Process of respiration - Biological processes in human body - science lessons for life


Tuesday, December 20, 2016

Process of respiration - Biological processes in human body

Process of Respiration
Respiration is a biological process. Inhaling and exhaling can be observed in some animals.

Respiration in a human is a complex process and it occurs in three stages.
1. Gas exchange between external environment and lungs
2. Gas exchange in alveoli
3. Cellular respiration

Intake of oxygen into lungs and removal of gaseouse waste in cells occurs in ventilation.
Engage in the following activity to demonstrate external gas exchange

Activity 01
Demonstration of gas exchange using a model
Materials required :- Small bell jar, gas tube, a cork bore, two rubber balloons, balloon membrane or polythene sheath, several rubber bands
Method :- Set the apparatus as shown in the diagram. Push and release the balloon membrane and observe the condition of balloons

According to the above activity when rubber membrane is pulled down the volume inside the bell jar increases. Then external gas enters and balloons get inflated. When rubber sheath is released, gas inside balloons go out as the volume of bell jar decreases. Likewise gas exchange between external environment and lungs occurs due to changes of volume of lungs.

The system involved in entering O2 into lungs and release of gaseous waste products produced during biological processes is the respiratory system. The diagram given below shows the human respiratory system.

Nasal cavity, pharynx, trachea, larynx, bronchi, bronchioles and alveoli are the main parts of respiratory system.

Internal surface of nasal cavity is covered with mucus. Due to the presence of mucus in the nasal cavity, the lining of it is moist. There are numerous cilia present on the lining of the nasal cavity. The bacteria, dust and other wastes found in inhaled air stick onto the mucus. This prevents the entry of them into the lungs. By rhythemic movement of cilia the waste materials are sent out. The materials that are collected at pharynx are removed out with saliva.

The changes that take place when inhaled air passes through the nasal cavity are as follows.

  • Moisturizing/ Humidifying inhaled air
  • Warming up of inhaled air
  • Removal of wastes from inhaled air

During inspiration, air enters into lungs. For that, the volume of the lungs should increase. To increase the volume of the lungs volume of the thoracic cavity should be increased Inter-costal muscles contract, therefore ribs move up and sternum moves forward.

At the same time the diaphragm contracts and reduce its curvature.Due to above activities the volume of the thoracic cavity increases and with that volume of lungs increase. So air enter into lungs through the nose.

For expiration to occur, the volume of the thorasic cavity should decrease to reduce the volume of the lungs. Inter-costal muscles relax. So the sternum and ribs move into its original position. The diaphragm relax and becomes curved. Due to these activities the volume of the lungs decreases, thereby gas inside lungs move out through trachea and then nasal cavity.

The gas exchange that takes place in alveoli
The inhaled air finally reach the alveoli, through nasal cavity, trachea, bronchi, and bronchioles. The O2 concentration in alveoli is greater than that of the blood capillary network around it. Therefore O2 diffuse out of the alveoli into the blood capillaries. Similarly CO2 and water vapor concentration is greater in blood capillaries than air inside alveoli, diffuse into the exhaled air.

Accordingly, the respiratory surface of human is the wall of alveoli. The exchange of gases takes place by diffusion.

Air exchange between alveoli and blood capillaries

Characteristics of a respiratory surface
The adaptations of the respiratory surfaces for efficient gas exchange are as follows.

  • Surface should be moistened and permeable for gas exchange
  • Surface should be thin for diffusion of gases
  • A larger surface area to exchange large volume of gas according to the needs of animals
  • Surface should be highly vascularized

In many animals body cover acts as the respiratory surface and gases exchange through the body cover. The respiratory surface of human is the wall of alveoli and the adaptations of the alveoli for efficient gas exchange are as follows.
  • Presence of a blood capillary network around alveoli
  • Thin alveolar wall
  • Moist alveolar surface
  • Presence of large number of alveolar sacs
Cellular respiration
Oxygen moved through alveoli reacts with simple organic compounds (glucose) in cells. In this chemical reaction energy is produced, therefore respiration is the process of oxidation of simple foods within living cells. Let us build a word equation for respiration

The balanced chemical equation for respiration is given below.
According to the requirement of oxygen two types of respirations can be identified.

Aerobic respiration and Anaerobic respiration

We discussed the respiration that takes place inside cells in the presence of oxygen. It is called aerobic respiration.
Organisms can respire without O2 . Respiration carried out by organisms without O2 is known as anaerobic respiration.
Anaerobic respiration that takes place in plants is known as alcohol fermentation. The anaerobic respiration that takes place inside plant cells can be given by the following word equation.

When Yeast carries out anaerobic respiration during fermentation, CO2 and Ethyl alcohol is produced. This process is an example for alcohol fermentation.

Animals including human cells also perform anaerobic respiration. The anaerobic respiration that takes place within animal cells is referred to as lactic acid fermentation. The products of that is given in the equation given below.

Have you faced an incident of muscle pain and cramp due to an instant activity like 100m race. That is due to lactic acid, collected in muscles. That is a result of anaerobic respiration.

Energy produced during aerobic respiration is higher than energy produced during anerobic respiration. This is because of the incomplete break down of glucose in anerobic respiration and complete break down of glucose in aerobic respiration.

Energy is produced during anaerobic respiration as well as in aerobic respiration and part of this energy is lost as heat and rest will be deposited in ATP (Adenosine Tri - Phosphate) as chemical energy.
The energy needed for biological processes is produced during formation or break down of ATP

Functions of ATP

  • Storage of energy
  • Release of energy
  • Act as an energy carri
Diseases associated with respiratory system

  • Common cold

Causative agent is a virus. Headache, sneezing, running nose, cough are the symptoms. There is no medical treatment as it is a viral infection. But can treat for symptoms. By avoiding dust and mist like conditions which are good for viral growth can recover quickly.

  • Pneumonia

This disease occurs due to a bacterium or a virus. The lungs are infected and a fluid may accumulate in the lungs. Prolong cold and cough are the main symptoms for pneumonia.

  • Asthma

Asthma is an inflammation that occurs in the body. Dust, pollen, saw dust, fur, smoke are some causative agents. Due to those substances, the bronchioles get inflammated and the cross area of them are reduced causing difficulty in breathing.

  • Bronchitis or bronchiolar inflammation

The bronchioles swell up due to inflammations that occur by viral or bacterial infections. Heavy cough and difficulty in breathing are symptoms. Other than bronchioles, larynx may get infected. As a result, voice may not exit properly.

  • Tuberculosis

Tuberculosis is caused by a bacterium. Due to multiplication of the particular bacterium within the lungs, the tissues are damaged. Mainly, the lungs are infected. But it may affect other parts in the body too. Parts of tissue can be released with phlegm. The lungs are deteriorated and get perforated. Blood release with phlegm due to breakdown of blood vessels.

Symptoms of tuberculosis

  • Tiredness
  • Loss of apetite
  • Fever
  • Release of blood during coughing
  • Weight loss
Tuberculosis can be prevented by vaccines and proper treatment

Diseases associated with smoking
Smoking cause, lung cancer, bronchitis and some other diseases. Sometimes it may cause death.

Carbon monoxide (CO) in cigarette smoke is absorbed into blood. CO readily binds with haemoglobin and avoid binding of O2 with haemoglobin. Therefore O2 carrying capacity of blood reduces.
Nicotine found in cigarette smoke increases the heart rate temporally.

Due to destruction of cilia in the respiratory tract, bronchioles may swell up due and get inflammations, and it may cause difficulty in breathing. As these epithelial cells expose to cigarette smoke, they may form abnormal cells which develop into cancers. Passive smokers also get same ill effects due to cigarette smoke.

Workers work in quarries, coal mines and glass industry expose to silicon containing componds. When these people inhale air with those componds, they accumalate in alveoli. So lung tissues get deteriorated gradually
This disorder occurs due to inhalation of air containing asbestos particles and fibres. Due to accumulation of these particles tissues of respiratory tract get destroyed.

source by internet and books

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