Respiration in Organisms (For 

Classes 7 and 10)

By  PK Verma

The food material taken in during the process

of nutrition is used in cells to provide energy for

various life processes.

Diverse organisms do this in different ways – 

some use oxygen to break-down glucose 

completely into carbon dioxide and water, 

some use other pathways that do not involve 

oxygen. 

In all cases, the first step is the break-down of glucose, a 
six-carbon molecule, into a three-
carbon molecule called pyruvate. This process takes place 
in the cytoplasm. 


What happens to Pyruvate in different conditions?


Further, the pyruvate may be converted into ethanol and 
carbon dioxide. This process takes place 
in yeast during fermentation. Since this process takes place
in the absence of air (oxygen), it is 
called anaerobic respiration. 


Break- down of pyruvate using oxygen
takes place in the mitochondria. 

This process breaks up the three- carbon 
pyruvate molecule to give threemolecules of 
carbon dioxide. The other product is water. 
Since this process takes place in the presence 
of air (oxygen), it is called aerobic respiration. 

Sometimes, when there is a lack of oxygen in our muscle 
cells, another pathway for the break-down of pyruvate is 
taken. Here the pyruvate is converted into lactic acid 
which is also a three-carbon molecule. This build-up of 
lactic acid in our muscles during sudden activity causes
cramps.

Animals have evolved different organs for the

uptake of oxygen from the environment and

for getting rid of the carbon dioxide

produced. Terrestrial animals can breathe 

the oxygen in the atmosphere, but animals 

that live in water need to use the oxygen

dissolved in water.

Why does fishes have very high breathing rate?

The main respiratory organ of fishes are gills. Water 

contains less amount of Oxygen  than air and 

water is also heavier than air, so it's harder to move 

into the fish's gills. Since there's less oxygen in the 

water and the water is harder to move around, fish 

need to breathe more quickly.

Respiration is the catabolic process which involve 

exchanges of environmental oxygen and body’s  Carbon 

dioxide through liquid medium to utilize the oxygen for 
the oxidation of glucose in the mitochondria to produce 
the energy.

Respiration may be aerobic (which involves intake  of oxygen and liberation of 
carbon dioxide) and anaerobic (which does not use oxygen in the breakdown of 
respiratory substrata), also called fermentation in micro­ organisms like yeast 
and some bacteria.

Anaerobic respiration is also occurs in intestinal  parasites (such as tapeworm, 
liver fluke etc) and mammalian RBC’s and under O ₂ deficiency in skeletal muscles. 
Erythrocytes perform only anaerobic respiration  as they do not have mitochondria.

External and internal respiration

The respiration (aerobic)in higher animals is  brought  about in 2 phases - external respiration (or breathing or  ventilation) in which intake of O₂   from the surrounding medium and elimination of   CO ₂ into that medium; and  internal respiration (or  tissue or cellular respiration) in which oxidation  of nutrients in the cells producing CO ₂ and energy. 

Types of respiration   with examples
             

        Cell surface respiration  

        Examples are Protozoans sponges, coelenterates

        Cutaneous respiration  

        Examples are  Earthworm, leech, frog 

        Branchial respiration  

        Examples are  Prawn, Unio, fish etc.

            Tracheal respiration 

        Examples are  Insects and myriapods  

  

       Book lung, book gill

       Examples are Spider, Limulus, frog respectively.

     

       Tube feet  

  
       Examples are Echinoderms 

       Pulmonary respiration  

       Examples are  Reptiles, birds, mammals  

       Cloacal respiration  

       Examples are Some turtles

Pharynx, Larynx and epiglottis

Pharynx serves as a common passage for both air  and food.

Larynx (or voice box) is composed of cartilages, ligaments, muscles and a mucosal surface and  prevents indigested solids and liquids from  entering the 

respiratory system and also contains  the vocal cords which produce speech sounds.

Larynx is called Adam’s apple in man.

Pharynx serves as a common passage for both air and food. 

Epiglotts is the structure (containing elastic cartilage) that prevents the entry of food into respiratory tract during swallowing.

Trachea, bronchi and bronchioles



Trachea (or wind pipe) which carries air between  the larynx and the bronchi are supported by incomplete rings of C shaped cartilage (hyoid bone) in its wall.

Mucous gland present in ciliated epithelium of trachea protects the respiratory system for infections by holding the bacteria and dust particles coming in system with air. 

Trachea (lower part) branches into two bronchi,  one to each lung and these branch within lungs into many smaller bronchioles. 

Bronchi (air passages) have a pseudostratified    ciliated  columnar epithelium containing numerous goblet cells, macrophages and fibroblast.

Bronchioles are of three types ­ large bronchioles (having simple columnar epithelium of  ciliated cells), terminal bronchioles (most distal simple bronchioles) and respiratory bronchioles (having alveoli in their walls).  

Protective Covering of Lung and walls of Air Sacs, 

Importance of Surfactant

The covering of the lung is called pleura. The outside of  each lung is covered by a thin membrane called the visceral pleural membrane. 

The right lung is divided into three lobes and left into two.  

The left lung is smaller than right and has a concavity, the cardiac notch, where the heart lies.  

Mammalian lungs are composed of millions of alveoli (made of simple squamous cells) that  provide a huge surface area for gas exchange. Number of alveoli in human pulmonary system is 300 ­ 400 million with surface area of 100 sq.mt. 

Walls of air sac form hollow air cells or alveoli  which are the ultimate unit of bronchial tree to participate in gaseous  exchange.  


Wall of alveoli is thin membrane and lined by 2  types of epithelial cells - -    
Type I cell---- ­ Flat cells with large cytoplasmic  extension and are primary lining cell. 

Type II cell--- (granular pneumocyte) ­ Thicker  and contains numerous lamellar inclusion bodies.   

These cells secretes surfactant.  Surfactant is a lipid surface tension lowering agent  which  prevents alveoli from collapsing during respiration.  

The ability to secrete surfactant doesn’t develop   untill around the eight or ninth month of pregnancy so there frequently is a problem in premature babies with the lack of surfactant causing the alveoli to stick together when the body exhales. 

Role of Diaphragm

The diaphragm is a thin musculomembranous  dome shaped muscle that separates the thoracic and abdominal  cavities. The diaphragm is the main muscle of respiration  and its action is only partly under control of will. 

The contraction of diaphragm assists  in inspiration, micturition (passing of urine), defaecation (the passing of  faeces) and parturition (childbirth).

Diaphragm

Rate of breathing is 40 - ­60/ min in neonates, 14 - 18 min in adolescents, 12 - ­14/ min in human adults and 18 -­ 22/ min in children.

During inspiration,  the diaphragm and the  intercostal muscles contract. The diaphragm moves downwards increasing the volume of the thoracic  (chest) cavity, and the intercostal muscles pull the ribs up expanding the rib cage and further increasing  this volume. 

The gaseous exchange takes place between external environment and blood through respiratory organs.   

The site of gaseous exchange in lungs is alveoli.  The gaseous exchange is the diffusion of oxygen from alveolar air into the blood and diffusion of CO ₂ from blood to alveolar air.  

Carbon monoxide poisoning     

Haemoglobin has much more about 250 times more affinity for carbon monoxide than for  oxygen. In the presence of carbon monoxide, it readily combines to form  stable compound  called carbonmonoxyhaemoglobin 

(COHb). 

The  oxygen combining power decreases and as a result tissues suffer from oxygen starvation. It  leads to asphyxiation and in extreme cases to  death. The person needs to be administered with  pure oxygen­carbon dioxide mixture to have a  very high pO ₂   level to dissociate carbon monoxide from haemoglobin. 

Carbon monoxide  poisoning occurs often in closed rooms with open stove burners or furnaces or in garages  having running automobile engines.

Respiratory Diseases

Asthma

Asthma is defined as a common, chronic respiratory 

condition that causes difficulty breathing due to 

inflammation of the airways. 

Asthma symptoms include dry cough, wheezing, chest tightness and shortness of breath.

Chronic Obstructive Pulmonary Disease (COPD)

Chronic obstructive pulmonary disease is an umbrella 

term that encompasses several respiratory illnesses 

that cause breathlessness, or the inability to exhale 

normally. People usually experience symptoms, 

including shortness of breath, and normally cough up 

sputum (mucus from the lungs), especially in the 

morning. 

This disease is generally associated with cigarette 

smoking. It’s rare to see people with COPD who 

haven’t been exposed to some sort of smoking. People 

can experience varying severity levels of COPD. At its 

most severe, it can cause people difficulty doing every 

day activities.

Chronic Bronchitis

Chronic bronchitis is a form of COPD emphasized by a 

chronic cough. Usually people cough up sputum 

(mucus from the lungs), especially in the morning.

Whooping Cough (Pertussis)

Whooping cough (pertussis) is caused by the Bordetella pertussis bacterium. Uncontrollable, violent coughing that can make it difficult to breathe is characteristic of this lung infection. The whooping sound comes from an ill person sucking in air after a coughing fit. Anyone, including adults, can get pertussis, but infants stand a particularly severe, even life-threatening, risk.

Swine Flu (H1N1)

Swine flu (H1N1) is a respiratory illness caused by the Influenza-A virus. A virus's genetics allow that particular virus to live inside a specific species, like a human, cat, dog, monkey, and others. The swine flu gets its name because the viruses that causes swine flu (H1N1v viruses) show genetic similarities to viruses that infect pigs.

Bird Flu (Avian Flu H5N1)

Avian (bird) flu is an illness also caused by an influenza- A virus. Most human illnesses from avian flu have been caused by the LPAI (low pathogenic avian flu) H7N9 and HPAI (high pathogenic avian flu) H5N1 variants that have genetic similarities to viruses found to infect birds.

Bacterial Pneumonia

One common cause of pneumonia is bacterial infection. Bacterial pneumonia usually causes a cough that produces mucus from your lungs (sputum). Anyone can be infected, but some people stand a greater risk, including those who:

• suffer from a viral infection,
• have another respiratory disease, or
• are recovering from surgery.

Viral Pneumonia

Viral pneumonia is a lung infection that can occur in anyone of any age, but is more common in young children and the elderly. Common causes include Influenza A or B ("the flu"), respiratory syncytial virus (RSV), parainfluenza, and adenovirus. Worldwide, viral pneumonia is the leading cause of death among children younger than 5 years old.

Coronavirus Infections

The seven known coronavirus infections that make people sick range from mild to severe, depending on the virus type. This virus family is known to infect various animals, and is also known to mutate easily. Sometimes coronavirus types that infect animals (including bats, civet cats, and camels) mutate to infect humans, and this can have deadly consequences.

A mild-to-moderate coronavirus infection is like the common cold, according to the CDC. Worldwide, people get sick from the four coronavirus types that cause milder infections every day. But three types—the ones that cause SARS, MERS, and COVID-19 (SARS-CoV-2)--have the potential to be fatal, and each of these has led to a significant global outbreak.

Coronavirus COVID-19 Symptoms

As with other lung infections, people with COVID-19 may experience cough and fever, along with shortness of breath. There have been some reports of patients with stomach problems such as diarrhea and vomiting. Although many only experience mild/moderate symptoms (about 80%of those infected), others (about 20%) experience more severe symptoms, which may include pneumonia, severe acute respiratory syndrome, kidney failure, and death (about 1-3%).

SARS (Severe acute respiratory syndrome)

Severe acute respiratory syndrome (SARS) is a severe viral respiratory infection caused by coronavirus SARS-CoV. The SARS virus outbreak began in China in 2003 and spread worldwide, infecting over 8,000 people before it was contained. SARS virus spreads mainly through person-to-person contact. Since 2004, there have been no known SARS virus cases reported.

MERS (Middle East Respiratory Syndrome)

MERS (Middle East respiratory syndrome) is caused by coronavirus MERS-CoV. This viral infection was first reported in Saudi Arabia in 2012, and the original source of the virus is unknown but is suspected to have come from camels.

MERS can cause a fever above 100.4°F (38°C) with chills or shivering, sore throat, coughing up blood, difficulty breathing, vomiting, abdominal pain, diarrhea, and muscle aches.