BIO 301
Human Physiology
& Body Defenses I
Functions of Blood:
1 - Transportation:
o
o
o
oxygen & carbon dioxide
nutrients
waste products (metabolic wastes, excessive water, & ions)
2 - Regulation - hormones & heat (to regulate body temperature)
3 - Protection - clotting mechanism protects against blood loss & leucocytes
provide immunity against many disease-causing agents
Components of Blood - average adult has about 5 liters (about 5 qts):
1 - Formed elements:
o
o
o
Red blood cells (or erythrocytes)
White blood cells (or leucocytes)
Platelets (or thrombocytes)
2 - Plasma = water + dissolved solutes
Red blood cell, platelet, and white blood cell
Red Blood Cells (or erythrocytes):
1 - biconcave discs
2 - lack a nucleus & cannot reproduce (average lifespan = about 120 days)
3 - transport hemoglobin (each RBC has about 280 million hemoglobin
molecules)
4 - Typical concentration is 4-6 million per cubic mm (or hematocrit [packed cell
volume] of about 42% for females & 45% for males)
5 - contain carbonic anhydrase (critical for transport of carbon dioxide)
Determining the hematocrit
Erythropoiesis = formation of erythrocytes




the body must produce about 2.5 million new RBCs every second
in adults, erythropoiesis occurs mainly in the marrow of the sternum, ribs,
vertebral processes, and skull bones
begins with a cell called a hemocytoblast or stem cell (below)
rate is regulated by oxygen levels:
o
o
o
hypoxia (lower than normal oxygen levels) is detected by cells in the
kidneys
kidney cells release the hormone erythropoietin into the blood
erythropoietin stimulates erythropoiesis by the bone marrow
training.seer.cancer.gov
Hemoglobin




composed of globin (made up of 4 highly folded polypeptide chains) + 4 heme
groups (with iron)
each molecule can carry 4 molecules of oxygen
called oxyhemoglobin when carrying oxygen & called reduced hemoglobin when
not carrying oxygen
can also combine with carbon dioxide & helps transport carbon dioxide from the
tissues to the lungs
White blood cells (or leucocytes or leukocytes):



have nuclei & do not contain hemoglobin
typical concentration is 5,000 - 9,000 per cubic millimeter
types of WBCs:
o granular white blood cells include:
 neutrophils (50 - 70% of WBCs)
 eosinophils (1 - 4%)
 basophils (less than 1%)
o agranular (or non-granular) white blood cells include:
 lymphocytes (25 - 40%)

monocytes (2 - 8%)
Granular white blood cells contains numerous granules in the cytoplasm, & their nuclei
are lobed. Agranular white blood cells have few or no granules in the cytoplasm & have a
large spherical nucleus. Granular white blood cells are produced in the bone marrow,
while agranular white blood cells are produced in lymph tissue, e.g., Lymph nodes
(specialized dilations of lymphatic tissue which are supported within by a meshwork of
connective tissue called reticulin fibers and are populated by dense aggregates of
lymphocytes and macrophages).
The primary functions of the various white blood cells are:





Neutrophils - phagocytosis (bacteria & cellular debris); very important in
inflammation
Eosinophils - help break down blood clots & kill parasites
Basophils - synthesize & store histamine (a substance released during
inflammation) & heparin (an anticoagulant); functions(s) remain unclear
Monocytes - phagocytosis (typically as macrophages in tissues of the liver,
spleen, lungs, & lymph nodes)
Lymphocytes - immune response (including production of antibodies)
Some important characteristics of White Blood Cells (particularly neutrophils):
1 - phagocytic
2 - capable of diapedesis (also called extravasation)
3 - capable of ameboid movement
4 - exhibit chemotaxis (attracted to certain chemicals, such as those released by
damaged cells)
Phagocytosis
Lymph system
Chemotaxis & ameboid movement
Neutrophil moving to site of infection
Platelets (or thrombocytes)
1 - formed in the bone marrow from cells called megakaryocytes
2 - have no nucleus, but can secrete a variety of substances & can also contract
(because they contain actin & myosin)
3 - normal concentration in the blood is about 250,000 per cubic millimeter
4 - remain functional for about 7 - 10 days (after which they are removed from the
blood by macrophages in the spleen & liver)
5- play an important role in hemostasis (preventing blood loss)
Plasma:
1 - Water - serves as transport medium; carries heat
2 - Proteins



Albumins
o 60-80% of plasma proteins
o most important in maintenance of osmotic balance
o produced by liver
Globulins
o alpha & beta
 some are important for transport of materials through the blood
(e.g., thyroid hormone & iron)
 some are clotting factors
 produced by liver
o gamma globulins are immunoglobulins (antibodies) produced by
lymphocytes
Fibrinogen
o important in clotting
o produced by liver
Twenty-two proteins constitute 99% of the protein content of plasma (Tirumalai et al. 2003).
3 - Inorganic constituents (1% of plasma) - e.g., sodium, chloride, potassium, & calcium
4 - Nutrients - glucose, amino acids, lipids & vitamins
5 - Waste products - e.g., nitrogenous wastes like urea
6 - Dissolved gases - oxygen & carbon dioxide
7 - Hormones
Hemostasis - prevention of blood loss from broken vessel (check this Hemostasis
animation):
1 - Vascular spasm - vasoconstriction of injured vessel due to contraction of smooth
muscle in the wall of the vessel. This 'spasm' may reduce blood flow & blood loss but
will not stop blood loss.
2 - Formation of a platelet plug - platelets aggregate at the point where a vessel ruptures.
This occurs because platelets are exposed to collagen (a protein found in the connective
tissure located just outside the blood vessel). Upon exposure to collagen, platelets release
ADP (adenosine diphosphate) & thromboxane. These substances cause the surfaces of
nearby platelets to become sticky and, as 'sticky' platelets accumulate, a 'plug' forms.
3 - Blood coagulation (clotting):
Used with permission of Michael W. King, Ph.D / IU School of Medicine
The result of all of this is a clot - formed primarily of fibrin threads (or polymers), but
also including blood cells & platelets.
Blood clots in the right places prevent the loss of blood from ruptured vessels, but in the
wrong place can cause problems such as a stroke (see below under inappropriate
clotting).
Clot retraction:


"tightening" of clot
contraction of platelets trapped within clot shrinks fibrin meshwork, pulling edges
of damaged vessel closer together
Over time (with the amount of time depending on the amount of damage), the clot is
dissolved and replaced with normal tissue.
Fibrinolysis:

dissolution of clot

mechanism = plasminogen (a plasma protein) is activated by many factors &
becomes PLASMIN. Plasmin then breaks down fibrin meshwork & phagocytic
WBCs remove products of clot dissolution
Inappropriate clotting:

thrombus - clot formed in an intact vessel, possibly due to:
o roughened vessel walls (atherosclerosis; see normal & occluded coronary
arteries below)
o slow-moving blood (e.g., in varicose veins) = small quantities of fibrin
form & accumulate
o check this animation about deep vein thrombosis

embolus - 'moving' clot
Source: http://www.ors.od.nih.gov/medart/portfolio/Donny/embolus.html
Thrombus and embolus
Excessive bleeding:


Hemophilia
o genetic 'defect'
o inability to produce certain factor(s)
Thrombocytopenia
o abnormally low platelet count
o most persons have idiopathic thrombocytopenia
(= unknown cause) while in others it's an
autoimmune disease
Understanding Anemia - the Basics
What Is Anemia?
Anemia is a condition that develops when your blood
lacks enough healthy red blood cells. These cells are the main
transporters of oxygen to organs. If red blood cells are also
deficient in hemoglobin, then your body isn't getting enough
iron. Symptoms of anemia -- like fatigue -- occur because
organs aren't getting enough oxygen.
Anemia is the most common blood condition in the U.S. It affects about 3.5 million
Americans. Women and people with chronic diseases are at increased risk of anemia.
Important factors to remember are:
DOCTOR recommended reading
Anemia Symptoms
What Are the Symptoms of Anemia?
The symptoms of anemia will vary according to the type of anemia, the underlying cause
and your underlying health problems. Anemia may be associated with other medical
conditions such as hemorrhage, ulcers, menstrual problems or cancer -- and specific
symptoms of those conditions may be noticed first.
Symptoms common to many types of anemia are:
The body also has a remarkable ability to compensate for early anemia. If your anemia is
mild or developed over a long period of time, you may not notice any symptoms.




Easy fatigue and loss of energy.
Unusually rapid heart beat, particularly with exercise.
Shortness of breath and headache, particularly with exercise.
Difficulty concentrating.
Read more about Anemia Symptoms
Related Anemia Terms
sickle cell, pernicious, aplastic, iron deficiency, causes, hemolytic, anemia and
pregnancy, treatment, types, Fanconi, Macrocytic



Certain forms of anemia are hereditary and infants may be affected from the time
of birth.
Women in the childbearing years are particularly susceptible to a form of anemia
called iron-deficiency anemia because of the blood loss from menstruation and
the increased blood supply demands during pregnancy.
Seniors also may have a greater risk of developing anemia because of poor diet
and other medical conditions.
There are many types of anemia. All are very different in their causes and treatments.
Iron-deficiency anemia, the most common type, is very treatable with diet changes and
iron supplements. Some forms of anemia -- like the anemia that develops during
pregnancy -- are even considered normal. However, some types of anemia may present
lifelong health problems
What Causes Anemia?
There are more than 400 types of anemia, which are divided into 3 groupings:



Anemia caused by blood loss
Anemia caused by decreased or faulty red blood cell production
Anemia caused by destruction of red blood cells
Anemia Caused by Blood Loss
Red blood cells can be lost through bleeding, which can occur slowly over a long period
of time, and can often go undetected. This kind of chronic bleeding commonly results
from the following:



Gastrointestinal conditions such as ulcers, hemorrhoids, gastritis (inflammation of
the stomach) and cancer
Use of nonsteroidal anti-inflammatory drugs (NSAIDS) such as aspirin or Motrin
Menstruation and childbirth in women, especially if menstrual bleeding is
excessive and if there are multiple pregnancies
Anemia Caused by Decreased or Faulty Red Blood Cell Production
The body may produce too few blood cells or the blood cells may not work properly. In
either case, anemia can result. Red blood cells may be faulty or decreased due to
abnormal red blood cells or the a lack of minerals and vitamins needed for red blood cells
to work properly. Conditions associated with these causes of anemia include the
following:





Sickle cell anemia
Iron deficiency anemia
Vitamin deficiency
Bone marrow and stem cell problems
Other health conditions
Understanding Anemia - the Basics
What Causes Anemia?
Sickle cell anemia is an inherited disorder that affects African-Americans. Red blood
cells become crescent-shaped because of a genetic defect. They break down rapidly, so
oxygen does not get to the body's organs, causing anemia. The crescent-shaped red blood
cells also get stuck in tiny blood vessels, causing pain.
Iron deficiency anemia occurs because of a lack of the mineral iron in the body. Bone
marrow in the center of the bone needs iron to make hemoglobin, the part of the red
blood cell that transports oxygen to the body's organs. Without adequate iron, the body
cannot produce enough hemoglobin for red blood cells. The result is iron deficiency
anemia. Iron deficiency anemia can be caused by the following:







An iron-poor diet, especially in infants, children, teens and vegetarians
The metabolic demands of pregnancy and breastfeeding that deplete a woman's
iron stores
Menstruation
Frequent blood donation
Endurance training
Digestive conditions such as Crohn's disease or surgical removal of part of the
stomach or small intestine
Certain drugs, foods, and caffeinated drinks
Vitamin deficiency anemia may occur when vitamin B-12 and folate are deficient.
These two vitamins are needed to make red blood cells. Conditions leading to anemia
caused by vitamin deficiency include the following:




Megaloblastic anemia: Vitamin B-12 or folate or both are deficient
Pernicious anemia: Poor vitamin B-12 absorption caused by conditions such as
Crohn's disease, an intestinal parasite infection, surgical removal of part of the
stomach or intestine, or infection with HIV
Dietary deficiency: Eating little or no meat may cause a lack vitamin B12, while
overcooking or eating too few vegetables may cause a folate dificiency
Other causes of vitamin deficiency: pregnancy, certain medications, alcohol
abuse, intestinal diseases such as tropical sprue and gluten-sensitive enteropathy
(celiac disease)
During early pregnancy, sufficient folic acid can prevent the fetus from developing neural
tube defects such as spina bifida.
Bone marrow and stem cell problems may prevent the body from producing enough
red blood cells. Some of the stem cells found in bone marrow develop into red blood
cells. If stem cells are too few, defective, or replaced by other cells such as metastatic
cancer cells, anemia may result. Anemia resulting from bone marrow or stem cell
problems include the following:



Aplastic anemia occurs when there's a marked reduction in the number of stem
cells or absence of these cells. Aplastic anemia can be inherited, can occur
without apparent cause, or can occur when the bone marrow is injured by
medications, radiation, chemotherapy, or infection.
Thalassemia occurs when the red cells can't mature and grow properly.
Thalassemia is an inherited condition that typically affects people of
Mediterranean, African, Middle Eastern, and Southeast Asian descent. This
condition can range in severity from mild to life-threatening; the most severe form
is called Cooley's anemia.
Lead exposure is toxic to the bone marrow, leading to fewer red blood cells.
Lead poisoning occurs in adults from work-related exposure and in children who
eat paint chips. Improperly glazed pottery can also taint food and liquids with
lead.
Anemia associated with other conditions usually occur when there are too few
hormones necessary for red blood cell production. Conditions causing this type of anemia
include the following:



Advanced kidney disease
Hypothroidism
Other chronic diseases – examples include cancer, infection, and autoimmune
disorders such as lupus or rheumatoid arthritis
Anemia Caused by Destruction of Red Blood Cells
When red blood cells are fragile and cannot withstand the routine stress of the circulatory
system, they may rupture prematurely, causing hemolytic anemia. Hemolytic anemia can
be present at birth or develop later. Sometimes there is no known cause (spontaneous).
Known causes of hemolytic anemia may include any of the following:






Inherited conditions, such as sickle cell anemia and thalassemia
Stressors such as infections, drugs, snake or spider venom, or certain foods
Toxins from advanced liver or kidney disease
Inappropriate attack by the immune system (called hemolytic disease of the
newborn when it occurs in the fetus of a pregnant woman)
Vascular grafts, prosthetic heart valves, tumors, severe burns, chemical exposure,
severe hypertension, and clotting disorders
In rare cases, an enlarged spleen can trap red blood cells and destroy them before
their circulating time is up