Chapter 34 Notes, The Circulatory,
Respiratory, and Excretory Systems
The Circulatory System
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the circulatory system is the body's transportation
system.
The circulatory system consists of the blood, the heart,
the blood vessels, and the lymphatic system.
The circulatory system transports oxygen, nutrients,
disease-fighting materials, cell fragments and proteins
used for blood clotting, and the circulatory system
distributes heat uniformly throughout the body.
The Circulatory System
Blood Vessels
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Just like a highway transportation system has
roads, on and off ramps, stop lights etc., the
circulatory system has a complicated network of
blood vessels that perform different functions.
Oxygen-rich blood is carried away from the
heart in blood vessels called arteries. Arteries
are strong thick-walled vessels that are elastic
and durable. They are able to withstand high
pressures exerted by the pumping heart.
Arteries
Blood Vessels
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When arteries get closer to their intended destination
(usually an organ or a tissue), they begin branching off
into thin-walled delicate vessels known as capillaries.
Capillaries are small, delicate blood vessels, that
sometimes are only 1 cell thick, where the exchange
of important substances and wastes occur.
After the blood travels through the capillaries they
enter the veins, which carry oxygen-poor blood back
to the heart.
Capillaries and Veins
Blood Vessels
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Veins do not have to withstand high pressures as the
arteries do. Once the blood has passed through the
capillaries, much of the blood pressure generated by
the heart has already been reduced.
Veins rely on the movement of skeletal muscles to
pump the deoxygenated blood back to the heart.
Veins also have one-way valves that prevent blood
from flowing backwards.
Arteries and Veins
The Heart
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The main function of the heart is to pump oxygenated
blood to the body, and to pump deoxygenated blood to
the lungs.
The heart is divided into four chambers.
The two chambers on the top of the heart are the right
atrium and left atrium (plural, atria).
The right atrium receives deoxygenated blood from the
body. The left atrium receives oxygenated blood from
the lungs.
Four-Chambered Heart
The Heart
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The two lower chambers of the heart, that pump blood
away from the heart are called the right and left
ventricles.
The strong thick-walled left ventricle pumps
oxygenated blood to the body. The thinner- walled
right ventricle pumps deoxygenated blood to the lungs.
The beating of the heart is controlled by a group of
cells in the right atrium called the pacemaker or
sinoatrial node (SA node for short).
The SA node causes the atria to contract, the
Atrioventricular (AV) node contracts the ventricles.
The Human Heart
The Blood
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Blood is made up of four components; plasma, red
blood cells, white blood cells, and platelets.
Plasma is a clear, yellowish fluid. More than 50% of
the blood is plasma. Plasma is about 90% water and
10% dissolved materials.
Plasma carries digested food, vitamins, minerals,
hormones, and waste products.
Red blood cells carry oxygen to all the body's cells.
Red blood cells look like donuts.
Composition of Blood
The Blood
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Red blood cells in mammals have no nuclei.
This is an adaptation that allows the blood cells to
carry more oxygen.
Red blood cells are made up of an iron-rich protein
known as hemoglobin.
Iron turns red in the presence of oxygen, giving blood
rich in oxygen its reddish color.
White blood cells are cells that fight off diseases.
Red and White Blood Cells
The Blood
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Platelets are cell fragments that form blood clots
when a cut occurs.
When a blood vessel is cut, platelets collect and stick
to the site of the wound.
The platelets then release chemicals that produce a
protein called fibrin.
Fibrin weaves a network of fibers across the cut that
traps more platelets and red blood cells.
As more platelets and red blood cells collect,
eventually a blood clot forms.
The Blood
Circulatory System Disorders
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Blood clots and deposits of fats can sometimes
lead to a blockage of arteries.
A disorder caused by the condition of blocked
arteries is referred to as atherosclerosis.
Signs of clogged arteries are high blood
pressure and high cholesterol.
Atherosclerosis can lead to diseases like heart
attacks or strokes.
Circulatory System Disorders
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Heart attacks occur when
blood is prevented from
returning to the heart.
Strokes occur when blood is
prevented from reaching the
brain.
Heart attacks result in
damage to the heart or death.
Strokes most often result in
brain damage.
Respiration
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In order to function, all of the body's cells need a
continuous supply of oxygen, and they need to expel
carbon dioxide produced from respiration.
The mechanical action that moves air into and out of
the lungs is called breathing.
External respiration is the exchange of gases that
occurs between the air and the blood.
Internal respiration is the exchange of gases
between the blood and the body's cells.
Breathing and Respiration
The Respiratory System
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The tissues and organs of the respiratory system
include the nasal passages, pharynx, larynx, epiglottis,
trachea, lungs, bronchi, bronchioles, alveoli, and the
diaphragm.
When air first enters the mouth or the nose, small
hairs in the nose and nasal passages filter out dust
and particles.
The filtered air then passes through the area of the
upper throat called the pharynx.
Nasal Passages and Pharynx
The Respiratory System
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A small flap of tissue called the epiglottis covers the
larynx (voice box). The epiglottis prevents food from
entering the trachea (windpipe).
After air passes through the larynx, it travels down the
trachea. The trachea branches into two large tubes
called the bronchi.
After the air passes through the bronchi it enters into
the lungs.
Once into the lungs, the bronchi branch off into smaller
tubes called bronchioles.
The Respiratory System
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At the end of the bronchioles are small air sacs that
are only one cell thick and surrounded by capillaries.
These air sacs are called alveoli.
Gas exchange takes place in the alveoli.
The lungs fill up with air when the muscular diaphragm
contracts. When the diaphragm muscles relax, the
lungs push air back out.
There are many common disorders of the respiratory
system like asthma, bronchitis, emphysema,
pneumonia, and lung cancer.
The Respiratory System
The Excretory System
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The main function of the excretory system is to
remove the body's wastes.
Another important function of the excretory system is it
helps regulate the body's fluids, salt concentrations,
and the pH of the blood.
The main organs of the excretory system include the
skin, lungs, liver, and kidneys.
The lungs excrete carbon dioxide, and the skin
excretes water and salt, but the kidneys are the most
important part of the excretory system.
The Human Excretory System
The Excretory System
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Small bean-shaped organs called kidneys do the
biggest job of the excretory system.
The kidneys are divided into three parts; the renal
cortex, renal medulla, and renal pelvis.
Inside the kidneys there are approximately 1 million
filtering units called nephrons.
In the nephrons, blood enters a structure called the
Bowman's capsule.
Inside the Bowman's capsule is a ball of capillaries
called the glomerulus.
The Excretory System
The Excretory System
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When the blood reaches the glomerulus and the
Bowman's capsule, high pressures filter urea out of
the blood.
Larger molecules like blood cells mostly stay in the
bloodstream.
The filtrate coming out of the Bowman's capsule
enters an area of the nephron called the convoluted
tubule and the loop of Henle.
This part of the nephron reabsorbs any of the good
substances like glucose and minerals.
Anatomy of the Kidneys
The Excretory System
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Eventually at the end of the nephron, the waste product
that will be removed is called urine.
Urine leaves the nephron through collecting tubules.
The collecting tubules lead to ureters. The ureters lead
to the urinary bladder, where urine is stored until it is
finally removed from the body.
Remarkably, even though kidneys filter about 180 L
(about 48 gallons) of blood each day, they only produce
about 1.5 L (almost ½ gallon) of urine each day.
The Kidneys and Nephron Filtration