Blood and Blood Vessels Module 3
Blood and Blood Vessels Module 3
Blood and Blood Vessels Module 3
Blood is the river of life that surges inside us, bringing almost all that must be
transported from one place to another. Long before modern medicine, blood was magical — an
elixir that retained the mysterious power of life — because life often departed when it was
drained from the body. Blood is also incredibly important in medical practice today. When
attempting to assess the cause of the disease in their patients, physicians examine it more
frequently than any other tissue.
Blood passes through blood vessels in the heart, which branch repeatedly until they
become tiny capillaries. Oxygen and nutrients exit the blood and enter the body tissues by
diffusing through the capillary walls, and carbon dioxide and waste move from the tissues into
the bloodstream. As the oxygen-deficient blood leaves the capillary beds, it flows into veins
which carry it back to the heart. Then the returning blood flows from the heart to the lungs,
where it takes up oxygen and then returns to the heart to be pumped back into the body.
Learning Outcomes
✓ Identify the primary functions of blood, its fluid and cellular components, and its physical
characteristics.
✓ Identify the most important proteins and other solutes present in blood plasma.
✓ Describe the formation of the formed element components of blood.
✓ Discuss the structure and function of red blood cells and hemoglobin.
✓ Classify and characterize white blood cells.
✓ Describe the structure of platelets and explain the process of hemostasis.
✓ Differentiate the structure and function of arteries, veins, and capillaries.
✓ Determine the body’s major arteries and veins and name the body region supplied by
each.
Topic 1: Blood
Learning Objectives
Erythrocytes normally account for about 45 percent of the total volume of a blood sample, a
percentage known as the hematocrit. White blood cells and platelets contribute less than 1
percent, and plasma makes up most of the remaining 55 percent of whole blood.
Blood is a sticky, dark substance that is heavier than water and about five times thicker,
or more viscous, owing in large part to the formed elements. The color of the blood ranges from
scarlet (oxygen rich) to a dark red or purple (oxygen-poor), depending on the amount of oxygen
it holds. It has a distinctive metallic, salty taste (something we sometimes discover as kids).
Blood is mildly alkaline, with a pH of 7.35 to 7.45. Its temperature (38 ° C, or 100.4 ° F) is often
slightly higher than that of the body due to the pressure that happens when blood passes through
the vessels. Blood accounts for about 8 percent of body weight and has a volume of 5 to 6 liters
or about 6 quarts in healthy adults.
Plasma, which is around 90 per cent water, is the blood's liquid component. Plasma
proteins are the plasma solutes with the highest number. Except for antibodies and protein-based
hormones, most plasma proteins are produced from the liver. The plasma proteins perform
several roles. For example, albumin acts as a carrier to shuttle those molecules through the
bloodstream, is an essential blood buffer and contributes to the blood's osmotic pressure, which
helps to maintain water in the blood stream. Clotting
proteins help reduce blood loss when a blood vessel is
broken and help defend the body against pathogens. Cells
for use as food sources or metabolic nutrients do not take
up plasma proteins, as do other solutes such as glucose,
fatty acids, and oxygen. Plasma composition is
continually variable as cells exchange substances with
blood.
Erythrocytes are small, flexible cells in the form of biconcave disks — flattened discs on
both sides with depressed centers. Because of their thinner cores, when viewed with a
microscope, erythrocytes appear like miniature doughnuts. Their small size and peculiar shape
provide a large surface area relative to volume, making them ideal for gas exchange.
RBCs outnumber white blood cells by about 1,000 to 1 and are the main contributing
factor to the viscosity of the blood. Although there are varying numbers of RBCs in circulation,
there are typically around 5 million cells per cubic millimeter of blood. (A cubic millimeter
[mm3] is a small decrease of blood, almost too small to be seen.) As the amount of RBC / mm3
increases, there is a rise in blood viscosity or thickness. Similarly, when the number of RBCs is
decreasing, blood thins and flows faster.
Although the amounts of RBCs are important, it is the amount of hemoglobin in the
bloodstream that really dictates how well the erythrocytes perform their task of transporting
oxygen at any time. The more RBCs contain hemoglobin molecules, the more oxygen they will
be able to carry. A single red blood cell contains about 250 million hemoglobin molecules, each
able to bind 4 oxygen molecules, each of these tiny cells can hold about 1 billion oxygen
molecules. However, the fact that normal blood contains 12–18 grams of hemoglobin per 100
milliliters of blood, is far more clinically significant. The amount of hemoglobin is higher for
men (13–18 g / ml) than in women (12–16 g/ml).
Leukocytes, or white blood cells, are much less numerous than red blood cells, they are
vital to body defense. On average, blood is 4,800 to 10,800 WBCs / mm3, and it accounts for
less than 1 percent of the overall blood volume. White blood cells comprise nuclei and the
ordinary organelles, making them the only complete cells in blood.
Leukocytes form a protective, mobile army that helps protect the body from damage
caused by bacteria, viruses, parasites, and tumor cells. Red blood cells are confined to blood
stream. White blood cells, by contrast, can slip into and out of the blood vessels—a process
called diapedesis.
WBCs can detect tissue damage and infection areas in the body by reacting to certain
chemicals that disperse from the cells that are injured. That capability is known as positive
chemotaxis. If they have "caught the scent," the WBCs travel through amoeboid motion through
the tissue spaces (they form flowing cytoplasmic extensions, which help move them along).
They pinpoint areas of tissue damage by following the diffusion gradient and gather around in
large numbers to kill microorganisms and dispose of dead cells. Any time WBCs mobilize for
action, the body speeds up its production, and within a few hours as many as twice the normal
number of WBCs will appear in the blood. A total number of WBCs greater than 11,000 cells /
mm3 is referred to as leukocytosis.
Platelets are not cells, instead a fragment of bizarre multinucleate cells called
megakaryocytes, which pinch thousands of "pieces" of anucleate platelets that easily seal off the
surrounding fluids. The platelets appear as darkly stained, irregularly formed bodies spread
among the other cells of blood. The usual count of platelets in the blood is about 300,000 cells
per mm3. Platelets are needed for the clotting process that stops blood loss from broken blood
vessels.
What are the two major groups of White Blood Cell? Identify and describe each type.
Read the Chapter 5 & 12 of Cardiopulmonary Anatomy & Physiology Essentials by
Respiratory Care 7th edition by Terry des Jardins and answer the questions below.
Explain the formation of red blood cell and white blood cell.
Read the Chapter 5 & 12 of Cardiopulmonary Anatomy & Physiology Essentials by
Respiratory Care 7th edition by Terry des Jardins and answer the questions below.
Identify the different factors that may inhibit or enhance the blood-clotting process.
Topic 2: Blood Vessels
Learning Objectives
✓ Explain the unique features of the arterial circulation of the brain, and hepatic portal
circulation.
✓ Discuss the unique features of the arterial circulation of the brain, and hepatic portal
circulation.
Presentation of Content
Blood circulates within the blood vessels which form a closed system of transport called
the vascular system. The theory that blood circulates through the body, or "forms rounds," is just
about 300 years old. Ancient Greeks believed that blood was flowing through the body like an
oceanic tide, first going out of the heart and then returning to it in the same vessels to get rid of
its impurities in the lungs. It was not until the seventeenth century that the English physician
William Harvey proved that blood flowed in circles. The vascular system, like a road system, has
its freeways, side roads, and alleys. When the heart beats it propels blood out of the heart into the
large arteries. Blood passes as the large arteries branch through successively smaller and smaller
arteries, and then into the arterioles, which feed the tissue capillary beds. Venules drain the
capillary beds, which in turn discharge into veins that converge and eventually discharge into the
great veins that enter the heart.
The arteries that carry blood away from the heart, and the veins that drain the tissues and
send the blood back to the heart, are conducting vessels — the freeways and sideways. Only the
tiny hair-like capillaries that stretch and branch through the tissues and link the tiniest arteries
(arterioles) to the tiniest veins (venules) serve the body cells' needs directly. The capillaries are
the side streets or alleys that intertwine closely between the body cells and provide access to
individual "homes." Interactions between tissue cells and the blood can only take place through
their walls. Notice that we frequently represent red arteries, and blue veins.
Identify and describe the different layers of the blood vessel walls.
Blood emergencies for even a few minutes cause the delicate brain cells to die, and a
regular flow of blood to the brain is vital. Two pairs of arteries in the brain, the internal carotid
arteries, and the vertebral arteries. The internal carotid arteries, branches of the general carotid
arteries, pass through the neck and pass through the temporal bone into the skull. Once inside the
cranium, each divide into the anterior cerebral artery and middle cerebral artery which supplies
most of the cerebrum. At the base of the neck the paired vertebral arteries pass upward from the
subclavian arteries. The vertebral arteries come together within the skull to form the single
basilar artery.
The hepatic portal circulation veins drain the digestive organs, spleen, and pancreas and
carry the blood through the hepatic portal vein to the liver. The hepatic portal blood, when you
have just eaten, contains vast quantities of nutrients. The liver is a vital body organ involved in
preserving optimal blood concentrations of glucose, fat, and protein, this mechanism requires
blood to 'take a detour' to ensure that the liver absorbs these substances before they enter the
systemic circulation. The liver also helps to detoxify blood by removing and processing toxins
absorbed by the intestines and stomach. As blood slowly flows through the liver, some of the
nutrients are removed to be stored or processed for later release into the blood in various ways.
The liver is drained by the hepatic veins which enter the inferior vena cava.
Blood consists of a matrix of non-living fluids (plasma) and formed elements. Depending
on the amount of oxygen delivered, it is scarlet or dull red. The average volume of adult blood is
5 to 6 liters. Nutrients, gases, hormones, contaminants, proteins, salts, and so on, are dissolved in
plasma (primarily water). As body cells remove or add substances to it, the plasma composition
changes but homeostatic mechanisms work to keep it relatively stable. Plasma accounts for 55
percent of whole blood.
The conducting vessels are arteries that transport blood away from the heart, and by veins
that carry blood back into the heart. In actual exchanges with tissue cells, only the capillaries
play a part. Blood vessels are made of three tunics except for capillaries: The tunica intima
creates a pressure that decreases the vessel's lining. The thick middle layer of muscle and elastic
tissue is the tunica media. The tunica externa is the protective, outermost layer of connective
tissue. Only the intima tunica is formed of capillary walls.
All major systemic circulation arteries are branches of the aorta, leaving the left ventricle
behind. They branch into smaller arteries, and then into the arterioles, which feed the body tissue
capillary beds. The systemic circulation 's major veins eventually converge upon one of the vena
cava. All veins that are superior to the diaphragm drain into the upper vena cava, and those
below the diaphragm drain into the lower vena cava. Both vena cava get into the right heart
atrium.
Feedback
Read the following and encircle your answer.
1. The most abundant plasma protein in the blood is:
a. albumin
b. globulin
c. amino acid
d. clotting factors
7.When cardiac ejection ceases during diastole, what is the most important factor
maintaining blood flow in arteries of the body?
a. Contraction of skeletal muscle
b. Closing the venous valves
c. Elastic recoil of the arteries close to heart
d. Contraction of the atria
10. Which capillaries allow cells and plasma proteins to enter or leave their lumen?
a. Continuous
b. Fenestrated
c. Sinusoidal
d. Anastomatic
Reflection:
1. What is the most important thing you have learned from this topic?
3. Is this topic easier to understand as compared with the first two topics? Defend your
answer.
4. What additional resources do you have that can help you to further understand the
topic?
References