Breathing and Exchange of GasBreathing/Ventilation- First step of respiration, refers to the movements that send fresh air or with dissolved in water to the respiratory organs (inspiration) and removes foul air or water from them(expiration).External Respiration- Intake of oxygen by the blood from water or air in the respiratory organs and elimination of carbon dioxide.Internal Respiration- involves uptake of oxygen by tissue cells via tissue fluid, oxidation of food in tissue cells leading to production of carbon dioxide, water and energy, storage of energy in the form of ATP and release of CO2 from tissue cells into blood via tissue fluid.Respiration - Biochemical process of ATP energy production by oxidation of food materials within cell.C6H12O6 + 6O2 6CO2 + 6H2O + Energy (Glucose) (oxygen) (Released) (Reuse) (stored as ATP) ATP Hydrolysis ADP +Pi + Energy used in life activitiesAerobic Respiration involves use of molecular oxygen for breakdown of respiratory substrate and release of carbon dioxide simultaneously. Occurs in most animals and plants.Anaerobic Respiration does not utilize molecular oxygen, for the breakdown of organic substrate and CO2 may or may not be released.i. In Yeast C6H12O6 2C2H5OH + CO2 + Energy (Glucose) (Ethanol)ii. In Certain Bacteria and Parasitic Worms ( Ascaris, Tapeworm)C6H12O6 2CH3CHOHCOOH + Energy

Types of Respiration Cutaneous respiration - Exchange of respiratory gases through the thin, moist, permeable and highly vascularised skin.Buccopharyngeal respiration - Exchange of respiratory gases through thin, vascular lining of buccopharyngeal cavity.Branchial respiration - Exchange of respiratory gases in gills.Pulmonary respiration Exchange of gases through lungs. (Lactic Acid)

Respiratory Pigment greatly increase the capacity of blood to carry oxygen and carbon dioxide.Haemocyanin - respiratory pigment in plasma in crustaceans and mollusks.Haemoglobin respiratory pigment in the red blood cells in vertebrates and in annelids in the plasma.

LungsVertebrataMammalsBirds

Reptiles

1.Skin 2.Buccophyngeal

Body SurfaceProtozoaSpongesCnidariansPlatyhelminthesMoist Skin1. Prawn Gills(Branchial respiration)2. Insects Tracheae (Tracheal respiration)3.Scorpion Book Lungs4.King Crab Book Gills ArtropodaCtenidia (Gills) and Pulmonary SacMolluscaDermal Branchae and Tube FeetEchinodermsPharyngeal WallHemichordataGillsCyclostomes, FishesAmphibiansPharyngeal WallUrochordataPharyngeal WallCephalochordataNemathelminthesAnnelidaChordataRespiratory organs in different animals

Human Respiratory SystemSchematic diagram of lungs and thorax

PASSAGE OF AIR

AlveoliAlveolar DuctsBronchiolesBronchiTracheaLarynxLaryngopharynxOropharynxNasopharynxNostrils

1.Nasal Cavity - Moist epithelium and nasal hairs help in i. Filtering airii. Preventing entry of microbes iii. Making air temperature according to body temperature2.Larynx / Voice Box i. It is cartilaginous box which have vocal cords to produce sound. ii. Epiglottis prevent entry of food into glottis. 3.Glottis Aperture in laryngopharynx which opens into trachea. 4.Trachea i. It is a straight tube upto mid-thoracic cavity.ii. Wall of trachea and bronchi have C-shaped cartilaginous rings.iii. After entering in lungs, bronchi divide into primary, secondary and tertiary bronchioles and finally end into irregular balloon shaped structure called Alveoli.5.Lungs Two cone shaped spongy lungs are present which are covered by a doubled layered pleura membrane with pleural fluid between them.6.Diaphragm It is a domb shaped cartilaginous structure which is present on lower side of lungs.7.Alveolar Wall is very thin (0.0001mm) wall composed of simple moist, non-ciliated, squamous epithelium which easily recoil and expand during breathing. Number of alveoli is countless which increase the surface area of lungs, thus accelerating gaseous exchange in alveoli. It is closely surrounded by a network of pulmonary capillaries arising from pulmonary artery and rejoin to form pulmonary vein.

8.Respiratory membrane consists of alveolar epithelium, epithelial basement membrane , a thin interstitial space, capillary basement membrane and capillary endothelial membrane (total thickness = 0.3m). Hence, diffusion of gases between the blood and alveolar air occurs easily and quickly.Respiration involves the following steps:i. Breathing or pulmonary ventilation by which atmosphaeric air is drawn in and CO2 rich air is released out.ii. Diffusion of gases (O2 and CO2) across air is released out.iii. Transport os gases by the blood.iv. Diffusion of O2 and CO2 between blood and tissue.v. Utilisation of O2 by the cells for catabolic reaction and resultant release of CO2 .Advantages of lung breathing i. Lungs lie within the body, hence respiratory surface can be kept moist.ii. Air less dense than water, hence requires less energy to move the air to and from the respiratory surface.iii. A tidal flow (in and out) sufficient to ventilate lungs.

Advantage of nasal breathing over mouth breathingAir passing through nasal chamber is subjected warming, moistening, sterilization and cleaning specially by virtue of the presence of hair and mucus which holds the dust particles and bacteria of the passing air, which are absent.

Mechanism of BreathingBreathing involve 2 stagesa) Inspiration In halation of atmospheric air into lungs. Inspiration is initiated by contraction of diaphragm and external intercostals muscles, which lift up the ribs and the sternum causing increase in volume of thoracic chamber. Volume increase cause decrease un pulmonary pressure which result inhalation of air from outside to lungs.b) Expiration Exhalation of air from lungs. Expiration is initiated by relaxation of diaphragm and contraction of internal intercostal muscles to their normal position causing decrease in volume of thoracic chamber. Volume decrease causes increase in pulmonary pressure which result in expulsion of air from lungs to outside.Note : Breathing rate 12-16 per minute.Spirometer is used to estimate air volume during breathing. Respiratory Volume and Capicities1. TV (500ml)Volume of air normally inspirited / expirated.2. IRV (2500ml)Volume of additional air forcefully inspired.3. ERV (1000ml)Volume of additional air forcefully expired.4. I.C = TV + IRV = 500 + 2500 = 3000ml5. E.C = TV + 1000 = 1500ml6. T.L.C = TV + ERV + RV + IRV = 500 + 1000 + 1100 + 2500 + 5100ml7. F.R.C = ERV + RV = 1000 + 1100 = 2100ml8. V.C = IRV + ERV + TV = 2500 + 1000 + 500 = 4000mlExchange of GasesAlveoli are the site of gaseous ecchange between air and blood.Gaseous exchange occur by simple diffusion mainly based on partial pressure of O2 and CO2.Diffusion of gases occur through 3 layers :a) Thin epithelium of alveoli.b) Thin endothelium of blood capillaryc) Basement between them.

Transport of Gases1. Transport of oxygen97% O2 transport by RBC.3% O2 transport by PlasmaO2 can bind with haemoglobin in a reversible manner to form oxy-haemoglobin. Hb + 4O2 Hb(O2)4(A) High pO2 (B) Low pO2Low pCO2 High pCO2Low pH (H+ conc.) High pH ( H+ Conc.)Low temperature High temp.

A sigmoid curve is obtained per cent saturation of haemoglobin with O2 is plotted against pO2.

Saturation of Hb. With O2

pO2Note : Every 100ml of oxygenated blood can delivery about 5ml of O2 to tissues.2. Transport of CO2 a) As caramino haemoglobin 20 25%Hb + CO2 Hb. CO2 Carbamino HaemoglobinI. High pCO2 and low pO2II. Low pCO2 and high pO2b) As bicarbonate ion (70%)CO2 + H2O H2CO3 HCO3- + H+ Carbonic Anhydrase Carbonic acidc) As dissolved state in plasma(7%)Note : Every 100ml of deoxygenated blood delivary about 4ml of CO2.Regulation of Respirationa) Respiratory Rhythm Centre Situated in medulla region. It regulates breathing rhythms acc. to demand of body tissue.b) Pneumotaxic Centre - Situated in pons region It can moderate function of respiration rhythm centre and thereby alter the respiratory rate.c) Chemosenstive Centre Situated near rhythm centre. It is very sensitive to CO2 and H+ ion.Disorders of Respiratory1. Asthma is a difficulty in breathing causing wheezing due to inflammation.2. Emphysema is a chronic disorder in which alveolar walls are damaged due to which respiratory surface is decreased. One of the major causes of this is cigarette smoking.3. Occupational Respiration Disorde In certain industries, especially those involving grinding or stone breaking, so much dust is produced that the defence mechanism of the body cannot fully cope with the situation. Long exposure can give rise to inflammation leading to Fibrosis ( proliferation of fibrous tissue) and thus causing serious lung damage. Works in such industries should wear protective masks.Eg. Silicosis and Asbestosis QuestionsQ1. How many oxygen molecules can be carried out by one haemoglobin molecule?Ans: 4 moleculesQ2.Give the name and function of a fluid filled double membranous layer which surrounds the lungs?Ans: Pleuron. It reduces the friction and keeps the two pleura together and the lungs in flated.Q3. Cigarette smoking causes emphysema. Give reason.Ans. Cigarette smoking damages alveolar walls due to alveolar sacs remaining filled with air leading to decreased respiratory surface for exchange of gases.Q4. How is the entry of food prevented in the respiratory tract?Ans. During swallowing, a cartilaginous flap like structure called epiglottis covers the glottis and prevents the entry of food into respiratory tract.Q5. What are occupational respiratory disorders? What are their harmful effects? What precautions should a person take to prevent such disorder?Q6. Explain the role of neural system in regulation of respiration in human? Q7. Name the organ of respiration in the following organisms.a) Flatworms b) Birds c) Frog d) Cockroach