Respiratory System (Gas Exchange)

IB Biology SL Core Topic 6.2

Jeff JewettAmerican College of Sofia

February 2010

Ventilation

• “movement of the respiratory medium over the respiratory surface” (CR p917)

• Moving air into (inspiration) and out of (expiration) the lungs

• In mammals, this is done by “negative pressure”, pulling the air in

• Lung expanding/contracting http://www.youtube.com/watch?v=oKH7CtsEgHw

• Diaphragm motion animation http://www.youtube.com/watch?v=hp-

gCvW8PRY&feature=PlayList&p=C0655CEFFEB5B4DE&index=5

• Inspiration/Expiration– http://faculty.stcc.edu/AandP/AP/AP2pages/Units21to23/respiration/inspirat.htm

Intracostal Muscles

• Surround the ribs• External – contract to expand the rib cage,

pulling in air (INSPIRATION)• Internal – contract for forced expulsion of

air (talking, playing a wind instrument, hard breathing, etc)

• Inhalation is active (always the diaphragm, sometimes the external intercostals and others)

• Exhalation is usually passive (diaphragm relaxing, rib elastic fibers returning to normal)– Abdominal muscles also help with forced exhalation

Negative Pressure Breathing

Pulling air in (not pushing)

MORE Volume = less pressureless Volume = more pressure

Gas flows from HIGH low pressure

Gas Exchange

• This is DIFFERENT than cellular respiration!

• Uptake of O2 from environment and discharge of CO2 to environment

• Respiration animation http://www.youtube.com/watch?

v=HiT621PrrO0&feature=PlayList&p=CEE41F232E0E67CF&index=3&playnext=2&playnext_from=PL

Label the parts of the mammalian respiratory system!

• Trachea and bronchi are surrounded by rings of cartilage to prevent collapse

• Bronchioles have smooth muscle fibers, allowing expansion/contraction

Gas Exchange

• Gas exchange occurs across plasma membrane must keep surface MOIST

• Movement of gases by diffusion • Rate of diffusion is proportional to:

– Surface area– Distance2

– Respiratory surfaces tend to be LARGE and thin

Structure of Alveoli

• Tiny air sacs (~0.2 mm in diameter) surrounded by dense network of capillaries

• Groups of alveoli attached to end of bronchiole• Alveoli walls only one layer of epithelium cells

thick, the cells have little cytoplasm (keep thin!)• < 1 μm between alveolus and erythrocyte• hundreds of millions of alveoli = HUGE surface

area (~80 m2)• Surfaces kept wet