Respiratory system structure of gills, lungs & air sacs; accessory respiratory organs.pptx

Respiratory system structure of gills, lungs & air sacs; accessory respiratory organs.pptx

1. Respiratory system: Structure of gills, lungs & Air sacs and (Accessory respiratory organs) Dr Showkat Ahmad Wani

2. Introduction Definition: The respiratory system enables gas exchange – intake of oxygen (O₂) and removal of carbon dioxide (CO₂). Importance: Oxygen is vital for cellular respiration , ATP synthesis, and energy metabolism. CO₂ removal maintains blood pH . Respiratory organs: Gills, lungs, air sacs, and accessory organs. Adaptation: Respiratory organs are specialized according to environment (aquatic vs terrestrial vs aerial).

3. Gills Definition: Gills are specialized organs in aquatic animals that extract dissolved O₂ from water. Structure: Gill arches: Bony or cartilaginous supports. Gill filaments: Long, thin projections from arches; increase surface area . Lamellae: Secondary folds on filaments; extremely thin, rich in capillaries; site of gas exchange. Gill rakers: Protect gill filaments from debris and prevent food particles from damaging delicate structures. Operculum (in bony fish): Protective flap covering internal gills.

4. Mechanism of Gas Exchange: Countercurrent flow: Water moves over gills in the opposite direction to blood in lamellae → maximizes O₂ absorption. Oxygen diffuses into blood; CO₂ diffuses out into water. Efficiency: Fish can extract up to 85–90% of dissolved oxygen. Types of Gills: External gills: Project outside the body; highly vascular; seen in amphibian larvae and some fish. Internal gills: Enclosed in a chamber; operculum protects them; seen in bony fish. Additional Functions: Ion regulation (Na⁺, Cl⁻) in marine/freshwater fish. Nitrogenous waste excretion in some species. Biochemical Note: Hemoglobin in blood binds O₂ efficiently, with affinity influenced by temperature, pH, and CO₂ (Bohr effect).

5. Lungs Definition: Lungs are internal, sac-like organs for air-breathing in terrestrial vertebrates. Structure: Trachea → bronchi → bronchioles → alveoli . Alveoli: Millions of thin-walled sacs with dense capillary networks; primary site for gas exchange. Pleura: Double-layered membrane; reduces friction and maintains negative pressure.

6. Mechanism: Inhalation: Diaphragm contracts → thoracic cavity expands → air enters lungs. Exhalation: Diaphragm relaxes → air exits. Vertebrate Variations: Amphibians: Simple sac-like lungs + skin respiration. Reptiles: More complex alveolar lungs. Mammals: Highly branched alveolar lungs for maximal surface area.

7. Air Sacs (Birds) Definition: Thin-walled, elastic sacs connected to lungs that enhance ventilation efficiency . Structure: Typically 9 air sacs : cervical (2), clavicular (1), anterior thoracic (2), posterior thoracic (2), abdominal (2). Not directly involved in gas exchange ; act as bellows to move air.

8. Mechanism of Airflow (Unidirectional): First inhalation: Air bypasses lungs → fills posterior air sacs . First exhalation: Air moves from posterior sacs → lungs → gas exchange in parabronchi. Second inhalation: Air from lungs → anterior air sacs . Second exhalation: Air expelled from anterior air sacs → environment.

9. Advantages: Provides continuous airflow through lungs → high O₂ extraction efficiency. Reduces body weight → aids flight. Maintains high O₂ levels during strenuous activity (flight). Additional Features: Parabronchi: Tiny tubes where O₂ diffuses into blood; cross-current mechanism increases efficiency. Air sacs also act as thermoregulatory organs , helping to dissipate heat during flight.

10. Accessory Respiratory Organs Definition: Structures that supplement primary respiratory organs. Examples: Skin (cutaneous respiration): Amphibians, earthworms; thin, moist, vascularized skin. Buccal cavity (oral respiration): Amphibians; vascularized floor of mouth assists in gas exchange. Modified lungs as swim bladders: Certain fish (lungfish) can use lungs for respiration in hypoxic water.

11. Comparative Summary Organism Group Respiratory Organ Key Adaptation Fish Gills Countercurrent flow, high SA, ion regulation Amphibians Skin + Lungs Cutaneous respiration, simple lungs Reptiles Lungs More alveolar structure Birds Lungs + Air Sacs Unidirectional flow, efficient O₂ extraction, lightweight

12. Clinical / Biochemical Relevance Hypoxia: Reduced O₂ due to gill/lung dysfunction. CO₂ retention: Leads to acidosis. Hemoglobin-O₂ affinity: Affected by pH, temperature, CO₂ (Bohr effect). Adaptations: Critical in high altitude, aquatic, or flying animals.

13. Conclusion Respiratory organs are highly specialized for the environment . Efficiency depends on surface area, blood supply, and mechanical ventilation . Accessory organs ensure survival in challenging or hypoxic conditions .

14. Thank You