Respiratory System Structures

Spiracles

Openings in the side of an insect.

Trachea

Tubes going through an insect.

Gas Exchange

Gas

Can dissolve in liquids.

Moves randomly (brownian motion).

Move faster in air than in liquids.

Diffuse down their concentration gradient.

Most gasses don't have a charge and can easily diffuse across hydrophobic membranes.

Maximizing Gas Exchange

More airflow

More blood flow

Increase surface area (branching pathways).

Minimize distance for diffusion (thin tissues).

CO₂ comes from the Krebs cycle. O₂ is needed to bind free electrons from ETC.

Fish Gills

Have folds for increases surface area.

Oxygen diffuses out of the water and into the blood.

Countercurrent flow of blood and water maximizes oxygen diffusion.

Ventilation

Bird Circulation

Unidirectional Flow

Continuous gas exchange

Air sacs act as bellows.

Gas exchange in parabronchi between air sacs.

Air capillaries allow for crosscurrent gas exchange.

Trachea > Bronchi > Branchioles > Aveol

Aveoli

Small, thin walled air sacs for gas exchange.

Enveloped by capillaries with lots of surface area.

Since circulatory system is closed, gas diffusion across two very thin membranes (blood vessel and aceoli).

Mucus secretions in lung tissue

Prevents water loss

Traps pathogens

Remove particulate matter.

Cilia movement, beat in unison to expel mucus + particles.

Amphibian Lungs

Precursors to terrestrial reptiles/mammals.

Have outcroppings to increase surface area.

Folding/branching increases as evolution develops.

Surfactants

Lungs have lipids and proteins to reduce surface tension and adhesion, avoids sticking and collapse.

Tidal Ventilation

Airflow not unidirectional, not continuous.

Same path for inhaling as for exhaling.

Not countercurrent.

Study Guide

• What is Brownian motion?
  • Random movement of particles in a fluid.
• How does diffusion work regarding concentrations of molecules?
  • Molecules diffuse from a high concentration gradient to a low concentration gradient.
  • Is diffusion faster in liquid or air?
    • Diffusion is faster when molecules move faster, so in air.
• Where is gas diffusion occurring in animals - is that in liquid or in air?
  • It occurs in skin, lungs, gills, or trachea. May diffuse to/from either liquids or air.
• What gases are diffusing in animals, and in which direction is each diffusing?
  • Oxygen, carbon dioxide, and nitrogen. Oxygen diffuses in, carbon dioxide diffuses out.
• What are three main ways to maximize gas exchange in animals?
  • Countercurrent flow, thin tissues, more surface area, more airflow, more blood flow.
• Why do animals perform gas exchange?
• How is animal ventilation linked to cellular respiration?
  • Oxygen is needed as a terminal electron receptor and carbon dioxide must be removed.
• What is cellular respiration, and why is oxygen needed, what happens to oxygen?
  • Oxygen is needed as a terminal electron receptor.
  • What does it create?
    • It creates water.
• Is oxygen turned into carbon dioxide?
  • No, glucose metabolism creates carbon dioxide. Oxygen accepts a free electron from the ETC and turns into water.
• Where is carbon dioxide made in animal cells?
  • In the mitochondria.
  • In heterotrophs, where did those carbons in CO₂ originally come from?
• What cells and what protein carries both oxygen and carbon dioxide through vertebrate bodies?
  • In 4 heme molecules of a hemoglobin inside a red blood cell.
• How do terrestrial insects breath?
  • Through spiracles, hole in their skin. Air diffuses throughout their open circulatory system.
• Why is it important that fish gills have folds called lamellae?
• What is “countercurrent” and how does is help with gas exchange (hint: oxygen concentrations)?
  • Countercurrent flow is an evolutionary mechanism for efficient gas diffusion across membranes.
  • By running two liquids in opposite directions next to each other, 100% of oxygen can diffuse across the gradient.
  • Does countercurrent happen in liquid (water) or gas (air) interfaces?
    • Countercurrent occurs in liquid (blood).
• What two motions pushes water through a fish, to get fresh gas exchange?
• Why is countercurrent flow of blood important - does this apply to all animals?
  • All that exist today, it evolved fairly quickly in the phylogenetic timeline due to its high efficiency.
• Why are amphibians a snapshot in evolution regarding gas exchange?
  • Because they take absorb oxygen through gills when young, lungs and skin after metamorphosis.
• How do lungs maintain elasticity and structure – not collapse, what substance helps?
• What is ‘tidal’ respiration? How is that different than unidirectional airflow?
  • Tidal respiration uses the same entrance and exit for gasses entering and leaving.
  • Unidirectional airflow uses different entrances and exits for gasses for near-continuous exchange.
• What are alveoli?
• How do cilia function in the lung – what is critical for cilia to do their job?
  • Cilia help expel foreign substances from your lungs. They require mucus to do their job.
• Why is mucus important in vertebrate lungs?
  • It provides a sticky trap for foreign substances and acts like a lava flow to expel the substances.
• How are bird lungs different than human lungs? What 'special' structure?
• What is ‘unidirectional’ breathing? How is that different than 'tidal' airflow? Why is this difference essential for birds?
• We did not cover the breathing of other reptiles, but their respiration is similar to birds ... makes sense, they are evolutionarily related!National Geographic Article on Reptile Breathing.