Unit 2: Human Respiratory System — Short Questions

Gaseous Exchange Gaseous exchange is the process in which oxygen present in the inhaled air (in lungs) moves into blood, and carbon dioxide from the blood moves into the air to be exhaled. Gaseous exchange helps in respiration.

Breathing Breathing is the process in which animals move air into and out of their body. Breathing help in gaseous exchange.

Breathing (i) Breathing is used for the process through which animals take air in bodies to get oxygen from it and then give out the air for getting rid of carbon dioxide.
(ii) It is only the mechanical or physical process for exchange of gases.
(iii) It occurs at respiratory system.
(iv) Energy is utilized.

Cellular Respiration (i) Cellular respiration is the process in which the C-H bonds in food are broken by oxidation reduction reactions and the energy is transformed into ATP.
(ii) It is a mechanical and biochemical process.
(iii) It occurs at cellular level i.e. mitochondria and cytoplasm.
(iv) Energy is released.

In the walls of trachea, C-shaped cartilages are present. While the walls of bronchi have plate-like cartilages. These cartilages prevent trachea and bronchi from collapsing even when there is no air in them.

At rest, human's breath 16 – 20 times per minute in normal conditions while during exercise or hard job the breathing rate increases upto 30 – 40 times per minute.

Alveoli maximize gas exchange through their huge surface area (millions of sacs), extremely thin walls (one cell thick for short diffusion), moist lining (for dissolving gases) and rich capillary network (to maintain steep concentration gradients).

These features allow oxygen to rapidly diffuse from inhaled air into the blood and carbon dioxide to move from the blood into the alveoli to be exhaled.

Bronchitis is the inflammation of bronchi and bronchioles.

Causes Infections by viruses or bacteria, and chemical irritants (e.g., tobacco smoke).

Symptoms Coughing, wheezing, fever, chills and shortness of breath.

Treatment Medications (cough suppressants) to ease breathing, antibiotics (if it is due to bacterial infection), antiviral medicines (if it is due to viral infection), and avoiding irritants like smoke and pollution.

In emphysema, the inner walls of alveoli become weak and then rupture. Thus, one larger air space is created instead of many small ones. So, the space for gaseous exchange decreases and the patient cannot inhale properly.

Symptoms Shortness of breath, chronic cough (with or without mucus), wheezing and chest tightness.

Treatment Medicines to relieve cough and breathing problems. Emphysema cannot be cured completely.

A carcinogen is any substance, agent or exposure (Physical, chemical or biological) that can cause cancer or significantly increase the risk of developing it by damaging DNA and disrupting normal cell growth, leading to uncontrolled cell division. e.g., Nicotine, Carbon monoxide etc.

Feature | Inspired Air | Expired Air
Oxygen | 21% | 16%
Carbon dioxide | 0.04% | 4%
Nitrogen | 79% | 79%

The following is the path of air:

Nasal cavity → Pharynx → larynx → trachea →bronchus→bronchioles→alveolar ducts→ alveoli

We should breathe through the nose and not through the mouth to keep ourselves healthy. Because breathing through nose can help filter out dust and allergens, boast oxygen uptake, and humidify the air we breathe in. Mouth breathing, on the other hand, can dry out our mouth and lungs.

(a) Pharynx and Larynx

Pharynx

• The nasal cavity leads into the pharynx which is about 4 – 5 inches long muscular passage. It is lined by mucous membrane.
• It surrounds the upper part of trachea.

Larynx

• The air goes from the pharynx into the larynx. The larynx is a box of cartilage. It is also called the voice box.
• It is present between pharynx and trachea.

(b) Bronchi and Bronchiole

Bronchi The trachea divides into two bronchus (plural bronchi) the one leading to each lung.

Bronchiole Inside the lungs each bronchus divides again and again to form a mass of very fine branches called bronchioles.

(c) Glottis and Epiglottis

Glottis Larynx is a cartilaginous structure situated above the trachea, its cavity is called glottis. Glottis is a narrow opening at the floor of pharynx which leads into larynx.

Epiglottis The glottis is guarded by a flap of tissue called the epiglottis. It prevents the entry of food into the trachea.

The rate of breathing is controlled by the respiratory centre in the brain. The respiratory centre is sensitive to the concentration of carbon dioxide in the blood. When we do exercise or some hard job, our muscle cells carry out cellular respiration at greater rate. It results in the production of more carbon dioxide which is released in the blood. This greater than normal concentration of carbon dioxide stimulates the respiratory centre of brain. The respiratory centre sends messages to the rib muscles and diaphragm to increase the rate of breathing so that the excess carbon dioxide present in blood can be removed out of body. During exercise or other hard physical works, the breathing rate may increase up to 30-40 times per minute.

Diagram B shows the process of exhalation.

Reasons 1. The ribs are down because rib muscles are contracted.
2. The diaphragm is relaxed and normal dome-shape is attained.
3. The area of the thoracic cavity is decreased, which enhances the pressure on lungs.
4. As a result, the lungs inflated and the air pressure within them increased.
5. The air is forced out from the lungs to the surrounding air

(a) I. Inspired air chart
II. Expired air chart
X. Percentage of carbon dioxide
Y. Percentage of nitrogen
Z. Percentage of oxygen

(b) Because in inspired air percentage of X gas (Carbon dioxide) is 0.04%.

(c) Percentage of X gas (Carbon dioxide) is increased due to breathing out X gas during expiration.

(a) Disease name is emphysema and part B of the figure is showing that alveoli are affected.

(b) Part B of the figure shows the destruction of the walls of the alveoli. Resulting in larger sacs and less surface area for gaseous exchange.

(c) Symptoms:
1. Shortness of breath
2. Recurrent respiratory infections

(a) Alveoli
(b) X = Carbon dioxide, Y = Oxygen
(c) Oxygenated blood

(a) Bronchitis and Pneumonia

Bronchitis It is the inflammation of lining of air passages like trachea, bronchi and bronchioles.
It results in excessive secretions of mucous into the tubes, leading to swelling of tubular walls and narrowing of tube.

Symptoms Cough, mild wheezing, fever, chills, shortness of breath.

Treatment Inhalers or antibiotics may be prescribed.

Pneumonia Pneumonia is defined as an inflammation of alveoli of lungs caused by acute infection.
The most common cause of pneumonia is bacteria Streptococcus pneumoniae.

Symptoms Fever, shakings chills, chest pain, cough, headache, sore throat, nausea, diarrhoea etc.

Treatment Antibiotics are prescribed for bacterial pneumonia.

(b) Smoker and Passive Smoker

Smoker Inhalation of smoke from filter end is called active smoking and the person who involved in it, is called active smoker / smoker.

Passive Smoker Passive smoking is the inhalation of smoke from another's smoking. The person who is involved in it, is passive smoker.

If the diaphragm stops working properly, we will experience shallow breathing. Shortness of breath, fatigue and poor oxygenation leading to increased heart rate, confusion and inability to take deep breaths especially when lying down or exerting yourself.

Smoke particles are dangerous because:

• They trigger inflammation and tissue damage.
• Disrupt oxygen transfer
• Impair the lung's natural cleaning mechanisms.
• The smallest particle can even enter the bloodstream to affect other organs including the heart and brain.

The trachea has C – shaped cartilage to keep the airway permanently open and prevent collapse during breathing while bronchioles lack them because they are smaller, more numerous and need more smooth muscles for airflow control as they lead to gas exchange alveoli, where structural rigidity is not as crucial as air regulation and flexibility.

During asthma attacks, inflammation and muscle constriction narrow the bronchial tubes airways, making it harder for patients to exhale than to inhale.