### exchange:

Gas exchange
* All gas exchange occurs through the integument.
* Most gas exchanges occur in regions.
* Some gas exchanges occur across body surfaces.
* Some gas exchanges occur across entire body surfaces
* Some gas exchanges occur across external body surfaces
* Some gas exchanges occur at capillaries
  - cellular levels
  - during respiration
* Some gas exchanges occur in alveoluses
  - gills
  - lungs
* can only take place if the skin is moist.
* happens in the alveoli.
* is accomplished by stomata, which have a pore that opens and closes
  - by diffusion
* is carried on through stomata, small pores in the plant's surface
  - out by simple diffusion
  - completed by small pores in the leaf surface called stomata
  - extremely important in maintaining homeostasis
  - facilitated by the presence of stomates
  - from tracheal tubes that go down into body through exoskeleton, book lungs, both
  - inside the animal with sinuses
  - part of breathing
  - performed via gills located under the carapace
* is the movement of oxygen into the blood and carbon dioxide out of the blood
  - way the body gets oxygen in, and carbon dioxide out
  - through paired gills
* is via evaginations of the posterior gut
  - gills, lungs, or the body surface
  - the gills of the fetus being pressed up to the uterine wall
* occurs across the body wall
  - surface of the tracheoles to the tissues immediately next to it
  - at body surface
* occurs at the level of the air capillaries
  - tiny ends of the tracheae
* occurs by diffusion through moist surfaces
* occurs by diffusion, aided by the movement of water through the sponge cavity
  - thus the rate of gas exchange is dependent on surface area
  - directly through their cell wall
  - in lung through diffusion mechanism
* occurs in the air capillaries of the lung
  - sacs where oxygen is exchanged with carbon dioxide
  - alveoli deep in the lungs
* occurs in the alveoli of the lungs that provide a large surface area
* occurs in the alveoli, air sacs clustered at the tips of the tiniest bronchioles
  - which are surrounded by a capillary network
  - alveolus, where venous blood exchanges carbon dioxide for oxygen
  - through the gills or the lining of the mantle cavity
* occurs via book lungs or tracheal tubes or both
  - diffusion through the body surface
  - within the gill tubes and on the outer tissue surface
* refers to the physical method that org.
* takes place across moist membranes
  - by dififusion from sea water to the coelomic fluid inside
  - in internal gills
+ Respiratory system, Ventilation: Physiology
  * To inhale, the lungs expand, decreasing the air pressure in the lungs. As the air pressure inside the lungs are lower when it has expanded, air from outside at higher pressure comes rushing in to the area of low pressure in the lungs. Biology Made Simple'. The lungs are made up of many tubes or branches. As air enters the lungs, it first travels through branches called the bronchus, then through smaller branches called bronchioles, and finally into the air sacs. Gas exchange occurs in the air sacs where oxygen is exchanged with carbon dioxide. The carbon dioxide in the air sacs now need to be exhaled, or breathed out. In the reverse process to inhaling, the diaphragm and the rib muscles relax, causing the lungs to be smaller. As the air pressure in the lungs is greater when the lungs are smaller, air is forced out. The exhaled air has a high concentration of carbon dioxide and a low concentration of oxygen. The maximum volume of air that can be inhaled and exhaled is called the vital capacity of the lungs and is up to five liters.