Justines Asthma pages

The main purpose of breathing is to supply the body with enough oxygen and to remove access amounts of carbon dioxide. Respiration can be examined at two levels, one large and one small. At the lung or large level, respiration brings about gas exchange by breathing. At the cellular or small level, oxygen transforms the food we eat into energy, producing carbon dioxide as one by-product. The focus here first off all is on the lung level. This is because you really cannot understand what asthma is, unless you have a basic understanding of the respiratory system. 

The nose is not simply the passage way to our throats. With in the scull, it is an extensive array of passages with inner walls covered by a sticky layer of mucus.The walls are richly supplied with heat-radiating blood vessals. The nose is like an air-conditioner. It prepares or conditions the air for the lungs. When you breath through your nose the air is:

  Warmed by the blood vessels, so it is at the right temperature when it reaches   the bottom of the throat (the lungs have a strong adversion to cold air)

  Filtered - dust particals are trapped by tiny wee hairs and mucus in the nose (which then travels to the throat to be swallowed) Yip.

  Humidified - the air is 100% humidified by the mucus in the nose.

This treated air passes down the throat, and into the trachea. The airways are built like an upside down tree, with the trunk (trachea) branching out into a series of medium sized branches (bronchi) that seperate into smaller branches (bronchioles). The trachea, bronchi and bronchioles are collectively know as the airways and thet are wrapped in a layer of smooth muscle.

The inner lining of the bronchial tube is a delicate membrane called the bronchial mucosa. During an asthma attack, this membrane becomes swollen and imflamed. Wrapped around the walls of the bronchial tubes is a layer of smooth muscle, which is capable of contracting, producing airway narrowing or bronchoconstriction. Mucus glands located within the layers of the bronchial linning (still with it ) can produce large quantities of extremley thick mucus when stimulated. (YIP).

At the end of the smallest bronchioles and at the edge of the lungs are millions of air sacs or alveoli. Think of these air sacs surrounding the bronchioles as a bunch of grapes hanging off a stem. The walls of your alveoli are only one cell thick. This combined with the moist atmosphere of the lungs allows oxygen and carbon dioxide molecules to pass through. Outside the lungs and surrounding the air sacs is a network of capillaries, which also have walls one cell thick. the alveoli contain air rich in oxygen and low in carbon dioxide. The blood in the capillaries contains less oxygen but more carbon dioxide. Gas always tries to equalise pressure levels and so oxygen passes from the alveoli into the capillaries. Simultaneously carbon dioxide passes from the blood into the alveoli. The blood now leaves the alveoli oxygen-rich and the excess carbon dioxide is breathed out. This is gas exchange at the large (lung) level. Oxygen combines with haemoglobin and travels from the lungs to the heart. Now with haemoglobin full of oxygen, the blood is pumped around the body,supplying oxygen to the cells and tissue.

Gas exchange at the smaller or cellular level is the reverse of that of the large (lung) level. Tissue cells have high levels of carbon dioxide and low levels of oxygen. In the tiny blood vessels running past the tissue, oxygen are high and carbon dioxide levels are low. Both the cell walls and the capillary walls are one cell thick and so gases move from one to the other equalising the pressure. The tissue cells to make energy use oxygen. As a result, carbon dioxide and water are produced. They pass from the cell to the bloodstream and oxygen moves in to produce more energy. The gas exchange cycle repeats it's self continuously (more than 60 times a minute) at both the large and small levels.

The respiratory centre in the brainstem is responsible for controlling your breathing rate. It sends a message to your respiratory muscles telling them when to breathe. This control is automatic and continuous. You do not have to consciously think about it. However, this control can be influenced by emotions, talking and calculated thoughts such as when you dive into a swimming pool.

It know's how to control the breathing rate by the amount of carbon dioxide in the anterior blood. For example when you exercise, carbon dioide levels increase which excite the respiratory centre. It strengthens the signal- stimulating the breathing. Responding to this stronger signal, the respiratory muscles increase both the speed and depth of breathing. The increased respiration gets rid of the bodys excess carbon dioxide and supplies the body with more oxygen, which is needed when you exercise. When the level of carbon dioxide in the anterior blood returns to normal levels and the respiratory centre is no longer stimulated and the breathing becomes quiet and relaxed. Carbon dioxide acts as a marker. When carbon dioxide levels reach a certain point, the respiratory centre in our brains sends a message to the muscles used for the breathing to take in more air.