Biology of Health and Illness

The body’s first line of defence against pathogens uses mostly physical and chemical barriers such as sweat, skin, tears, mucus, stomach acid, and so on. Our skin and other membranes which line the body passages are fairly effective in keeping most pathogens out of the body. Mucus can trap pathogens, which are then washed away or destroyed by chemicals. Tears, sweat, and saliva have certain chemicals which can kill different pathogens. Bacterial spores and fungi are naturally present in the environment. The spores are so small they can only be seen by a microscope.

However, they play a large role in the decomposition of organic matter in the open, such as breaking down the components of fallen leaves or dead trees. However, when found indoors, bacterial spores pose a serious health risk. The type and harshness of the symptoms of inhaling bacteria are dependent on how much bacteria was inhaled or ingested, and they also vary based upon the person and the person’s sensitivities or allergies.

One of the most common symptoms of inhaling bacteria is experiencing allergic reactions. These symptoms bear a resemblance to those of hay fever; they include sneezing, runny nose and watery eyes that appear red.

You may also experience skin rashes, nasal congestive, and sensitivity to light, headaches, and tiredness. People with asthma problems are highly susceptible to attacks which include wheezing, tightening of the chest and difficulty in breathing. People who have weakened immune systems are more vulnerable to infections caused by the inhalation of bacteria. They attack the eyes, skin and lungs. The first line of defence helps the body’s defence system stop most of the bacterial spores and fungi be inhaled by using the nasal hair and mucus. If microbes get past your first line of defence, it is up to the second line

of defence, your immune system, to keep you from getting sick. The immune system is made up of lots of different cells that are always patrolling your body and fighting any bad microbes they find. Your body is exposed to many different types of microbes every day, so your immune system is always working. When you get a cut or scrape, immediately bacteria and germs try to get into your body. This is when the immune system takes over. The immune system is made of various cells and proteins. The complement system is the first area that meets antigens, or foreign invaders, and takes action.

It is made up of phagocytes and lymphocytes. Phagocytes are responsible for finding and eliminating bacteria and viruses. The three main types are granulocytes, macrophages and dendritic cells. Lymphocytes are white blood cells. The two main cells for the lymphatic system are T cells and B cells. The first thing that happens when you get a cut is granulocytes, macrophages and dendritic cells, or phagocytes, devour the bacteria and viruses. Both the macrophages and dendritic cells activate one kind of T cells, the helper T cells, by presenting the antigen. Meanwhile, B cells find certain antigens that they are specialised for.

The helper T cell then activates the B cells, which causes the B cell to divide into a plasma cell and a memory cell. The plasma cell is able to send out antibodies that attach to the foreign invader. Although the phagocytes are able to destroy antigens without antibodies, they prefer those with antibodies. The antibodies cause the phagocytes to eliminate more at the time. The memory cell later remembers that antigen, so if it invades again, the immune system is able to attack it quicker. Pathogens contain certain chemicals that are foreign to the body and are called antigens.

White blood cells called lymphocytes carry a specific type of antibody – a protein that has a chemical ‘fit’ to a certain antigen. When a lymphocyte with the appropriate antibody meets a dangerous foreign body (pathogen containing antigen), the lymphocyte reproduces quickly, and makes many copies of the antibody that neutralises the pathogen. Antibodies neutralise pathogens in a number of ways: They bind to pathogens and damage or destroy them. They coat pathogens, clumping them together so that they are easily ingested by phagocytes and they bind to the pathogens and release chemical signals to attract more phagocytes.

TASK 2 Aids (Acquired Immunodeficiency Syndrome), is named HIV (Human Immunodeficiency Virus). Aids is the condition whereby the body’s specific defence system against all infectious agents no longer functions properly. There is a focused loss over time of immune cell function which allows intrusion by several different infectious agents, the result of which is loss of the ability of the body to fight infection and the subsequent acquisition of diseases such as pneumonia.

HIV damages the body’s immune system and makes it susceptible to infections and certain types of cancers. A single HIV viral particle is called virion. The viron is surrounded by the viral envelope which contains the proteins gp120 and gp41. The matrix lies below the viral envelope. The capsid is the viral core and houses HIVs genetic material (RNA) and the enzymes required for viral replication. HIV is a retrovirus; therefore it is capable of copying RNA into DNA. The enzymes required for HIV viral replication are reverse transcriptase, integrase and protease.

The major steps in the HIV infection and replication cycle are attachment, entry, reverse transcription, integration, protein processing and maturation. Gp 120 is a protein present on the viral envelope. This protein binds to the CD4 receptor that is present on T-helper cells. Once the virus enters the T-helper cell, it is uncoated and the viral RNA undergoes reverse transcription to become proviral DNA. This DNA is transported into the T cell nucleus. The HIV integrase enzyme then incorporates the proviral DNA into the T-helper cell genome.

When the provirus is activated, HIV viral polyproteins are expressed using the T-helper cell machinery. Polyproteins are cleaved by the HIV protease enzyme and the virion buds from the host cell. The budding process destroys the T cell. The T cell can also be destroyed when the virus overwhelms the host T cell machinery. Mature viral particles go on to infect more cells. k TASK 4 The main function of the respiratory system is gaseous exchange. This refers to the process of Oxygen and Carbon Dioxide moving between the lungs and blood.

Diffusion occurs when molecules move from an area of high concentration (of that molecule) to an area of low concentration. This occurs during gaseous exchange as the blood in the capillaries surrounding the alveoli has a lower oxygen concentration of Oxygen than the air in the alveoli which has just been inhaled. Both alveoli and capillaries have walls which are only one cell thick and allow gases to diffuse across them. The same happens with Carbon Dioxide (CO2). The blood in the surrounding capillaries has a higher concentration of CO2 than the inspired air due to it being a waste product of energy production.

Therefore CO2 diffuses the other way, from the capillaries, into the alveoli where it can then be exhaled. The air we breathe contains approximately 21% Oxygen and 0. 04% Carbon Dioxide. When we exhale there is approximately 17% Oxygen and 3% Carbon Dioxide. This shows a decrease in Oxygen levels (as it is used in producing energy) and an increase in Carbon Dioxide due to it being a waste product of energy production. TASK 5 Three factors which affect the normal functioning of the respiratory system are airborne infections, physical injury and lifestyle choices. Airborne infections.

Airborne particles are a major cause of respiratory ailments of humans, causing allergies, asthma, and pathogenic infections of the respiratory tract. During a sneeze, millions of tiny droplets of water and mucus are expelled. The droplets contain virus particles or bacteria. This is a major means of transmission of several diseases of humans. Some important diseases of humans transmitted from person to person by inhaled airborne particles are chicken pox, influenza and measles these are viral diseases and some bacterial diseases are whooping cough, meningitis and tuberculosis (TB).

Some other diseases are acquired by inhaling particles from environmental sources, not directly from an infected person. Some of these are Psittacosis which is a serious disease acquired by handling birds or by inhaling dust from bird faeces. Legionnaire’s disease which is a fairly common form of pneumonia in older people, this is acquired by droplets from air-conditioning systems, water storage tanks, etc. , where the bacterium grows. Physical injury A rib fracture is a break or fracture in one or more of the bones making up the rib cage.

The middle ribs are the ones most commonly fractured. Fractures usually occur from direct blows or from indirect crushing injuries. The weakest part of a rib is just anterior to its angle, but a fracture can occur anywhere. The most commonly fractured ribs are the 7th and 10th. A lower rib fracture has the complication of potentially injuring the diaphragm, which could result in a diaphragmatic hernia. Rib fractures are usually quite painful because the ribs have to move to allow for breathing. Even a small crack can inflame a tendon.

When several ribs are broken in several places a flail chest results, and the detached bone sections will move separately from the rest of the chest. Rib fractures can occur without direct trauma for example after sustained coughing and in various sports – for example, rowing and golf – often in athletes. They can also occur as a consequence of diseases such as cancer or infections which is called pathological fracture. In extreme cases such as a car crash a broken rib could puncture the lung in this condition, the lung collapses after minimal or no trauma.

Lifestyle choices Cigarette smoke harms the respiratory system through two means: the smoke and the tar. Throat inflammation – The hot smoke has the tendency to irritate the tender linings of the nasal and tracheal passage. Cilia clogging – The presence of 4000 harmful chemicals produced by the combustion of tobacco leads to the clogging of the hair like cilia along the nasal passage and trachea. Such a clogging causes the cilia to lose its fluidity; it’s found that one cigarette can slow down the motion of cilia for 20 minutes.

Mucus congestion – When the cilia slow down, the mucus is not passed along and gets clogged up along the trachea. The common symptoms of “smoker’s cough” are produced due to excessive mucus clogging which the body tries to remove by inducing irritation along the throat causing cough and Carcinogenic deposits – Tar is highly sticky substance and it tends to gel along the nasal and tracheal passage causing damage to the cilia. Moreover the tar sticks to the tender surface of the alveoli reducing its surface contact with blood vessels.

Continued accumulation of tar leads to the onset of cancer in the lungs, preceded by problems like chronic bronchitis or emphysema. Bibliography Beltina, 2011, Bronchus [online], visited on 29/11/11, Beltna. org, available at http www. beltina. org/health-dictionary/bronchus-definition—function. html The free dictionary, 2010, The free medical dictionary [online], visited on 20/11/11, medical dictionary, available at http://medical-ictionary. thefreedictionary. com/air=sac