Test: Respiratory System- Human Physiology- 2

30 Questions MCQ Test Biology Class 11 | Test: Respiratory System- Human Physiology- 2

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Respiration is


Respiration is a physiological process that is a combination of both physical and chemical changes in all organisms that modulate their respiration. In the simplest of organisms that can respire, bacteria, they depend upon the physical principle of diffusion to supply O2 to their respiratory machinery which are associated with their plasma membrane. If the diffusion of O2 from the environment is restricted they turn their metabolism to anaerobic which is a chemical process but is modulated by the physical access to O2 diffusion supply. Higher metazoans do not depend upon simple diffusion but often have a physical respiratory apparatus such as a tidal lung of terrestrial vertebrates controlled by muscular breathing, or in insects with a tracheolar system controlled by physically controlled spiracular valves to allow diffusion of O2 in and CO2 out of the insect body without losing too much water vapor. Respiration in all organisms thus has both a physical and a chemical component.


Larynx is a modified portion of


It connects the inferior part of the pharynx (hypopharynx) with the trachea. The laryngeal skeleton consists of six cartilages: three single (epiglottic, thyroid and cricoid) and three paired (arytenoid, corniculate, and cuneiform).


 Thoracic cavity is enlarged by contraction of


The diaphragm functions in breathing. During inhalation, the diaphragm contracts and moves in the inferior direction, thus enlarging the volume of the thoracic cavity (the external intercostal muscles also participate in this enlargement). This reduces intra-thoracic pressure.


Cartilaginous rings in trachea are incomplete at which surface.


The trachea (windpipe) is a tube that extends from the lower edge of the larynx to the upper part of the chest (above the heart). It has a framework of cartilages to keep it open. These cartilages are shaped like a tiny horseshoe or the letter C and are found along the entire length of the trachea. All the open sections of these cartilages are at the dorsal surface so that the oesophagus can bulge into the open section during swallowing. The purpose of the trachea is to conduct air between the larynx and the lungs.
So, the correct answer is option A


Breathing by ribs is more pronounced in


Many pregnant women notice that as the baby gets bigger, it gets harder to breathe or that breath feels more “shallow.” This is because the top of our core system, our diaphragm muscle, gets pushed up by the uterus as pregnancy progresses, making it harder to breathe well.

The correct means of breathing is called “Diaphragmatic Breathing” or “Belly Breathing.” When a growing uterus, during pregnancy, pushes up onto the diaphragm muscle and breathing gets harder, our body will find a way to compensate or breathe easier. In other words, we may not even know that our body has found a different, easier way for us to breathe while pregnant. Chest and shoulder breathing are two common solutions our bodies come up with to breathe comfortably while pregnant. When we chest breathe, we’re breathing into our chests instead of into our bellies. Then, because we’re using chest muscles to do a job that shouldn’t be theirs, we take them off their regular job, so to speak. This can mean compromising other stability systems. It’s important that we proactively work to return to optimal breathing, Belly Breathing, after pregnancy.


The most important muscular structure in respiratory system of rabbit is


The diaphragm is the dome-shaped sheet of muscle and tendon that serves as the main muscle of respiration and plays a vital role in the breathing process. The diaphragm separates the thoracic cavity containing the heart and lungs, from the abdominal cavity and performs an important function in respiration: as the diaphragm contracts, the volume of the thoracic cavity increases and air is drawn into the lungs.


Wall of alveoli is composed of


Simple squamous epithelium lines the air sacs, or alveoli, of the lungs. The alveoli are sites where the air is exchanged in the lungs.
Simple squamous epithelial cells in the alveoli allow oxygen from the air to enter the blood in the capillaries of the lung. 
Carbon dioxide, a waste product, passes across the epithelium of the alveoli to be removed from the body. Striated, columnar and cuboidal epithelium is absent in the lines of alveoli. 
Therefore, the correct answer is option A.


Schneiderian membrane occurs on


The Schneiderian membrane is the membranous lining of the maxillary sinus cavity. It is histologically a bilaminar membrane with ciliated columnar epithelial cells on the internal (or cavernous) side and periosteum on the osseous side.
So, the correct answer is option B.


"Methemoglobin" refers to


Methemoglobin (metHb) is an oxidized derivative of hemoglobin in which heme iron is in the ferric (Fe3+) or oxidized state rather than the ferrous (Fe2+) or reduced state. Acquired methemoglobinemia can occur in normal individuals following exposure to chemicals that oxidize hemoglobin iron.


How much oxygen, blood supplies to tissues in one circulation


Blood supplies approximately 25% of oxygen to the tissues in one circulation as the partial pressure of oxygen in arterial blood is 75-95mmHg.


Opening to the trachea is covered by a small flap of tissues termed as the ______.


Inhibition of respiratory centre is termed


Temporary absence or cessation of breathing is called as apnoea. The respiratory center is located in the medulla oblongata. It controls the rate and depth of respiratory movements of the diaphragm and other respiratory muscles. Injury to this center may lead to apnoea. 


 Under normal condition 100 ml blood carry


Blood is the medium of transport for oxygen and carbon dioxide. About 97 per cent of oxygen is transported by RBCs in the blood. The remaining 3 per cent of oxygen is carried in a dissolved state through the plasma. Nearly 20-25 per cent of carbon dioxide is transported by RBCs whereas 70 per cent of it is carried as bicarbonate. About 7 per cent of carbon dioxide is carried in a dissolved state through plasma. Every 100 ml of deoxygenated blood delivers approximately 4 ml of CO2 to the alveoli.
Therefore, the correct answer is option A.


Haldane effect is due to


Oxyhaemoglobin is an acidic compound and thus releases H+ ions. Those ions combine with the bicarbonate ions to release the CO2 associated with them. This is known as Haldane effect.


The maximum volume of air contained in the lung by a full forced inhalation is called


If expiratory reserve volume is 1100 ml residual volume is 1200 ml and tidal volume is 500 ml, what shall be the functional residual capacity


Functional Residual Capacity (FRC) is the volume of air that will remain in the lungs after a normal expiration. This includes expiratory reserve volume i.e. 1100ml plus 1200ml or 2300ml. 


What percentage of CO2 flows in blood in form of bicarbonates


Carbon dioxide is transported in the blood in three ways: 10% is dissolved in plasma, 20% is carried on haemoglobin bound to globins, and 70% exists as bicarbonate, an important buffer of blood pH.


Effect of CO2 concentration on dissociation of oxyhaemoglobin is called

Solution: Bohr's effect because christian bohr told firstly about haemoglobin's binding efficiency with o2 which is inversely proportional to acidity and concentration of co2.

Which part of thyroid cartilage in larynx is closed


 The thyroid cartilage is a hyaline cartilage structure that sits in front of the larynx and above the thyroid gland. Ventral part of thyroid cartilage in the larynx is closed. The cartilage is composed of two halves, which meet in the middle at a peak called the laryngeal prominence, also called the Adam's apple.


The two nasal chambers are separated by which bone (in human) :


The ethmoid bone is a small unpaired bone, located in the midline of the anterior cranium – the superior aspect of the skull that encloses and protects the brain.


The term ‘ethmoid’ originates from the Greek ‘ethmos’, meaning sieve. This is reflected in its lightweight, spongy structure.



Oxygen in expired air

Solution: After a human breathes in Earth's air (roughly 78 percent nitrogen and 21 percent oxygen), he or she exhales a mixture of compounds similar to the air inhaled: 78 percent nitrogen, 16 percent oxygen, 0.09 percent argon, and four percent carbon dioxide.

Rate of breathing in rabbit


The normal respiration rate in an adult rabbit is 30 - 60/minute, but some breathe faster than this if they are hot or stressed.


Chloride shift for the transport of


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.

Carbon dioxide is produced in tissues as a byproduct of normal metabolism. It dissolves in the solution of blood plasma and into RBC, where carbonic anhydrase catalyzes its hydration to carbonic acid (H2CO3). Carbonic acid then spontaneously dissociates to form bicarbonate Ions (HCO3−) and a hydrogen ion (H+) in response to the decrease in intracellular partial pressure of CO2, more CO2 passively diffuses into the cell.

Hence, the chloride shift is essential for the transport of Carbon dioxide.

So, the correct  option is 'CO2'.


How oxygen enters in blood from alveoli of lungs


Gas exchange between the air within the alveoli and the pulmonary capillaries occurs by diffusion. The oxygen must first dissolve before passing through the respiratory epithelium. Gas moves from a region of high partial pressure to a region of low partial pressure, down a partial pressure gradient.


Pneumotaxic centre is present in


The hindbrain comprises pons, cerebellum and medulla oblongata. The Pneumotaxic centre is present in the upper part of the pons. The function of the pneumotaxic center is to control rate and pattern of breathing. Hence pneumotaxic center is present in pons region of the brain.


During inspiration muscles of diaphragm


The diaphragm is the membranous structure in the abdomen. The muscles of the diaphragm contracts during inspiration. Muscle contraction allows the diaphragm to become flat which helps to increase the volume of the thoracic cage. This allows the air to be taken in the lungs.
During the process of expiration, the diaphragm becomes dome shaped and the muscles relax. This reduces the volume of the thoracic cage and helps to pump the CO2 out from the lungs. 
Thus, the correct answer is option A.


Air filled in dead space is


During each breath, about 150cc of fresh air never reaches the alveoli but remains in the rest of the respiratory tract, this is termed respiratory dead space. Anatomical dead space is that portion of the airways (such as the mouth and trachea to the bronchioles) which conducts gas to the alveoli. No gas exchange is possible in these spaces.


Azygous lobe is part of


In human anatomy, an azygos lobe is a congenital variation of the upper lobe of the right lung. Embryologically, it arises from an anomalous lateral course of the azygos vein in a pleural septum within the upper lobe. As it has no bronchi, veins, and arteries of its own, it is not a true, or even accessory pulmonary lobe, but rather an anatomically separated part of the upper lobe.
So, the correct answer is option A.


Very high number of alveoli present in a lung is meant for


The structure of the lung maximizes its surface area to increase gas diffusion. Because of the enormous number of alveoli (approximately 300 million in each human lung), the surface area of the lung is very large (75 m2).


Expiration involves


Expiration is a process by which the foul air (carbon dioxide) is expelled out from the lungs. It is a passive process which occurs in the diaphragm and internal intercostal muscles in the following manner-
i) Diaphragm: The muscle fibres of the diaphragm relax making it convex, decreasing the volume of tge thoracic activity.
ii) Internal intercostal muscles: These muscles contract so that they pull the ribs downward and inward decreasing the size of the thoracic activity. So, the correct answer is option (A) .