Air and Respiratory System Study Notes

Composition of Air

• Air is a mixture of gases:

  • Nitrogen: 78%

  • Oxygen: 21%

  • Other Gases: < 1% (e.g., carbon dioxide for photosynthesis)

Respiratory System Overview

• Definition of Respiratory System:

  • System responsible for taking in air and facilitating gas exchange in the body.

• Key components of the respiratory system:

  • Nose

  • Windpipe (trachea)

  • Lungs

  • Air sacs

  • Diaphragm

Parts of the Respiratory System

Nose

• Function:

  • Takes in various types of air (nitrogen, oxygen, carbon dioxide, etc.).

• Characteristics:

  • Contains nose hairs to filter bacteria and unwanted substances.

Windpipe (Trachea)

• Function:

  • Tube connecting the nose to the lungs.

• Associated structure:

  • Larynx (voice box)

  • Hyoid bone, tracheal cartilages, branched to primary bronchi (right and left lungs).

Lungs

• Function:

  • Site for gaseous exchange between oxygen and carbon dioxide.

• Characteristics:

  • Left lung is smaller to accommodate the heart.

Air Sacs (Alveoli)

• Function:

  • Oxygen from air passes through air sac walls into the bloodstream.

  • Blood transports oxygen throughout the body.

  • Carbon dioxide moves from blood to air sacs to be exhaled.

Diaphragm

• Function:

  • Elastic muscle sheet at the base of the lungs.

  • Inhaling: Contracts and moves down, increasing lung volume.

  • Exhaling: Relaxes and moves up, pushing air out.

Conceptual Model of the Respiratory System

• Model components:

  • Straw: acts as the windpipe

  • Balloons: represent lungs

  • Rubber sheet: simulates diaphragm's movement for inhalation and exhalation.

Working Principle of the Model

• Inhalation Process:

  • Pulling the rubber sheet increases volume in the balloons (lungs), allowing air to rush in.

• Exhalation Process:

  • Pushing the rubber sheet decreases volume, pushing air out of the balloons.

How Fish Breathe

• Breathing through Gills:

  • Gills contain blood vessels that absorb dissolved oxygen from water.

  • Carbon dioxide is expelled back into the water.

How Plants Breathe

• Stomata Function:

  • Air enters through stomata on the underside of leaves.

  • During photosynthesis, carbon dioxide enters and oxygen exits.

  • Water vapor is also released through stomata.

Recap Points

• Major components of respiratory system: Nose, windpipe, lungs, air sacs, diaphragm.

• Composition of air: Nitrogen (78%), Oxygen (21%).

• Gaseous exchange location: Lungs and air sacs.

• Breathing methods: Fish use gills; plants use stomata.

Sample Exam Questions

• Multiple Choice (MCQ):

  • Which gases are found in air?

  • Options:
    A) oxygen
    B) nitrogen
    C) carbon dioxide
    D) water vapour

  • Correct answer: (4) A, B, C, and D.

• Open-ended Questions include:

  • Function of the human respiratory system and gases involved.

  • Naming three parts of the respiratory system.

  • Describing how the respiratory system works with the circulatory system.