Mammalian Respiratory System

Question 1

Challenge of Getting Oxygen: Gas Exchange

Answer 1

Different organisms have different ways of getting oxygen to their cells. As organisms increase in size, more oxygen to function.

Oxygen crosses into the system of an organism through a respiratory surface. There are 2 main requirements for a respiratory surface:

1. This surface must have a large enough surface area to allow oxygen and carbon dioxide to be exchanged at a rate that meets the organism’s needs
2. The surface must also be moist, so that oxygen gas and carbon dioxide are dissolved

Question 2

Terrestrial Animals

Answer 2

• lungs have evolved to obtained maximum oxygen from the air
• surface must be kept moist, so lungs are internal
• surface area increases by alveoli

Question 3

Diaphragm

Answer 3

Diaphragm
• piece of skeletal muscle (dome shaped, separates chest cavity from abdominal cavity)
• major muscle involved in breathing
• acts like a piston

Question 4

External Intercostal Muscles

Answer 4

• attached to outside of rib cage
• during inspiration, pull up rib cage up and out (increasing volume in chest cavity)
• when relaxed, rib cage falls and pushes air out of lungs

Question 5

Internal Intercostal Muscles

Answer 5

• used only for forced exhalation - blowing out a candle, exercising, etc.
• pull rib cage down and out
• not used in regular breathing

Question 6

Pressure Differences

Answer 6

Air will flow into the lungs (inspiration) when:
The pressure in the lungs is lower than the pressure outside.

Air will flow out of the lungs (exhalation) when:
The pressure in the lungs is higher than the pressure outside.

Question 7

Single-celled organisms

Answer 7

• breathe through diffusion of gases across the cell membrane
• e.g. protists, algae, fungi

Question 8

Annelida (segmented worms)

Answer 8

• breathe by diffusion of gases through skin

* e.g. earthworm

Question 9

Insects

Answer 9

• holes in side of body called spiracles allow air to enter
• air moves to cells through tubes called tracheae
• e.g. flies, grasshoppers

Question 10

Aquatic Animals

Answer 10

• gills are designed to extract oxygen from water

* surface area is increased by filaments - thin tissues with blood flowing through

Question 11

How do we breathe?

Answer 11

• breathing = air moving in/out of lungs
• gases move because of pressure differences
• gases will move from higher pressure to lower pressure
• to breathe we rely on two main factors:
1. Diaphragm
2. Differences in pressure

Question 12

Diaphragm and Boyle’s law

Answer 12

Boyle’s Law
• decreasing volume increases collisions and increases pressure
How They Work Together
• when it contracts, it pulls down the floor of the diaphragm
- enlarges the volume of the intrapleural space
- decreases the pressure in this space
• when the diaphragm relaxes from contraction
- decreases volume of the intrapleural space
- increases the pressure in this space