Respiratory organs in humans - class-XII

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The trachea is prevented from collapsing by

  1. Complete cartilaginous rings

  2. Incomplete cartilaginous rings

  3. Bony rings

  4. Chitinous rings

Correct Option: B
  • The trachea is a rigid tube that conducts air from your larynx to your bronchi.
  • The trachea's rigidity is maintained by a series of incomplete cartilaginous rings arranged along its length called C-shaped cartilage rings. Hence, The trachea is prevented from collapsing by Incomplete cartilaginous rings.
So, the correct answer is 'Incomplete cartilaginous rings'.

Which of the following correctly illustrates the passage of oxygen in the respiratory system?

  1. Nostrils--> trachea--> bronchus--> bronchiole--> alveoli

  2. Nostrils--> trachea--> bronchiole--> alveoli

  3. Nostrils--> bronchiole--> alveoli

  4. Nostrils--> alveoli

Correct Option: A
  • The pathway of air through the respiratory system is through 
nasal cavities (or oral cavity) > pharynx > trachea > primary bronchi (right & left) > secondary bronchi > tertiary bronchi > bronchioles > alveoli (site of gas exchange). Hence, Nostrils--> trachea--> bronchus--> bronchiole--> alveoli  is   the passage of oxygen in the respiratory system.
So, the correct answer is 'Nostrils--> trachea--> bronchus--> bronchiole--> alveoli'.

The short tube leading from the nose is

  1. Pharynx

  2. Bronchi

  3. Trachea

  4. Alveoli

Correct Option: A

  • The pharynx, or throat, is the passageway leading from the mouth and nose to the oesophagus and larynx. 
  • The pharynx permits the passage of swallowed solids and liquids into the oesophagus, and conducts air to and from the trachea, or windpipe, during respiration. 
  • The pharynx also connects on either side with the cavity of the middle ear by way of the Eustachian tube and provides for equalization of air pressure on the eardrum membrane, which separates the cavity of the middle ear from the external ear canal. Hence, The short tube leading from the nose is pharynx.
So, the correct answer is 'pharynx'

Diaphragm is 

  1. Dome shaped muscle

  2. Oblique muscle

  3. Round muscle

  4. Elongated muscle

Correct Option: A

  • The diaphragm is a part of the abdominopelvic cavity.
  •  It is located below the thoracic cavity and above the pelvic cavity.
  •  Its dome-shaped roof is the thoracic diaphragm, a thin sheet of muscle under the lungs, and its floor is the pelvic inlet, opening into the pelvis. Hence, the diaphragm is a dome-shaped muscle.
So, the correct answer is 'dome-shaped muscle'.

Air goes from pharynx to.

  1. Trachea

  2. Bronchus

  3. Bronchi

  4. Bronchiole

Correct Option: A

  • The nasal cavity and the mouth meet at the pharynx, or throat, at the back of the nose and mouth. 
  • From there, air quickly enters the second part of your respiratory system, the trachea or windpipe. 
  • The trachea is a tube that delivers air to the lungs, the third and most important part of your respiratory system. Hence, Air goes from the pharynx to. trachea.
So, the correct answer is 'trachea'.

Bronchi divide into

  1. Bronchus

  2. Bronchioles

  3. Alveoli

  4. Air sacs

Correct Option: B

  • The bronchi (or bronchus) are the air passages into the lungs that begin at the end of the trachea. 
  • There are two bronchi, one for each lung. 
  • The bronchus divides into smaller branches known as segmental bronchi, which divide again into bronchioles, Hence, Bronchi divide into bronchioles.
So, the correct answer is 'bronchioles'.

Major part of $CO _2$ is transported to respiratory surface as.

  1. $HCO _3$ ions

  2. $H _2CO _3$

  3. $Hb-CO _2$

  4. Free $CO _2$

Correct Option: A

Respiratory system is derived from.

  1. Endoderm

  2. Mesoderm

  3. Ectoderm

  4. None of the above

Correct Option: A

What is correct about human respiration?

  1. About $90\%$ of $CO _2$ is carried by haemoglobin as carbaminohaemoglobin

  2. Neural signals from pneumotaxic centre of pons can increase duration of inspiration

  3. Workers in grinding and store breaking industries may suffer from lung fibrosis

  4. Cigarette smoking leads to inflammation of bronchi

Correct Option: B

Which is not function of 'conductiing part' of respiratory system?

  1. Clears the air from foreign particles

  2. Humidifies the air

  3. Brings the air to body temperature

  4. It is site for diffusion of oxygen and carbon dioxide

  5. Transports air to alveoli

Correct Option: D

Choose the correct statements with regard to human respiration:
(a) Inspiration is faciliated by contraction of phrenic and internal intercostal muscles
(b) Healthy human can inhale or exhale about $2000-3000$ml of air/min
(c) Functional residual capacity represents the volume of left out air in lungs after expiration
(d) Total lung capacity is the total volume of air that would be accomodated in the lunds after forced inspiration.

  1. a, c

  2. b, d

  3. c, d

  4. a, b

Correct Option: C

Respiratory quotient for three different substrates was calculated and tubulated as shown here.

Substrate R.Q.
XYZ 0.911.3

Identify X, Y and Z and select the correct option regarding them.

  1. X - Protein, Y - Fats, Z - Glucose

  2. X - Glucose, Y - Protein, Z - Organic acid

  3. X - Protein, Y - Glucose, Z - Organic acid

  4. X - Organic acid, Y - Protein, Z - Fats

Correct Option: C

Respiratory quotient if the protein is 0.8-0.9

For glucose- 1
For  organic acids -1.3
So, the correct option is 'X - Protein, Y - glucose, Z - organic acids'.

Which of the following can be considered as odd one?

  1. Larynx

  2. Glucagon

  3. Testosterone 

  4. Prolactin

Correct Option: A
Larynx is the sound box while the rest three glucagon, testosterone and prolactin are hormones.
So, the correct answer is 'Larynx'.
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