Questions: Breathing and Exchange of Gases

Q1. Why is the alveolar region the only site of gas exchange?

Answer (English): The alveolar wall is only one cell thick and is covered by a thin film of moisture, so gases dissolve easily and have a short distance to diffuse. The alveoli are surrounded by a dense network of capillaries, which keeps the concentration gradient steep. The rest of the respiratory tract has thicker walls and a poor blood supply, so it conducts air but cannot exchange gases efficiently.

Hinglish: Alveoli ki wall ek cell moti hoti hai, moisture hoti hai aur capillaries ka jaal hota hai, isliye diffusion fast hota hai. Baaki respiratory tract sirf air conduct karta hai.

Q2. Distinguish inspiration from normal expiration.

Answer (English): Inspiration is active: the diaphragm contracts and the external intercostals lift the ribs and sternum, the thoracic volume rises, the pulmonary pressure falls below atmospheric pressure and air enters. Normal expiration is passive: the diaphragm and intercostals relax, the thoracic volume falls, the pulmonary pressure rises above atmospheric pressure and air moves out. Forced expiration uses the abdominal muscles and internal intercostals.

Hinglish: Inspiration active process hai jisme muscles contract karke volume badhate hain aur pressure girne se air andar aati hai; normal expiration passive hai jisme muscles relax karte hain aur air bahar nikal jati hai.

Q3. Define tidal volume and residual volume.

Answer (English): Tidal volume is the volume of air inspired or expired during one normal breath, about 500 mL in a resting adult. Residual volume is the air that a person cannot push out even by the hardest possible expiration; it stays at about 1100 to 1200 mL and is the reason the lungs never empty completely.

Hinglish: Tidal volume normal saans mein andar-bahar aayi air hai, lagbhag 500 mL. Residual volume forcible expiration ke baad bhi lungs mein bachi air hai, lagbhag 1100-1200 mL.

Q4. How is vital capacity calculated and why is it important?

Answer (English): Vital capacity is the largest breath a person can move after filling the lungs completely, measured as the air expelled after a maximum inspiration. It is the sum of expiratory reserve volume, tidal volume and inspiratory reserve volume, which for a healthy adult is about 3500 to 4500 mL. It is important because it measures how much air the lungs can actually move, and a fall in vital capacity points to a restrictive lung or chest wall problem.

Hinglish: Vital capacity maximum inspiration ke baad maximum expiration ki air hai: ERV + TV + IRV. Yeh lungs ki usable breathing capacity batati hai aur restrictive diseases mein kam ho jati hai.

Q5. Explain the oxygen dissociation curve.

Answer (English): The oxygen dissociation curve plots the percentage saturation of haemoglobin with oxygen against the partial pressure of oxygen. It is sigmoid because haemoglobin has four binding sites: the first oxygen binds with some difficulty, each further binding changes the protein and makes the next easier, and at high pO2 the curve flattens as the sites fill. The sigmoid shape allows quick loading in the lungs and quick unloading in the tissues.

Hinglish: Oxygen dissociation curve haemoglobin ki saturation ko pO2 ke against plot karti hai. Yeh sigmoid hai kyunki haemoglobin ke chaar binding sites hain aur har binding agla binding aasan banati hai.

Q6. In what forms is carbon dioxide transported in the blood?

Answer (English): About 70 per cent of carbon dioxide is carried as bicarbonate ions in the plasma, about 20 to 25 per cent is carried as carbaminohaemoglobin attached to the globin part of haemoglobin, and about 7 per cent is dissolved in the plasma. The enzyme carbonic anhydrase in the red blood cells speeds up the conversion of carbon dioxide to bicarbonate.

Hinglish: CO2 lagbhag 70 per cent bicarbonate ke roop mein plasma mein, 20-25 per cent carbaminohaemoglobin ke roop mein aur 7 per cent plasma mein ghulkar travel karti hai.

Q7. What is the Bohr effect and when does it help the animal?

Answer (English): The Bohr effect is the shift of the oxygen dissociation curve to the right when the partial pressure of carbon dioxide and the hydrogen ion concentration rise and the pH falls. In an active tissue, respiration raises pCO2 and H+ and the temperature, and all three make haemoglobin release oxygen more readily exactly where oxygen demand is highest. The effect therefore matches oxygen delivery to the metabolic activity of the tissue.

Hinglish: Bohr effect mein pCO2 aur H+ badhne se oxygen dissociation curve right shift hota hai aur haemoglobin oxygen jaldi chhodta hai. Active tissue mein yahi hota hai, isliye oxygen wahan milti hai jahan zaroorat zyada hai.

Q8. Why does carbon dioxide diffuse faster than oxygen across the alveolar membrane?

Answer (English): The diffusion rate depends on the solubility of the gas in the membrane as well as on the pressure difference. Carbon dioxide is about twenty times more soluble in the diffusion membrane than oxygen, so for the same partial pressure difference much more carbon dioxide crosses per unit time. Oxygen is therefore the gas that limits gas exchange, even though carbon dioxide has a smaller pressure difference to overcome.

Hinglish: CO2 membrane mein oxygen se lagbhag bees guna zyada soluble hai, isliye same pressure difference par zyada CO2 diffuse hoti hai. Isi wajah se exchange ki rate oxygen se limit hoti hai.

Q9. How is breathing regulated by the nervous system?

Answer (English): The respiratory rhythm centre in the medulla oblongata sets the basic rhythm of breathing. The pneumotaxic centre in the pons moderates this rhythm, and when stimulated it reduces the duration of inspiration. The chemosensitive area near the rhythm centre responds to a rise in carbon dioxide and hydrogen ions and increases the rate and depth of breathing. Carbon dioxide is the main chemical regulator; oxygen plays only a minor role.

Hinglish: Medulla ka rhythm centre basic rhythm deta hai, pons ka pneumotaxic centre use moderate karta hai, aur chemosensitive area CO2 aur H+ badhne par breathing tez kar deta hai. Main regulator CO2 hai.

Q10. Name the types of respiratory disorders and one cause of each.

Answer (English): Asthma is narrowing and inflammation of the bronchi and bronchioles, often triggered by allergens. Emphysema is damage to the walls of the alveoli, and cigarette smoking is its major cause. Occupational respiratory disorders are caused by long exposure to dust and fumes in mines and factories. All three reduce the efficiency of gas exchange.

Hinglish: Asthma mein bronchi-bronchioles inflame hote hain, emphysema mein alveolar walls damage hoti hain aur smoking iska bada karan hai, aur occupational disorders dust-fumes ke exposure se hote hain.

Quiz pointer. A five question chapter quiz follows this page. Attempt it without looking back and read the explanation for every question you miss, because the quiz retests the volume sums and the gas transport routes used above.