3 interactive concept widgets for Breathing and Exchange of Gases. Drag any slider, change any number, and watch the formula and the answer update live. Built so you understand how each NEET problem actually works, not just the final number.
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Click any part of the human respiratory tract to see its role and the NEET fact tested about it.
A labelled diagram of the human respiratory system. Click any pin or chip to see what each part does and the key NEET fact about it.
Trachea (Windpipe)
About 11 to 12 cm long. Kept open by C-shaped cartilaginous rings (the open side faces the oesophagus). Lined with ciliated mucus epithelium that sweeps debris upward. Divides at the carina into two primary bronchi.
NEET fact
Trachea has C-shaped cartilaginous rings. The right primary bronchus is wider, shorter and more vertical, so foreign objects more often lodge there.
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Toggle between inspiration and expiration to see the diaphragm, intercostal muscles, thoracic volume and pressure changes.
Toggle between inspiration and expiration to see how the diaphragm, intercostal muscles, thoracic volume, and air pressure change. A side-by-side comparison table shows all changes at a glance.
Inspiration (Inhalation)
Both the diaphragm and external intercostal muscles contract simultaneously. The thoracic cavity expands. Because the lungs are attached to the chest wall via the pleura, they expand too. The increased volume lowers the air pressure inside the lungs below atmospheric pressure, so air flows in.
NEET fact
Inspiration is an ACTIVE process: muscles must contract. Quiet expiration is largely PASSIVE (muscles relax).
Feature
Inspiration
Expiration
Diaphragm
Contracts and flattens downward
Relaxes and domes upward
External intercostals
Contract: ribs pulled upward and outward
Relax: ribs fall back
Internal intercostals
Relaxed
Contract in FORCED expiration (e.g. coughing, exercise)
Thoracic cavity volume
Increases (both vertical and lateral dimensions increase)
Decreases
Intra-pulmonary pressure
Falls to about 1 to 3 mm Hg below atmospheric pressure
Rises to about 1 to 3 mm Hg above atmospheric pressure
Air movement
Air rushes IN (from high pressure outside to lower pressure inside)
Air is pushed OUT (from higher pressure inside to atmospheric outside)
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Shift the oxygen-haemoglobin dissociation curve with pCO2, pH and temperature to see the Bohr effect.
An interactive sigmoid O2 dissociation curve. Use the sliders to change pCO2, pH and temperature and watch the Bohr effect shift the curve left or right. See how much O2 is loaded in the lungs and delivered to the tissues.
pCO2: 40 mm Hg
20 (low)
70 (high)
pH: 7.4
7.1 (acid)
7.7 (alk)
Temperature: 37 °C
30 (cold)
43 (fever)
Normal (P50 = 26.5 mm Hg)
Normal physiological conditions (pH 7.4, pCO2 40 mm Hg, 37 C)
Sat at Lung (pO2 100)
97.3%
Sat at Tissue (pO2 40)
75.2%
O2 Delivered
22.1%
NEET key facts
!
The dissociation curve is S-shaped (sigmoid) due to cooperative binding of O2 to haemoglobin.
!
P50 = the pO2 at which haemoglobin is 50% saturated. Normal value ~26.5 mm Hg.
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Right shift (higher P50): caused by high pCO2, low pH, or high temperature. Haemoglobin releases more O2.
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Left shift (lower P50): caused by low pCO2, high pH, or low temperature. Haemoglobin picks up O2 more readily.
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The Bohr effect means active tissues (high CO2, low pH, high temp) automatically receive more O2.
!
97% of O2 is transported as oxyhaemoglobin; only 3% is dissolved in plasma.
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