Circulatory, Respiratory, and Excretory Systems

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Circulatory, Respiratory, and
Excretory Systems
section ●
Circulatory System
Before You Read
-!). )DEA
Press the tips of two fingers to the inside of your wrist, at a
point just below your thumb. Can you feel the regular pulsing
of your blood? Count the number of beats you feel in fifteen
seconds. Record that number on the line below. Multiply
the number by four. Then read the section to learn what the
number means and how your heart creates its regular rhythm.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Read to Learn
Blood delivers substances, such
as oxygen, to cells and removes
wastes, such as carbon dioxide,
from cells.
What You’ll Learn
the main functions of the
circulatory system
■ how blood flows through the
heart and body
■ the major components of blood
Make Flash Cards Make
Functions of the Circulatory System
The circulatory system is the body’s transport system. It
delivers oxygen and nutrients to the cells and removes waste
products. The parts of the circulatory system are blood, the
heart, blood vessels, and the lymphatic system. These parts
work together to maintain homeostasis in the body. The heart
pumps blood through tubes inside your body called blood
vessels. In Chapter 37, you will learn about the lymphatic
system, which also is part of the immune system.
In addition to oxygen and nutrients, the circulatory system
transports disease-fighting materials produced by the immune
system. The blood contains cell fragments and proteins for
blood clotting. It also distributes heat throughout the body
to help to control body temperature.
a flash card for each key term
in this section, with the term
on one side and the definition
on the other side. Use the flash
cards to study.
1. Name the three major
types of blood vessels.
Blood Vessels
Blood vessels circulate blood throughout the body. They help
to keep blood flowing to and from the heart. The three major
types of blood vessels are arteries, capillaries, and veins.
Reading Essentials
Chapter 34 Circulatory, Respiratory, and Excretory Systems
Why do arteries have a thick inner layer?
Take Notes Make a folded
table Foldable, as shown below.
As you read, take notes and
organize what you learn about
the circulatory, respiratory, and
excretory systems in this chapter.
Chapter 34
Arteries (AR tuh reez) are large blood vessels that carry
oxygen-rich, or oxygenated, blood away from the heart.
Arteries are made of three layers: an outer layer of connective
tissue, a middle layer of smooth muscle, and an inner layer of
endothelial tissue. The endothelial layer of an artery is thicker
than that of other blood vessels because blood is under higher
pressure when it is pumped from the heart.
What is the function of capillaries?
Capillaries (KAP uh ler eez) are microscopic blood vessels
where the exchange of important substances and wastes
occurs. These vessels are so small that red blood cells move
single-file through them. Capillary walls are only one cell
thick. As a result, the blood and body cells can easily exchange
materials through the capillary walls.
After blood moves through the capillaries, it enters the
veins—the largest blood vessels. Veins (VAYNZ) carry
oxygen-poor, or deoxygenated, blood back to the heart. The
endothelial walls of veins are thinner than those of arteries
because by the time blood reaches the veins, the heart’s original
pushing force has lessened. The contractions of skeletal muscles
keep the blood moving. Larger veins have flaps of tissue called
valves that prevent blood from flowing backward. Breathing
movements squeeze against veins in the chest, forcing blood
back to the heart.
The Heart
The heart is a hollow, muscular organ that pumps blood
throughout the body. It is located in the center of the chest.
The heart performs two pumping functions at the same
time—it pumps oxygenated blood throughout the body,
and it pumps deoxygenated blood to the lungs.
What are the parts of the heart?
2. Identify the heart
chambers that push the
blood through the body.
(Circle your answer.)
a. atria
b. ventricles
The heart is made of cardiac muscle. This unique muscle
can create and conduct electrical impulses for muscular
contractions. The heart is divided into four chambers, as
shown in the figure on the next page. The two chambers in
the top half of the heart are the right atrium (plural, atria)
and left atrium. The atria receive returning blood. The right
and left ventricles, below the atria, pump blood away from
the heart. Valves keep blood flowing in one direction.
Chapter 34 Circulatory, Respiratory, and Excretory Systems
Reading Essentials
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Where do veins carry blood?
How does the heart beat?
First, the atria fill with blood. Next, the atria contract,
filling the ventricles with blood. Once the ventricles are full,
they contract to pump the blood out of the heart and into the
lungs and body.
The heart works in a regular rhythm. A group of cells in the
right atrium, called the pacemaker or sinoatrial (SA) node,
send out signals that tell the heart muscle to contract. The
SA node receives signals about the body’s need for oxygen. It
then responds by adjusting the heart rate. The signal from the
SA node causes both atria to contract. This signal then travels
to the atrioventricular (AV) node, causing both ventricles to
contract. This two-step contraction is one complete heartbeat.
running hard as you play
soccer. How do you think
the SA node will respond to
this situation?
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
3. Apply Suppose you are
Picture This
4. Determine When blood
is returning from the body
to the heart, which chamber
of the heart does the blood
enter first?
What causes a pulse?
During the Before You Read activity, the beat you felt in your
wrist was your pulse. As your left ventricle contracts, it pushes
blood through your arteries, causing the arteries to expand.
Between contractions, the arteries relax. The pulse is the
alternating expansion and relaxation of the artery wall. The
number of times your artery pulses is the number of times
your heart beats. The heart beats approximately 70 times
per minute.
Reading Essentials
Chapter 34 Circulatory, Respiratory, and Excretory Systems
5. Calculate Suppose Cory’s
blood pressure is 125 at its
highest point. To return his
blood pressure to normal,
Cory must reduce it by
what percentage? (Show
your work.)
What does a blood pressure reading mean?
Blood pressure is a measure of how much pressure the blood is
applying against the vessel walls. Blood pressure readings provide
information about the health of arteries. The contraction of the
heart, or systole (SIS tuh lee), causes blood pressure to rise to its
highest point. Relaxation of the heart, or diastole (di AS tuh lee),
causes blood pressure to drop to its lowest point. A normal
blood pressure reading for a healthy adult is about 120 (systolic
pressure)/80 (diastolic pressure).
How does blood flow through the body?
In the figure below, notice that blood flows in a figure
eight pattern. In the first loop, blood travels from the heart
to the lungs and back to the heart. In the second loop, blood
is pumped from the heart through the body and back to the
heart. The right side of the heart pumps oxygen-poor, or
deoxygenated, blood to the lungs. The left side of the heart
pumps oxygen-rich, or oxygenated, blood through the body.
Picture This
6. Highlight the blood’s
To the lungs and back When blood from the body flows
into the right atrium, it contains a little oxygen and a lot
of carbon dioxide. From the right atrium, the oxygen-poor
blood flows into the right ventricle and into the lungs. The
air in the lungs has a lot of oxygen. Oxygen diffuses through
the capillaries of the lungs into the blood. At the same time,
carbon dioxide diffuses from the blood into the capillaries of
the lungs and then into the air. Oxygen-rich blood then flows
to the left atrium of the heart to be pumped through the body.
Chapter 34 Circulatory, Respiratory, and Excretory Systems
Reading Essentials
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
path from the heart to the
body and back.
To the body and back The second loop of the figure eight
begins as the left atrium fills with oxygen-rich blood from
the lungs. The blood moves from the left atrium to the left
ventricle. The left ventricle pumps the blood into the largest
artery in the body called the aorta. From there, the blood
flows into the capillaries throughout the body. The capillaries
are in close contact with body cells. Oxygen is released from
the blood into the body cells. Carbon dioxide moves from the
cells into the blood. The oxygen-poor blood then flows back
to the right atrium through the veins.
Blood Components
7. Draw Conclusions
Blood contains living cells. It is made up of plasma, red
and white blood cells, and cell fragments called platelets.
What is the role of plasma?
Plasma is the clear, yellowish fluid part of blood. Plasma
is mostly water. It carries the products of digested food, such
as glucose and fats. It also transports vitamins, minerals, and
chemical signals. Waste products are carried away by plasma.
Which best describes the
role of carbon dioxide in the
body? (Circle your answer.)
a. nutrient
b. waste product
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What do red blood cells transport?
Red blood cells carry oxygen to all body cells. They develop
in the bone marrow. Red blood cells do not have a nucleus,
and are made mostly of a protein called hemoglobin.
Hemoglobin binds with oxygen and carries it to the body’s
cells. Some carbon dioxide is carried by the hemoglobin, but
most carbon dioxide is carried by plasma.
How do white blood cells fight disease?
White blood cells are the body’s disease fighters. Some
recognize disease-causing organisms and alert the body. Other
white blood cells produce chemicals to fight the invaders. Still
others surround and kill the invaders. There are many more
red than white blood cells.
8. Explain the importance
of hemoglobin.
Why does the body need platelets?
Platelets (PLAYT luts) are cell fragments that play an
important part in forming blood clots. When a blood vessel
is cut, platelets collect and stick to the vessel at the site of the
wound. Platelets release chemicals that produce a protein
called fibrin, also known as a clotting factor. Fibrin weaves
fibers across the cut that trap platelets and red blood cells.
As more platelets and blood cells get trapped, a blood clot
or scab forms, slowing and then stopping the flow of blood.
Reading Essentials
Chapter 34 Circulatory, Respiratory, and Excretory Systems
Blood Types
There are four types of blood. They are A, B, AB, and O.
What determines blood type?
Marker molecules attached to red blood cells determine
blood type. Type A blood has A markers. Type B blood has
B markers. Type AB has both A and B markers. Type O has
neither A nor B markers.
Why is blood type important?
If you need a blood transfusion, you can only receive certain
blood types, as shown in the table below. This is because plasma
contains antibodies that recognize “foreign” markers and cause
those red blood cells to clump together. For example, if your
blood is type B, the antibodies in your plasma will cause red
blood cells with A markers to clump, blocking blood flow.
9. Identify the blood type
that can be transfused into
Marker Molecules
Can Donate
Blood To:
Can Receive
Blood From:
marker molecule: A
antibody: anti-B
A or AB
A or O
marker molecule: B
antibody: anti-A
B or AB
B or O
marker molecules: AB
antibody: none
A, B, AB, or O
marker molecules: none
antibodies: anti-A, anti-B
A, B, AB, or O
How does Rh factor affect blood transfusion?
The Rh factor is another marker on the surface of red blood
cells. Clumping will result if someone without the Rh factor
(Rh-negative) receives a transfusion of blood with the Rh
factor (Rh-positive).
Circulatory System Disorders
10. Name two causes of
death that can result from
Blood clots and fats can block blood flow through arteries.
The condition of blocked arteries is called atherosclerosis
(ar thir re oh skluh ROH sus). Signs include high blood
pressure and high cholesterol levels. Atherosclerosis can lead
to heart attack or stroke, two leading causes of death. Heart
attacks occur when blood does not reach the heart muscle.
Strokes occur when clots form in blood vessels supplying
oxygen to the brain.
Chapter 34 Circulatory, Respiratory, and Excretory Systems
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Picture This
Circulatory, Respiratory, and
Excretory Systems
section ●
Respiratory System
Before You Read
-!). )DEA
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Breathing happens automatically. You do not think about
every breath you take. Look at the clock and count how many
breaths you take in a minute. Write that number on the lines
below. Then write one sentence describing a time when you
did think about your breathing. In this section you will learn
what happens in your body as you breathe.
The respiratory system
exchanges oxygen and
carbon dioxide between the
atmosphere and the blood
and between the blood and
the body’s cells.
What You’ll Learn
the difference between internal
and external respiration
■ the path of air through the
respiratory system
■ the changes that occur in the
body during breathing
Read to Learn
Main Ideas As you read the
The Importance of Respiration
Your body’s cells need oxygen. Recall that cells use oxygen
and glucose to produce energy-rich ATP molecules needed for
cellular metabolism. This process is called cellular respiration.
Cellular respiration releases energy. It also releases carbon
dioxide and water.
section, highlight the main ideas
in each paragraph.
How is breathing different from respiration?
The respiratory system supports cellular respiration by
supplying oxygen to body cells and removing carbon dioxide
waste from cells. Two processes make up the respiratory
system: breathing and respiration.
First, air enters the body. Breathing is the mechanical
movement of air into and out of the lungs. Second, gases
are exchanged. External respiration is the exchange of gases
between the atmosphere and the blood. Internal respiration is
the exchange of gases between the blood and the body’s cells.
Reading Essentials
1. Explain why one form
of respiration is called
Chapter 34 Circulatory, Respiratory, and Excretory Systems
The Path of Air
As you read about the path air travels through your body,
follow along in the figure below. First, air enters your mouth
or nose. Hairs in your nose filter out dust in the air. Hairlike
cilia that line your nasal passages trap particles from the air
and sweep them toward the throat. This keeps particles from
entering the lungs. Mucous membranes beneath the cilia warm
and moisten the air, while trapping foreign particles.
through which air passes on
its way through your nose
and nasal passages.
What structures does air pass through as it
travels to the lungs?
Filtered air then passes through the upper throat, or pharynx
(FER ingks). A flap called the epiglottis covers the opening
to the larynx (LER ingks). The epiglottis allows air to pass
while keeping food out of the respiratory tubes. Air moves
through the larynx to a tube in the chest called the trachea
(TRAY kee uh), or windpipe. The trachea branches into two
large tubes, called bronchi (BRAHN ki). The bronchi lead
to the lungs, where gas exchange takes place. Each bronchus
branches into smaller bronchioles (BRAHN kee ohlz).
Branching continues until each branch ends in an air sac called
an alveolus (al VEE uh lus) (plural, alveoli). Alveoli have walls
that are one cell thick and are surrounded by capillaries.
How does gas exchange occur?
Picture This
3. Identify Circle the name
of the structure in which
oxygen diffuses.
Oxygen in the air diffuses across the thin walls of the
alveoli into capillaries and then into red blood cells. The
blood carries the oxygen to the cells. At the same time, carbon
dioxide moves from the blood into the capillaries. It diffuses
into the alveoli to be returned to the atmosphere.
Chapter 34 Circulatory, Respiratory, and Excretory Systems
Reading Essentials
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
2. Identify three filters
Your brain directs the rate of your breathing. If you have a
lot of carbon dioxide in your blood, you need more oxygen, so
you breathe faster.
As shown in the figure below, the rib and diaphragm
muscles contract during inhalation. This increases the size of
the chest cavity, allowing air to move into the lungs. During
exhalation, the rib and diaphragm muscles relax. This reduces
the size of the chest cavity, allowing air to flow out.
Picture This
4. Compare how the
diaphragm moves during
inhalation and exhalation.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Respiratory Disorders
The table below lists common disorders that affect the
respiratory system. Smoking irritates respiratory tissues and
inhibits cellular metabolism. Allergic reactions to particles in
the air can also lead to respiratory problems.
Lung Disorder
Picture This
Respiratory pathways become irritated and
bronchioles constrict.
Infected respiratory pathways result in coughing
and production of mucus.
Alveoli break down, resulting in reduced surface
area needed for gas exchange.
Infection in the lungs causes alveoli to collect mucus.
A bacterium infects the lungs, harming the
capillaries surrounding the alveoli and inhibiting
gas exchange.
Lung cancer
Uncontrolled cell growth in the lungs can lead to
persistent cough, shortness of breath, bronchitis or
pneumonia, and death.
5. Identify the lung disorder
that damages the alveoli.
Chapter 34 Circulatory, Respiratory, and Excretory Systems
Circulatory, Respiratory, and
Excretory Systems
section ●
Excretory System
-!). )DEA
The kidneys help maintain
homeostasis in the human body.
What You’ll Learn
the steps of the excretion of
wastes from the Bowman’s
capsule to the urethra
■ the difference between filtration
and reabsorption
Before You Read
You might be responsible for taking out your family’s trash.
On the lines below, describe what might happen if no one
removed the trash from your home for several months. Read
the section to learn how the body gets rid of wastes.
Read to Learn
Read for Understanding
As you read this section,
highlight any sentences that you
do not understand. Reread the
highlighted sentences to make
certain that you understand
their content. Ask your teacher
to help you with anything that
you still do not understand.
1. Describe the function of
the kidneys.
Parts of the Excretory System
The lungs, skin, and kidneys make up the excretory system.
The lungs excrete carbon dioxide. The skin excretes water and
salts in sweat. The main excretory organs are the kidneys.
What is the purpose of the excretory system?
The body produces wastes, such as toxins and carbon
dioxide, during metabolism. The excretory system removes
these wastes. The excretory system also controls the amount
of fluids and salts in the body and maintains the pH of the
blood. All of these activities help maintain homeostasis.
The Kidneys
The kidneys are two bean-shaped organs that filter out
wastes, water, and salts from the blood. The kidneys are
divided into two regions: the outer renal cortex and the inner
renal medulla. The body’s filters are found in the renal pelvis
in the center of the kidney.
Chapter 34 Circulatory, Respiratory, and Excretory Systems
Reading Essentials
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How do the nephrons filter the blood?
Nephrons, shown above, are the kidney’s filters. Each
kidney contains approximately one million nephrons. Blood
enters each nephron through a long tube. A ball of capillaries
called the glomerulus (gluh MER uh lus) (plural, glomeruli)
surrounds the tube. The glomerulus lies within the Bowman’s
The renal artery transports nutrients and wastes to the
kidney. This artery branches into smaller blood vessels,
eventually reaching the capillaries in the glomerulus. The
walls of the capillaries are very thin. The force of the blood
pushes water and substances dissolved in water, such as
the nitrogenous waste product urea (yoo REE uh), through
the capillary walls into the Bowman’s capsule. Larger
molecules, such as red blood cells and proteins, remain
in the bloodstream.
Picture This
2. Highlight each structure
in the figure as you read
about it.
How is urine formed?
Materials collected in the Bowman’s capsule flow through
the renal tubule. Water and useful materials, such as glucose
and minerals, return to the capillaries in a process called
reabsorption. Urine, which is waste and unneeded fluids,
leaves the kidney through ducts called ureters (YOO ruh turz).
The urine is stored in the urinary bladder until it exits the body
through the urethra (yoo REE thruh). The process of filtering
wastes and reabsorbing useful materials requires large amounts
of energy. The kidneys account for only 1 percent of a person’s
body weight, but they use 20 to 25 percent of the body’s
oxygen to generate the energy needed to function properly.
Reading Essentials
3. Predict what might
happen if the excretory
process did not include
Chapter 34 Circulatory, Respiratory, and Excretory Systems
Kidney Disorders
Kidney infection is a common problem. Symptoms include
fever, chills, and mid- to low-back pain. To avoid permanent
damage to the kidneys, antibiotics are used to treat a bacterial
infection. The table below lists other common excretory disorders.
Kidneys can also be damaged by other diseases in the body,
such as diabetes and high blood pressure. In addition, kidneys
can be damaged by prescription drugs and by illegal drug use.
4. Identify the disorder that
can correct itself sometimes
through the normal process
of excretion.
Excretory Disorder
painful swelling of the glomeruli; large particles
in the blood become lodged in the glomeruli
Kidney stones
crystallized solids form in the kidneys; small
stones pass out of the body in urine; larger
stones can block urine flow
Urinary tract
abnormal formation at birth can block urine
Polycystic kidney
genetic disorder in which many fluid-filled
cysts grow in the kidneys; can reduce kidney
function or lead to kidney failure
Kidney cancer
uncontrolled cell growth that often begins
in the lining of kidney tubules; can spread to
other organs; can lead to death
Kidney Treatments
If kidney problems are not treated or kidney damage occurs,
wastes accumulate in the body, leading to coma, seizure, and
death. Modern medicine offers two possible treatments.
How is dialysis performed?
5. Explain why kidney
transplants do not occur
more often.
Dialysis is a procedure that filters out wastes from the patient’s
blood. In one type of dialysis, the patient’s blood passes through
a machine that filters the blood and returns it to the patient’s
body. This procedure requires three sessions a week.
A second type of dialysis uses the membrane lining the
abdomen as an artificial kidney. A special fluid is injected
through a tube attached to the body. The patient’s waste fluid
is drained. This procedure is performed daily.
What is a kidney transplant?
In a kidney transplant, a healthy kidney from a donor is
placed in the patient’s body during surgery. Transplants are
becoming more successful. However, the supply of donated
kidneys is far below the number of kidneys needed.
Chapter 34 Circulatory, Respiratory, and Excretory Systems
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
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