The Respiratory System

Function of the Respiratory System-

The function of the respiratory system is essentially to transport air to the alveoli and facilitate the diffusion of oxygen into the bloodstream. It also aims to facilitate the diffusion of carbon dioxide and expel it from the lungs.

1. The Pathway Of Air-
2. 1) Air enters the body and is warmed as it travels through the mouth and nose.
3. 2) It then enters the trachea.
4. 3) The trachea divides into two bronchi. One bronchus enters each lung.
5. 4) Each bronchus branches out into smaller tubes called bronchioles. Air travels through these bronchioles.
6. 5) At the end of the bronchioles, the air enters one of the many millions of alveoli where gaseous exchange takes place.The air travels through the alveolar ducts, into the alveloar sacs where it is met with capillary networks. 

The Efficiency of the Respiratory System-

We assess the performance of the respiratory system by measuring how much air is inspired or expired each minute. This is called minute ventilation. To calculate minute ventilation, we also need to know about breathing rate and tidal volume.

Tidal Volume (TV) - the amount of air inspired or expired in a normal breath. The average resting tidal volume is approximately 500ml.

Minute ventilation (VE) - the volume of air inspired or expired in one minute. It can be calculated by using the equation: minute ventilation = tidal volume multiplied by respiratory rate/ breathing rate.The average resting minute ventilation is 7500 ml/min or approximately 7.5 litres per minute.

Respiratory rate/ breathing rate (or frequency,f)- the number of breaths taken in one minute.T

Geaseous Exchange Introductuion-

Gaseous exchange refers to the exchange of carbon dioxide and oxygen between the blood and  lungs by the process of diffusion. It occurs at the alveoli in the lungs which are surrounded by capillaries so oxygen and carbon dioxide diffuse between the air in the alveoli and the blood in the capillaries. Gaseous exchange is important for physical activity because it means the process of respiration (oxygen + glucose --> carbon dioxide + water + energy) can continue and so provide cells with the energy needed. 

Oxygen diffuses into the blood from the alveoli because there is a high concentration of oxygen in the alveoli but there is a low concentration of oxygen in the blood.

Carbon dioxide diffuses from the blood into the alveoli because there is a high concentration of carbon dioxide in the blood and a low concentration in the alveoli.

Carbon dioxide and oxygen are both capable of combining with haemoglobin - an iron-rich protein found in the blood. Haemoglobin carries oxygen to be exchanged at the working muscle and carbon dioxide to be exchanged at the lung.

Features that Assist Gaseous Exchange-

• The alveoli in the lungs are covered in tiny capillaries. Both the walls of the capillaries and alveoli are very thin (just one cell thick) and they are made of semi-permeable membranes which means oxygen and carbon dioxide can pass through them. 

• A large blood supply also assists gaseous exchange ? because an increased red blood cell content increases the amount of oxygen supplied to muscles and other body tissues.Oxygen combines with the red blood cells to form oxyhaemoglobin. The same haemoglobin also transports carbon dioxide back from the tissues to the lungs.

• Capillaries very near to alveoli, so diffusion distance is very short

• Large surface area of alveoli allows diffusion

• Moist thin walls (one cell thick) of the cells promotes quick diffusion

• Gases will always move from areas of high concentration to areas of a low concentration

Breathing Introduction-

Breathing is the term given to the process of taking air into and out of the lungs. It can increase up to 5-9 times higher than at rest to cope with exercise demands.

Two important structures for breathing are the diaphragm and intercostal muscles.

The diaphragm is a sheet of muscle that separates the chest (or thoracic) cavity from the rest of the body.

The intercostal muscles are found between the ribs and they control rib movement.

Inspiration and Expiration-

During inspiration (breathing in):

• The diaphragm contracts. It pulls down and flattens out the floor of the rib cage.
• The intercostal muscles contract, causing the ribs to lift upwards and outwards and the chest to therefore expand
• This increases both the size of the chest and lungs
• The pressure inside our lungs falls as they expand. the higher pressure of the air outside means air is now sucked into the lungs through the nose and mouth

During expiration (breathing out):

• The diaphragm relaxes and moves back to its domed shape
• The intercostal muscles relax so the ribcage moves inwards and downwards under their own weight
• This decreases the size of the chest and increases the air pressure in the chest so air is forced out of the lungs

Anaerobic Exercise-

Anaerobic respiration formula: Glucose --> Energy + Lactic Acid

The anaerobic respiratory system supplies energy very quickly for sports such as vaulting in gymnastics or throwing a javelin where the activity only lasts a few seconds. Glucose is derived from carbohydrates and is able to supply energy very quickly.

Anaerobic exercise is exercise performed in the absensce of oxygen and it is both high intensity and short duration exercise.With no oxygen available, glucose is still used but this is broken down into energy and lactic acid (this causes fatigue) by the system. These exercises can only be performed for a short duration mainly becuase of the build up of lactic acid. Lactic acid is a fatiguing by-product of the lactic acid energy system and causes pain and discomfort in the working muscles. It is for this reason that the winner of a 400 m race is typically the athlete who slows down the least.

Examples of anaerobic activities include sprinting, long jump, making a tackle in football, shooting at goal in netball and serving in tennis.

Oxygen Debt-

Oxygen debt refers to the body's oxygen deficiency resulting from strenuous physical activity.The anaerobic systems require the oxygen to restore the lack of oxygen and build-up of lactic acid (of which both of these cause fatigue.)

After taking part in exercise, a person continues to breathe more deeply and rapidly than when at rest to take in additional oxygen to repay this oxygen debt.

The oxygen is then used to:

• break down lactic acid to carbon dioxide and water
• replenish the creatine phosphate stores

Aerobic Exercise-

Aerobic respiration formula: Glucose + Oxygen --> Energy + Water + Carbon Dioxide 

 The aerobic respiratory system is responsible for producing the majority of our energy while our bodies are at rest or taking part in low-intensity exercise for long periods of time such as jogging or long-distance cycling.

Aerobic exercise takes place in the presence of oxygen and it is both lower intensity and longer duration exercise. Aerobic exercise can be maintained for a prolonged period of time because there is lots of glucose available and no great build-up of lactic acid.Glucose from carbohydrates and fats supply the energy for the aerobic energy system and can supply energy for long periods of time.Carbohydrate food sources include rice, bread, potatoes, bananas and energy drinks. Fat food sources include butter, oils, cheese, milk and nuts.

Examples of aerobic activities include marathon running, 5,000 metres, distance swimming, jogging back to reposition in football, dancing, canoeing and cross-country skiing.