Systems of Defense
Animal Systems
Yesterday, you illustrated a diagram of skin in
your notebook!
What are the three layers found in skin?
Contains keratin for
elasticity and
waterproofing
 Contains melanin for
pigmentation

A
B
C

Functional layer of skin
that contains nerve cells,
blood vessels, hair
follicles, and specialized
skin cells.
Made mostly of fat
Lies beneath the dermis
acting as a shock
absorber and an insulator.
 Anchors the skin to
underlying organs


Yesterday, you illustrated a diagram of skin in
your notebook!
What are the three layers found in skin?
•Protection from injury
•Prevents the body
from drying out
•1st Line of Defense
against Disease
Why do we need skin?
Now let’s look at your diagram of
the structure of bone.
•Made of fat for energy storage.
Yellow bone marrow
Blood vessels
•Supplies nutrients to
the bone
Periosteum
•Tough exterior membrane
•Contains blood vessels
Spongy bone
•Porous inner core
filled with red bone
marrow
•Production of
blood cells and
platelets begins
Compact bone
•Hard outer covering
Now let’s look at your diagram of
the structure of bone.
Spongy bone
Bone marrow
Blood vessels
Compact bone
Periosteum
Why do we need bones? •Protects internal organs
•Provides shape & support
•Along with muscles, enables
movement.
Both of these provide defense
and protection to the animal.
 What do we need protection from?
 Injury & Illness
 How do they protect us?
 Provides a physical barrier
 A physical barrier from what???
Skin and mucous membranes are the
1st Line of Defense against pathogens!
 What are pathogens?
 An agent that causes disease.
 Examples: viruses, bacteria, fungi, protists, allergens
How does the body recognize pathogens?
 Body cells have surface markers that indicate they belong
in the body.
Like an ID Badge
 When a pathogen infects a body cell, the infected body
cell displays an antigen on the surface.
 The antigen triggers an immune response.
Like little red flags
Let’s look at a few pathogens in
more detail!!!
Viruses
 Non-living. Why?
 Needs a host cell to replicate
 Do not grow, metabolize, or
maintain homeostasis.
 Only pathogenic (causes disease).
 Viruses are specific to certain kinds of cells.
 Ex: HIV infects only Helper T cells
 Before a virus can replicate, it must infect a living
cell, called the host cell.
Virus Replication
 Once in a host, the virus can take one of two paths.
1. Lytic Cycle
2. Lysogenic Cycle
Virus Replication- Lytic Cycle
Infection
Cell destruction
Replication
Virus Replication- Lysogenic Cycle
 Does not destroy host cell.
 Results in two infected
host cells.
 Virus gene is
inserted into host
chromosome
(called a provirus).
 Each time the cell
divides, the provirus
also divides.
Common Viral Infections
Cold sores
Influenza (the flu)
SARS
Viral pneumonia
Chicken pox
Herpes
HIV/AIDS
Small pox
Warts
Hepatitis
Bacteria
 Remember Bacteria?
 Prokaryotes-No nucleus
 Obtain energy by autotrophy (photosynthetic or
chemosynthetic) or heterotrophy
 Can be harmful (cause disease) or helpful (food-making,
mining, nitrogen fixing for the environment)
How do Bacteria cause disease?
 Bacteria can cause disease by metabolizing
nutrients in their host (competition for resources) or
by releasing toxins, which damage the host.
 Bacteria are identified by their shape and cell wall
type.
Important Bacterial Infections
Ear infections
Cavities
Tuberculosis
Carbuncles
Upper Respiratory Infection
Stomach Ulcers
Impetigo
Food Poisoning
How can we treat infections?
 Only bacterial infections can be treated with an
antibiotic.
 Why?
 Let’s look at the word—
against
life
ANTIBIO
 Unfortunately, viruses can only be treated with rest
and fluids until your immune system destroys the
cells infected with viruses.
What other methods are used to
protect against pathogens?
 Prevention by vaccines!
 How does it work?
 A weakened or heat-killed strain of a virus or
bacteria is injected into your body.
 Your immune system responds to the vaccine by
creating B cells, the memory cells.
 If the pathogen enters your body again, it is quickly
recognized and destroyed.
Viruses
Bacteria
Draw this t-chart on the left
side of your IN.
Complete the t-chart by
comparing and contrasting
viruses and bacteria..
What happens if the pathogen gets
past the 1st Line of Defense?
 Draw a four square diagram in your notebook on
 Label the four boxes as shown below.
the next right hand side.
Inflammatory Response
Complement System
Temperature Response
White Blood Cells
What happens if the pathogen gets
past the 1st Line of Defense?
Inflammatory Response
Temperature Response
•Local blood vessels dilate.
•Increased blood flow to the area
brings more white blood cells
Complement System
White Blood Cells
What happens if the pathogen gets
past the 1st Line of Defense?
Inflammatory Response
Temperature Response
•Fever.
•Bacteria can only grow within a
certain temperature range. A fever
raises the temperature so the
Complement
Systemcannot survive.
White Blood Cells
bacteria
What happens if the pathogen gets
past the 1st Line of Defense?
Inflammatory Response
Temperature Response
•Made of about 20 different proteins
•Travels the bloodstream punching
holes in the cell membranes of
pathogens.
Complement System
Blood Cells
• Interferon, a protein White
released
by
virus-infected cells, prevents viruses
from making proteins and RNA.
What happens if the pathogen gets
past the 1st Line of Defense?
Inflammatory Response
Temperature Response
•Neutrophils-engulfs and destroys
pathogens
•Macrophages-ingest and kills
pathogens and clears dead cells and
White Blood Cells
Complement System
debris
•Natural Killer Cells-attacks cells
infected with pathogens, punctures
their cell membranes
What happens if the pathogen gets
past the 1st Line of Defense?
2nd Line of Defense
Inflammatory Response
•Local blood vessels dilate.
•Increased blood flow to the area brings
more white blood cells
Temperature Response
•Fever.
•Bacteria can only grow within a certain
temperature range. A fever raises the
temperature so the bacteria cannot
survive.
Complement System
•Made of about 20 different proteins
•Travels the bloodstream punching holes
in the cell membranes of pathogens.
•Interferon, a protein released by virusinfected cells, prevents viruses from
making proteins and RNA.
White Blood Cells
•Neutrophils-engulfs and destroys
pathogens
• Macrophages-ingest and kills
pathogens and clears dead cells and
debris
• Natural Killer Cells-attacks cells
infected with pathogens, punctures their
cell membranes
What happens if the pathogen gets
past the 1st Line of Defense?
2nd Line of Defense
Inflammatory Response
•Local blood vessels dilate.
•Increased blood flow to the area brings
more white blood cells
Temperature Response
•Fever.
•Bacteria can only grow within a certain
temperature range. A fever raises the
temperature so the bacteria cannot
survive.
Complement System
•Made of about 20 different proteins
•Travels the bloodstream punching holes
in the cell membranes of pathogens.
•Interferon, a protein released by virusinfected cells, prevents viruses from
making proteins and RNA.
White Blood Cells
•Neutrophils-engulfs and destroys
pathogens
• Macrophages-ingest and kills
pathogens and clears dead cells and
debris
• Natural Killer Cells-attacks cells
infected with pathogens, punctures their
cell membranes
What if the 2nd Line of Defense
doesn’t stop the pathogen?
 Specific Immune Response-
3rd Line of Defense
 What does it mean to be
SPECIFIC?
def: of a special or particular
kind
Then what
is a specific
immune
response?
So how does it work?
Helper T cells recognize
the antigens that are given
off by macrophages that
have ingested pathogens.
The helper T cells then
activate B cells and
cytotoxic t cells.
B cells become memory cells
that help recognize the
pathogen as soon as it is
reintroduced to the body.
Cytotoxic T cells destroy
infected cells
Reflection:
 On the left hand side of your IN, write a description
of the body defenses that are involved in the
following scenario:
Joe was slicing an apple when
the knife slipped and sliced his thumb.
Ouch!