Respiratory system questions | PDF - Free Printable

Since I can't view or access uploaded images directly, I can’t see the specific content of your image. However, based on the text you've provided, it appears to be a worksheet titled "Respiratory System and Respiration" with several questions related to human respiration, gas exchange, and physiology.

I’ll solve each question step-by-step, explaining the reasoning clearly. If any part of the problem differs from what's listed here (e.g., different numbers or context), please clarify.

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1. Why do you think breathing through the nose is better than through the mouth? Give reasons.

Answer:
Breathing through the nose is generally better than through the mouth because:

- Filtration: Nasal hairs and mucus trap dust, bacteria, and other particles.
- Humidification: The nasal passages moisten the air, preventing dryness in the lungs.
- Warming: Blood vessels in the nasal lining warm the air to body temperature before it reaches the lungs.
- Olfaction: The nose allows for smell, which helps detect harmful substances.

These functions protect the respiratory system and optimize gas exchange.

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2. Which muscles are involved in the respiratory stages (inspiration and expiration)?

Answer:
- Inspiration (inhalation):
- Primary muscle: Diaphragm (contracts and flattens, increasing thoracic volume).
- Accessory muscles: External intercostal muscles (lift the rib cage upward and outward).

- Expiration (exhalation):
- Passive during quiet breathing: Diaphragm relaxes and returns to dome shape; internal intercostals may assist slightly.
- Active during forced exhalation: Internal intercostal muscles and abdominal muscles contract to push air out.

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3. Why does the blood that arrives in the lungs contain a high proportion of CO₂?

Answer:
The blood arriving in the lungs (deoxygenated blood) has a high proportion of CO₂ because:
- CO₂ is a waste product of cellular respiration in tissues.
- As cells produce CO₂, it diffuses into the bloodstream and is transported via veins to the lungs.
- This deoxygenated blood travels through the pulmonary arteries to the lungs for gas exchange.

So, the high CO₂ level reflects the body’s metabolic activity and need to eliminate this waste gas.

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4. The air we inhale contains a certain amount of CO₂, why does this gas pass to the capillary in the alveoli?

Answer:
Although inhaled air contains a small amount of CO₂ (~0.04%), it still passes into the capillaries due to diffusion gradients:
- In the alveoli, the partial pressure of CO₂ (PCO₂) is lower than in the blood.
- CO₂ moves from areas of higher concentration (blood) to areas of lower concentration (alveolar air).
- But note: the *net movement* of CO₂ is from blood to alveoli, not the other way around.
- The presence of CO₂ in inhaled air doesn’t prevent this — the gradient ensures CO₂ continues to diffuse out of the blood into the alveoli.

So, even though some CO₂ is in the inhaled air, the partial pressure gradient favors CO₂ moving from blood → alveoli → exhaled air.

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5. The following table shows the amount of oxygen (O₂) found in 100ml of blood when the blood stream reaches the muscle and when it leaves it.

| Bloodstream reaching muscle | Bloodstream leaving muscle |
|----------------------------|-----------------------------|
| O₂ = 21 ml | O₂ = 3 ml |

#### a. How does the blood change when passing through the muscle? Why?

Answer:
- The blood loses 18 ml of oxygen per 100 ml as it passes through the muscle.
- This happens because muscle cells use oxygen for aerobic respiration to produce energy (ATP).
- Oxygen diffuses from the blood into the muscle tissue where it is consumed.

Thus, oxygen levels decrease as blood flows through active muscles.

#### b. What are the differences between the resting and active muscle? What are these differences due to?

Answer:
- Resting muscle: Requires less oxygen → blood delivers less O₂; more O₂ remains in blood after passage.
- Active muscle: Requires more ATP → increases oxygen demand → more O₂ extracted from blood → greater drop in O₂ levels.

This difference is due to increased metabolic rate during physical activity. Active muscles extract more O₂ from the blood to support higher energy production.

*(Note: While the table doesn’t specify "resting vs active," this question implies comparison. You might need to assume one scenario is active and another is resting.)*

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6. Imagine the type of changes (in the same blood) if we measured the carbon dioxide (CO₂) instead of the oxygen.

Answer:
- CO₂ levels would increase as blood passes through the muscle.
- Muscles produce CO₂ as a byproduct of cellular respiration.
- CO₂ diffuses from muscle cells into the blood.
- So, blood leaving the muscle would have higher CO₂ than blood entering it.

In contrast to O₂ (which decreases), CO₂ increases in venous blood after passing through active tissues.

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7. As an average, humans do 12 inspirations per minute. The mean volume of air that we intake is 500 cm³. Using this data, calculate the volume of air that your lungs move during one minute.

Answer:
- Volume per breath = 500 cm³
- Breaths per minute = 12

$$
\text{Minute ventilation} = 500 \times 12 = 6000 \text{ cm}^3/\text{min}
$$

Or 6 liters per minute.

✔ Answer: 6000 cm³/min (or 6 L/min)

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8. Remember we do about 12 inspirations per minute.

#### a. How many inspirations do you do a day?

Answer:
- Inspirations per minute = 12
- Minutes in a day = 24 × 60 = 1440

$$
12 \times 1440 = 17,280 \text{ inspirations per day}
$$

✔ Answer: 17,280 breaths per day

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#### b. What is the volume of air that has reached your lungs in one day?

Answer:
- Volume per breath = 500 cm³
- Total breaths per day = 17,280

$$
500 \times 17,280 = 8,640,000 \text{ cm}^3 \text{ per day}
$$

Convert to liters:
$$
8,640,000 \div 1000 = 8,640 \text{ liters per day}
$$

✔ Answer: 8,640 liters of air per day

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#### c. Air contains 21% oxygen (O₂) (in volume). Of this, only a quarter (¼) is captured by blood in the alveoli. Using previous data, what is the quantity of oxygen that your cells receive in one day? Would it be different if you did intense physical effort such as sports?

Answer:

##### Step 1: Total air inhaled per day = 8,640 L
##### Step 2: Oxygen in inhaled air = 21% of 8,640 L

$$
0.21 \times 8,640 = 1,814.4 \text{ L of O}_2 \text{ inhaled per day}
$$

##### Step 3: Only ¼ of this O₂ is actually absorbed by blood

$$
\frac{1}{4} \times 1,814.4 = 453.6 \text{ L of O}_2 \text{ absorbed per day}
$$

✔ Answer: About 453.6 liters of oxygen are delivered to cells daily.

##### Now, would it be different during intense physical effort?

Yes. During sports or exercise:
- Breathing rate and depth increase → more air moved per minute.
- Oxygen extraction by muscles increases.
- More O₂ is taken up by the blood.
- Therefore, more oxygen is delivered to cells.

So, under physical exertion, the amount of O₂ received by cells increases significantly.

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✔ Summary of Answers:

| Question | Answer |
|--------|--------|
| 1 | Nose filters, warms, and humidifies air. |
| 2 | Inspiration: diaphragm & external intercostals. Expiration: passive (diaphragm relaxation), active (internal intercostals, abdominals). |
| 3 | Blood carries CO₂ from tissues to lungs as a waste product. |
| 4 | CO₂ moves from blood to alveoli due to partial pressure gradient. |
| 5a | O₂ decreases from 21 to 3 ml/100ml due to muscle usage. |
| 5b | Active muscle extracts more O₂ than resting muscle due to higher metabolism. |
| 6 | CO₂ increases in blood after passing through muscle. |
| 7 | 6000 cm³/min (6 L/min) |
| 8a | 17,280 breaths/day |
| 8b | 8,640 L of air/day |
| 8c | ~453.6 L O₂ absorbed/day; increases during exercise. |

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