Gas exchange in humans

GAS EXCHANGE IN HUMANS

  • Overview of the human gas exchange system essential for respiration and maintaining homeostasis.

LEARNING OBJECTIVES

  • Core

    • Identify parts of the breathing system:

      • Lungs

      • Diaphragm

      • Ribs

      • Intercostal muscles

      • Larynx

      • Trachea

      • Bronchi

      • Bronchioles

      • Alveoli

      • Associated capillaries

    • Investigate composition differences between inspired and expired air using limewater for carbon dioxide.

    • Describe differences in the composition of inspired versus expired air:

      • Oxygen

      • Carbon dioxide

      • Water vapor

    • Investigate effects of physical activity on breathing rate and depth.

  • Extended Only

    • Describe features of gas exchange surfaces in humans:

      • Large surface area

      • Thin surface

      • Good blood supply

      • Good ventilation

    • Explain differences in gas compositions in inspired vs expired air.

    • Link between physical activity, increased carbon dioxide concentration, and the effects on breathing rates and depth.

FUNCTIONS OF THE HUMAN GAS-EXCHANGE SYSTEM

  • Provides oxygen for cells to release energy (ATP) during respiration.

  • Eliminates carbon dioxide, which can be harmful if accumulated in the body.

STRUCTURE OF THE HUMAN GAS-EXCHANGE SYSTEM

  • Main components include:

    • Nasal Cavity

    • Oral Cavity

    • Larynx

    • Trachea

    • Bronchi

    • Bronchioles

    • Alveoli

    • Diaphragm

    • Intercostal muscles

TRACHEA AND LARYNX

  • Trachea:

    • Also known as the windpipe.

    • Contains about 20 rings of cartilage for support.

    • Composed of epithelial and muscle tissue; contains ciliated cells.

  • Larynx:

    • Also known as the voice box; houses vocal cords.

    • Maintained open by cartilage rings.

BRONCHI AND BRONCHIOLES

  • Bronchi:

    • The largest branches of the respiratory tract made of cartilage for structural stability.

  • Bronchioles:

    • Smaller branches with connective and smooth muscle tissue to regulate air flow to alveoli.

ALVEOLI

  • Structures resembling small balloons, consist of:

    • One layer of epithelial tissue (one cell thick).

    • Elastic fibers allowing expansion during inhalation.

    • Surrounded by numerous capillaries for efficient gas exchange.

    • Total surface area in lungs exceeds 100m².

GOBLET AND CILIATED CELLS

  • Goblet Cells:

    • Secrete mucus to trap debris and pathogens.

  • Ciliated Cells:

    • Sweep debris upwards to keep airways clear.

    • Clara cells: involved in detoxification processes.

PERCENTAGE OF GASES IN INHALED AND EXHALED AIR

  • Typical composition:

    • Nitrogen: 78.0% (both inhaled and exhaled)

    • Oxygen: 21.0% (inhaled) vs 16.0% (exhaled)

    • Argon: 0.9% (both inhaled and exhaled)

    • Carbon Dioxide: 0.04% (inhaled) vs 4.0% (exhaled)

    • Water vapor: variable.

UNDERSTANDING KEY TERMINOLOGY

  • Breathing: refers to ventilation.

  • Inhalation (inspiration): occurs when atmospheric pressure is greater than lung pressure.

  • Exhalation (expiration): occurs when lung pressure exceeds atmospheric pressure.

  • Muscle movements affecting air pressure include diaphragm and intercostal muscles.

EXERCISE AND BREATHING RATE

  • Resting breathing rate: 12-20 breaths per minute.

  • Exercise increases demand for oxygen and produces more carbon dioxide, increasing the breathing rate and depth for gas exchange.

EFFECTS OF SMOKING

  • Nicotine: addictive and harmful chemical.

  • Cigarette smoke contains toxic substances causing lung damage.

  • Results in increased mucus, loss of cilia, bronchitis, and/cancer risk and impacts gas exchange efficiency.

SUMMARY QUESTIONS

  • What is the larynx?

  • Function of cilia in the respiratory passage?

  • Where does gas exchange occur in humans?

  • The number of cells oxygen passes to enter blood from alveolus?

  • Features of alveoli that facilitate efficient gas exchange?

FINAL EXERCISE

  • Review provided resources and attempt associated tests for further understanding.