Comparative Vertebrate Anatomy - Respiratory System Notes PDF

2024/02/11 O2 CO2 1 Passive diffusion Surface area Distance Resistance Partial pressure difference Unaided – 0.5 mm Pumps – partial pressure gradient Respiratory and circulatory systems int...

2024/02/11 O2 CO2 1 Passive diffusion Surface area Distance Resistance Partial pressure difference Unaided – 0.5 mm Pumps – partial pressure gradient Respiratory and circulatory systems interlinked 2 Respiration External vs. internal Ventilation vs. perfusion Evolution Unidirectional Bidirectional (tidal) 3  2024/02/11 4 5 6  2024/02/11 Involves gulping air Other organs with a dual function (p417 – 418) 7 Anamniotes Skin Birds/reptiles Porous shell Chorioallantois 8 Cilia Surfactant Muscular pumps Medium Mechanism Water Dual pump + RAM Air Buccal pump Air Aspiration pump 9  2024/02/11 Continuous Unidirectional Two-stroke 10 E.g.: Amphibians (most) African lungfish Two-stroke: 11 E.g.: Amphibians (aquatic) Lungfishes Four-stroke: 12  2024/02/11 Does not push air Air sucked in (aspirated) Bidirectional (tidal) Feeding and respiration decoupled 13 Agnathans / Cyclostomes E Jawless V e.g. lamprey, hagfish O Cartilaginous fishes Elasmobranchs L e.g. sharks, skates, rays U Bony fishes T Teleosts I Lungfishes Amphibians O Reptiles & Mammals N Birds 14 15  2024/02/11 16 17 Septal gills Dual pump RAM 18  2024/02/11 Spiracle 19 Opercular gills Dual pump 20 Skin Gills Lungs Buccal pump (two stroke) 21  2024/02/11 Pharyngeal gill slits – embryo Aspiration pump Mechanism differs between groups Change lung shape = airflow Intercostal muscles move ribs Inhalation = ribs forwards and outward Exhalation = ribs back and inward 22 Length of body Advanced = 1 lung Ribs and muscles Prey swallowing Vascular Bellows during prey swallowing Avascular 23 24  2024/02/11 Problem = shell/fixed ribs – can’t use ribs Lungs and viscera in single cavity Changes in volume affects lungs Legs in and out Reduced plastron 25 Limiting membranes Muscle contraction Viscera change position Compress/expand lungs LUNG Shoulder girdle 26 Limiting membranes Muscle contraction Viscera change position Compress/expand lungs LUNG Shoulder girdle 27  2024/02/11 Limiting membranes Muscle contraction Viscera change position Compress/expand lungs LUNG Shoulder girdle 28 Aspiration pump Bidirectional Structural components Diaphragm Unlike crocodile Anterior to liver Acts directly on pleural cavity Rib cage External/internal intercostal muscles Muscles Transversus abdominus Serratus Rectus abdominus 29 INTERCOSTAL Inhalation 1. External intercostal 1 Ribs/sternum forward and outward Increases pleural cavity vol. 3 2. Diaphragm LUNG Contracts and flattens out Increases pleural cavity vol. 3. Lungs Elastic and fills pleural cavity 2 Reduced pressure DIAPHRAGM Air rushes in 30  2024/02/11 INTERCOSTAL Exhalation 1 1. Internal intercostal Ribs/sternum backward Decreases pleural cavity vol. 3 2. Diaphragm LUNG Relaxes and resumes dome shape Decreases pleural cavity vol. 3. Lungs Elastic energy & gravity 2 Increased pressure DIAPHRAGM Air forced out 31 Quiet breathing Inhalation = diaphragm Exhalation = elastic & gravity Vigorous breathing Ribs, diaphragm and muscles Quadruped locomotion Ground reaction forces via forelimbs change ribcage shape Viscera move forward and backwards Similar to crocodile piston Cursorial mammals - synchronisation 32 Specialised for flight Aspiration pump Unidirectional Continuous Structural components No blind ending alveoli Parabronchi = tiny one-way passages Small air capillaries = gas exchange 33  2024/02/11 9 avascular air sacs Among viscera & in long bones 34 2° Diffusion 2x 35 36  2024/02/11 Respiratory and circulatory systems coupled Orient blood flow Maintains partial pressure gradient Efficiency of gas exchange 37 Ventilation : perfusion Efficiency of respiration 38 Partial pressure Extraction rate Density & viscosity Unidirectional vs. tidal NB: Acid-base regulation 39  2024/02/11 p446 – p449 NB: water-to-land transition Fish to tetrapod Water-breathing to air-breathing 1. Air breathing organs Seasonal hypoxic environments low O2 = gills cant obtain enough Fish ancestor + selective pressure = lung/gas bladder (e.g. lungfish) Immediate advantage but not anticipation Preadaptation 40 2. Ventilatory mechanism Dual pump = water across gills (e.g. fish) Dual pump → buccal pump (e.g. amphibian) Buccal cavity enlarged Opercular cavity lost Amphibian buccal cavity respiration & feeding Buccal pump → Aspiration pump Decouple ventilation from feeding (e.g. reptiles) 41 Medium Group Cavities Pump Water Fish Buccal & opercular Dual Air Fish Buccal Buccal Modified Air Amphibians Opercular lost buccal Air Reptiles Lungs Aspiration Air Mammals Lungs Aspiration Specialised Air Birds Lungs & air sacks aspiration 42  2024/02/11 43