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CONCEPTUAL LIFE SCIENCE
Circulation and Transport
TRANSPORT IN SELECTED ORGANISMS
Cytoplasmic streaming (cyclosis)
Cytoplasmic streaming is a circulation of the cytoplasm inside a cell. It is
noticeable under the microscope in plant cells. The cells of the leaf circulate their
cytoplasm pushing the chloroplasts along. It is possible to see them move.
Transport in vascular plants
Xylem transports water and minerals upward from the roots. Phloem carries
nutrients to all living cells in the plant. Phloem can transport materials both upward and
downward.
Circulation in the earthworm (closed system)
The earthworm has five pairs of specialized blood vessels on each side of the
digestive system near the mouth. The earthworm has a closed circulatory system because
the blood is always contained within blood vessels. As the 10 pumping blood vessels
contract, they push blood back toward the rear of the animal. The blood at the rear
moves forward and is circulated by the pumping vessels.
Circulation in the grasshopper (open system)
In the grasshopper, blood is pumped forward through a main blood vessel known
as the aorta. After it is pumped forward it passes through the end of the blood vessel and
into a large space inside the body cavity known as a blood sinus. The blood flows freely
through the blood sinus to the rear of the animal at which point it is taken back into the
blood vessel and pumped forward again. This type of circulatory system is called an
open circulatory system because sometimes the blood is not found within blood vessels.
Most molluscs and all arthropods have an open circulatory system.
CIRCULATION IN THE HUMAN
The heart
The heart is a specialized pumping organ. Heart muscle can contract on its own.
Specialized pacemaker cells regulate the contractions of the heart muscles. The
pacemaker cells produce electrical signals that cause the heart muscles to contract.
Systole is the contraction of the heart. Diastole is the relaxation period between heart
contractions.
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Blood enters the heart through atria. The atria contract and pump the blood into
the ventricles. Then the ventricles contract and pump the blood out of the heart. The
closing of the heart valves after the contractions produces the heart sounds.
Arteriosclerosis and atherosclerosis
Arteriosclerosis is a disease of old age. It is characterized by a loss of elasticity
of the arteries. In older times it was known as “hardening of the arteries.”
Atherosclerosis can occur at any age. It is produced as a result of the closing of
the lumens of the arteries by buildup of cholesterol deposits and calcification.
Arteries
Blood is carried away from the heart by arteries. The pulmonary arteries carry
blood from the right ventricle of the heart to the lungs. The aorta leaves the left ventricle
and carries blood to the rest of the body. The aorta is the largest artery in the body.
Other arteries going to the body branch from it.
 Blood to and from the lungs is called the PULMONARY CIRCULATION.
 Blood to and from the body is called the SYSTEMIC CIRCULATION.
 Blood to and from heart muscle tissue is the CORONARY CIRCULATION.
Table XI-1. Major arteries.
Artery
Left and Right Carotid
Left and Right Subclavian
Left and Right Renal
Left and Right Iliac
Mesenteric
Hepatic
Coronary
Target Organ
Brain
Arms
Kidneys
Legs
Intestines
Liver
Heart
Veins
Veins carry blood back to the heart. Veins contain valves to prevent the blood
from flowing backward in them. The pulmonary veins leave the lungs and go tot he left
atrium. All other veins enter the right atrium through the superior and inferior venae
cavae. There is one exception. The hepatic portal vein carries blood from the intestines
to the liver. This enables the liver to remove all of the nutrients from digestion before the
blood is sent to other parts of the body. The blood leaves the liver and returns to the heart
via the hepatic vein and the inferior vena cava.
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Table XI-2. Major veins.
Vein
To superior vena cava
Jugular
Subclavian
To inferior vena cava
Iliac
Renal
Hepatic
Other: Hepatic portal vein
Origin
From brain
From arms
From legs
From kidneys
From liver
From intestines to the liver
Blood
Blood is a solution of plasma and cells. Plasma is 92% liquid and 8% solids.
Plasma contains water, ions, proteins, nitrogenous wastes (such as creatinine, urea and
uric acid), glucose, amino acids, cholesterol, gases and hormones. Blood is slightly
alkaline with a pH of 7.4.
Pathway of the blood
Blood leaves the heart and travels to one or more arteries that branch into smaller
arteries and finally into capillaries. Blood from the capillaries is collected in venules that
transfer it to veins that return it to the heart.
Blood pressure
Blood pressure is the pressure required to close off an artery. It depends on
whether or not the heart is contracting. Systolic pressure is the pressure required to close
off an artery during systole, the contraction of the heart. Diastolic pressure is the
pressure required to close off an artery during diastole, the relaxation period between
heart contractions.
BLOOD CELLS
Red blood cells
Red blood cells contain hemoglobin. Hemoglobin carries O2 for the circulatory
system. The red blood cells, which are called erythrocytes, have many types of antigens
on their surfaces. The ABO system is the most widely known, followed by the Rh
system. These cells have no nuclei. They last about 90 days.
Sickle-cell anemia is a hereditary (genetic) condition in which there is a slight
alteration in the amino acid sequence of the hemoglobin protein. This alteration causes
the erythrocytes to sickle, or become flattened, when they are not carrying oxygen.
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White blood cells
There are five types of white blood cells, which are also called leukocytes. The
prefix “leuko-“ means lacking color or without color. Thus, these are the colorless blood
cells. They are really not white in color. There are two major groups called the granular
(polymorphonuclear) leukocytes and the agranular (mononuclear) leukocytes.
The granular leukocytes have tiny spots or granules visible when they are stained.
They are called polymorphonuclear (“poly” means many, “morpho” refers to shape or
form) because the nuclei of these cells take on many shapes. The most numerous cells of
this type are the neutrophils. These cells are phagocytic and move around in the body
looking for foreign material to phagocytize.
The agranular leukocytes do not have visible granules in their cytoplasm when
they are stained. They are also called mononuclear because these cells each have a large,
prominent nucleus. The lymphocytes are the cells that produce the antibody molecules
for the immune system. The monocyte is a type of leukocyte that is motile and
phagocytic.
Table XI-1. White blood cells.
Granular (Polymorphonuclear) Leukocytes
Neutrophils (60-70%)
Eosinophils (1-3%)
Basophils
(0.3%)
Agranular (Mononuclear) Leukocytes
Lymphocytes (20-35%)
Monocytes (3%)
How blood clots
Formation of blood clots is important to keep blood from leaking out of the body
due to wounds or breaks in the capillaries. When blood clots form, it is the result of a
series of five steps. These steps involve platelets, which are formed elements in the
blood. Platelets are not really blood cells per se, but they are not blood proteins either.
The other materials involved are fibrinogen, a protein that leads to formation of fibrin, the
clotting protein; and a series of blood proteins called factors. Hemophilia is a disease
characterized by a lack of Factor VIII. In people with hemophilia, the absence of Factor
VIII prevents their blood from clotting normally.
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The immune system
The blood cells in the immune system are primarily the monocytes and the
lymphocytes. Both types are white blood cells of the agranular category. The monocytes
can behave like amoebas and move out of the bloodstream into the connective tissue
space. When they are in the connective tissue space, their name changes to
macrophages. The macrophages engulf and devour foreign matter such as bacteria.
Then they process the molecules of the bacteria.
There are two types of lymphocytes involved in the immune response. The Tlymphocytes (T-cells) recognize the molecules that the macrophages are carrying and
make antibodies against them. The second type of lymphocyte is the B-lymphocyte (Bcell), which assists the T-cells by making high concentrations of antibodies against the
foreign molecules. These antibodies are blood proteins that bind and react with the
foreign molecules (such as bacterial surface proteins) and combat disease by the bacteria.
Human Immunodeficiency Virus (HIV) is a virus that attacks the T-cells. Viruses
are different from bacteria in that they cannot reproduce independently. They must
invade a host cell. In the case of HIV, the host cell is the T-cell. Antibiotics that kill
bacteria do not work against viruses. Acquired Immunodeficiency Syndrome (AIDS) is a
series of infections and other medical problems that result in people with the HIV virus
because their immune system does not function properly due to the activity of the HIV
virus.
The lymphatic system
The lymphatic system is a series of ducts in the body. These ducts serve as
collection conduits for tissue fluid, which is otherwise known as lymph. Tissue fluid is a
liquid found in all the body spaces between cells and surrounding body structures and
organs. These locations are generally known as the connective tissue space. The lymph
ducts contain lymph nodes where macrophages, T-cells and B-cells are ready to respond
to any bacteria or viruses they encounter. The tissue fluid is eventually returned to the
bloodstream.