Breathing and Exchange of Gases

Class 11 · Biology

5 ideas in Class 11 Biology, explained in plain words, with games and quizzes to practise.

Respiratory Organs and Human Airway

Part of: Airways and Breathing

Sponges diffuse, worms breathe skin, insects pipe air, fish gill, land forms lung. Human air runs nostrils to alveoli past sound-box larynx, food-guarding epiglottis and ringed tubes; conducting paths condition while alveoli exchange under pleural glide.

Why it matters. Habitat picks the organ. Path order explains every breath sound.

Key words

Larynx: : The voice box where sound is produced in the human airway.
Epiglottis: : The flap that guards the airway while swallowing food.
Trachea: : The ringed windpipe that stays open during airflow.
Alveoli: : The tiny air sacs where oxygen and CO2 exchange with fluid.
Diffusion membrane: : The three-layered sheet across which gases diffuse by gradient.

Try it in two minutes

Order nostrils to alveoli.
Split conducting from exchange.
Name three airway guards.

Try at home. Feel chest rise and fall.

Mechanism of Breathing

Part of: Airways and Breathing

Thorax expands via diaphragm and rib muscles, lowering lung pressure to suck air; relaxation raises pressure to expel. Adults cycle twelve to sixteen times a minute moving five hundred millilitres; spirometers measure the volumes.

Why it matters. Pressure logic replaces muscle-mystery. Rates and volumes diagnose lungs.

Formulas

A healthy human breathes 12 to 16 times per minute at rest.
Air moved per minute is about 6000 to 8000 mL at rest.

Key words

Inspiration: : The diaphragm and rib muscles expand the thorax to draw air in.
Expiration: : Relaxation of thorax muscles raises pressure and pushes air out.
Pressure gradient: : The pressure difference between lungs and air that drives airflow.
Spirometer: : The instrument that measures lung air volumes in clinical tests.
Pleural lining: : The slippery double covering that lets lungs glide in the chest.

Try it in two minutes

Lower pressure to inspire.
Raise pressure to expire.
Multiply rate by volume.

Try at home. Count breaths for one minute.

Volumes and Gas Exchange

Part of: Volumes, Exchange and Transport

Tidal five hundred plus reserves sum into inspiratory, expiratory, residual, functional, vital and total capacities; ERV plus RV rests functional while VC plus RV totals lungs. Gradients run O2 alveoli to fluid to tissues and CO2 reverse, boosted by twenty-fold solubility across triple-layer membranes.

Why it matters. Capacity sums diagnose lungs. Gradient tables predict every diffusion.

Formulas

Tidal volume is about 500 mL per normal breath.
Inspiratory capacity is tidal volume plus inspiratory reserve volume.
Expiratory capacity is tidal volume plus expiratory reserve volume.
Functional residual capacity is expiratory reserve volume plus residual volume.
Vital capacity is expiratory reserve plus tidal plus inspiratory reserve volumes.
Total lung capacity is vital capacity plus residual volume.
O2 flows from alveoli to fluid to tissues while CO2 flows the reverse way.

Key words

Tidal volume: : Air inspired or expired in one normal breath, about 500 mL.
Inspiratory reserve: : Extra air a forcible inspiration can draw beyond tidal volume.
Expiratory reserve: : Extra air a forcible expiration can push beyond tidal volume.
Residual volume: : Air left in lungs after forcible expiration, about 1100 to 1200 mL.
Vital capacity: : Maximum air breathed out after a forced inspiration.
Total lung capacity: : All lung air at end of forced inspiration, capacity plus residual.
Partial pressure: : The individual gas pressure, written pO2 for oxygen, that sets gradients.

Try it in two minutes

Add ERV to RV for FRC.
Read O2 down its gradient.
Read CO2 up its gradient.

Try at home. Compute VC from textbook values.

Gas Transport

Part of: Volumes, Exchange and Transport

Red cells ferry nearly all O2 as four-per-haemoglobin loads, unloading where O2 falls and acid warms; CO2 rides red cells, bicarbonate and plasma while carbonic anhydrase swaps trapped bicarbonate back to gas at alveoli; hundred millilitres trade about five O2 for four CO2.

Why it matters. Loading zones mirror gradients. Enzyme shuttles dominate CO2 traffic.

Formulas

About 97 percent of O2 travels in red cells and 3 percent dissolved in plasma.
About 20 to 25 percent of CO2 travels in red cells and 70 percent as bicarbonate.
Each haemoglobin molecule carries at most four O2 molecules.
Every 100 mL of oxygenated circulating fluid delivers about 5 mL of O2 to tissues.
Every 100 mL of deoxygenated circulating fluid delivers about 4 mL of CO2 to the alveoli.
CO2 dissolves 20 to 25 times more readily than O2 across the membrane.

Key words

Red corpuscle: : Red cells that ferry nearly all oxygen as four-per-haemoglobin loads.
Haemoglobin: : The red protein that binds O2 reversibly to form oxyhaemoglobin.
Carbonic anhydrase: : The enzyme in red cells that swaps trapped bicarbonate back to gas.
Bicarbonate carrier: : The bicarbonate form that carries most CO2 from tissues to air sacs.
Carbamino compound: : Haemoglobin bound to CO2 that unloads the gas at the alveoli.
Dissociation curve: : The curve plotting haemoglobin saturation against oxygen pressure.

Try it in two minutes

Load four O2 per haemoglobin.
Split CO2 three ways.
Trade five for four.

Try at home. Chart loading versus unloading zones.

Regulation and Disorders

Part of: Control and Disorders

Medulla rhythms while pons trims inspiration; CO2 and acid sensors in brain, aorta and carotid tune rates while O2 barely matters. Inflamed airways wheeze asthma, smoked walls balloon emphysema, and dusty lungs scar unless masked.

Why it matters. CO2 sensors explain rate changes. Disorder names match their damage.

Key words

Rhythm centre: : The medulla centre that sets the basic breathing rhythm.
Pneumotaxic centre: : The pons centre that trims inspiration length and adjusts rate.
Chemosensitive area: : Sensors in brain, aorta and carotid that track CO2 and acid levels.
Asthma: : Inflamed airways that narrow and wheeze during attacks.
Emphysema: : Smoke-damaged air sacs that trap air and strain breathing.

Try it in two minutes

Place rhythm and trim centres.
Name three sensors.
Match three disorders.

Try at home. Time breathing after exercise.

What your child will practise

Gas Transport: Space Quick Fire (Quick Fire)
Mechanism of Breathing: Ocean Puzzle (Clue Puzzle)
Regulation and Disorders: Jungle Quest (Flip and Match)
Respiratory Organs and Human Airway: Candy Quick Fire (Quick Fire)
Volumes and Gas Exchange: Desert Puzzle (Clue Puzzle)

Quiz: Gas Transport (8 questions)
Quiz: Mechanism of Breathing (8 questions)
Quiz: Regulation and Disorders (8 questions)
Quiz: Respiratory Organs and Human Airway (8 questions)

Breathing and Exchange of Gases

Class 11 · Biology

5 ideas in Class 11 Biology, explained in plain words, with games and quizzes to practise.

Respiratory Organs and Human Airway

Part of: Airways and Breathing

Why it matters. Habitat picks the organ. Path order explains every breath sound.

Key words

Larynx: : The voice box where sound is produced in the human airway.
Epiglottis: : The flap that guards the airway while swallowing food.
Trachea: : The ringed windpipe that stays open during airflow.
Alveoli: : The tiny air sacs where oxygen and CO2 exchange with fluid.
Diffusion membrane: : The three-layered sheet across which gases diffuse by gradient.

Try it in two minutes

Order nostrils to alveoli.
Split conducting from exchange.
Name three airway guards.

Try at home. Feel chest rise and fall.

Mechanism of Breathing

Part of: Airways and Breathing

Why it matters. Pressure logic replaces muscle-mystery. Rates and volumes diagnose lungs.

Formulas

A healthy human breathes 12 to 16 times per minute at rest.
Air moved per minute is about 6000 to 8000 mL at rest.

Key words

Inspiration: : The diaphragm and rib muscles expand the thorax to draw air in.
Expiration: : Relaxation of thorax muscles raises pressure and pushes air out.
Pressure gradient: : The pressure difference between lungs and air that drives airflow.
Spirometer: : The instrument that measures lung air volumes in clinical tests.
Pleural lining: : The slippery double covering that lets lungs glide in the chest.

Try it in two minutes

Lower pressure to inspire.
Raise pressure to expire.
Multiply rate by volume.

Try at home. Count breaths for one minute.

Volumes and Gas Exchange

Part of: Volumes, Exchange and Transport

Why it matters. Capacity sums diagnose lungs. Gradient tables predict every diffusion.

Formulas

Tidal volume is about 500 mL per normal breath.
Inspiratory capacity is tidal volume plus inspiratory reserve volume.
Expiratory capacity is tidal volume plus expiratory reserve volume.
Functional residual capacity is expiratory reserve volume plus residual volume.
Vital capacity is expiratory reserve plus tidal plus inspiratory reserve volumes.
Total lung capacity is vital capacity plus residual volume.
O2 flows from alveoli to fluid to tissues while CO2 flows the reverse way.

Key words

Tidal volume: : Air inspired or expired in one normal breath, about 500 mL.
Inspiratory reserve: : Extra air a forcible inspiration can draw beyond tidal volume.
Expiratory reserve: : Extra air a forcible expiration can push beyond tidal volume.
Residual volume: : Air left in lungs after forcible expiration, about 1100 to 1200 mL.
Vital capacity: : Maximum air breathed out after a forced inspiration.
Total lung capacity: : All lung air at end of forced inspiration, capacity plus residual.
Partial pressure: : The individual gas pressure, written pO2 for oxygen, that sets gradients.

Try it in two minutes

Add ERV to RV for FRC.
Read O2 down its gradient.
Read CO2 up its gradient.

Try at home. Compute VC from textbook values.

Gas Transport

Part of: Volumes, Exchange and Transport

Why it matters. Loading zones mirror gradients. Enzyme shuttles dominate CO2 traffic.

Formulas

About 97 percent of O2 travels in red cells and 3 percent dissolved in plasma.
About 20 to 25 percent of CO2 travels in red cells and 70 percent as bicarbonate.
Each haemoglobin molecule carries at most four O2 molecules.
Every 100 mL of oxygenated circulating fluid delivers about 5 mL of O2 to tissues.
Every 100 mL of deoxygenated circulating fluid delivers about 4 mL of CO2 to the alveoli.
CO2 dissolves 20 to 25 times more readily than O2 across the membrane.

Key words

Red corpuscle: : Red cells that ferry nearly all oxygen as four-per-haemoglobin loads.
Haemoglobin: : The red protein that binds O2 reversibly to form oxyhaemoglobin.
Carbonic anhydrase: : The enzyme in red cells that swaps trapped bicarbonate back to gas.
Bicarbonate carrier: : The bicarbonate form that carries most CO2 from tissues to air sacs.
Carbamino compound: : Haemoglobin bound to CO2 that unloads the gas at the alveoli.
Dissociation curve: : The curve plotting haemoglobin saturation against oxygen pressure.

Try it in two minutes

Load four O2 per haemoglobin.
Split CO2 three ways.
Trade five for four.

Try at home. Chart loading versus unloading zones.

Regulation and Disorders

Part of: Control and Disorders

Why it matters. CO2 sensors explain rate changes. Disorder names match their damage.

Key words

Rhythm centre: : The medulla centre that sets the basic breathing rhythm.
Pneumotaxic centre: : The pons centre that trims inspiration length and adjusts rate.
Chemosensitive area: : Sensors in brain, aorta and carotid that track CO2 and acid levels.
Asthma: : Inflamed airways that narrow and wheeze during attacks.
Emphysema: : Smoke-damaged air sacs that trap air and strain breathing.

Try it in two minutes

Place rhythm and trim centres.
Name three sensors.
Match three disorders.

Try at home. Time breathing after exercise.

What your child will practise

Gas Transport: Space Quick Fire (Quick Fire)
Mechanism of Breathing: Ocean Puzzle (Clue Puzzle)
Regulation and Disorders: Jungle Quest (Flip and Match)
Respiratory Organs and Human Airway: Candy Quick Fire (Quick Fire)
Volumes and Gas Exchange: Desert Puzzle (Clue Puzzle)

Quiz: Gas Transport (8 questions)
Quiz: Mechanism of Breathing (8 questions)
Quiz: Regulation and Disorders (8 questions)
Quiz: Respiratory Organs and Human Airway (8 questions)