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Animal Respiration

About Animal Respiration

Cells continually use oxygen (O2) for the metabolic reactions that release energy from nutrient molecules and produce ATP. At the same time, these reactions release carbon dioxide. Since an excessive amount of CO2 produces acidity that is toxic to cells, the excess CO2 must be eliminated quickly and efficiently. The two systems that cooperate to supply O2 and eliminate CO2 are the cardiovascular system and the respiratory system. The respiratory system provides for gas exchange, intake of O2 and elimination of CO2, whereas the cardiovascular system transports the gases in the blood between the lungs and body cells. Failure of either system has the same effect on the body: disruption of homeostasis and rapid death of cells from oxygen starvation and buildup of waste products. In addition to functioning in gas exchange, the respiratory system also contains receptors for the sense of smell, filters inspired air, produces sounds, and helps eliminate wastes.

what is Respiration

Respiration is the exchange of gases between the atmosphere, blood and cells. It takes place in three basic steps :
(1) Pulmonary ventilation : The first process, pulmonary (pulmo = lung) ventilation, or breathing, is the inspiration (inflow) and expiration (outflow) of air between the         atmosphereand the lungs    
(2) External (pulmonary) respiration : This is the exchange of gases between the air spaces of the lungs and blood in pulmonary capillaries.   The blood gains O2 and loses CO2.
(3) Internal (tissue) respiration : The exchange of gases between blood in systemic capillaries and tissue cells is known as internal (tissue) respiration. The blood loses O2 and  gains CO2. Within cells, the metabolic reactions that consume O2 and give off CO2 and give off CO2 during production of ATP are termed cellular respiration.

Types Of Respiration

It is of two types

Anaerobic Respiration

In lower organisms like bacteria, yeast, etc. the nutrients are oxidised without using O2 and lactic acid or ethyl alcohol is the end product. It also occurs in some multicellular animals and some tissues (skeletal muscle and RBC) of higher animals. Anaerobic respiration occurs outside mitochondria.

Aerobic Respiration

In most animals the tissue oxidation occurs in presence of O2 with end products CO2 and H2O. It requires exchange of O2 and CO2 between the organisms and the surroundings. Aerobic respiration takes place inside mitochondria.

Difference between aerobic and anaerobic respiration

Aerobic respiration / Metabolism

Anaerobic respiration / Metabolism

It uses molecular oxygen.

It does not use molecular oxygen.

Always release CO2.

May or may not release CO2.

It produces water.

It does not produce water.

It produce much more energy (whole energy present in glucose).

It produce less energy (only 5% of that available in glucose).

It yields inorganic end products only.

It yields organic end products with or without inorganic product.

It is found in majority of animals.

It found in some parasitic worms. (Ascaris, Taenia).

Respiratory System In Cockroach

A well developed system of ectodermal cuticular tubes called trachea which open to outside by 10 pairs of spiracles or stigmata on the dorso-lateral margin of the tergum.
Respiratory System In Cockroachanimal respiration

Fig. The main tracheal trunks in cockroach                  Fig. Tracheal end cells and tracheoles:
(ventral trunks and tracheae are shown ringed)            A–filled with fluid in resting cockroach;
    B–filled with air in active cockroach

  • Bound by peritreme, the spiracle opens behind into atrium (2 pairs thoracic and 8 pairs abdominal).
  • From the atrium 3 pairs of main tracheae arise which are connected through transverse commissures.
  • Trachea branches distally into tracheoles (without cuticular rings) within tissue or the cell known as the transition or stellate cells or tracheoblasts.
  • The trafficking of air through spiracles is guided by valves. Most of these (all abdominal) spiracles remain closed during expiration in order to prevent the loss of water from body.

Respiration in Scorpion or Spider

Respiratory organs are book lungs. A book lung is a chamber containing a series of thin, vascular, parallel lamellae arranged like the leaves in a book. Fresh air is drawn into the chamber and after exchange of gases in the lamellae, the foul air is expelled by muscular action.

Respiration In Fishes

Respiratory organs in fish are gills. In elasmobranchs 5-7 pairs of gills and spiracles are present. This type of respiration taking place through gills is the branchial respiration. Each gill is made up of two rows of gill filaments that project from the pharyngeal wall into the gill chamber. Each gill filament has a series of thin, leaf like gill lamellae. Each gill lamella contains a network of capillaries covered by a thin epithelium. For branchial respiration water enters through mouth.
Respiration In Frog
Frog respires both on land as well as in water. Frog has three types of respiration :

  1. Cutaneous respiration :  Skin acts as a respiratory organ. The skin of frog is thin and naked with a large number of blood capillaries in the dermal part. The skin is kept moist by water and mucus. Exchange of gases takes place by diffusion. Cutaneous respiration is the method of respiration both inside water as well as outside. It is the only method of respiration during hibernation and aestivation.
  2. Buccopharyngeal respiration : Exchange of gases occurs through the lining of buccopharyngeal cavity. The mouth, gullet and glottis are kept close while the external nares remain permanently open. The upward and downward movements of the throat is brought about by the contraction and relaxation of two special sets of muscles namely sternohyal and pterohyal muscles. It causes aspiration and expiration of air.
  3. Pulmonary respiration : It occurs with the help of lungs. There are two ovoid, pinkish translucent and inelastic lungs, one on each side of the heart. Lung is covered by a fold of peritoneum and has a large number of small shallow chambers called alveoli. Both the lungs join together to form a common bronchus that is connected with laryngotracheal chamber. This chamber leads into the buccapharyngeal cavity through a longitudinal slit called glottis.

Respiratory System Of Human

Type of human Respiratory system

Human respiratory system is derived from endoderm. Human respiratory system may be divided into two components.

(i) Respiratory tract or conducting portion        (ii) Respiratory organs
(i) Respiratory tract or conducting portion : It is the passage for the air. In this part gaseous exchange does not takes place. It is also called dead air space. It is divided in following parts :
(a) Nose : (Latin-Nasa) (Greek-Rhine) cavity of nose is called nasal cavity. Nasal cavity is divided into two parts by nasal septum called mesenthmoid. Each part is called nasal chamber. Each nasal chamber opens out side by external nares. Nasal septum has two part. First part is small and is made of cartilage (hyaline). Second part is major and it is bony. Vomer is the main bone. Each nasal chamber has three region.
(1) Vestibular region : Vestibular region also known as vestibule, lined by non keratinized squamous epithelium, it is ectodermal in origin  and have sebaceous gland, sweat gland and hair. Vestibule is also found in inner air larynx, mouth and vagina. It acts like a seive to check the entry of large dust particles and other things.
(2) Respiratory region : Middle region lined by respiratory epithelium which is ciliated pseudostratified columnar epithelium. It contains mucus and serous cells. Mucus cells produce mucus and serous cells produce watery fluid. Respiratory epithelium is highly vascular and appears pink or reddish. Respiratory region acts as a air conditioner and makes the temperature of in going air nearly equal to body. It also acts as a filter not give entry to dust particles, flies or mosquitoes.
(3) Olfactory region : It is upper region. It is lined by olfactory epithelium. This is also called Schneiderian epithelium. Olfactory region is the organ of smell and detect the odour of inspired air. Inspiration is stopped if odour of air is foul or offensive. According to new researches pheromone receptors are found in nasal cavities.
(b) Nasal conchae : Lateral wall of nasal cavity have three shelves like structures called conchae or turbinate. 3 pairs of nasal conchae are found. Nasal conchae are covered with mucus membrane. They increase the surface of nasal chamber. Both the chambers of nasal cavity open into nasopharynx by their apertures called internal nostrils or conchae. Adjacent to internal nostril there are opening of eustachian tube. Names of these three conchae and names of the bones that form them are given below.
(1) Superior conchae : The dorsal most chochae is supported mainly by nasal bone called nasoturbinate. It is the smallest conchae.
(2) Middle conchae : Ethmoid bone called ethmoturbinate.
(3) Inferior conchae : The ventral most conchae supported by maxilla bone called maxilloturbinate. It is a separate bone itself.
(c) Pharynx : It is the short vertical about 12 cm long tube. The food and air passages cross here. It can be divided in 3 parts -
(1) Nasopharynx : Nasopharynx is only respiratory upper part in which internal nares open. There are 5 opening in its wall; two internal nares, two eustachian
tube opening and opening into oropharynx.
(2) Oropharynx : Middle part is called oropharynx. In this part oral cavity open known as fauces. Two pair tonsils the palatine and lingual tonsils are found in the oropharynx.
(3) Laryngopharynx or hypopharynx : Lowest part is called laryngopharynx. It leads into two tubes. One at the front is wind pipe or trachea and one at the back is food
pipe or oesophagus. Both oro and laryngo pharynx is both a respiratory and a digestive pathway.
Respiratory System In Cockroach

(d) Larynx or Voice box : It is found both in frogs and rabbits. Larynx does not help in respiration. It is present on tip of trachea and is made up of 9 cartilages such as thyroid (single) has a prominence called pomum admi or adam’s apple, cricoid (single), arytenoid (paired) are piece of hyaline cartilage. While epiglottis (single), carniculate (paired) cuniform (paired), santorini are piece of elastic cartilage. Clinically, the cricoid cartilage is the landmark for making an emergency air way.
(e) Trachea : It is a tubular structure of about 12 cm. in length and 2.5 cm in diameter. The wall of trachea is made of fibres, cartilage muscles and the mucus membrane. In middle of thorax at the level of 4th and 5th thoracic vertebra it divides into two branches called right and left primary bronchi. Right primary bronchus is short and broad and divides into three branches called lobes or secondary bronchi which extend separately into the three lobes of right lung. Left primary bronchus divides into two lobes or secondary bronchi that pass into two lobes of left lung. At the point of bifurcation trachea has projection of cartilage called carina. Further division of secondary bronchi is given in form of arrow diagram.

(ii) Respiratory organs : In men the respiratory organ are a pair of lung. Some snakes have unpaired lungs. Respiration by lungs is called pulmonary respiration. Lungs are found in all vertebrates except fishes. In Lung fishes such as protopterus, neoceratodus and lepidosiren air bladder is found, which is modified lung. Respiration in men and rabbit is pulmonary.
Lungs : Lungs lie in thoracic cavity on both side of heart in mediasternum space. Base of lung is attached to diaphragm. Right lung is divided into 3 lobes viz. Superior, Middle, Inferior and left lung is divided into two lobes Superior and Inferior. In rabbit, the left lung is divided into two lobes left anterior and left posterior where as the right lung has four lobes anterior azygous, right anterior, right posterior and posterior azygous. Lungs of reptiles are more complex than those of amphibians. In birds lungs are supplemented by elastic air sacs which increase respiratory efficiency. The narrow superior partion of lung is termed the apex or cupula.
Respiratory System

Difference between breathing and respiration

Breathing (Ventilation)


It is a physical process.

It is a biochemical process.

It is simply an intake of fresh air and removal of foul air.

It involves exchange of gases and oxidation of food.

No energy is released rather used.

Energy is released that is stored in ATP.

It occurs outside the cells, hence it is an extra-cellular process.

It occurs inside the cells, hence it is an intra-cellular process.

No enzymes are involved in the process.

A large number of enzymes are involved in the process.

Breathing mechanism varies in different animals.

Respiratory mechanism is similar in all animals.

It is confined to certain organs only.

It occurs in all living cells of the body.

  • Protoplasmic respiration refers to the respiration of proteins.
  • Polarography is employed to measure the concentration of oxygen in fluid.
  • Accumulation of blood in pleural cavity is called haemothorax.     
  • All pulmonary volume and capacities are about 20-25% less in females than males.
  • Accumulation of water is called hydrothorax.
  • Accumulation of pus is called pyothorax.    
  • Accumulation of air is called pneumothorax.
  • If chest wall is punctured, then pressure inside the pleural cavity become equal to atmospheric pressure so breathing stops.
  • Besides lungs, the term alveolus is associated with bony socket for tooth, and in mammary glands also.
  • Vital capacity represents the maximum amount of air one can renewed in respiratory system in a single respiration.
  • Values of vital capacity is higher in athletes, sportsmen, mountain dwellers, males than females, young’s than olds.
  • Pregnancy and some diseases like emphysema, pleural effusion, ascites (collection of water in abdominal cavity) reduce the vital capacity. VC decreases as much as 35% in age 70.
  • Measurement of expansion of chest during recruitment of police is done in the hope of getting an idea about vital capacity (greater expansion = greater vital capacity).
  • In general, a man respires about 16 - 18 time in a minute.
  • A new born child respires 32/min.
  • A five year old child respires 26/min.
  • A fifty year old man respires 18/min.
  • Respiratory rate is lowest while sleeping (10 minute in human), respiratory rate during sitting (12 minute in human).
  • No respiratory pigment in cockroach.
  • In all vertebrate respiratory pigment is Hb, except ishfish and angula fish larva.
  • Orthinolarynology – The branch of medicine deals with the diagnosis and treatment of diseases of the ears, nose and throat.
  • Tertiary bronchi also known as segmental bronchi.
  • Located in the walls of bronchi and bronchioles within the lungs are receptor sensitive to stretch called bororeceptor or stretch receptor.
  • Rhinoplasty – or ‘Nose job’ surgically change in shape of external nose.
  • Smaller the animal higher the respiratory rate.
  • Rate of respiration is directly proportional to concentration of CO2 in blood.
  • Inspired air has 20.48 ml. O2 in its 100 ml.
  • Expired air has 15.70 ml. O2 in its 100 ml.
  • Metabolic rate of body is directly proportional to the total pulmonary ventilation.
  • Intra aortic balloon pump is inflated by helium.
  • In pregnant woman diaphragm does not take part in breathing.
  • Respiratory tree is present in Holothurea (Echinodermata) .
  • In living fishes (Protopterus, Lepidosiren and Neocaratodus) lungs are present.
  • In frog larynx and trachea fused together to for larynngo tracheal chamber.
  • Air sacs are presentin birds.
  • A copressure of about 0.7 mm mm Hg concentration of 1% in alveolar air can be lethal.
  • Medullary respiratory centre is constantly under direct chemical control.
  • Impulse for voluntary forced breathing starts in cerebral hemisphere.
  • Lungs of frog acts as negative pressure pump, while lungs of mammal acts as positive pressure pump.
  • Spirometer also known as respirometer.
  • Disorder such as asthma and emphysema can greatly reduce the expiratory reserve volume.
  • Fetal lungs contain no air, and so the lung of a still born baby will not float in water.
  • At birth, as soon as lungs fills with air, O2 starts to diffuse from the alveoli into blood, through the interstitial fluid, finally into the cells.
  • In general, lung volumes are larger in males, taller persons, younger adults and smaller in females, shorter persons, and the elderly.
  • Carbonic, anhydrase is the fastest enzyme.
  • Carbon monoxide combines with Hb more rapidly than O2 to form carboxyhaemoglobin.
  • Carbon monoxide has 200-250 times more affinity of Hb as compared to O2.
  • At about 4 weeks fetal development, the respiratory system begins as an outgrowth of endoderm of foregut, known as laryngotracheal bud.
  • After 6 months, formation of alveoli of lungs.
  • The medullary rhythmicity area in medulla oblongata.
  • The pneumotoxic and the apneustic area in pons.
  • The function of the medullary rhythmicity area is to control the basic rhytum of respiration.
  • If arterial PCO2 is more than 40 mm Hg, a condition called hypercapnia.
  • If arterial PCO2 is lower than 40 mm Hg, a condition called hypocapnia.
  • Double Bohr effect refers to the situation in the placenta where the Bohr effect is operative in both the maternal and foetal circulation.
  • Man uses only 25% of the O2 of inhaled air, where as fishes use 80% O2 of water.
  • Ozone, a strong oxidizing agent, oxidises iron of Hb and forms a stable compound methaemoglobin which can not release O2.
  • The exchange of gases in gills is called bronchial respiration.
  • External gills are present in some annelids (e.g. arenicola, amphitrite) young ones of certain insect (e.g., dragonflies, damsel flies) some tailed amphibians (e.g., necturus, siren, proteus) axolotal larva of tiger salamander and tadpole of frog.
  • Internal gills are found in prawn, unio, pila, fish and tadpole of frog.
  • Counter flow system, is a system for maximum gaseous exchange where blood and water flow in opposite direction (present in gills).
  • Cutaneous respiration can occur both in air and water.
  • Air bladder, also known as swim bladder found in all bony fishes except lophius and cyanoglossus.
  • Air bladder perform the functions of hydrostatic organ, sound production, audition and respiration.
  • Air bladder two types i.e. physostomus air bladder (associate with oesophagus by pneumatic duct) e.g., Lepidostelus, lepidosiren, arnia and physoclistous air bladder (without pneumatic duct) e.g., Anabas, cod, toadfish and hadhock.
  • Foetal Hb takes O2 from mother haemoglobin across the placenta due to double Bohr effect.
  • The foetal Hb has a sigmoid dissociation curve which is shifted to left relative to adult Hb dissociation curve because they have lower P50 (18 to 20 mm Hg) than adult (26.5 mmHg). This means fetal Hb has a higher oxygen affinity.
  • In embroys of mammals, respiration takes place by chorion.
  • In lungs of birds are capillaries are present in place of alveoli.
  • Exchange of O2 takes place twice in lungs of birds. It is called double respiration.
  • Aquatic salamander in lungless amphibians.
  • In snakes, only right lung in functional, left lung is reduced.
  • In penguins double trachea is present.
  • Lungs of frog are air filled chambers and lungs of mammals are spongy.
  • Rate of breathing of a normal man during heavy exercise is 40–50 times/minute.
  • Diaphragm plays 75% part in breathing (abdominal breathing).
  • Ribs and sternum plays 25% part in breathing (thoracic breathing).
  • In pregnant females most part during breathing is played by intercostal muscles.
  • Whales and other aquactic mammals suffocate on land because their intercostal muscles can not expand their chest due to their massive body weight.
  • In elephant, diaphragm plays important role during respiration.
  • In monkeys, kangaroo and other jumping animals, intercostal muscles play important role in breathing.
  • In hibernating animals breathing rate decreases to a lowest limit.
  • At any given pressure the diffusion of CO2 is 20 times faster than O2.
  • If P50 value of Hb rises to 100 mm Hg, a person will die of O2 deficiency because now Hb will not be able to bind or release O2.

Aging and respiratory system, with advancing age -

  • Alveoli, respiratory tract less elastic.
  • Lungs become less elastic.
  • Decreases in lung capacity.
  • Decreases in 35% vital capacity.
  • Decreases level of O2 in blood.
  • Elderly persons are more susceptible to pneumonia, bronchitis, emyphysema.
  • Smoke inhalation injury – Has three components that occur in sequence
  • Inhibition of O2 delivery and utilization.
  • Upper airway injury from heat.
  • Lung damage from acid and aldehyde in smoke.
  • Why smokers have lowered respiratory efficiency.
  • Nicotine constricts terminal bronchioles and this decreases air flow into and out of lungs.
  • Carbon monoxide in smoke birds to haemoglobin and reduces its oxygen carrying capacity.
  • Irritants in smoke cause increased fluid secretion by mucosa of bronchial tree, inhibits the movement of cilia in lining of respiratory system.
  • Destruction of elastic fibres in lungs.

SARS - Severe Acute Respiratory Syndrome -

  • SARS is a highly infectious disease caused by corona virus.
  • Corona virus in RNA virus, its genome was sequenced with in 15 days.
  • The origin of SARC is from South China, from South China this disease spread to Hongkong.
  • Bird sellers and presous in contact with birds to suffer from SARS.
  • Symptoms of infections are flue like symptoms. Fever occurs with dry cough. There is difficult in breathing. Fluid filled in lungs and death occurs with in one week of infection from respiratory failure.
  • Rate of death was initially 4% but now death rate has increased to 10%.
  • Line of treatment is quarnatine and ribovinin durgs.
  • The causative agent of SARS was identified by Dr. Malik Peiris of Microbiology Department of Honkong University.

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