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BL 1021 – Unit 4.9 – 4.14
The Respiratory and Defense Systems
4.9 Respiratory Systems
• One of the major duties of the circulatory system is
to move gases from place to place in the body.
Living cells need a fresh supply of oxygen and need
waste carbon dioxide removed.
• The respiratory system works to take in new oxygen
from the environment and expel carbon dioxide. By
working together, all of the cells of the body get the
oxygen they need.
4.9 Respiratory Systems
• Oxygen is picked up in
the blood during the
pulmonary circuit.
Carbon dioxide is
released into the lungs
at this same time.
• During the systemic
circuit, the oxygen is
delivered to all of the
body’s tissues and
carbon dioxide is
picked up from cells.
4.9 Respiratory Systems
• Some oxygen is carried
in the blood by being
dissolved into the liquid,
or plasma, component
of the blood.
• The majority, however,
is carried by red blood
cells called
erythrocytes. These a
specialized cells filled
with the protein
hemoglobin which is an
oxygen carrier.
4.9 Respiratory Systems
• Hemoglobin has a
special bonding
relationship with
oxygen.
• It strongly binds oxygen
in oxygen-rich areas
(lungs) but releases
oxygen in oxygen-poor
areas (body tissues).
• This allows hemoglobin
to deliver oxygen
where it is most
needed.
4.10 Types of Respiratory Surfaces
• For a gas like oxygen to be taken up, a special set
of cells called a respiratory surface must exist.
• This surface must be thin enough to allow gases to
diffuse in and out easily.
• This surface must be moist to allow gases to be able
to dissolve into the liquid to be absorbed.
• Respiratory surfaces come in a variety of forms:
4.10 Types of Respiratory Surfaces
• Skin
• (Frogs, earthworms)
• Some organisms will
have a very thin skin
layer with capillaries
close enough to the
surface to allow gas
exchange.
• In these type of
animals, the skin must
be kept moist to
breathe.
4.10 Types of Respiratory Surfaces
• Gills
• (Fish and most aquatic
animals)
• Gills have a series of
capillaries close to the
surface.
• Gills do not need to worry
about drying out as they
re in the water.
• Gills typically have some
sort of protective cover to
keep out dirt and
parasites.
4.10 Types of Respiratory Surfaces
• Tracheae
• (insects)
• As insects live on land,
they need an
internalized system to
reduce the water lost
from the respiratory
surface.
• Tracheae are small
tube inlets on the body
that branch out within.
4.10 Types of Respiratory Surfaces
• The majority of the
tracheae is dry, with
only the “dead end”
regions coated in
water to allow diffusion.
• Tracheae branch out
to reach all the cells of
the body due and thus
insects are limited in
size as these simple
tubes only work on a
small scale.
4.10 Types of Respiratory Surfaces
• Lungs
• (mammals)
• Lungs are an internal
respiratory
compartment with a
highly-branched
structure.
• Lungs work with the
circulatory system to
deliver their gases.
4.10 Types of Respiratory Surfaces
• Lungs are localized to
one area and do not
need to reach all of the
body because the
closed circulatory
system is capable of
delivering all the gases
between the lungs and
the body.
4.11 Human Respiratory System
• The human respiratory
system, is found in the
body cavity, is
protected by the rib
cage, is lined on the
bottom by the
diaphragm and is
entered through the
nasal/mouth cavity.
4.11 Human Respiratory System
• The diaphragm pulls
on the lungs,
expanding them and
creating a negative
pressure that pulls air in.
• When the diaphragm
relaxes, the lungs
decrease in volume,
pushing air out.
4.11 Human Respiratory System
• The respiratory system is
made up of two lungs,
a left and right. Air
enters through the
nasal cavity or mouth.
• The nasal cavity
conditions the air to
make it safe for the
sensitive tissues of the
lungs.
• The nasal cavity acts as
a filter and humidifier of
the air.
4.11 Human Respiratory System
• From the nasal cavity
air travels through the
larynx. This is the voice
box that contains the
vocal cords.
• The vocal cords move
in order to cause
different vibrations
which create different
sounds to speak.
4.11 Human Respiratory System
• From the larynx, air
continues down the
trachea (windpipe)
and into two bronchi,
tubes which lead to
each lung.
• No gas exchange
occurs at this stage,
these are just piping to
feed air into/out of the
lungs.
4.11 Human Respiratory System
• The bronchi further
branch within the lung
into several smaller
tubes called
bronchioles. Each
bronchiole ends in a
series air sacs called
alveoli, which appear
like clusters of grapes.
4.11 Human Respiratory System
• The alveoli are thinwalled spheres with a
very thin liquid coating
on the inside.
• This is the site of gas
exchange.
• By having all these
small sacs, the surface
for gas exchange is
maximized.
4.11 Human Respiratory System
• Special chemicals exist
in the fluid of the lungs
that keep a thin
coating of liquid on all
of the lung’s inner
surface.
• Excess fluid buildup, like
in pneumonia, is
dangerous as it acts as
a barrier to gas
exchange, preventing
normal breathing.
4.11 Human Respiratory System
• Special chemicals exist
in the fluid of the lungs
that keep a thin
coating of liquid on all
of the lung’s inner
surface.
• Excess fluid buildup, like
in pneumonia, is
dangerous as it acts as
a barrier to gas
exchange, preventing
normal breathing.
4.12 The Defense Systems
• The first line of defense in the body is a general
series of barrier against multiple threats.
• These nonspecific external defense mechanisms
are in place to block all invaders. If an infectious
organism cannot get inside the body, it cannot
infect the body.
4.12 The Defense Systems
• The nonspecific external defense systems:
• The Skin acts as a physical barrier
• Oil and acids are produced on the skin to kill off
microorganisms
• Hairs in the nasal tract
• Mucus in internal membranes traps invaders
• Cilia in mucous membranes move mucus out
• Sweat, saliva and tears have anti-bacterial
materials
• Stomach acid kills swallowed bacteria
4.12 The Defense Systems
• The body also has internal nonspecific defences.
 White blood cells (leukocytes) destroy foreign particles and
dead cells.
 Interferon (proteins produced by virus-infected body cells)
help healthy cells resist viruses
 Complement proteins coat the surface of microbes making
them easier for white blood cells to identify them
 The inflammatory response (injured cells and invading
microorganisms release chemicals that trigger the release of
chemicals such as histamine which causes site to swell which
promotes healing)
 Damaged cells release prostaglandins which increase blood
flow to area
 Cells may release pyrogens which can stimulate a fever
4.13 The Lymphatic System
• The lymphatic system
carries fluid around the
body and is the major
carrier of the immune
system.
• The system also collects
lipids from the digestive
system as they are
extracted from food.
4.13 The Lymphatic System
• The lymphatic system is
an open system; it
collects fluid from the
spaces between the
tissues and then feeds it
back into the
circulatory system.
• The fluid that is carried
through is lymph.
4.13 The Lymphatic System
• Germs captured by the
lymph are filtered out in
the lymph nodes. These
are small masses of
tissue in the network of
lymph vessels.
• Antibodies are made in
the nodes. Antibodies
are used to label and
trap invaders.
4.13 The Lymphatic System
• At lymph nodes,
invading cells can also
be destroyed by white
blood cells.
• When lymph filters
through the spleen,
special white blood
cells destroy bacteria,
dead tissue and foreign
material.
4.13 The Lymphatic System
• At lymph nodes,
invading cells can also
be destroyed by white
blood cells.
• When lymph filters
through the spleen,
special white blood
cells destroy bacteria,
dead tissue and foreign
material.
4.14 The Immune System
• The immune system is a series of defenses to
specifically target invaders.
• The cells that are part of this defense system are
white blood cells, or leukocytes. They come in two
basic types which work together to seek out and
destroy the organisms or substances that cause
disease.
• Leukocytes are produced and stored in the thymus,
spleen and bone marrow but will move throughout
the body to fight infections.
4.14 The Immune System
• The immune system is a series of defenses to specifically
target invaders.
• The cells that are part of this defense system are white
blood cells, or leukocytes. They come in two basic types
which work together to seek out and destroy the
organisms or substances that cause disease.
• Leukocytes are produced and stored in the thymus,
spleen and bone marrow but will move throughout the
body through the lymphatic vessels to fight infections.
4.14 The Immune System
• Two major types of leukocytes:
• Phagocytes engulf and destroy invaders
• Lymphocytes allow the body to label, remember,
and recognize invaders, allowing the body to better
fight off invaders in repeated infections. There are
two major types: one labels invaders while the other
works more to destroy them.
4.14 The Immune System
• Two major types of lymphocytes:
• All lymphocytes begin life in the bone marrow.
Some cells will remain there and mature into B
Lymphocytes.
• These cells detect antigens (any invading
substance) and create antibodies that latch onto
them, labeling them for destruction.
4.14 The Immune System
• Antibodies stay in the body and thus the body is
able to easily fight off an infection much easier
during repeated infections.
• Vaccinations work by giving the body a weakened
or dead version of an antigen to learn from and
create antibodies from. This allows the body to be
ready for certain infections and when the body
encounters them again. This is not always 100%
effective as bacteria can evolve and change so
that they are not recognized by antibodies.
4.14 The Immune System
• Other lymphocytes will move from the bone marrow
to the thymus gland and mature into T
lymphocytes.
• T cells work to destroy cells that it recognizes as
invaders. This may be done directly or by detecting
cells labeled by antibodies. Thus, B cells and T cells
work together in many cases to destroy invaders. Tcells can also call in other white blood cells to help
destroy the invaders in some cases.
4.14 The Immune System
• There are two general
pathways for immune
defense:
• Humoral or AntigenMediated immunity
involves B cells creating
new antibodies by
“sizing-up” the invaders
and then circulating
those antibodies
around the body to
label all of the invaders.
4.14 The Immune System
• Humoral immunity
works well on bacteria,
microorganisms, and
fungi as it can easily
label them for
destruction.
4.14 The Immune System
• The other major type of
immunity is Cellmediated immunity.
• This system targets
infected cells for
destruction directly
using T-cells.
4.14 The Immune System
• Cell-mediated
immunity is best at
destroying viruses and
other invaders that get
inside of the body’s
cells as it will destroy
the host cell as well.
4.14 The Immune System
• With both types of immunity, cells can be mistakenly
labeled as harmful.
• In auto-immune diseases, immune cells label a
certain type of cell in the body as harmful and
destroy them. This causes damage to healthy tissues
and loss of function. Type I diabetes is caused b the
body destroying the cells of the pancreas that
produce insulin. Without these cells, the body
cannot regulate its blood sugar levels properly.
4.14 The Immune System
• Blood transfusions can cause problems too. If a
person receives blood that is a different type than
theirs, the body may label the new blood cells as
invaders and destroy them – causing clots of dead
cells to form in the blood vessels.
• Similarly, when a person receives a new organ from
a donor, the body may label the new cells as
invaders and destroy the organ in a process known
as rejection. The organ recipient may have to take
drugs to supress the immune system for the rest of
their lives. This may make them more vulnerable to
other infections.