues regarding blood.  Some people faint at the site of it.  The religious beliefs of Jehovah’s Witnesses, forbids them to receive blood transfusions.  Before 1985, blood banks did not have a means of testing blood for contamination.  Therefore many people contracted blood-borne diseases from transfusions received before testing was developed.  Many women suffer heavy menstrual cycles as they age, causing them to seek gynecological treatment for the condition.  (I often think about the Biblical story of the woman with the ‘issue of blood’.  The Bible did not say what her issue was, but I suspect she had heavy periods.  Back then women had to sleep in a tent away from others during their monthly cycles.  That poor lady probably rarely saw the inside of her house.)  You get my point by now, which is that blood makes some people very uncomfortable.

I was always fascinated and intrigued by blood.  My first position in the hospital was in the hematology lab.  I was a medical technician during my junior and senior years of college.  I hated getting up at 4 a.m., since I am a night owl.  But the paycheck was worth it.  I called home to inform my parents that I was rich.  (I think minimum wage was about $6.00 in the mid-80’s and I earned over twice that.)  I worked from 6 a.m.-10 a.m. including weekends.  I scheduled classes from 11 a.m. to 3 p.m.  Some evenings I went back to relieve the full-time people who needed time off.  My manager allowed me to study on the clock and even leave a little early sometimes.  Every morning before class I had to draw as many as 400 vials of blood from patients ranging from the NICU to the psychiatric ward.  Then I had to spin my blood down in a centrifuge and deliver them to the other sections within the clinical lab.  My next technical job before applying to professional school was as a medical technician in the emergency department.  I will never forget vitals and IV’s in the gunshot wound victims in North Philadelphia.  I received plenty of practice setting up successful IV’s in the arms of patients who were addicted to drugs.  By 20-years-old, I was a master.  My undergraduate exposure to the hospital solidified my choice to devote my life to diseases and cures.

No matter what your opinion of blood, it is a unique substance.  What is blood?  Simply stated, it is connective tissue with a fluid matrix.  That matrix is plasma.  Cells, corpuscles, and cell fragments are the formed elements.  Where is blood formed?  The answer depends.  In the fetus, blood is formed in the liver and bone marrow.  In adults blood is formed in bone marrow and lymphatic tissue.  Some white blood cells are formed in the lymphatic tissue, also.  According to the textbooks, children have 3 quarts of blood.  Today’s children are much larger so I question the validity of that measurement.  (We are in science, and are supposed to measure using the scientific system.  You know quarts, cups, and “drops” drove me to run away in the third grade!)  Adults have approximately 5 quarts.

Functions of Blood

1 – Transport formed elements

2 – Transport nutrients and gases (O2 andCO2)

3 – Transport waste

4 – Transfers hormones, enzymes, and buffers (maintain a constant hydrogen ion concentration)  (Endocrinology – we will discuss later)

5 – Help maintain body temperature

We will take a break for now.  Do well with this information!  We just covered a few points today, but do not worry.  This survey may take as many as ten lectures and the details are plentiful.  Appreciate your blood because it has an important job.  The next time you get a minor scape and see that vital life fluid, relax as you cleanse the wound and apply a dressing.


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