PathologyPathology

Diseases and DefensesDiseases and Defenses

Section OneSection One

PathogensPathogens

DiseaseDisease

Disease is a condition in which the body or one of its parts is not functioning normally.

Pathogens are the agents that cause disease. Parasites cause many different diseases. They

are pathogens. A parasite is an organism or a virus that is

dependent on another organism (the host) and causes damage in the process.

Let’s look at some of the parasites that affect humans.

ParasitesParasites

Parasites can be passed from one person to others.

Parasites that invade the body can cause infections.

Let’s look at some of the parasites that can cause infectious diseases…

BacteriaBacteria

Most of these one-celled protists are extremely small and some are pathogenic.

They have a variety of shapes and sizes. Bacteria usually have one of three general

shapes: Round (cocci) Coil-shaped (spirilla) Rod-shaped (bacilli)

CocciCocci

Some cocci bacteria can cause rheumatic fever, gonorrhea, scarlet fever and many other diseases.

BacilliBacilli

Some bacilli bacteria can cause tetanus, diphtheria and many other diseases.

SpirillaSpirilla

Some spirilla bacteria can cause Asiatic cholera and syphilis.

Bacterial GrowthBacterial Growth

What conditions favor the growth of bacteria that invade the body? Think about it!

In the laboratory, bacteria grow on nutrients in petri dishes to form colonies that you can see.

One bacterium can produce a colony of millions of identical bacteria.

With the proper living conditions, bacteria can divide every 20 to 60 minutes.

Bacterial GrowthBacterial Growth

Bacterial growth increases as temperature increases up to an optimal temperature of 38°C.

The rate of bacterial growth is zero at 5°C and 50°C.

Bacterial growth is greatest when the amount of light is low or zero (absolute dark).

Bacterial growth is also dependent upon water – moist conditions are best.

The amount of available nutrients also affects the growth rate – more concentrated (higher) nutrient levels promotes more growth.

InformationInformation

The interior of the human body is warm, dark, very moist and has a concentrated food supply.

Based on this information and what we discovered on the previous slide, you can conclude that when bacteria enter the body they often grow rapidly.

InformationInformation

The optimum conditions for the growth of most bacteria are found in the interior of the human body.

Some bacteria destroy body cells. Other bacteria cause harm by secreting toxins

(poisonous chemicals). Food poisoning and tetanus are examples of

diseases caused by toxins. Let’s look at viruses next…

VirusesViruses

Viruses are so small that you cannot see them with ordinary light microscopes.

Some viruses can cause colds, measles, mumps, influenza, polio and other diseases.

Some scientists do not consider viruses to be living. They do not contain protoplasm and depend upon other living organisms to reproduce.

VirusesViruses

This is how viruses enter the body: By inhalation. By ingestion. Through a wound.

Viruses travel in the body until they reach a specific type of cell.

Different viruses attack different cells. Some viruses enter the cells. Others attach

themselves to the surface of a cell.

Viral InfectionViral Infection

Some viruses inject their nucleic acid (either DNA or RNA) into a cell.

The viral nucleic acid directs the infected cell to manufacture more viruses.

As many as 100 viruses can be produced. The virus also directs the cell to produce an enzyme that

breaks the cell open. This kills the cell and releases new viruses. Many more viruses can now attack other cells. This is how a viral infection spreads.

ProtozoaProtozoa

Protozoa are one-celled animals that cause malaria and dysentery.

FungiFungi

Fungi are organisms that lack chlorophyll. They can cause ringworm, athlete’s foot and

lung infections.

WormsWorms

Several species of nematodes (round worms) and annelids (segmented worms) cause disease.

Hookworm, tapeworm and trichinosis are examples.

ParasitesParasites

How do parasites enter the body? Bacteria and fungi typically enter through cuts in the

skin. Viruses, bacteria and some kinds of fungi spores

can be inhaled. Bacteria and protozoa can enter with our water.

Bacteria, fungi and worms can enter with our food. Let’s examine a parasite the enters the body in

this third manner.

TapewormTapeworm There are two main parts to a tapeworm:

The head with hooks and suckers. Many small square sections.

A tapeworm grows within the host by adding new sections behind its head.

It can become ten meters long. Mature sections containing self-fertilized eggs, break off

and leave the host during excretion. The next host, a pig or a cow, may eat the section with

its food.

TapewormTapeworm The next host, a pig or a cow, may eat the section with

its food. Larvae hatch from the eggs and burrow into the animal’s

muscles to form cysts. Each cyst contains a fully developed tapeworm head. Tapeworms enter the human body when they are eaten. If infected meat is not properly cooked, tapeworms

emerge from the cysts as the meat passes through the intestines.

Tapeworms have no digestive system. They absorb food directly from the digested material in the intestines.

ReviewReview

Some bacteria, viruses, protozoa, fungi and worms are parasites that cause infectious diseases.

Bacteria grow best in warm, dark, moist places that have concentrated nutrients.

Parasites, such as tapeworms, can have more than one host.

Viruses direct affected cells to produce more viruses.

Fungi cause skin infections.

Select The Letter Of The Correct Select The Letter Of The Correct Answer From The List Below:Answer From The List Below:

A. infectious D. host

B. bacterial E. virus

C. genetic F. fungi

1. A parasite that infects the body causes a(n) __________________ disease.

2. A parasite can have more than one _________________.

3. Skin infections are most frequently caused by __________________.

4. A(n) __________________ reproduces by directing an invaded cell’s genetic material.

1. A parasite that infects the body causes a(n) __________________ disease.

2. A parasite can have more than one _________________.

3. Skin infections are most frequently caused by __________________.

4. A(n) __________________ reproduces by directing an invaded cell’s genetic material.

Answers:Answers:

infectious

host

fungi

virus

Section TwoSection Two

The Body’s DefensesThe Body’s Defenses

The Three Lines of DefenseThe Three Lines of Defense

How does the body fight off pathogens? There are three lines of defense. First Line: Unbroken Skin

The skin acts as a barrier to pathogenic organisms. Second Line: White Blood Cells

A phagocyte is a type of white blood cell that destroys pathogens after they invade the body.

Third Line: The Immune System The immune system produces chemicals that

deactivate pathogens in the body. The immune system is most important when there are more pathogens than the phagocytes can destroy.

Examples…Examples…

Unbroken skin is the line of defense that would protect you against bacteria that grow in shoes.

Unbroken skin is also the line of defense that would defend against soil bacteria touched while gardening.

White blood cells would be the line of defense that fights bacteria that enter a small cut on your finger.

The immune system would be the line of defense that would fight an invasion by millions of measles viruses.

InformationInformation

Fungi often compete with bacteria for nutrients. Fungi produce antibodies to inhibit or kill

bacteria. Refined antibodies are used to inhibit or kill

bacteria in an infected person.

AntibioticsAntibiotics

Antibiotics kill or inhibit dividing bacteria. Why aren’t antibiotics useful for killing viruses? Think about it!

Remember what a virus is – a nucleic acid surrounded by a protein coat. It is not a cell and therefore does not divide. It enters a living cell to make more viruses.

Bacteria are cells and reproduce by cell division. Since viruses function only in living cells, the only way to

chemically destroy them is to kill infected cells. This method destroys too many cells.

Virus

VirusesViruses

Since antibiotics are ineffective in destroying viruses, how do you suppose the body fights viruses?

A) By the immune system and white blood cells.

B) By digestion in the stomach.

C) Competition from bacteria kills them.

D) Body heat destroys them.The second and third lines of the body’s defenses are designed to destroy all types of pathogens. Your body heat is too low to kill a virus.

Immune SystemImmune System

Antigens are foreign substances in the blood. Antigens have special shapes. They are found on the surfaces of viruses or bacteria.

Lymphocytes are white blood cells with antibodies that interact with antigens.

The interaction causes the lymphocyte to grow and divide.

Memory cells rapidly respond to the antigen if it is encountered again.

Plasma cells secrete antibodies that attack antigens. Let’s examine how antibodies interact with antigens.

AntibodiesAntibodies

Antibodies form weak bonds with antigens. Antibodies can bond with two antigens. This causes clumping (sticking together) of the antigens

and antibodies. The antigen-antibody clump can then be engulfed by a

white blood cell called a phagocyte.

Clumping

InformationInformation

Immunity is the ability to resist and fight off infection.

In the body, immunity is due to the presence of antibodies and lymphocytes.

After a pathogen is destroyed, memory cells remain in the body.

These cells, as well as free (unattached) antibodies, attack pathogens that can invade the body in the future.

ImmunityImmunity

There are two ways to become immune to a disease without catching the disease.

One way is to stimulate antibody formation in the body by injecting it with dead or weakened germs. This is called active immunity.

Another way is to inject antibodies into the blood. This is called passive immunity because the body does not produce its own antibodies.

Giving an individual immunity without catching the disease is called vaccination.

ReviewReview

These are the three lines of defense against disease: Unbroken skin. White blood cells. Immune system.

Antibodies inhibit or destroy bacteria. Antigens are any foreign matter that enters the

body. Antibodies are chemicals that bond with the

special shapes of antigens.

ReviewReview

White blood cells called lymphocytes attach to specific antigens.

Lymphocytes divide to form memory cells and plasma cells.

Plasma cells release antibodies. Antibodies attach to antigens and cause

clumping.

Select The Best Matching Choice:Select The Best Matching Choice:

Answer Column:

A. Has plasma cells

B. A red blood cell

C. First line of defense

D. Any foreign matter

E. Engulfs clumps

F. Inhibits bacteria

G. Has antigens

H. Attaches to antigens

Antibody:Correct Answer: H

Antigen:Correct Answer: D

Antibiotic:Correct Answer: F

Unbroken skin:Correct Answer: C

Virus:Correct Answer: G

Phagocyte:Correct Answer: E

Section ThreeSection Three

Genetic DisordersGenetic Disorders

InformationInformation

Mutations are changes in the genetic material that can be inherited.

Mutations can cause genetic disorders. Sometimes mutations occur when gamete

(sperm and egg) producing cells divide. Let’s see how this occurs…

Gamete-Producing CellGamete-Producing Cell The gamete-producing cell produces gametes with one-half the number of

chromosomes (meiosis). The gametes pass the chromosomes to the next generation.

Chromosomes

NondisjunctionNondisjunction Sometimes chromosomes do not separate properly during meiosis. This is called nondisjunction.

Chromosomes

Notice that the distribution of chromosomes is uneven – one gamete has more than the correct number of chromosomes; one has less than the correct number.

Down’s SyndromeDown’s Syndrome Observe the way Down’s syndrome begins in this simplified

gamete-producing cell. Nondisjunction results in two abnormal gametes – C & D.

Chromosomes

Normal FertilizationNormal Fertilization Observe the fertilization of a normal female gamete (egg) by a

normal male gamete (sperm).

Egg

Sperm

Correct Chromosome Number

Down’s Syndrome FertilizationDown’s Syndrome Fertilization Observe the fertilization of a abnormal female gamete (egg) by a

normal male gamete (sperm).

Egg

Sperm

Incorrect Chromosome Number

Normal vs. Abnormal ZygotesNormal vs. Abnormal Zygotes

The zygote (fertilized egg) with the correct number of chromosomes develops into a normal individual.

The zygote (fertilized egg) with the incorrect number of chromosomes develops into an individual with Down’s syndrome.

Correct Chromosome Number

Incorrect Chromosome Number

InformationInformation

Nondisjunction of a chromosome pair (usually number 21) during egg formation causes the egg to receive an extra chromosome.

The total chromosome number in victims of Down’s syndrome is usually 47 as opposed to 46 in most people.

About 0.2% of newborn children suffer from Down’s syndrome.

These children are mentally retarded and are highly susceptible to many diseases.

Other Types of Chromosomal Other Types of Chromosomal MutationsMutations

Sometimes chromosomes break and are altered. Let’s look at some common chromosome

alterations such as: Deletions Translocations Inversions

DeletionsDeletions When a chromosome breaks, a piece can be lost. This

form of alteration is a deletion. The genes in this deleted piece can be lost. In humans, one form of leukemia is associated with a

deletion in the white blood cells.

(Deleted)

TranslocationsTranslocations Sometimes part of a chromosome transfers to another chromosome

that is not homologous with it. This is a translocation. Translocations are found in parents who have many stillbirths, or in

children who have serious defects in development.

(End Product)

ReviewReview

Chromosome mutations often occur when an egg (female gamete) or a sperm (male gamete) is produced.

Nondisjunction, inversion, deletion and translocation can cause genetic disorders such as:

Stillbirth Sterility Leukemia

However, not all mutations result in genetic disease.

InversionsInversions An inversion is another common alteration. A portion of a

chromosome breaks out, and fuses back in its original position with its ends reversed.

Inversion can cause sterility or defects in the offspring of affected individuals.

(End Product)

Select The Best Matching Choice:Select The Best Matching Choice:

Answer Column:

A. Fertilized egg

B. Reversed segment

C. Down’s syndrome

D. Lost chromosome piece

E. Male gamete

F. Translocation

G. Meiosis

H. Female gamete

Nondisjunction:Correct Answer: C

Inversion:Correct Answer: B

Deletion:Correct Answer: D

Sperm:Correct Answer: E

Egg:Correct Answer: H

Zygote:Correct Answer: A

Changes In A Gene Can Cause Changes In A Gene Can Cause ProblemsProblems

Genes contain the genetic code for the production of specific enzymes.

Enzymes regulate chemical reactions in a cell. Each step in a chemical reaction requires the presence of a specific enzyme.

Chemical A

Chemical B

Chemical C

End Product

Enzyme A

Enzyme B

Enzyme C

Changes In A Gene Can Cause Changes In A Gene Can Cause ProblemsProblems

If an enzyme is missing, the reaction stops. For example, if Enzyme B is missing, Chemical B

cannot be converted into Chemical C.

Chemical A

Chemical BEnzyme A

No Enzyme BNo Chemical C

A Question…A Question…

What is the effect of missing Enzyme B?

A) Chemical A builds up in the body.

B) Chemical B builds up in the body.

C) Chemical C is converted to the end product.

D) End Product is produced in great amounts.

If Chemical B cannot be converted to Chemical C, then it remains in the cell. The reaction stops at Chemical B and no end product is produced.

Phenylketonuria (PKU)Phenylketonuria (PKU) Phenylketonuria (PKU) is an example of a disease caused by a

defective gene. The accumulation of phenylalanine (an amino acid) causes PKU. A gene controls the synthesis of an enzyme that converts

phenylalanine into tyrosine. Tyrosine is converted into skin and hair pigments as well as the

hormone thyroxin.

Phenylalanine TyrosineEnzyme

-Pigment-Thyroxin-Other Chemicals

PKUPKU PKU is caused by a defective gene that does not produce the

enzyme responsible for the conversion of phenylalanine to tyrosine. Phenylalanine builds up in the blood and damages the nervous

system. Phenylalanine eventually oxidizes to form phenylpyruvic acid. Phenylpyruvic acid is then excreted by the individual with PKU. Phenylpyruvic acid is not present in the blood of normal people.

Phenylalanine TyrosineEnzyme

-Pigment-Thyroxin-Other Chemicals

Phenylpyruvic Acid

Select The Best Matching Choice:Select The Best Matching Choice:

Answer Column:

A. Phenylalanine

B. Phenylketonuria

C. Regulates a reaction

D. Hormone

E. Codes, enzymes

F. End product

G. Gamete

H. Phenylpyruvic acid

Enzyme:Correct Answer: C

PKU:Correct Answer: B

Amino Acid:Correct Answer: A

Gene:Correct Answer: E

Thyroxin:Correct Answer: D

PKU Excretion:Correct Answer: H

Section FourSection Four

Noninfectious DiseasesNoninfectious Diseases

Noninfectious DiseasesNoninfectious Diseases

Noninfectious diseases are those that are not caused by pathogens.

These are some of the causes of noninfectious diseases: Genetic defects. Damage to the body. Poor or insufficient diet. Substances that promote allergic reactions. Congenital (birth) defects.

Noninfectious DiseasesNoninfectious Diseases The heart and the lungs are the sites frequently affected

by noninfectious diseases. Let’s remove a section of a heart to study some of these

diseases.

LungsLungs

The alveoli are sac-like structures, in the lungs, through which oxygen and carbon dioxide pass during respiration.

A person with emphysema, a respiratory disease, has a great deal of difficulty exchanging oxygen and carbon dioxide.

Emphysema is linked to cigarette smoking. Smoking causes the alveoli to break down and

the remaining walls to thicken.

AortaAorta

The aorta is the large artery that supplies blood to the body. It is composed of several layers of muscle and connective tissue.

Several diseases can weaken an arterial wall. This is called an aneurysm.

The aneurysm can suddenly burst, resulting in internal bleeding or death. An aneurysm in the brain can cause a stroke.

Heart ValveHeart Valve

The heart valves keep the blood flowing in one direction.

Rheumatic fever can produce abnormalities in the heart valves.

These abnormal valves can permit the backward flow of blood.

This can produce heart murmurs and insufficient blood flow to the head and the body.

SeptumSeptum

The septum separates the right side of the heart from the left side.

This prevents deoxygenated (oxygen-poor) blood from mixing with oxygenated (oxygen-rich) blood.

Some people have an opening in the septum. This can cause a condition in infants known as

“blue baby.” These infants have a blue color in their skin due

to a general lack of oxygen in their tissues. Blood in these infants, as in other people, is red.

Blood is never blue.

Heart WallsHeart Walls

The walls of the heart are composed of cardiac muscle cells.

A blocked artery leading to an area of the heart can cause the cells in that area of the heart to die.

This is called an infarct. As dead cells break down, a tough scar tissue

covers the area. This causes the remaining heart muscles to

work harder.

Coronary ArteryCoronary Artery

The coronary artery supplies the heart’s muscles with nutrients and oxygen.

A person with atherosclerosis has a reduced blood supply to the muscles of the heart due to plaque.

The build up of plaque is linked to saturated fats in the diet.

Clots can form on the plaque, break off and block a smaller artery in the heart.

This can cause a heart attack.

Quiz: Fill In The Blanks…Quiz: Fill In The Blanks…

Many noninfectious diseases attack the heart and the lungs. A disease that breaks down the alveoli in the lung is called ______________. The build up of plaque in the coronary artery is characteristic of the disease _______________. This condition may cause a heart attack. A weakened arterial wall that balloons outward produces a(n) ________________. Heart valves are also subject to disease. A leaking valve often produces a heart sound called a ______________.

emphysema

atherosclerosis

aneurysm

murmur

Section FiveSection Five

Testing Your KnowledgeTesting Your Knowledge

This Is A Test of What You Have This Is A Test of What You Have Learned…Learned…

There are 10 questions on this test. Try to correctly answer all of the questions. If you miss a question, watch the screen for

an explanation of the correct answer.

Select The Best Matching Select The Best Matching Choice:Choice:

Answer Column:

A. Forms plasma cells

B. Invades living cells

C. Causes emphysema

D. Produces antibodies

E. Causes dysentery

F. Causes trichinosis

G. Causes ringworm

H. Forms memory cells

Protozoa:Correct Answer: EProtozoa are responsible for causing dysentery. This is a disease that affects the large intestine. During excretion, victims of the disease pass large quantities of blood and mucus.

Virus:Correct Answer: BA virus invades a living cell in order to reproduce. Once in the cell, the viral nucleic acid directs the cell to create more viruses.

Select The Best Matching Select The Best Matching Choice:Choice:

Answer Column:

A. Forms plasma cells

B. Invades living cells

C. Causes emphysema

D. Produces antibodies

E. Causes dysentery

F. Causes trichinosis

G. Causes ringworm

H. Forms memory cells

Worm:Correct Answer: FA worm in poorly cooked meat causes trichinosis. The trichina (trichinosis worm) invades the victim’s muscles and uses them for food.

Fungus:Correct Answer: GA fungus causes the disease called ringworm. The fungus grows from a central point in an ever-expanding ring. There are no worms in ringworm.

Select The Best Choice To Select The Best Choice To Complete Each Analogy:Complete Each Analogy:

46 chromosomes are to most people as 47 chromosomes are to most victims of ___________________.

A. heart attacksB. PKUC. measlesD. tapewormE. Down’s syndrome

Down’s syndrome

Since most people have 46 chromosomes in their body cells, the best analogy is victim’s of Down’s syndrome, most of whom have 47 chromosomes in their body cells.

Select The Best Choice To Select The Best Choice To Complete Each Analogy:Complete Each Analogy:

Many alveoli are to healthy lungs as few alveoli are to lungs with _______________.

A. tapewormsB. emphysemaC. virusesD. bacteriaE. PKU

emphysema

Since healthy lungs have many alveoli, the best analogy is lungs with emphysema that have few alveoli. These alveoli also have thick walls that slow down gas exchange in the lung.

Fill In The Blanks…Fill In The Blanks…

There are many diseases that affect people. A pathogenic disease that can be passed from one person to another is called a(n) ____________ disease. The ability of an individual to resist such a disease is called ____________. A genetic disease is one that can be ____________ from a parent. Diseases that are not infectious, and therefore cannot be passed from one person to another, are called ______________ diseases.

infectious

immunityinherited

noninfectious

PathologyPathology~Diseases and Defenses~~Diseases and Defenses~