Lesson 13 Gas Exchange 1

AIM: How have mechanisms for gas exchange evolved?

DO NOW: Go over pp. 247-248

HW: Read Ch. 34 pp. 698 – 702

STUDY

Basic Vocab

• Respiration vs. gas exchange

• Respiratory surface

• Respiratory medium (air vs. water)

• Ventilation

• Countercurrent mechanism

• Positive vs negative pressure breathing

• Form fits function (alveolus)

• Simple diffusion

Terrestrial Organisms

• Problem of desiccation

• Need respiratory organs w/i the organism’s body

• Evolution of lungs from swim bladder of fish

Respiratory Surfaces

Must maximize diffusion:

• Thin

• Large surface area

• Moist

Adaptations for Gas ExchangeMonera, Protista,

Porifera,

Cnidaria

Platyhel-minthes

Anneli-da

(Earth-worms)

Arthropoda (grasshop-per)

Fish Amphibia Mammalia & Aves

Countercurrent mechanism(Water flows over O2-rich blood first.)

Mammalian Lungs(Negative Pressure Breathing)

Negative Pressure Breathing• deep breath contraction of rib muscles

volume of rib cage P in lungs air rushing from area of high P (outside body) to the area of lower P (inside lungs).

Gas exchange in humans:

• Nose pharynx larynx trachea bronchi bronchioles alveoli

V of lungs P air rushing in by bulk flow

• Negative pressure breathing

Alveolus: Form Fits Function

How O2 and CO2 enter/exit the blood: diffusion between capillary & alveolus

Diseases of the Respiratory System

1. Pharyngitis2. Laryngitis 3. Bronchitis 4. Pneumonia5. Asthma6. Cystic fibrosis7. Emphysema (COPD)8. Lung cancer