Breathing and Exchange of gases MCQ

Ans. d) Both a and b

Explanation: The organs of the thoracic cavity are the thymus gland, the heart, the lungs, the tracheobronchial tree, and the pleurae. Thoracic Cavity is a hollow space in the human body. It can also be referred to as the chest cavity. The thoracic cavity is surrounded by the upper respiratory tract that comprises the pharynx, the nose, and the upper respiratory tract organs which are located outside the chest structure.

Ans. c) Total lung capacity

Explanation: The total lung capacity refers to the total volume of air that is filled in the lungs through a forced inhalation. For a healthy man, the lung capacity is estimated to be about 6000 ml. It can be determined by TLC = TV + ERV + IRV + RV.

Ans. d) The visceral pleura and the chest wall are in direct contact with each other.

Explanation: The pleural cavity is known as the potential space that exists between two pleurae of the lungs or visceral parietal. The pleura can be understood as a membrane that folds back on itself and forms a membrane of two layers. The visceral pleura, therefore, is closely connected to the chest wall. This close attachment of the chest wall helps to transmit pressures to the surface of the visceral pleura and therefore to the lung.

Ans. a) Bicarbonates

Explanation: Carbon dioxide in the body is transferred as:

• 20 to 25 percent of the carbon dioxide in the body is carried through Red Blood Cells (RBCs)
• About 70% of the carbon dioxide is carried as the Bicarbonates.
• 7 percent of carbon dioxide is carried through plasma in a dissolved state.

Ans. a) Abdominal muscles do not participate in the process of respiration.

Explanation: The muscles of the thorax, abdomen, and neck are all involved in changing the volume and therefore the pressure present in the thoracic activity. Abdominal muscles play an important role in the breathing process. When these muscles contract, abdominal pressure is raised and it pushes a diaphragm against the lungs so that the air is pushed out.

Ans. b) Hyaline Cartilage

Explanation: Hyaline Cartilage is glass-like and translucent cartilage that is found on most joint surfaces. Most commonly it is found in the nose, larynx, trachea, and ribs. It has a firm consistency and consist of a good amount of collagen. In the absence of the nerves and blood vessels, therefore has a very simple structure.

Ans. b) It regulates inspiration

Explanation: The pneumotaxic centre is located in the pons in the brain. This centre helps in regulating the functioning of the respiratory rhythm centre. It sends neural signals so that the duration of inspiration can be reduced which further affects the rate of respiration.

Ans. d) Inflammation of bronchioles & decreased respiratory surface

Explanation: Asthma is known as inflammatory lung disease. The airways of the lungs in this condition narrows down and swell, thereby producing an excess of mucus. As a result of this, the respiratory surface also decreases. The symptoms of asthma include shortness of breath, reversible airflow obstruction, wheezing, bronchospasm, shortness of breath, and coughing.

Emphysema is another disease of the lungs that causes shortness of breath. This causes the lung airways to collapse while producing inflammation of the bronchioles. The symptoms of emphysema include shortness of breath, coughing, and wheezing.

Ans. b) Epiglottis

Explanation: If a person starts coughing suddenly while they are swallowing food, it is a result of the improper movement of the epiglottis. If the glottis is not closed properly, some of the food can enter the respiratory tract which can eventually result in coughing.

Ans. c) Nostrils - pharynx - larynx - trachea - bronchi - bronchioles - alveoli

Explanation: Air is inhaled through the nostrils of the nose.

• The air then travels down to the pharynx that is at the back of the throat.
• It then passes through your voice box, which is known as the larynx.
• Then it goes into the trachea, the windpipe.
• The trachea is further divided into two passages of air that is known as bronchial tubes.
• One of the tubes leads the air to the left lung while the other leads it to the right lung.
• The bronchial tubes divide the air into bronchi and then leads it to bronchioles.
• From the bronchioles, the air is passed on to the tiny air sacs that are known as alveoli. Oxygen here is transferred from the air that is inhaled to the blood.

Ans. b) carbaminohaemoglobin and as well as carbonic acid

Explanation: When carbon dioxide is bound to the haemoglobin, another molecule known as carbaminohaemoglobin is formed. This binding of carbon dioxide to the haemoglobin present in the blood is reversible. Hence, when it reaches the lungs, the carbon dioxide in the blood can freely dissociate from the haemoglobin and therefore can be expelled from the body.

Ans. d) 1500 mL

Explanation: We are given-

Tidal Volume = 500 mL

Expiratory Reserve Volume = 1000 mL

The formula for expiratory capacity = TV + ERV

= 500 + 1000

= 1500 mL

Therefore, the expiratory capacity is 1500 mL.

Ans. d) Atmospheric oxygen (O₂) level is lesser and therefore more RBCs are needed in order to absorb the required amount of oxygen for surviving.

Explanation: At higher altitudes, the air composition remains the almost same as it is at sea level. However, the density or the barometric pressure of air decreases gradually. As a result of this, arterial p02 also decreases, known as hypoxemia. Due to high altitudes, human body has to acclimatize to complex conditions. The number of red blood cells per unit volume of the blood is likely to be high in a person who lives at high altitudes. This is because the air is less dense at high altitudes. Therefore, more RBCs are needed in order to trap oxygen from the air having a low partial pressure of oxygen.

Ans. c) The thoracic volume increases

Explanation: For mammals, their internal body cavity is divided via a muscular diaphragm into an abdominal cavity and a thoracic or chest cavity. The thoracic cavity is airtight and it contains the lungs. The thoracic cavity follows Boyle's law as it is airtight. As per Boyle's law, the volume and pressure and related inversely. During inspiration, the volume of the thoracic cavity increases, the pressure decreases. During expiration, the thoracic cavity's volume decreases, pressure increases and the air moves out of the lungs.

Ans. c) Lungs

Explanation: Pleura is a double-layered membrane that is responsible for covering the lungs in the human body. It is a thin and large sheet of tissue that is wrapped outside the lungs and lines the inside of our chest cavity. The pleura has two thin tissue layers that cushion and protects the lungs. The inner layer is around the lung and is stuck to it tightly while the outer layer lines the inside of our chest wall.