Other respiratory parts include the trachea, and the hyaline cartilage. The lungs is one of the major respiratory organ containing the bronchus which are divided repeatedly into smaller branches known as bronchi which in turn form numerous bronchioles of less than 1mm. The final ducts of bronchial tree are the alveolar ducts that also have alveolus and alveolar sac. A dense mesh of capillaries surrounds each of the alveolus. Present are capillary walls that comprise of endothelial cells that are surrounded by slender basement membrane. The main function of human respiratory system is supplying the blood with oxygen so that the blood can deliver this oxygen to other body parts.
PART I THE RESPIRATORY SYSTEM
The human respiratory system is divided into two major parts the upper and lower respiratory systems. The respiratory system is made up of several structures each with unique functions that supplement each other.
The upper respiratory system comprises of the nostrils, the mouth, turbinate, the oropharynx, nasopharnyx, the glottis and the trachea.
The nostril is a cartilage structure located on the anterior portion of the face. It has two openings the nasal cavities through which air entry takes place. The lining of the nasal cavity is moist and has membranous hair structures that promote absorption of the inhaled air. (Marieb, 2001)
The turbinates located at the superior portion of the nasal cavity enclosed with the two bones, these turbinates increase the surface area for air absorption. Equally the turbinates increases the surface area or the distance through which inhaled air has to move through this helps to allow maximum cooling of the air as well as trapping of the particles by the nasal hairs.(Marieb,2001)
The pharynx lies inferior to the turbinates behind the oral and nasal cavity hence the oropharynx and the nasopharnyx.the pharynx allow the passage of the inhaled air down to the trachea. (Marieb, 2001)
The glottis is a small structure but of great importance to the respiratory system it is made up of elastic cartilage. This structure together with the epiglottis open and close simultaneously during inhalation and swallowing of food to prevent food particles from slipping into the trachea. (Marieb, 2001)
The trachea a cartilage ring structure located form the glottis to the bifurcation of the bronchi it allows air to move down to the bronchi. (Marieb, 2001)
The Lower Respiratory System
This portion of the respiratory system is made up of the right and left bronchus, bronchioles, the lungs, the alveoli, the diaphragm and the intercostals muscles.
The bronchus is also a cartilage structure that starts where the trachea ends and begins at the bifurcation, where one portion branches to the left and the other to the right. The bronchi lead to the bronchioles which further branches deep into the lung surface.
Bronchioles-the bronchioles divide form the main bronchus in each part of the lung, they are made up of small and tiny capillaries at their end where they further branch to from the alveoli. (Marieb,2001)
The alveolus is the only place where actual gas exchange takes place. Each lung contains approximately 300 million alveoli that provide a large surface area of about 160m2 enough for gaseous exchange. The alveolus contains both arteries and veins that supply blood through which gaseous exchange takes place. (Marieb, 2001)
The diaphragm is an elastic structure located in the lower part of the thoracic cavity it divides the body cavity. It separates the thoracic cavity that contains the heart and the lungs from the abdominal cavity that contains the viscera like the stomach and the intestines. The diaphragm is elastic in nature and is able to contract as well as to expand during the breathing process (Marieb,2001).
The Function of the Respiratory System
Respiratory System Gas exchange
The primary function of the respiratory system is to exchange gas between the an organisms circulatory system and the external environment. In mammals and humans, this exchange enables oxygenation of the blood with a connected removal of carbon dioxide and other gaseous metabolic wastes from the circulation system. As gas exchange happens, the acid-base balance of the body is preserved as part of homeostasis. If correct ventilation is not maintained, two opposing conditions could take place respiratory acidosis which is a life threatening condition, and respiratory alkalosis (Marieb,2001).
During inhalation, gas exchange takes place at the alveoli, the tiny sacs which are the essential functional parts of the lungs. The walls of alveolar are extremely thin these walls are made up of a single layer of epithelial cells (type I and type II epithelial cells) in close immediacy to the pulmonary capillaries which are made up of a single layer of endothelial cells. The close immediacy of these two cell types permits permeability to gases hence, gas exchange. This entire mechanism of gas exchange is carried by the simple phenomenon of difference in pressure. When the atmospheric pressure is low in the external environment air from lungs flow out but when the air pressure is low inside, then the air from lungs flow in.
Oxygen Delivery System
The respiratory system supplies blood with oxygen so that the blood is able to deliver oxygen to all components of the body. This is done through breathing when we breathe in, we inhale oxygen and when we breathe out we exhale carbon dioxide. This exchange of gases is the respiratory systems methods of supplying oxygen to the blood.
Respiration is attained through the nose, mouth, lungs, trachea, and diaphragm. Oxygen gets in the respiratory system through the nose and the mouth. The oxygen then goes through the larynx and the trachea which is a tube that goes up to the chest cavity where the trachea separates into two smaller tubes called the bronchi. Each bronchus then segregates again forming the bronchial tubes. The bronchial tubes lead into the lungs (directly) where they separate into many smaller tubes which join to tiny sacs called alveoli. The average adults lungs hold about 600 million of these spongy, air-filled sacs that are enclosed by capillaries.
The oxygen that is inhaled passes into the alveoli and then diffuses through the capillaries into the arterial blood. In the meantime, the waste-rich blood from the veins discharges its carbon dioxide into the alveoli. The carbon dioxide follows the same path out of the lungs when a person exhales (Marieb,2001).
The diaphragms function is to assist pump the carbon dioxide out and pull the oxygen into the lungs. The diaphragm is a sheet of muscles that lies across the base of the chest cavity. As it contracts and relaxes, breathing takes place. When the diaphragm contracts, oxygen is pulled in the lungs and when it relaxes, carbon dioxide is pumped out of the lungs.
The mechanisms of breathing
Inspiration- During inspiration human beings breathe air in and in the process the intercostals muscles between that ribs contracts pulling the chests walls up and out. The diaphragm muscle below the lungs contracts and flattens increasing the size of the chest. This leads to the increase of the lung size so that the pressure inside the lungs falls lower than the atmospheric pressure. This causes air to rush in through the nose or the mouth. (Marieb,2001)
Expiration-During expiration air is breathing out. The intercostals muscles between the ribs relax so that the chest walls move in and down. The diaphragm muscle below the lungs relax and bulges up this effect reduces the chest wall size, the lungs equally reduce in size so that the pressure inside increases and air is pushed up the trachea and out through the nose and the mouth. (Marieb,2001)
Gas exchange at the alveoli- The inhaled air passes through the thin walls of each alveolus and capillary into the blood stream and equally the gases diffuse from the blood stream into the alveoli. Blood from the pulmonary artery contains high amounts of carbon dioxide, it moves through the semi-permeable wall of alveolus out of the blood into the alveolus while oxygen diffuses from the alveoli into blood. The oxygenated blood moves out of the lungs through the pulmonary veins into the heart for distribution to the rest of the body. (Marieb,2001)
The central control of breathing is mediated by the cells located in the medulla oblongata. These cells respond to rise in levels of carbon dioxide by increasing the activity of the motor nerves that control the intercostals muscles and diaphragm. Equally the carotid body located on the walls of the carotid arteries responds to a drop in oxygen especially in the high altitude areas. The local control of breathing occurs in the walls of the bronchioles which are made of the smooth muscles. These muscles are sensitive to the concentration of the carbon dioxide. When the level of the carbon dioxide rises, the bronchioles dilates lowering the airway resistance and thus increases the flow of air in and out of the lungs. (Marieb,2001)
Breathing during exercise
When a person performing an exercise, the respiratory system reacts by increasing the breathing rate of the individual, this is due to the fact the muscles needs extra oxygen so a person breathes in deeply and quickly in supply the needed oxygen. However, upon stopping the exercise, the breathing rate reduces and the individual will start recovering. Another aspect from the respiratory system due to exercise is the tidal volume, this volume increases in response to the exercise, this is brought about by the need more oxygen in the muscles.
During exercise the body especially the muscle cells use up more oxygen and produces increased amount of carbon dioxide. This means that the lungs have to work extra harder to supply the needed oxygen and remove the carbon dioxide. (Marieb,2001)
In the course of this process the breathing rates increases and the heart rate also increases in order to transport the oxygenated blood to the muscles.
During exercise several changes occur when one is breathing. On the short term the muscle cells uses more
oxygen and thus the level of carbon dioxide rises. The rise leads the brain to send signals to the lungs to increase the rate of breathing. The breathing rates and the volume of air in each breathe increases thus more gaseous exchange takes place. The heart also responds by pumping more blood into the lungs for gaseous exchange. Hence the more oxygenated blood gets to the muscles and more carbon dioxide is removed.
The long term effect of regular exercise is that it strengthens the respiratory system. The respiratory muscles get stronger so that the chest cavity becomes larger. This means that the larger chest cavity allows more air to be inspired therefore increasing the vital capacity. At the same time more blood capillaries form around the alveoli so that more gaseous exchange can take place. (Ray, 2009)
Breathing during exercise
SHAPE MERGEFORMAT
The exercise-stimulated challenge to the acidity levels in the body has got two varying origins. One, foodstuffs that act as energy sources used for the exercise (the carbohydrates and fats) contains mostly hydrogen, carbon as well as oxygen atoms. During body exercise, the hydrogen atom are taken away to connect with oxygen to give energy, a good example is glucose process,
C6H 12O6 6O2 6H2O 6CO2
This results in the body releasing the carbon and oxygen as carbon dioxide in the air. This is because the body s CO2 production is nearly equal to the oxygen consumed during the exercise or sports. However, supposing the ventilation fails to increase sufficiently in the course of the exercise, the level of oxygen in the blood tissue will decrease and the level of carbon dioxide will increase, such aspect will increase the acidity level in the blood.
Response of the respiratory system to anaerobic exercise
For the body to suddenly meet the immediate increased energy requirement, the stored ATP is the first source in supplying this needed energy. However, this energy lasts only for about two seconds.
The stored ATP is broken down into phosphocreatine, however, the ATP-PC system is only able to last for a period of 8-10 seconds after which the PC energy is depleted.
After this, the lactic acid system has to take over the duty of providing energy required for the body to continue with its exercise.
Supposing the exercise goes on at an increase rate, and no enough oxygen is available, then the production of the lactic acid within the body will reach a level that it hinder the normal functioning of the muscle. At this point the muscles will start getting fatigue (McAedle et al., 2000)
PART II The Energy Systems
Having an understanding of energy systems underlines the effect sports and exercise activities have on the body system. One of the most important aspects of sports is having bioenergetics knowledge. However, modern model of the human energy systems seem to challenge the previous models of bioenergetics. This section highlights the three main energy pathways.
ATP (Adenosine Triphosphate) the body energy currency
The body requires energy to carry out any bodily activities such as development, repair, maintenance and even transportation of different substances. Whether a person is running or playing tennis, the skeletal muscles are powered by just one compound adenosine triphosphate (ATP). ATP is a molecule containing adenosine and three inorganic phosphate groups. Energy from the ATP is released when the molecule combines with water molecule that is hydroysis, thus splitting the phosphate group releasing energy. This leaves now an adenosine phosphate or ADP. When this process occurs in presence of oxygen it is known as aerobic metabolism or oxidative phosphorylation if it occurs without oxygen it is labeled as anaerobic metabolism. (McAedle et al., 2000)
Nonetheless, the body is able to store a very small amount of this particular energy currency into its cells to power it for merely a few seconds of body exercise. Thus, the body has to replace ATP continuously. Understanding the way it replaces this ATP is key to knowing energy systems. There are several energy sources that replenish the ATPs these includes the energy substrates such as the creatine phosphate, fat, carbohydrate and protein.
1. The ATP-Pcr System (Phosphate Energy system)
It is made up of ATP and the creatine phosphate. It is regulated by an enzyme known as creatine kinase. This system can operate with or without oxygen. It is most relied systems of energy during the first 5 seconds of exercise, regardless of the intensity. The ATP Pcr system can sustain exercises for 3-15 seconds and it is during this time period that the power output is at the greatest. (Baechle and Earle, 2000)
This system mainly produces energy in short span of time thus is mostly used during short sprints or short distance races like 100meters. This means that during the prolonged activity will need the body to rely on another system to produce ATP.
2. The Glycolytic System
This system breaks down glucose through a series of enzymatic reactions. The end product is pyruvic acid. The pyruvic acid formed is funneled through Krebs cycle or it is converted into lactic acid. There are two types of glycolysis the fast glycolysis in which the end product is Lactic acid and slow glycolysis in which the Pyruvate is funneled through the Krebs cycle. Fast glycolytic system produces energy at a greater rate, but this leads to accumulation of lactic acid which causes extreme muscle fatigue.
The fast glycolytic systems is most useful after the initial 10 seconds of exercise when the maximal muscle power output drops because the phosphate energy system begins to wear down. (McArdle et al.,2000)
3. The Oxidative System.
It comprises of four processes that produces ATP, this includes the slow glycolysis, Krebs cycle (lactic acid cycle or tricarboxylic acid cycle), Electron transport chain and beta oxidation. The slow glycolysis metabolizes glucose to form two ATPs and the end product pyruvic acid is converted to Acetyl coenzyme-A. (Wilmore Costill, 2005)
The Krebs cycle- It continues the oxidization of glucose that started during glycolysis. Acetyl coenzyme A enters the Krebs cycle and is broken down into carbon dioxide and hydrogen forming two more ATPs. The hydrogen produced in this phase and in the glycolysis phase combines with two enzymes called NAD and FAD. The hydrogen is then transported to the electron transport chain. (McArdle et al.,2000)
Electron Transport Chain-Hydrogen produced in the glycolysis process and the Krebs cycle is carried through a series of chemical reactions and it combines with oxygen to form water to prevent acidification in the body muscles. In this process a total of 34 ATPs are produced and oxygen is used as well in the process. (McArdle et al.,2000)
Beta oxidation-this process involves the reduction of broken down fatty acids into acetyl coenzyme A and hydrogen before they enter the Krebs cycle.(Wilmore Costill,2005)
Protein metabolism-Protein subunits, amino acids, can be converted into glucose or acetyl coenzyme A, thus allowing the protein to make a vital contribution during prolonged exercise activity. During rest and low intensity exercise the body muscles utilizes energy form the oxidative system. It takes approximately 90 seconds for the oxidative system to set up and produce maximal power output however this time can be lowered by proper training. (Baechle and Earle, 2000)
In summary, this paper has looked at the structures and function of the respiratory system. The mechanism of breathing during both normal rest period and during exercises have been discussed, as well as the three energy system that supply the adenosine triphosphate which is the energy molecules in the muscles. Therefore adequate and proper functioning respiratory system is essential for good exercise activities.
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