Test: Human Physiology: Respiratory System - 1 - NEET MCQ

Expiration muscles come into action when you force expiration. The expiratory muscles are the abdominal muscles and intercostals. It is rare if a patient is contracting abdominal muscles for quiet breathing and he is trying to force expiration.

• Alveoli is a thin, irregular walled and vascularized bag-like structure.
• It is the main site for diffusion of gases.
• Terminal bronchioles give rise to alveoli.
• Lungs without alveoli is a dead lung as they play a major role in respiration.

Mucus helps to moisten and protect the airways. Mucus lines the ciliated cells of the trachea to trap inhaled foreign particles that the cilia then waft upward toward the larynx and then the pharynx where it can be either swallowed into the stomach or expelled as phlegm.

'Motile' (or moving) cilia are found in the lungs, respiratory tract and middle ear. These cilia have a rhythmic waving or beating motion. They work, for instance, to keep the airways clear of mucus and dirt, allowing us to breathe easily and without irritation. They also help propel sperm.

Chloride shift also known as the Hamburger phenomenon is a process which occurs in a cardiovascular system and refers to the exchange of bicarbonate (HCO₃⁻) and chloride (Cl⁻) across the membrane of red blood cells (RBCs).

Oxygen haemoglobin dissociation curve gives the relationship between the saturation of haemoglobin and oxygen tension.
The curve obtained by plotting percent saturation of Hb against time is sigmoid, at 30°C and pH7.4. Dissociation of oxyhaemoglobin can be promoted by rise in the body temperature and low pH (high CO₂).

The oxygen-carrying capacity of hemoglobin determines how much oxygen is carried in the blood.

In addition, other environmental factors and diseases can also affect oxygen-carrying capacity and delivery; the same is true for carbon dioxide levels, blood pH, and body temperature.

When carbon dioxide is in the blood, it reacts with water to form bicarbonate (HCO^{3 −}) and hydrogen ions (H⁺). As the level of carbon dioxide in the blood increases, more H+ is produced and the pH decreases.

The increase in carbon dioxide and subsequent decrease in pH reduce the affinity of hemoglobin for oxygen. The oxygen dissociates from the Hb molecule, shifting the oxygen dissociation curve to the right.

Therefore, more oxygen is needed to reach the same hemoglobin saturation level as when the pH was higher.

• Bronchi, bronchioles, and alveoli together comprise the lung.
• They are the main vital organs compared to other secondary parts.
• They have a perfect network for respiration to take place.

The correct option is Option C.

In emphysema, the inner walls of the lungs' air sacs (alveoli) are damaged, causing them to eventually rupture. This creates one larger air space instead of many small ones and reduces the surface area available for gas exchange. Emphysema is a lung condition that causes shortness of breath.

Oxygenation literally means the addition of oxygen to a chemical substance or physical system. Thus binding of oxygen with haemoglobin can also be reffered as oxygenation. Oxyhemoglobin is formed when oxygen binds to the heme component of the protein hemoglobin in red blood cells, during physiological respiration.
Whereas oxidation is a loss of electron, which can be either in the form of gaining of oxygen or loss of hydrogen and reduction is a gain of electron, which can be either in the form of loss of oxygen or gaining of hydrogen.

• Trachea is a straight tube extending up to the anterior part of the thoracic cavity.
• It is also known as the windpipe.
• The trachea connects the soundbox to the bronchi.
• Also, it provides the passage for air.

• Radial muscles are present in diaphgram.
• By the contraction in these muscles, diaphragm becomes flattened in shape, so, volume of thoracic cavity increases in anterior posterior axis.

• The respiratory centre is made up of three major respiratory groups of neurons, two in the medulla and one in the pons.
• In the medulla, they are the dorsal respiratory group and the ventral respiratory group. In the pons, the pontine respiratory group includes two areas known as the pneumotaxic centre and the apneustic centre.
• The respiratory centre is responsible for generating and maintaining the rhythm of respiration Hence, Inhibitory centre and pneumotaxic centre concerned with breathing.

• whole passage is divided into two parts one is conducting region and other is respiratory region.
• Conducting zone do not play any role in exchange of gases but respiratory zone does.
• Alveolar duct & alveoli are the part of respiratory tree and are involved in gaseous exchange.

Chloride shift is a process which occurs in a cardiovascular system and refers to the exchange of bicarbonate and chloride across the membrane of red blood cells.

Tidal volume is the amount of air inspired or expired during normal breathing. Its value for man is 500ml, out of which 150ml is dead space volume which remains in the respiratory tract.

The important derivatives of the three germ layers are given below :

A. Endoderm : 1) Gut tube epithelium 2) Liver 3) Respiratory system 4) Pancreas

B. Mesoderm : 1) Connective tissue 2) Bone 3) Muscles 4) Cardiovascular system 5) Lymphatics 6) Urogenital structure

C. Ectoderm : 1) Epidermis 2) Nervous system 3) Adrenal medulla

In mammals like humans inspiration and expiration are carried out by creating pressure gradients between the atmosphere and the alveoli with the help of specialised muscles -intercostals and diaphragm. Diaphragm is dome shaped muscular separation between abdominal and thoracic cavities. It is characteristic of mammals. 

The epiglottis moves back and forth to prevent the passage of food and liquids into the lungs. The usual upright position of the epiglottis allows air to flow into the lungs and the larynx. When you swallow, the epiglottis flattens backward to cover the entrance to your larynx and prevent food from entering the lungs and windpipe. The epiglottis returns to its usual position after swallowing. 
Thus, the correct answer is option D.

Injury-related pneumothorax: A puncture wound to the chest, such as a gunshot, etc. A one-way valve mechanism prevents air from escaping the pleural cavity. If the patient is not treated immediately, death can result.

• We have the ability to increase the strength of inspiration and expiration with the help of additional muscles called abdominal muscles.
• This is called as forceful breathing.

The throat, or pharynx, connects to the voice box, or larynx, through a narrow opening called the glottis. This opening is protected by a flap of cartilage known as the epiglottis. When we swallow, the epiglottis covers the glottis, acting like a lid to prevent food particles from entering the airway.

The alveolar membrane is the gas-exchange surface. Carbon dioxide rich blood is pumped from the rest of the body into the alveolar blood vessels where, through diffusion, it releases its carbon dioxide and absorbs oxygen.

In frogs the process of respiration takes place through three respiratory surfaces - skin, lungs and lining of the mouth. However, when submerged in water, the frog respires through its cutaneous membranes on the skin as it is quite permeable to water and contains a large network of blood vessels. The cutaneous membrane allows the respiratory gases to readily diffuse directly. Even when out of water, mucus glands present in the skin help in the cutaneous respiration.

Therefore, the correct answer is option D.

Oxyhemoglobin is formed during physiological respiration when oxygen binds to the heme component of the protein hemoglobin in red blood cells. This process occurs in the pulmonary capillaries adjacent to the alveoli of the lungs.

Alveoli are tiny air sacs in the lungs where the exchange of gases takes place. They are surrounded by a network of capillaries and do not have cartilaginous rings for support. The bronchial tree, on the other hand, is supported by cartilaginous rings which help to maintain their patency and prevent their collapse. The primary bronchioles, secondary bronchioles, and tertiary bronchioles are part of the bronchial tree and are supported by cartilaginous rings. The trachea, also known as the windpipe, is also part of the bronchial tree and is supported by C-shaped cartilaginous rings.

• Carbonic Anhydrase: Carbonic anhydrase is an enzyme that catalyzes the reversible hydration of carbon dioxide to form bicarbonate ion and a proton.


• Cofactor: A cofactor is a non-protein chemical compound or metallic ion that is required for an enzyme's activity. In the case of carbonic anhydrase, the cofactor is Zn (Zinc).


• Role of Zn: Zinc ions play a crucial role in the catalytic mechanism of carbonic anhydrase by coordinating with water molecules and assisting in the conversion of carbon dioxide to bicarbonate.


• Importance of Zn: Without the presence of zinc as a cofactor, carbonic anhydrase would not be able to efficiently catalyze the hydration of carbon dioxide, leading to a disruption in physiological processes such as acid-base balance in tissues.


• Conclusion: Therefore, the correct cofactor of carbonic anhydrase is Zn (Zinc), making option B the correct answer.