Breathing AND Exchange OF Gases flash cards

1. 1.Define breathing (external respiration).

   The physical process of exchange of O2 from the atmosphere with CO2 produced by cells; also called ventilation. It involves inspiration and expiration of air.

   Hint: Physical exchange of gases, not the biochemical part.

2. 2.Why do organisms need to breathe?

   O2 is required for oxidation (catabolic breakdown) of nutrients to release energy for cellular activities, and CO2 (harmful) produced must be released out of the body.

   Hint: O2 for energy release, CO2 removal.

3. 3.How do sponges, coelenterates and flatworms exchange gases?

   By simple diffusion of gases directly across the entire body surface, since they have no specialised respiratory organs.

   Hint: Diffusion over body surface.

4. 4.What is the respiratory organ in earthworms?

   The moist cuticle (skin), which is used for cutaneous respiration by diffusion.

   Hint: Moist skin — cutaneous.

5. 5.Which respiratory organs do insects (arthropods) use?

   A network of tracheal tubes (tracheae) that carry air directly to tissues, opening outside through spiracles.

   Hint: Tracheal tubes and spiracles.

6. 6.What is the respiratory organ in aquatic arthropods and molluscs?

   Gills (branchial respiration), which are vascularised structures for gas exchange in water.

   Hint: Gills — branchial.

7. 7.Which respiratory organs are used by vertebrates?

   Gills (in fishes, aquatic forms) or lungs (in terrestrial forms). Amphibians can also use their moist skin.

   Hint: Gills or lungs; frog also skin.

8. 8.QUESTION: Arrange the respiratory structures with their animals — cutaneous, tracheal, branchial, pulmonary.

   Cutaneous = earthworm/frog skin; Tracheal = insects; Branchial = gills in fishes/prawns; Pulmonary = lungs in reptiles, birds, mammals.

   Hint: Skin, trachea, gills, lungs.

9. 9.Why are lungs more efficient than skin for terrestrial gas exchange?

   Lungs provide a large, internal, moist, highly vascular surface protected from drying, allowing efficient exchange in air on land.

   Hint: Large moist protected internal surface.

10. 10.Name the parts of the human respiratory system in order of airflow.

    External nostrils → nasal chamber → pharynx → larynx → trachea → primary bronchi → secondary/tertiary bronchi → bronchioles → terminal bronchioles → alveoli.

    Hint: Nose to alveoli.

11. 11.What is the function of the nasal chamber?

    It filters (dust), warms, and moistens (humidifies) the incoming air before it reaches the lungs.

    Hint: Filter, warm, moisten.

12. 12.What is the larynx and its role?

    The larynx is a cartilaginous box (sound/voice box) at the trachea's beginning that helps in sound production.

    Hint: Voice/sound box.

13. 13.What is the epiglottis and its function?

    A thin elastic cartilaginous flap that covers the glottis during swallowing to prevent food from entering the larynx/trachea.

    Hint: Flap that guards the glottis while swallowing.

14. 14.Describe the structure of the trachea.

    A straight tube extending to the mid-thorax, supported by C-shaped (incomplete) cartilaginous rings that prevent it from collapsing.

    Hint: C-shaped cartilage rings keep it open.

15. 15.At what level does the trachea divide, and into what?

    At the level of the 5th thoracic vertebra it divides into a right and left primary bronchus, one entering each lung.

    Hint: 5th thoracic vertebra — two primary bronchi.

16. 16.Trace the branching of bronchi within a lung.

    Primary bronchus → secondary and tertiary bronchi → bronchioles → terminal bronchioles → each ending in alveoli.

    Hint: Bronchi to bronchioles to alveoli.

17. 17.What are alveoli and why is their structure important?

    Alveoli are thin, irregular-walled, vascularised bag-like air sacs; they are the primary sites of gas exchange, providing a very large surface area.

    Hint: Thin, vascular sacs = exchange surface.

18. 18.What together form the 'respiratory' or exchange part of the tract?

    The bronchioles, alveolar ducts and alveoli form the conducting-to-exchange respiratory portion; the alveoli are where actual exchange occurs.

    Hint: Alveolar region does exchange.

19. 19.Which part forms the conducting part of the respiratory system?

    From external nostrils up to the terminal bronchioles — it transports, clears, humidifies, warms air but does no exchange.

    Hint: Nostrils to terminal bronchioles; no exchange.

20. 20.Where are the lungs situated and what covers them?

    In the thoracic chamber, covered by a double-layered pleura with pleural fluid in between, which reduces friction on the lung surface.

    Hint: Double pleura + pleural fluid.

21. 21.How is the thoracic chamber anatomically sealed?

    It is air-tight, bounded dorsally by the vertebral column, ventrally by the sternum, laterally by ribs, and below by the dome-shaped diaphragm.

    Hint: Vertebrae, sternum, ribs, diaphragm.

22. 22.Why is the air-tight thoracic chamber important for breathing?

    Any change in the volume of the thoracic cavity is reflected in the lung cavity, allowing pressure changes that drive air in and out.

    Hint: Thoracic volume change = lung volume change.

23. 23.What are the two main stages of breathing?

    Inspiration — atmospheric air is drawn in; and Expiration — alveolar air is released out.

    Hint: Air in, air out.

24. 24.What is the fundamental principle driving air movement in breathing?

    Air moves along a pressure gradient — it flows from a region of higher pressure to lower pressure. Breathing is achieved by creating such gradients.

    Hint: High to low pressure.

25. 25.How is inspiration initiated (pressure-wise)?

    Intra-pulmonary (intra-alveolar) pressure is made LESS than atmospheric pressure, so air rushes into the lungs.

    Hint: Alveolar pressure < atmospheric.

26. 26.How is expiration achieved (pressure-wise)?

    Intra-pulmonary pressure is made HIGHER than atmospheric pressure, forcing air out of the lungs.

    Hint: Alveolar pressure > atmospheric.

27. 27.What role does the diaphragm play in inspiration?

    Contraction of the diaphragm flattens it, increasing the volume of the thoracic chamber in the antero-posterior (front-to-back) axis.

    Hint: Diaphragm contracts and flattens.

28. 28.What role do the external intercostal muscles play in inspiration?

    Their contraction lifts the ribs and sternum upward and outward, increasing thoracic volume in the dorso-ventral (side-to-side) axis.

    Hint: Ribs and sternum move up and out.

29. 29.Explain the sequence of events during inspiration.

    Diaphragm + external intercostals contract → thoracic volume increases → pulmonary volume increases → intra-pulmonary pressure falls below atmospheric → air rushes in.

    Hint: Muscles contract, volume up, pressure down, air in.

30. 30.Explain the sequence of events during expiration.

    Diaphragm + external intercostals relax → diaphragm and ribs return to normal → thoracic and pulmonary volume decrease → intra-pulmonary pressure rises above atmospheric → air is expelled.

    Hint: Muscles relax, volume down, pressure up, air out.

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