Immunity System

 Pathogens

Pathogens are biological agent or viruses that cause a disease. Pathogens are for example,

• viruses
• bacteria
• protists
• worms    etc

Against these pathogens, immune system can senses foreign particles + cells and they guard the body through blood and tissues.
Differences between bacteria and viruses are presence of cell. Bacteria has cells so they are alive but viruses are not.

this is virus of influenza

Viruses and their work
Viruses are small infectious agents which replicate only inside the host cells. When they are found outside of host cells, they exist as a protein coat or capsid. Most of them are really small so we cannot see without a microscope. They were found by Friedrich Loeffler and Paul Frosch in 1898. The evidence was that the cause of foot-and-mouth disease in livestock was an infectious particle smaller than any bacteria.

How to work?

1. Viruses' genome which exists in them enters inside the host cell
2. Genome is replicated and transcribed
3. Viral mRNAs are formed and proteins processed
4. Particles assemble inside the host cell, and they go out

Bacteria
Bacteria are large domain single-cell that are prokaryote microorganisms(metabolism and cell wall). They can grow up in  soil, acidic hot spring, radioactive waste, water and deep in the Earth's crust. There are more than one million of kind of bacteria on the earth. However, only one thousand of them were found.

Antibiotics and their works

Antibiotics are substances that defend against metabolic pathways that are found in bacteria, and cure infections. Antibiotics are selective poison. It has been chosen so that it will kill the desire bacteria, but not the cell in our body. There are different type of antibiotic and each of them affects different type of bacteria in different ways. However, antibiotics don't work for viruses since they don't have a metabolism which is affected by antibiotics, they are not blocked by them.


antibiotic destroy only cell wall so it doesn't break human cells



Defense system of the body
First step
The goal is to stop pathogens from entering the body. Our body has some ways that make pathogens to get in the body.

• Skin: Skin have layers that are epidermis and dermis. Epidermis are dead layer superficial and contain keratin that is impermeable as protecting cells. Dermis are thicker than epidermis and contain cells, glands, hairs, capillaries, sensory receptors. Also skin contain acidic environment and keep bacteria from growing. On our skin, there are already some bacteria which we are used to it and have no harm and they prevent other bacterias from working.
• Mucus: Some pathogens enter through air that we breathe. So the respiratory paths have mucous membrane. Cells of mucous membranes create and secrete a lining of sticky mucus. Mucus trap pathogens that are coming into the body, so pathogens cannot reach the cell that would be infected. Mucus locate at trachea, nasal passages, urethra, and vagina.
• Stomach Acid: Some pathogens enter into the body through food and water. So the acidic environment in stomach can kill these pathogens.

Second step
This is for the pathogens that once go inside the body. There are phagocytosis to deal with them.

• Leucocytes: Leucocytes also white blood cells can fight with pathogens that are  already in our body. One type of them is macrophage that works early in the process of fighting with pathogens. They are big white blood cells, and they can change their shape to surround pathogens and take it in through the process of phagocytosis. A macrophage meets a cell and recognizes whether it is a part of the body (self) or not(not-self) based on the protein molecules. If a macrophage meets self cells, they are left alone, and if it meets not-self cells, they are engulfed. Many phagocytes contain lysosome organelles, so they can help digestion chemically.
• Antigen: It is something strange for our body and causes anti-body formation.
• Anti-body: It is protein that recognize and defense antigen.

How to produce antibodies?
After macrophage destroy pathogens by lysosome with enzyme, some pieces of pathogens called antigens remain on the surface of macrophage.

1. Macrophage present antigen to lymphocyte T(T cell).
2. T cells bind to antigens and T calls are activated.
3. T cells present antigens to B cells.
4. B cells are activated and produce anti-bodies. They are specific to each antigens.
5. Anti- bodies stick to antigens and defense their functions.




right virus is with anti-bodies

  Antigens are molecles that are found in cell, and can be found in pathogen. They are anything that are strange for the body.








HIV and Its Issue
HIV(Human Immunodeficiency Virus) is a virus that causes AIDS(acquired immunodeficiency syndrome). AIDS is an illness which is disorder of immunity systemin in the human body. HIV is caused by the transfer of blood, semen, vaginal lubrication, and mother's milk.

Some Issues Related to AIDS
Issues are social discrimination, the expensive of drug treatment, and so on. So some people cannot get job only because they have AIDS, and there are many orphanned children. The cost for treatment of AIDS is expensive such as medicine, so not all patients can take good health cares.

Transport System

Blood
There are some components in our blood, such as plasma, erythrocytes(red blood cell), leukocytes(white blood cell), and platelets.



job of red blood cell

 

• erythrocytes: produced in bone marrow and transport O₂and CO₂
• leukocytes: produced in bone marrow and have a role of defense against bacteria or foreign body substance by phagocytosis
• platelets: help blood clotting
• plasma: contain water, salts, plasma proteins, and transport nutrients, urea, gases(CO₂and O₂), hormones, and heat

 

job of white blood cell



Human Heart
Our heart has two sides with different functions. Right side is for receiving blood and pumping it to the lungs, and left side is for receiving blood and pumping it to around the body. Moreover, each side has two chambers that are atrium and ventricle.

• Right atrium: It is connected to superior vena cava and inferior vena cava, and blood with carbon dioxide enters.
• Right ventricle: Blood is collected in right ventricle with carbon dioxide. And it is connected to pulmonoary artery and blood goes to lung.
• Left atrium: Blood from lung enters with oxygen.
• Left ventricle: Blood is collected in here with oxygen and it is pumped to around the body through the arteries.

Since right side and left side have different jobs, the structures are a little bit diffrent each other. Left side has to pump blood around the body, so it has thick muscle and it is hard. On the other hand, right side has thin mucle and soft.

Blood Vessels

There are three types of blood vessles in our body.

• Arteries: It carries blood with a lot of oxygen to the body. So the pressure inside the arteries is really high. To endure the high pressure, they have thick wall, and elastic fibers, and they have outer fibrous coats to prevent arteries from rupturing. Also they have lumen small to maintain high pressure.
• Veins: It carries blood with carbon dioxide to lung. The pressure inside the veins is lower than arteries. So they have thin wall, more collagen, and small muscle. And they have lumen large to facilitate blood flow.
• Capillaries: They are thinner and smaller than arteries and veins. To do fast exchange, they have pores and wall is one cell thick.

Flow of Blood

1. Blood is carried through superior/inferior vena cava to right atrium. When blood is collected and pressure increases enough, atrio-venticular valve opens and blood can enters to right ventricle.
2. Blood is collected in right ventricle. When the pressure inside ventricle increases, semi-lunar valve opens and blood is pumped to lung through pulmonary artery.
3. Blood comes to left atrium from lung with oxygen through pulmonary veins. When pressure becomes high, atrio-ventricular valve opens.
4. In left ventricle, blood is collected. After pressure increaases, the semi-lunar valve opens. And blood can be carried to the body through aorta.

Heart Beat
Heart is made up cardiac muscle, and this muscle contracts and relaxes spontaneously. This is known as myogenic contraction.

1. Sino-Atrial node(SA node) generates electrical impulse frequency.
2. That impulse goes to both atria and atria contract together.
3. Atrio-Ventricular node(AV node) picks up that impulse and conduces to ventricles through fibers.
4. Ventricle contracts.

Also during exercise, we can feel that our hearts move faster than usual. It is because when we are doing exercise, cell metabolism produces more CO2, and that CO2 is dissolved in blood as forming H2CO3 that makes blood pH lower. So the receptors in the brain perceivedecreasing of the pH in the blood and send signals to increase hertbeat.

Coronary Heart Disease

This is a disease that cardiac muscle cannot get enough blood. Inside coronary arteries, lipid and cholesterol(plaque) are built up. So arteries become harder and less flexible and the spaces for blood to pass become narrow. This disease is cased by many factors. Forexample, age, gender, cholesterol levels, smooking, stress, and so on. The researcher said that stoping smoking can dcrease risk of coronary heart diesase effectively.

Dissection of pig heart!
In a class, we dissected pig's heart with scissors and knife. The heart had a lot of fats, and we could see blood vessels. We cut the heart from top to bottom. We saw that muscle on the left side of heart was bigger and thicker and riht side was small. Also left side was much harder than right side.