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Chapter 42

BIOL 2200 Chapter 42: 42.5-42.7 Textbook Notes

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University of Virginia
BIOL 2200
Jessamyn Manson

Chapter 42 Respiratory System Pages 933-943 42.5 Gas Exchange occurs across specialized respiratory surfaces  Gas exchange- uptake of molecular O2 from the environment and discharge of CO2 into the environment  Partial Pressure Gradients in Gas Exchange o Partial pressure – pressure exerted by a particular gas in a mixture of gases  Respiratory Media o Air is a mixture of gases from which we extract CO2 from o Easier to extract O2 from air than water o Adaptations evolved for aquatic animals to do gas exchange more efficiently  Respiratory Surfaces o Always moist o Movement of O2 and CO2 takes place by diffusion o Amount of gas exchange depends on amount of surface area o More basal organisms use skin as respiratory organ, but this body surface area is not enough to perform gas exchange for the whole body o Evolutionary adaptation – extensively folded organ (lungs, gills, trachea)  Gills o Ventilation – maintains partial pressure of O2 and CO2 by moving gills in water or moving water over gills o Water enters the mouth, then slits of pharynx, flows over gills, then exits body o Countercurrent exchange – exchange of substance between 2 fluids going in opposite directions for more efficient gas exchange  Tracheal System in Insects o Tracheal system – network of air tubes that branch throughout the body  Lungs o Localized, unlike tracheal systems o Circulatory system needed to transport O2 to the rest of the body o Mammalian Respiratory System  Air enters through nostrils and is filtered by nose hairs  Pharynx – where air and food cross  Then larynx, trachea, bronchi  Bronchi leads to lungs  Bronchioles – finer tubes  Lined with epithelium lining and mucus, which traps unwanted public  Alveoli – where gas exchange occurs  Oxygen diffuses from alveoli into surrounding capillaries  CO2 diffused in opposite direction  White blood cells engulf particles and protect from infection  Surfactant reduced surface tension 42.6 Breathing Ventilates Lungs  Breathing – alternates inhalation and exhalation  How Amphibians Breathe o Positive pressure breathing – inflating lungs with forced airflow o Inhalation  Muscles lower floor of oral cavity  Air drawn in through nostrils  Nostrils and mouth closed, floor of oral cavity rises and air forced down trachea o Exhalation  Air forced out of lungs by elastic recoil and compression of muscular wall  How Birds Breathe o Air sacs act as bellows that keep air flowing through lungs o Sites of gas exchange aren’t alveoli, but parabronchi o Passage through respiratory system required 2 cycles of inhalation and exhalation  Cycle 1: air passes over gas exchange surface in one direction
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