first two lines of defense

chemical barriers

In addition to mucus, your body releases a variety of fluids, including tears, saliva, and sweat. These fluids contain enzymes called lysozymes. Lysozymes break down the cell walls of bacteria and kill them. Your stomach contains a very strong acid, called hydrochloric acid. This acid kills most pathogens that enter the stomach in food or water. Urine is also acidic, so few pathogens are able to grow in it.

physical barriers

The skin is a very important barrier to pathogens. It is the bodys largest organ and the most important defense against disease. It forms a physical barrier between the body and the outside environment. The outer layer of the skin, called the epidermis, consists of dead cells filled with the protein keratin. These cells form a tough, waterproof covering on the body. It is very difficult for pathogens to get through the epidermis. The inside of the mouth and nose are lined with mucous membranes. Other organs that are exposed to substances from the environment are also lined with mucous membranes. These include the respiratory and digestive organs. Mucous membranes arent tough like skin, but they have other ways of keeping out pathogens. One way mucous membranes protect the body is by producing mucus. Mucus is a sticky, moist secretion that covers mucous membranes. The mucus traps pathogens and particles so they cant enter the body. Many mucous membranes are also covered with cilia. These are tiny, hair-like projections. Cilia move in waves and sweep mucus and trapped pathogens toward body openings. You can see this in the diagram in Figure 21.10. When you clear your throat or blow your nose, you remove mucus and pathogens from your body.

textbook_image

first line of defense

Your bodys first line of defense is like a castles moat and walls. It keeps most pathogens out of your body. The first line of defense includes physical, chemical, and biological barriers.

phagocytosis

The white blood cells that go to a site of inflammation and leak into damaged tissue are called phagocytes. They start eating pathogens and dead cells by engulfing and destroying them. This process is called phagocytosis. You can see how it happens in Figure ??. You can see it in action in the animation at this link: http://commons.wikim

textbook_image

inflammation

If bacteria enter the skin through a splinter or other wound, the area may become red, warm, and painful. These are signs of inflammation. Inflammation is one way the body reacts to infections or injuries. It occurs due to chemicals that are released when tissue is damaged. The chemicals cause nearby blood vessels to dilate, increasing blood flow to the area. The chemicals also attract white blood cells to the area. The white blood cells leak out of the blood vessels and into the damaged tissue. You can see an animation of the inflammatory response by watching this video: MEDIA Click image to the left or use the URL below. URL:

second line of defense

Did you ever get a splinter in your skin, like the one in Figure 21.11? It doesnt look like a serious injury, but even a tiny break in the skin may let pathogens enter the body. If bacteria enter through the break, for example, they could cause an infection. These bacteria would then face the bodys second line of defense.

textbook_image

biological barriers

Your skin is covered by millions of bacteria. Millions more live inside your body, mainly in your gastrointestinal tract. Most of these bacteria are helpful. For one thing, they help defend your body from pathogens. They do it by competing with harmful bacteria for food and space. They prevent the harmful bacteria from multiplying and making you sick.

fever

Phagocytes also release chemicals that cause a fever. A fever is a higher-than-normal body temperature. Normal human body temperature is 98.6 F (37 C). Most bacteria and viruses that infect people reproduce quickly at this temperature. When the temperature rises higher, the pathogens cant reproduce as quickly. Therefore, a fever helps to limit the infection. A fever also causes the immune system to make more white blood cells to fight the infection.

instructional diagrams

description_image

The diagram shows the process of phagocytosis in a phagocyte cell. Phagocytes are cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells. Phagocytosis is the process of taking in particles such as bacteria, parasites, dead host cells, and cellular and foreign debris by a cell. From the diagram, attachment first occurs after the bacteria is bound to molecules called receptors that are on the surface of the phagocyte. Ingestion then takes place as the phagocyte then stretches itself around the bacterium and engulfs it. Once inside the phagocyte, the bacterium is trapped in a compartment called a phagosome. Within one minute the phagosome merges with a lysosome with digestive enzymes to form a phagolysosome. The bacterium is then subjected to an overwhelming array of killing mechanisms and is digested and discharged from the cell.

description_image

This diagram shows the process called Phagocytosis. Through this process, our defense system fights bacteria and destroys them keeping them out of our system. An amoeba is a type of cell or organism which has the ability to alter its shape, primarily by extending and retracting pseudopods. Once the white blood cells detect any inflammation, they go to where damaged tissue is located and eat pathogens and dead cells by engulfing and destroying them. In order to do this, bacteria is digested and nutrients are absorbed and the waste products are expulsed out by the amoeba.

questions

Biological barriers to pathogens are

a. responses such as inflammation.

b. the skin and mucous membranes.

c. chemicals such as hydrochloric acid.

-->  d. bacteria that live in or on the human body.

It is very difficult for pathogens to penetrate the epidermis.

-->  a. true

b. false

Mucous membranes keep out pathogens because they are as tough as skin.

a. true

-->  b. false

Your bodys first line of defense against pathogens includes

-->  a. three types of barriers.

b. white blood cells called phagocytes.

c. a higher-than-normal body temperature.

d. all of the above

Few pathogens are able to grow in urine because it is too

a. basic.

b. warm.

-->  c. acidi

d. two of the above

Helpful bacteria defend your body from pathogens by competing with them for food and space.

-->  a. true

b. false

Your bodys first line of defense against pathogens includes phagocytosis and fever.

a. true

-->  b. false

What causes inflammation in damaged tissue?

-->  a. chemicals released when tissue is damaged

b. constriction of blood vessels near damaged tissue

c. development of a fever in damaged tissue

d. phagocytosis of damaged tissue

You develop a fever because of chemicals released by phagocytes.

-->  a. true

b. false

How do phagocytes help fight an infection?

a. They engulf and destroy pathogens.

b. They release chemicals that cause a fever.

c. They are a physical barrier to pathogens.

-->  d. two of the above

Physical barriers to infection include mucus and cilia.

-->  a. true

b. false

Inflammation reduces blood flow to an area of infection or injury.

a. true

-->  b. false

Type of barriers that make up your bodys first line of defense include

a. physical barriers.

b. chemical barriers.

c. biological barriers.

-->  d. all of the above

Most pathogens cannot survive in the stomach because it is too

a. wet.

b. warm.

-->  c. acidi

d. all of the above

Body fluids that contain lysozymes include

a. tears.

b. sweat.

c. saliva.

-->  d. all of the above

Inflammation occurs due to chemicals released by

a. invading bacteri

b. red blood cells.

-->  c. damaged tissues.

d. bone marrow.

The bodys second line of defense includes the production of mucus.

a. true

-->  b. false

Saliva and tears contain enzymes that can kill bacteria.

-->  a. true

b. false

Inflammation causes white blood cells to

-->  a. leak out of blood vessels.

b. lower the bodys temperature.

c. excrete wastes from the body.

d. become damaged and die.

Damaged tissue becomes red and warm because of increased blood flow to the area.

-->  a. true

b. false

Results of a fever include

-->  a. the immune system making more white blood cells.

b. bacteria reproducing so quickly they die of crowding.

c. cilia becoming more active so they remove pathogens more quickly.

d. two of the above

The normal temperature of the human body is about

a. 95.8 F.

b. 96.6 F.

-->  c. 98.6 F.

d. 100.8 F.

Phagocytes kill pathogens only if the pathogens are circulating in the blood.

a. true

-->  b. false

A fever is a sign that your body is losing its fight against an infection.

a. true

-->  b. false

__sticky secretion that traps pathogens on mucous membranes

a. lysozyme

b. hydrochloric acid

-->  c. mucus

d. inflammation

e. phagocytosis

f. skin

g. cilia

__process in which white blood cells engulf and destroy pathogens

a. lysozyme

b. hydrochloric acid

c. mucus

d. inflammation

-->  e. phagocytosis

f. skin

g. cilia

__organ that is the bodys most important barrier to pathogens

a. lysozyme

b. hydrochloric acid

c. mucus

d. inflammation

e. phagocytosis

-->  f. skin

g. cilia

__tiny, hair-like projections that cover many mucous membranes

a. lysozyme

b. hydrochloric acid

c. mucus

d. inflammation

e. phagocytosis

f. skin

-->  g. cilia

__chemical in the stomach that kills most pathogens in food or water

a. lysozyme

-->  b. hydrochloric acid

c. mucus

d. inflammation

e. phagocytosis

f. skin

g. cilia

__reaction to infection that causes redness, warmth, and pain

a. lysozyme

b. hydrochloric acid

c. mucus

-->  d. inflammation

e. phagocytosis

f. skin

g. cilia

__enzyme that breaks down the cell walls of bacteria

-->  a. lysozyme

b. hydrochloric acid

c. mucus

d. inflammation

e. phagocytosis

f. skin

g. cilia

diagram questions

question_image

What happens after the phagocyte consumes a foreign particle?

-->  a. A phagosome is formed.

b. It adheres to the microbe.

c. It is digested.

d. Waste material is discharged.

question_image

In the process of phagocytosis, what organelle fuses with the phagosome after a microbe has been ingested by the cell?

-->  a. Lysosome

b. Phagolysosome

c. Lysozyme

d. Pseudopod

question_image

What happens before ingestion of the microbe?

a. Discharge of waste materials

b. Formation of a phagosome

-->  c. Chemotaxis and adherence of microbe to phagocyte

d. Microbe passes through the plasma membrane

question_image

How many steps are there in phagocytosis?

a. 6

b. 8

-->  c. 7

d. 5

question_image

How many steps in the process of phagocytosis involve a phagolysosome?

a. 7

-->  b. 2

c. 5

d. 1

question_image

In the process of phagocytosis, what happens after the phagosome is formed?

a. Digestion

-->  b. Fusion of the phagosome with a lysosome to form a phagolysosome

c. Chemotaxis

d. Discharge of waste

question_image

What is needed to form a phagolysosome?

-->  a. Digestive enzymes

b. Residual body

c. Cytoplasm

d. Particles

question_image

What is the name of the process where a Phagocyte engulfs and destroys bacteria?

a. Ingestion

-->  b. Phagocytosis

c. Chemotaxis

d. Adherence

question_image

What process does the lysosome undergo after ingestion?

-->  a. Digestion

b. Chemotaxis

c. Adherence

d. Killing

question_image

Which organelle fuses with the pseudopod to digest the microbe?

a. Nucleus

b. Mitochondria

-->  c. Lysosome

d. Vacuole

question_image

How many phases comprise phagocytosis?

-->  a. 3

b. 6

c. 5

d. 4

question_image

How many phases of Phagocytosis are shown in the diagram?

a. 4

b. 6

-->  c. 5

d. 3

question_image

What is the phase after ingestion?

a. Chemotaxis

b. Adherence

c. Killing

-->  d. Digestion

question_image

Would the organism be digested if lysosomes are absent?

a. Data Insufficient

b. Yes

-->  c. No

d. Not sure

question_image

What is the first step in the process of phagocytosis?

a. Formation

b. Recycling

c. Delivery

-->  d. Detection

question_image

Which part breaks down cell walls and kills bacteria?

a. cell membrane

b. phagosome

c. nucleus

-->  d. lysosome

question_image

What happens after detection?

a. Delivery to lysosome

b. Digestion

-->  c. Phagosome formation

d. Small molecules recycled

question_image

What is the responsible for the recirculation of small invasor molecules?

a. Lysosome

b. Immune System

-->  c. Phagosome

d. Blood

question_image

How many processes are there in phagocytosis?

a. 5

-->  b. 4

c. 6

d. 3

question_image

How many stages are in phagocytosis?

a. 5

-->  b. 4

c. 2

d. 3

question_image

What is the next step after detection?

-->  a. Phagosome formation.

b. Delivery to lysosome and digestion.

c. Prevention.

d. Small molecules recycled.

question_image

In phagocytosis, what happens after the microbes are engulfed into cell?

a. Pseudopodia surround microbes.

b. Vacuole and lysosome fuse.

-->  c. Vacuole containing microbes forms.

d. Microbial debris is released by exocytosis.

question_image

What surrounds microbes at the beginning of the process?

-->  a. Pseudopodia

b. Lysosome

c. Enzymes

d. Vacuole

question_image

How many microbes are shown in the image?

a. 4

b. 5

-->  c. 8

d. 6

question_image

What happens after pseudopodia surround microbes?

a. Vacuole containing microbes forms.

-->  b. Microbes are engulfed into cell.

c. Toxic compounds and lysosomal enzymes destroy microbes.

d. Vacuole and lysosome fuse.

question_image

Identify the organelle that contains digestive enzymes that is involved in digestion and waste removal.

a. PAMPs

-->  b. Lysosome

c. Primary Granule

d. Phagosome

question_image

What stage shows the phagocyte expelling waste after destroying bacteria?

a. 3

-->  b. 5

c. 2

d. 1

question_image

How many stages are depicted in the diagram?

-->  a. 5

b. 9

c. 8

d. 1

question_image

How many phases are in the process of phagocytosis?

a. 3

b. 6

c. 4

-->  d. 5

question_image

From the diagram, what happens after bacterium is engulfed?

a. White cell moves towards bacterium

b. Waste products expelled

-->  c. Bacterium is digested

d. Waste products left

question_image

Describe how many steps there are in phagocytosis.

a. 3

b. 4

c. 8

-->  d. 5

question_image

How many phases are there in this diagram?

a. 4

-->  b. 5

c. 3

d. 6

question_image

On which step does the white cell move towards bacterium?

-->  a. first

b. second

c. third

d. fourth

question_image

What happens after a bacterium is engulfed by a white cell?

-->  a. bacterium is digested

b. bacterium takes over white cell

c. white cell moves away from bacterium

d. waste products are expelled

question_image

How many pseudopodia?

a. 6

b. 1

-->  c. 2

d. 4

question_image

Which part of the cell grabs the bacterium?

-->  a. Receptors

b. Phagosome

c. Lysosome

d. Phagolysosomes

question_image

What is an organelle in the cytoplasm of eukaryotic cells containing degradative enzymes enclosed in a membrane?

a. Receptors

b. Phagocytosis

-->  c. Lysosome

d. Phagosome

question_image

What happens to bacteria at the receptors?

-->  a. Phagosome is formed

b. Soluble debris are formed

c. Phagolysosomes are formed

d. Lysosomes are formed

question_image

What break down the cell walls of bacteria and kills them?

a. phagosome

-->  b. lysosome

c. receptors

d. phagocytosis

question_image

Which part ingests the bacterium?

-->  a. receptors

b. soluble debris

c. lysosome

d. cell wall

question_image

What is step 2 in the stages of phagocytosis?

a. Killing

b. Degradation

c. Attachment

-->  d. Ingestion

question_image

In what stage of phagocytosis do bacterium attach to the phagocyte?

a. Ingestion

b. Killing

-->  c. Attachment

d. Degradation

question_image

What is the fourth stage in the phagocytosis?

a. attachment

b. ingestion

c. killing

-->  d. degradation

question_image

What stage of phagocytosis comes after attachment?

a. killing

b. digestion

c. degradation

-->  d. ingestion

question_image

How many stages does phagocytosis have?

a. 5

-->  b. 4

c. 6

d. 3

question_image

How many stages of the phagocytosis are there?

a. 3

b. 5

-->  c. 4

d. 6

question_image

What do we call Phagocytosis?

a. Mucus

-->  b. a phagocyte engulfs bacteria, destroys them with chemicals, and excretes the wastes.

c. Fever

d. Digestion

question_image

What contains the digestive enzymes?

a. pseudopod

-->  b. Lysosome

c. food vacuole

d. exocytic vesicle

question_image

In phagocytosis, which part of the cell contains the digestive enzymes?

a. Pseudopods

b. Food vacuole

-->  c. Lysosome

d. Exocytic vesicle

question_image

How many food particles are shown in the diagram?

a. 3

b. 2

-->  c. 4

d. 1

question_image

How many pseudopods does the cell in the diagram have?

-->  a. 8

b. 6

c. 5

d. 7

question_image

What are temporary cytoplasm filled projections of eukaryotic cell membranes or unicellular protists?

-->  a. Pseudopods

b. Food Particle

c. Food Vacuole

d. Phagocytosis

question_image

Which direction does the white cell move?

a. away from bacterium

b. doesn't move

-->  c. toward bacterium

d. expelled