NDA (I) 2018 General Ability Test · Question 71 of 150

Correct — B, Bowman's capsule. Bowman's capsule belongs to the kidney, not to the respiratory system. It is the cup-shaped head of a nephron, and it surrounds a tuft of capillaries called the glomerulus. Blood arriving under pressure at the glomerulus is filtered across into the capsule, and the filtrate then passes down the tubule where useful substances are reabsorbed and the rest leaves as urine. That is excretion. The other three options are all parts of the path air takes or of the muscle that moves it, so the odd one out is the kidney structure.

• (a)Bronchi — The trachea divides into two bronchi, one entering each lung, and these branch again into finer bronchioles that end in the air sacs. They are the main airways inside the chest.
• (c)Diaphragm — The diaphragm is the sheet of muscle below the lungs that drives breathing. It flattens on contraction, enlarging the chest cavity so that air is drawn in, and relaxes and domes upward so that air is pushed out.
• (d)Trachea — The trachea, or windpipe, is the tube carrying air from the throat down towards the lungs. Rings of cartilage keep it from collapsing when the air pressure inside falls during inhalation.

Air entering the body passes through the nostrils, the nasal cavity, the pharynx, the larynx, the trachea, the two bronchi, the bronchioles and finally the alveoli, where oxygen crosses into the blood and carbon dioxide crosses out. The movement of air is produced by the diaphragm and the intercostal muscles between the ribs. The urinary system runs quite separately — each kidney contains about a million nephrons, and each nephron begins with a glomerulus enclosed in Bowman's capsule, where blood is filtered.

This is a spot-the-intruder item, and the way to make such items quick is to name the system each option belongs to instead of testing each one against the question. Three names here belong to the respiratory tract and one to the urinary tract, and the intruder falls out immediately. It is worth keeping the two vocabularies apart in your notes, because NDA draws from both. On the respiratory side the words to fix are trachea, bronchi, bronchioles, alveoli, diaphragm and pleura; on the urinary side they are nephron, glomerulus, Bowman's capsule, tubule, ureter, bladder and urethra. One further distinction is worth carrying — breathing is the mechanical movement of air, while respiration in the biological sense is the release of energy from food inside the cell, and an examiner may use either word.

• Bowman's capsule is the cup-shaped beginning of a nephron in the kidney and surrounds the glomerulus.
• Filtration of blood in the kidney takes place at the glomerulus into Bowman's capsule.
• The path of air runs nostrils, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, alveoli.
• The diaphragm and the intercostal muscles produce the movements of breathing.
• Exchange of oxygen and carbon dioxide happens across the thin walls of the alveoli.

• Recognising a term without placing it in its organ system.
• Confusing Bowman's capsule with the bronchioles or the alveoli on the strength of the sound of the word.
• Using breathing and respiration as though they meant the same thing.

NDA asks for the part that does not belong to a named system, or for the specific function of one structure such as filtration in the nephron.

• practice — not a real PYQ

  Filtration of blood in the kidney takes place in the

  • (a)ureter
  • (b)glomerulus and Bowman's capsule
  • (c)urinary bladder
  • (d)collecting duct

  Answer(b) glomerulus and Bowman's capsule — blood under pressure in the glomerulus is filtered into the capsule surrounding it.

• practice — not a real PYQ

  During inhalation the diaphragm

  • (a)contracts and flattens
  • (b)relaxes and domes upward
  • (c)does not move
  • (d)contracts and domes upward

  Answer(a) contracts and flattens — this enlarges the chest cavity, lowering the pressure inside so that air rushes in.