Respiration in Humans//Breathing and gaseous exchange of gases//Respiratory system

 

RESPIRATION IN HUMANS 

What is respiration?

Exchange of gases (CO₂ and O₂) and utilization of oxygen (O₂) to breakdown of food to release energy is called Respiration.

Respiration is a catabolic process.

The organs which help in different organism to respire are known as Respiratory organs.

These organs work together called Respiratory system of an organism.

In unicellular and lower multicellular organisms respiration occurs through general body surface.

In higher multicellular organism there is a system which transports oxygen in each and every cell of the body.

The process of respiration in higher animals involves two steps-

1.     External Respiration-

·        It involves breathing (inspiration and expiration) and gaseous exchange (O₂ and CO₂).

·        It involves respiratory organ like Lungs, trachea etc.

·        It is also known as Ventilation.

 

2.     Internal Respiration-

·        Internal respiration is also known as cellular respiration.

·        It involves the oxidation of food, using the oxygen for producing energy.

·        It involves a single cell only.

·        It can be aerobic (if oxygen is available to the cells) or anaerobic (when oxygen is not available to the cell).

 

 

 

The respiratory surface of animals must have following special features for efficient gaseous exchange-

·        The surface should be thin walled.

·        The surface should be moist to speed diffusion.

·        The surface should have a large surface area.

·        The surface should have a rich blood supply.

 

Different  animals with their respiratory surface
Animals	Respiratory surface
Amoeba and planaria	Cell membrane
Earthworm and leech	Moist skin (cutaneous respiration)
Fish, prawn, tadpole(aquatic animals)	Gills
Frog	Moist skin and Lungs
Grasshopper, mosquito and housefly	Spiracles and air tubes.
Birds, lizards and terrestrial animals	Lungs

 

RESPIRATION IN HUMAN BEINGS-

Like other animals, respiratory system in human being serves to provide fresh oxygen to all body cells and removes harmful carbon dioxide (CO₂) from the body.

The main organs of respiration are one pair lungs, so that the respiration in human is pulmonary.

The respiratory system of human being consist of following parts-

a.     Nostrils or External Nares-

The nose of human being has two small holes for intake of oxygen (O₂) and elimination of carbon dioxide (CO₂), these holes are called Nostrils.

b.    Nasal Chambers-

The nares lead internally into nasal cavity (nose), which is divided into two nasal chambers by a nasal septum (Each nostril opens into the nasal chamber of its side).

c.      Internal Nares-

Posterior region of the nasal chamber have small holes called internal nares, which lead into the nasopharynx.

d.    Pharynx-

·        Nasal chambers open into pharynx, which is common for both nasal cavity as well as buccal cavity.

·        Pharynx provides passage to both air and food.

·        It is divided into following parts-

 

1.     Nasopharynx –

·        The upper most part of pharynx called Nasopharynx.

·        At the base of the nasopharynx are the Soft palate and its pendulous Uvula.

·        On swallowing they raise upwards blocking of the nasopharynx so that food can’t reach the nasal cavity.

 

2.     Oropharynx-

·        Oropharynx extends  from the  soft palate to the upper border of the epiglottis.

·        Oropharynx deals with digestion and respiration both.

 

 

3.     Laryngopharynx-

·        Laryngopharynx is the lower part of pharynx.

·        It leads into larynx and oesophagous.

 

 

e.     Larynx-

·        It is located in the neck and help to protect trachea.

·        It also produces sounds so called as voice box or sound box.

·        Larynx is larger in male than in female because a bony growth can seen in male easily in the throat region which is known as Adam’s apple.

 

f.      Trachea-

·        It is a long tubular, hollow structure which opens into laryngopharynx through its opening called glottis (glottis is guarded by epiglottis).

·        It is a passage for entry and exit of respiratory gases.

 

 

 

g.    Bronchi-

·        Trachea is divided into two branches called primary bronchi (plural- bronchi and singular- bronchus).

·        Each bronchus extends into lungs of its side.

·        Each bronchus inside the lung divides into many secondary and tertiary branches which form bronchioles.

 

 

 

h.    Lungs-

·        Lungs are commonly known as Pulmonary sacs.

·        These are two in number or one pair.

·        These are balloon like structure.

·        These are primary organs for respiration which are located on the two sides of heart.

·        Left lung is smaller than right lung.

·        Each lung is enclosed in two membranes called the pleura.

·        Bronchi inside the lungs divide into smaller branches called bronchioles.

·        Each terminal bronchiole gives rise to a number of very thin, irregular walled and vascularised bag- like structures called Alveoli (plural- alveoli and singular- alveolus) inside each lung.

Note-

The branching network of bronchi, bronchioles and alveoli comprises lungs.

 

     Human Respiratory System

 

MECHANISM OF RESPIERATION –

Mechanism of respiration involves two steps-

1.     Breathing

2.     Gaseous exchange

 

1.     Breathing-

Human being take in oxygen from the atmosphere and release carbon dioxide in return is called breathing.

Breathing involves-

A.   Inspiration or Inhalation

B.   Expiration or Exhalation

 

A.   Inspiration or Inhalation-

It is the process of taking in oxygen (fresh air) from the atmosphere.

It occurs in following steps:

Step 1- Fresh air is taken into the body through nostrils where it is filtered by hairs and mucus.

Step 2- The fresh air then passes down through trachea.

Step 3- Chest cavity becomes larger by flattened diaphragm and lifted ribs.

Step 4- Fresh air (oxygen) is sucked into the lungs and fills the alveoli.

    B. Expiration or Exhalation-

It is the process of giving out carbon dioxide from lungs to the atmosphere.

It occurs in following steps:

Step 1- Carbon dioxide is transported in dissolved form in blood.

Step 2- From blood, carbon dioxide passes to the alveoli.

Step 3- Chest cavity is compressed due to relaxation of ribs and diaphragm.

Step 4- The air (CO₂) is forced out of lungs to atmosphere.

RATE OF RESPIRATION

Note – Normal rate of breathing is 14 to 18 per minute.

                       Mechanism of Breathing : (a) Inspiration    (b) Expiration

2.     Gaseous exchange-

Alveoli are the primary site of exchange of gases.

Exchange of gases also occurs between blood and tissues.

During this exchange oxygen is given to the lungs and in return carbon dioxide is given to the alveoli.

The sequence of exchange of blood vessels and alveoli is as follows;

·        Blood release carbon dioxide into alveoli that it brings from rest of the body.

·        Oxygen is taken up by blood from alveolar air to blood vessels.

·        Haemoglobin takes up oxygen from lungs and carries it to tissue which are deficient in oxygen.

·        Oxygen in blood is then transported to all cells in the body by respiratory pigment (in human, respiratory pigment is Haemoglobin) and due to diffusion pressure.

     

  

                                      Diagrammatic representation of exchange of gases

 

RESPIRATORY DISEASES -

Some respiratory diseases are-

i.       Asthma-

·        It is an allergic disease.

·        It is caused due to hypersensitivity of the bronchiole to the foreign substances present in the air during inhalation.

·        Symptoms include coughing, difficulty in breathing mainly during expiration.

      ii. Emphysema-

·        It is a chronic disease of lungs in which alveolar walls are damaged due to which respiratory surface is decreased.

·        It is usually caused by cigarette smoking.

·        Being a chronic disease its permanent cure is not possible.

    iii. Bronchitis-

·        It is caused by the inflammation of the bronchi.

·        It is also caused by cigarette smoking and also exposure to air pollutants like carbon monoxide.

·        Symptoms include regular coughing with thick greenish yellow septum.

   iv. Pneumonia-

·        It is an infection or inflammation of the alveoli of the lung.

·        It is caused by an infection of the bacterium named Streptococcus pneumonia.

·        It is an infectious disease and there treatment is suitable by the antibiotic therapy.

    v. Pulmonary tuberculosis-

·        It is caused by bacterium named Mycobacterium tuberculosis. The bacterium attacks the lungs.

·        This diseased is completely curable by the antibiotic therapy for a long time.