Chapter 34 Notes, The Circulatory,
Respiratory, and Excretory Systems
The Circulatory System



Simply put, the body's 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 lymphatic system is in chapter 37.
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


Just like a highway transportation system has
roads, on and off ramps, stop lights etc., the
circulatory system has blood vessels.
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.
Blood Vessels



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 microscopic blood vessels
where the exchange of important substances
and wastes occurs.
After the blood travels through the capillaries
they enter the veins, which carry oxygen-poor
blood back to the heart.
Blood Vessels



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 has been reduced.
Instead, 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




The function of the heart is to pump oxygenated
blood to the body, and deoxygenated blood to
the lungs.
The heart is divided into four compartments
called 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.
The Heart



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 thinnerwalled 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 Human Heart
The Blood




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.
The Blood





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.
The Blood





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




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



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




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 cellular
respiration.
The mechanical action of the movement of air in
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.
The Respiratory System



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 cilia in the 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




A small flap of tissue called the epiglottis
covers the larynx or voice box. The epiglottis
prevents food from entering the windpipe.
After air passes the larynx, it travels down the
windpipe or 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




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
Muscular Action of the Diaphragm
The Excretory System




The excretory system is very important,
because it removes most of 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, the lungs, and the 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 Excretory System





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




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.
The Excretory System



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 removed from the body.
Remarkably even though kidneys filter about
180 L of blood each day, they only produce
about 1.5 L of urine each day.
The Kidneys and Nephron Filtration