1. The Respiratory System Chapter 42 Campbell & Reece

2. Respiration: exchange of O2 for CO2
Two kinds:
Cellular Respiration: mitochondria --> ATP... (Chapter 7)
Uses O2 to turn glucose into energy (by-product is CO2)
Organismal Respiration: exchange of gases between cells and environment (Chapter 47)
Involves the exchange of O2 CO2 between cells/blood/lungs

3. Evolution of the Respiratory System:
Earliest animals simply diffused O2 through their skin
Insects = use "tracheae" (cuticle-lined tubules in abdomen) good for small animals only
First evolved respiratory organs were GILLS; probably arose as a feeding device, originally
Thin, one cell thick membranes; folded, layered (high surface area); increase respiratory surface; bring more blood in contact w/ O2
"Counter Current Exchange": circulatory vessels are arranged so blood is pumped through in opposite direction of water flow (O2). Maximizes O2 pickup.
LUNGS- internal cavities, also made of many thin, folded air sacs for lots of surface area (better gas exchange)
More efficient than gills (21% O2/Air, 0.5% O2 in Water)
Fish must process more H2O to get the same amount of O2 as in Air (Energy-Consuming)

4. Respiration in Large/Complex Animals
STEP 1: "Bulk-flow" of air into lungs (thin, close to blood vessels)
STEP 2: Diffusion of O2 across membrane into blood  animation
STEP 3: passage of O2 from blood into tissues
STEP 4: Diffusion of O2 into individual cells

5. Diffusion and Air Pressure
Oxygen enters the blood/tissues/cells enters blood via diffusion (from areas of high concentration to low)
If there’s more O2 in the air we breathe, it should diffuse into your red blood cells
Gas Exchange depends upon pressure and concentration differences between atmosphere and bloodstream
changes in the partial pressures of oxygen and carbon dioxide affect diffusion:  animation
Atmospheric pressure (mm Hg)  affects O2 diffusion into blood/tissues (higher altitude, lower pressure)
How does this affect our breathing at altitude?

6. The Human Respiratory System
Nasal passages (mucus,cilia)
Pharynx
Epiglottis
Larynx
Trachea
R&L bronchi
Bronchioles
Alveoli (alveolus) are tiny air sacs with thin walls (surrounded by capillaries)
gases exchanged through capillary/alveolar walls via diffusion
A thin Pleural Membrane encases lungs, secretes lubricants (mucus)

7. Alveoli

8. Asthma Smooth Muscles can dilate/constrict the bronchi, bronchioles
Asthma is a chronic disease that affects your airways
the inside walls of your airways become inflamed (swollen) and clogged with mucus
The inflammation makes the airways very sensitive, and they tend to react strongly to things that you are allergic to or find irritating.
When the airways react, they get narrower, and less air flows through to your lung tissue.
This causes symptoms like wheezing (a whistling sound when you breathe), coughing, chest tightness, and trouble breathing, especially at night and in the early morning.

9. Mechanics of Respiration:
Breathing- due to pressure changes w/in thoracic cavity
muscles:
Diaphragm
relaxes--> rises
contracts--> lowers
Abdominals/ Intercostals raise and lower the ribcage to adjust volume of thoracic cavity
Inspiration -vs- Expiration
breathing animation

10. Transport and Exchange of Gases
A. HEMOGLOBIN –
respiratory pigment
oxygen-carrying protein molecule w/ central iron (Fe) atom
Mollusks & Arthropods: “hemocyanin”, blue w/ O2
heme carried on RBC, can carry 4 Oxygen molecules each (O2 not very soluble in plasma)
Most CO2 is carried in the plasma as (1) carbon anhydrase (in RBC); or (2) carbonic acid; or (3) bicarbonate ion (HCO3)
B. MYOGLOBIN- respiratory pigment found is skeletal muscle
has higher O2 affinity than hemoglobin
O2 reserve for muscles under stress
"Diving Reflex" in marine mammals

11. Control of Respiration
Respiration is under control of brainstem (medulla)
Involuntary, but can be brought under voluntary control temporarily
Many "sensors" located throughout body that give feedback to brain resp. centers
sensors sensitive to CO2, O2, H+ levels
stretch sensors in lungs & chest
chemoreceptors in Carotid Arteries detect blood pH
ex: low pH (acidic) = high CO2 levels, breathing becomes faster/deeper
Practice!  online quizzes:
Respiratory system anatomy hive/wa_respiratory/wa_resps_1.html