Ch 22- Respiration- The Exchange of Gases

Ch 22- Respiration- The Exchange of Gases• Alveoli• Breathing control centers• Bronchi• Bronchioles• Countercurrent exchange• Diaphragm• Emphysema• Gas exchange• Gills• Hemoglobin• Hyperventilating• Larynx

• Lungs• Negative pressure breathing• Partial pressure• Pharynx• Respiration• Respiratory surface• Trachea• Tracheae• Tracheoles• Ventilation• Vital capacity• Vocal cords

Gas exchange

• Gas exchange- interchange of O2 and CO2 between an animal and it’s environment

• Mechanisms:– Breathing– Gases transported by circulatory system to body– Tissues take up O2 and release CO2 to the blood

• Animals exchange gases through moist body surfaces– Respiratory surfaces- must be wet to function properly, thin for O2 and

CO2 to diffuse easily

Respiratory Surfaces• Entire outer skin- ex: earthworm• Gills- for exchange in water

– Opening and closing of mouth and gills allows for increase in gas exchange efficiency (ventilation)

– Countercurrent flow of water enhances O2 transfer (80% can be removed!!!)

Countercurrent exchange

Respiratory Surfaces• Tracheal system- branching air tubes in body (tracheae) opens

to outside, narrowest-tracheoles- extend to nearly every cell in body

• * terrestrial animals spend less E on getting O2 because air is lighter and has more O2)

• Lungs- most terrestrial vertebrates

Human respiratory system

Human respiratory system• Air enters through nostrils- warmed, humidified and sampled• Pharynx- throat• Larynx- voice box- air rushing over cords creates sound• Trachea- windpipe- has rings of cartilage to maintain open

shape• Bronchi- 2 tubes, 1 to each lung• Bronchiole- get thinner and finer branching within lung• Alveoli- air sacs, end of branching, covered in capillaries,

where gas exchange takes place• Cilia and mucous throughout system- clean air • Diaphragm- muscle at bottom of chest cavity, facilitates

breathing

Breathing• Alternating inhaling and exhaling

– Diaphragm contracts, rib cage expands= air rushes in– Diaphragm relaxes, rib cage lowers= air’s pushed out– Negative pressure breathing- muscle contraction causes lower

pressure inside than outside and air rushes in– Vital capacity- max volume of air we can breathe in & out

Breathing

Controlling Breathing• Pons and medulla oblongata –

breathing control center• Nerve signals sent to contract

diaphragm and raise ribs by contraction of muscles

• Medulla monitors CO2 levels and regulates breathing in response, also monitors blood pH, cerebrospinal fluid and O2 levels in large arteries and when O2 levels in blood are severely decreased

• pH decreases when CO2 increases

Hyperventilation

• Shows how control center works• Purge blood of CO2 so there is a temporary signal to

stop breathing (b/c of low CO2 levels)

Circulation of gases

• O2 rich blood in lungs goes to heart to be pumped to body

• O2 poor blood in body goes to heart to be pumped to lungs to pick up O2

• Gas exchange occurs by diffusion• Hemoglobin- O2 carrier in RBC’s

– 1 hemoglobin can carry 4 O2 molecules– Fig 22.11A and B in text– CO2 forms H2CO3 (carbonic acid) in RBC’s it breaks to HCO3-

(bicarbonate ion) and H+ (which hemoglobin takes up so that blood doesn’t become acidic)• In lungs- reaction is reversed HCO3- binds with H+ then H2CO3 is

converted to CO2 and H2O which is diffused into alveoli

CO2 transport in the blood

Gas exchange in fetus• Uses placenta for exchange from mothers blood from lungs• Fetal hemoglobin-special type that has higher affinity for O2

• At birth – increase in fetus’s CO2 level triggers breathing control center to start breathing

Problems in respiratory system• Asthma- bronchi become inflamed due to allergic

reaction• Bronchitis- inflammation of bronchi due to pathogens

(ex: bacteria)• Smoking!!- cilia and mucous trap particles and sweep

them out before reaching alveoli– Macrophages also engulf particles and microorganisms– Smoking destroys cilia and macrophages- allowing toxins to

reach alveoli – Fig 22.7A- lung cancer– Emphysema- alveoli become brittle and rupture, decreases gas

exchange (not enough oxygen)