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Human lungs - class-XI

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Which of the following changes occur in diaphragm and intercostal muscles when expiration of air takes place? 

  1. Internal intercostal muscles relax and diaphragm contracts

  2. External intercostal muscles and diaphragm relaxes

  3. Internal intercostal muscles contract and diaphragm relax

  4. External intercostal muscles and diaphragm contract


Correct Option: C
Explanation:
  • When the internal intercostal muscles contract and diaphragm relax, the ribs move .downward and inward and the diaphragm becomes convex {dome shaped), 
  • thus decreasing the volume of the thoracic cavity and increasing the pressure inside as compared to the atmospheric pressure outside. This will cause the air to move out (expiration).

Read the given statements and select the correct option.


Statement 1 : Mammals can eat while breathing. 

Statement 2 : Mammals have negative-pressure breathing.

  1. Both statements 1 and 2 are Correct.

  2. Statement 1 is correct but statement 2 is incorrect.

  3. Statement 1 is incorrect but statement 2 is correct.

  4. Both statements 1 and 2 are incorrect.


Correct Option: A
Explanation:
Mammals like humans along with birds and reptiles have negative pressure breathing. They use their mouths for both eating and breathing. Breathing requires pressure gradient. Mammals create pressure gradient using their diaphragm. The high volume and low pressure in the lung cavity results in the air to be sucked in. They cannot swallow and breathe at once. However, it is possible for them to eat while breathing.
Thus, the correct answer is option (A).

Given below is a list of different steps (i-vi) involved in respiration.
(i) Utilisation of $O _2$ by the cells for catabolic reactions
(ii) Transport of gases by the blood
(iii) Pulmonary ventilation by which atmospheric air is drawn in and $CO _2$ is released out
(iv) Release of resultant $CO _2$
(v) Diffusion of $O _2$ and $CO _2$ between blood and tissues
(vi) Diffusion of gases ($O _2$ and $CO _2$) across alveolar tissues.
Select an option which has correct sequence of all the steps.

  1. (iii), (vi), (ii), (v), (i), (iv)

  2. (iii), (vi), (i), (v), (ii), (iv)

  3. (iv), (ii), (v), (iii), (i), (vi)

  4. (iv), (vi), (ii), (v), (i), (iii)


Correct Option: A
Explanation:

While respiration atmospheric air is drawn in a carbon dioxide is released out, diffusion of gases takes place in the alveolar tissue which is then carried by blood, then diffusion of gases take place between blood and tissues, oxygen is utilized by cells for catabolic reactions, and the resultant carbon dioxide is released from the body.

So, the correct option is '(iii), (vi), (ii), (v), (i), (iv)'.

Consider the following statements each with two blanks. 
(i)    Diaphragm contracts to help in __(1)   while the contraction of abdominal muscles helps in (2). 
(ii). Vital capacity of trained athletes is _
(3)__ than that of non-athletes while the vital capacity of non-smokers is (4) than that of smokers. 
(iii) Alveolar P$O {2}$ is  _(5)  than the venous P$O {2}$ while arterial P$O _{2}$ is __(6)_ than the alveolar P$O _{2}$.
Which of the following options gives the correct fill ups for the respective blanks numbers from (1) to (6) in the above statements?

  1. (1)-expiration, (2)-inspiration (5)-higher, (6)-lower

  2. (3)-higher, (4)-lower, (5)-lower, (6)-higher

  3. (1)-inspiration, (2)-forced expiration, (3)-higher, (4)-higher

  4. (1)-expiration, (2)-forced expiration, (5)-higher, (6)-lower


Correct Option: C
Explanation:

  (i) Diaphragm contracts to help in (1) inspiration while the contraction of abdominal muscles helps in (2) forced expiration.

(ii) Vital capacity of trained athletes is (3) higher than that of non-athletes while the vital capacity of non-smokers is (4) higher than that of smokers.

(iii) Alveolar PO2 is (5) higher than the venous PO2 while arterial PO2 is (6) lower than the alveolar PO2.

So, the correct answer is '(1)-inspiration, (2)-forced expiration, (3)-higher, (4)-higher'.


Complete the following sentence by selecting the correct option.
The breathing rhythm is generated in the (i) and is influenced by variation in levels of (ii)_ in the blood.

  1. (i)medulla 

    (ii)$CO _{2}$

  2. (i)medulla 

    (ii)$O _{2}$

  3. (i)frontal lobe 

    (ii)$CO _{2}$ and $O _{2}$

  4. (i)frontal lobe 

    (ii)$CO _{2}$


Correct Option: A
Explanation:
The basic rhythm of respiration is generated mainly in the dorsal respiratory group in the medulla. Changes in blood carbon dioxide are believed to stimulate the neurons in the chemosensitive area which affect the rhythm centre. $CO _{2}$ acts by forming carbonic acid which dissociates into H+and $HCO _{3}^{-}$. H+ has a direct effect on this. Oxygen does not have a significant direct effect on rhythm centre.
So the correct answer is 'A'.

The most important muscular structure in respiratory system of rabbit is

  1. External intercostal muscles

  2. Internal intercostal muscles

  3. Diaphgram

  4. Vertebral column


Correct Option: C
Explanation:

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.

Thoracic cavity is enlarged by contraction of

  1. Internal Intercostal muscles

  2. Diaphragm

  3. Lungs

  4. All of above


Correct Option: B
Explanation:

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.

Lungs ventilation movements is due to

  1. Costal muscle and diaphragm

  2. Costal muscle

  3. Diaphragm

  4. Wall of the lungs


Correct Option: A
Explanation:

Breathing involves two stages, inspiration during which atmospheric air is drawn in and expiration by which the alveolar air is released out. The movement of air into and out of the lungs is carried out by creating a pressure gradient between the lungs and the atmosphere. Inspiration can occur if the pressure within the lungs (intra-pulmonary pressure) is less than the atmospheric pressure, i.e., there is a negative pressure in the lungs with respect to atmospheric pressure. Similarly, expiration takes place when the intra-pulmonary pressure is higher than the atmospheric pressure. The diaphragm and a specialised set of muscles external and internal intercostals between the ribs, help in generation of such gradients.

Therefore, the correct answer is option A.

Hiccough (hiccup) is due to activity of

  1. Intercostal muscle

  2. Food in air tract

  3. Diapharagm

  4. Inadequate oxygne in environment


Correct Option: C
Explanation:
  • A hiccup is an involuntary contraction of the diaphragm involving a reflex arc, that may repeat several times per minute. 
  • Once triggered, the reflex causes a strong contraction of the diaphragm followed by about 0.25 seconds later by closure of the vocal cords, which results in the classic "hic" sound. 
  • Hiccups may occur individually, or they may occur in bouts. 

Which of the following structures are responsible for breathing process?

  1. The trachea and alveoli

  2. Larynx and bronchi

  3. Ribs and intercostal muscles

  4. Intercostal muscles and diaphragm


Correct Option: D
Explanation:

Breathing or pulmonary ventilation is a process where the nasal and oral cavities inhaled the air and enter into the lungs through the pharynx, larynx and trachea. Air is also exhaled through the same pathway. While larynx, pharynx and trachea are involved the changes to the volume and air pressure in the lungs trigger  breathing. During the process of  inhalation, the diaphragm and external intercostal muscles contract thereby elevating the rib cage. With the increase in the volume of the lungs, air pressure drops letting the air rush in. Similarly, during exhalation, the muscles relax letting the lungs become smaller, which raises the air pressure and helps to expel the air.

The exhaled air mainly contains

  1. Oxygen

  2. Carbon dioxide

  3. Nitrogen

  4. None of the above


Correct Option: B
Explanation:

Exhalation is a process to breath out.carbon dioxide is a waste product in the body that release out during exhalation, it is also saturated with water vapor.

So the correct answer is "carbon dioxide".

Rita breathes out on a mirror and finds water droplets on it. This activity helps to conclude the fact that

  1. Inhalation is faster than exhalation

  2. Water vapour is released during breathing

  3. Exhalation is faster than inhalation

  4. Both A and B


Correct Option: B
Explanation:

Carbon dioxide is released in the process of exhalation in large amount.$CO _2$ dissolves in water and can easily and reversibly form compounds such as carbonic acid and bicarbonates. when it is released out, it is saturated with water vapour and this is the reason for water droplets in the mirror.

So the correct answer is 'water vapour is released during breathing'.

Forced deep breathing during rest for some time is followed by temporary stoppage of breathing because of.

  1. Little $CO _2$ in blood

  2. High $CO _2$ content in blood

  3. High oxygen content in blood

  4. Little oxygen content in blood


Correct Option: A

To generate pressure gradients for faciliatating expiration and inspiration, the human body uses the intercostal muscles and.

  1. Alveolar sacs

  2. Bronchi

  3. Primary, secondary and tertiary bronchioles

  4. Diaphragm

  5. Wind pipe


Correct Option: D

Increase in $CO _2$ concentration shall cause.

  1. Slower and shallower breathing

  2. Slower and deeper breathing

  3. Faster and deeper breathing

  4. No effect on breathing


Correct Option: C

Which one of the following is a possibility for most of us in regard to breathing, by making a conscious effort?

  1. One can breathe out air totally without oxygen.

  2. One can breathe out air through Eustachian tube by closing both nose and mouth.

  3. One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all.

  4. The lungs can be made fully empty by forcefully breathing out all air from them.


Correct Option: B
Explanation:

During breathing, 20% oxygen is taken in and 15% oxygen is exhaled out. Movement of diaphragm is very important during breathing process. Ribs will also move in and out with the diaphragm. It is not possible to breathe by moving the diaphragm along without moving ribs. Even after forceful exhalation, lungs are never fully emptied. Residual volume, that is minimum amount of air in lungs always remain at all times. Eustachian tube connects middle ear cavity with nasopharynx and hence, one can breathe out air through it by closing both nose and mouth.

Thus, the correct answer is option B.

Read the following statements:
(A) Nasal chamber opens into nasopharynx which is a portion of pharynx
(B) Larynx produces sound during inspiration as well as expiration
(C) During swallowing gullet can be covered by a thin elastic cartilagenous flap called epiglottis
(D) Trachea is get divided at the level of the 6th thoracic vertebra into right and left primary bronchi.
(E) The braching network of bronchi, bronchioles and alveoli comprise the lungs.
How many statements are not correct-

  1. 2

  2. 3

  3. 4

  4. 1


Correct Option: A
Explanation:

A)Nasal chamber opens into nasopharynx which is a portion of pharynx – True because It also connects the nasal system of air chambers and the upper end of the trachea. The opening of the mouth into the pharynx is the oropharynx, and the nasal opening is the nasopharynx. The eustachian tube from the middle ear opens into the pharynx on each side.

B)Larynx produces sound during inspiration as well as expiration – True, because, the larynx commonly called the voice box, is an organ in the top of the neck of tetrapods involved in breathing, producing sound. They have skeletal muscle, cartilage of the upper larynx collapses inward during inhalation, causing airway obstruction, results in the creation of sounds.

C)During swallowing, gullet can be covered by a thin elastic cartilaginous flap called Epiglottis – false, because, the epiglottis is a flap in the throat that keeps food from entering the windpipe and the lungs. The flap is made of elastic cartilage covered with a mucous membrane, attached to the entrance of the larynx. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally.

D) The trachea is get divided at the level of 6th thoracic vertebra into right and left primary bronchi – False, because The trachea, commonly called the windpipe, is the main airway to the lungs It divides into the right and left bronchi at the level of the fifth thoracic vertebra, channeling air to the right or left lung.

E)The branching network of bronchi, bronchioles, and alveoli comprise the lungs – True.

So, the correct option is ‘2’.

During inspiration muscles of diaphragm

  1. Contracts

  2. Expands

  3. No effect

  4. Coiled like string


Correct Option: A
Explanation:

During inhalation, the diaphragm contracts, thus enlarging the thoracic cavity. This reduces intra-thoracic pressure: enlarging the cavity creates suction that draws air into the lungs. When the diaphragm relaxes, air is exhaled by elastic recoil of the lung and the tissues lining the thoracic cavity in conjunction with the abdominal muscles, which act as an antagonist, paired with the diaphragm's contraction.

Which of the following is true for $CO _2$ concentration ?

  1. More in alveolar air than in expired air

  2. More in expired air than in alveolar air

  3. More in inspired air than in alveolar air

  4. More in inspired air than in expired air


Correct Option: A
Explanation:

The concentration of expired air is more in the alveolar air than in expired air due to the partial pressure of carbon dioxide in alveoli is more than the atmosphere.

So the correct option is 'More in alveolar air than in expired air'

Hiccough (hiccup) is due to activity of

  1. Intercostal muscle

  2. Food in air tract

  3. Diaphragm

  4. Inadequate oxygen in environment


Correct Option: C
Explanation:

  • Hiccup is also called as a hiccough. It is an involuntary activity of the diaphragm. During hiccups, the diaphragm muscle shows several involuntary contractions. 
  • When the diaphragm muscle contracts, the opening between the vocal cords snaps shut to check the inflow of air. 
  • This results in the hic or hiccup sound. This results due to irritation of the nerves. 

Thus, the correct answer is 'Diaphragm.'

The diaphragm contracts, resulting in inhalation as the volume of thoracic cavity

  1. Decreases in anteroposterior axis

  2. Decreases in dorsoventral axis

  3. Increases in dorsoventral axis

  4. Increases in anteroposterior axis


Correct Option: A

Which of the following changes occur in diaphragm and intercoastal muscles when expiration of air takes place?

  1. External intercostal muscles relax and diaphragm contracts

  2. External intercostal muscles contracts and diaphragm relaxes

  3. External intercostal muscles and diaphragm relaxes

  4. External intercostal muscles and diaphragm contracts


Correct Option: A

The respiratory centre leading to faster breathing is on account of ________________.

  1. Venous blood entering the respiratory centre

  2. Arterial blood entering respiratory

  3. Venous blood leaving the respiratory centre

  4. Arterial blood leaving the respiratory centre


Correct Option: A
Explanation:

The medulla oblongata is the primary respiratory control centre. Its main function is to send signals to the muscles that control respiration to cause breathing to occur. The respiratory control centre increase respiratory rate on the account of decrease in blood pH, as the oxygenated blood through veins enter the system, decrease in $CO _2$ levels, increased respiratory rate.

Pneumoconiosis is a type of

  1. Emphysema

  2. Occupational renal disease

  3. Occupational respiratory disease

  4. Coronary artery disease


Correct Option: C
Explanation:
  • Pneumoconiosis is a disease of the lungs due to inhalation of dust, characterized by inflammation, coughing, and fibrosis. 
  • Pneumoconiosis is usually considered an occupational respiratory disease, and includes asbestosis, silicosis and coal workers' pneumoconiosis (CWP), also known as "Black Lung Disease."

So, the correct option is 'Occupational respiratory disease'.

Fatal degenerative lung disease caused by particulate asbestos is referred to as

  1. asbestosis

  2. asthma

  3. allergy

  4. sinusitis


Correct Option: A

Asbestosis increases the risk of developing all of the following except

  1. Carcinoma of the lungs

  2. Mesotheliomas

  3. Bronchiectasis

  4. Tuberculosis


Correct Option: D

Number of alveoli in human lung is about

  1. One million

  2. More than two millions

  3. More than five millions

  4. More than seven millions


Correct Option: D
Explanation:

(d) The number of alveoli in human lungs has been estimated to be approximately 750 million, exposing a surface area of nearly 100 $m^2$.

If the lung were punctured, which of the following would happen?

  1. The lung would collapse on the side of the puncture.

  2. Both the lung and the chest wall would collapse on the side of the puncture.

  3. Inspiratory signals from medulla become irregular

  4. Interpleural pressure decrease further


Correct Option: A

Lungs are enclosed in?

  1. Periosteum

  2. Perichondrium

  3. Pericardium

  4. Pleural membrane


Correct Option: A

Which one of the following statements is incorrect?

  1. The residual air in lungs slightly decreases the efficiency of respiration in mammals

  2. The presence of non-respiratory air sacs, increases the efficiency of respiration in birds

  3. In insects, circulating body fluids serve to distribute oxygen to tissues

  4. The principle of counter current flow facilities efficient respiration in gills of fishes


Correct Option: A

State if the following statement is True or False. Correct the False statement.
Our lungs eliminate metabolic wastes like urea from the body.

  1. True

  2. False


Correct Option: A

State if the following statement is True or False. Correct the False statement.
Bile pigments are the excretory products excreted by the lungs.

  1. True

  2. False


Correct Option: A

Serous membrane coverning of lung is?

  1. Pericardium

  2. Serosa

  3. Periosteum

  4. Pleura


Correct Option: D

Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because.

  1. Pressure in the lungs is higher than the atmospheric pressure

  2. There is negative pressure in the lungs

  3. There is negative intrapleural pressure pulling at the lung walls

  4. There is positive intrapleural pressure


Correct Option: C

Lungs are not affected by the disease.

  1. Pneumonia

  2. Bronchitis

  3. Polio

  4. Asthma


Correct Option: C

In human beings the number of lobes in right and left lungs is?

  1. $2$ and $3$

  2. $2$ and $2$

  3. $3$ and $2$

  4. $4$ and $2$


Correct Option: C

The covering of the lung is called.

  1. Pericardium

  2. Perichondrium

  3. Pleural membrane/pleura

  4. Peritoneum


Correct Option: C

Capacity of human lungs for air in a healthy person is?

  1. $3000$ml

  2. $1500$ml

  3. $1000$ml

  4. $500$ml


Correct Option: A

Which among the following serves the function of lung surfactant?

  1. Insulin

  2. Peptidoglycan

  3. Lecithin

  4. Chitin


Correct Option: A

Majority of $CO _2$ produced by our body cells is transported to lungs

  1. Attached to haemoglobin

  2. Dissolved in blood

  3. As bicarbonates

  4. As carbonates.


Correct Option: C

Inspiration occurs when there is a negative pressure in the lungs with respect to atmospheric pressure. This negative pressure is achieved when

  1. intrapulmonary pressure is less than the atmospheric pressure

  2. intrapulmonary pressure is greater than the atmospheric pressure

  3. intrapulmonary pressure is equal to the atmospheric pressure

  4. intrapleural pressure becomes more than the intra-alveolar pressure.


Correct Option: A
Explanation:

Because of the pressure gradient between the lungs and the atmosphere, the air moves into and out of the lungs. Inspiration occurs if the pressure within the lungs (intra-pulmonary pressure) is less than the atmospheric pressure i.e. there is a negative pressure in the lungs with respect to atmospheric pressure.

Choose the correct answer from the alternatives given.
The lung is enclosed in a double layered membrane called

  1. pericardium

  2. pleura

  3. periosteum

  4. perichondrium


Correct Option: B
Explanation:

The pleura refers to the double-layered membrane that covers the lungs. The space between the two membranes is called the pleural cavity. It is filled with a thin, lubricating liquid called pleural fluid, which acts as a lubricant and allows the pleurae to slide effortlessly against each other by reducing friction during respiratory movements. So, the correct option is 'pleura'.

The exchange of gases in human beings takes place in-

  1. In skin

  2. In mouth

  3. In nostrils

  4. In lungs.


Correct Option: D
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