Biology Question. Please help!!!?

Question

I have a project and one of the question sounds like this

Air sacs or alveoli are adapted for efficient gas exchange. Explain!

Please help to answer this question! Its urgent and I need it very much!

Rewarded 10 points for best answer! Please help!

Answer 1

The alveoli have a very thin pavement or squamous epithelial lining and are surrounded by many blood capillaries carrying deoxygenated blood. The short distance between air and blood allows oxygen and carbon dioxide to be exchanged efficiently by diffusion. Alveolar walls contain elastic fibres, which stretch during inspiration and recoil during expiration to help force out air. The elasticity allows alveoli to expand accordingly to the volume of air breathed in.

In the lungs, the alveoli are covered by a thin layer of moisture. Surface tension tends to pull water molecules together. This could cause the alveoli to stick together, so reducing the surface area for gas exchange. To prevent this, the alveolar cells secrete Surfactant(A surfactant is a chemical which is like detergent). The surfactant (1) reduces the surface tension of the moisture so that the alveoli do not stick together and breathing in is easy, (2) speeds up the transport of oxygen and carbon dioxide between the air and the liquid lining the alveoli, (3) helps to kill any bacteria which reach the alveoli.

The membrane around each alveolus is composed of a one cell thick, thin, flat cells called squamous or pavement epithelium (0.1 micrometer thick)

Capillaries closely surround each alveolus and the capillary wall is also one-celled thick. Thus, gases only have to diffuse across 2 thin cells between the alveolus and the blood. The short distance speeds up the rate of diffusion.

The diameter of the capillary is smaller than the diameter of the red blood cell. So red blood cell is forced through the capillary by blood pressure. The red blood cell bends into an umbrella shape so that a greater surface area is exposed for diffusion of oxygen.

The red blood cell moves relatively slowly around the alveolus to increase the time available for gaseous exchange to take place.

Answer 2

The epithelium of the lungs is extremely thin for easier diffusion of gases; the exchange surfaces are also kept moist to allow the passage of oxygen and carbon dioxide.

Also, the structure of the lungs provides an extremely high surface/volume ratio (the greater the surface area, the more the gaseous exchange). The most efficient lungs are those of birds, whose structure allows for continuous one-directional flow of air (as opposed to the sac-like lungs of other tetrapods, including us mammals). Our lungs contain very small bubble-like sacs called alveoli where gas exchange occurs, and these sacs are able to keep their structure and not collapse thanks to a special substance that coats them and reduces surface tension.

Answer 3

here are some ways in which alveoli are adapted fore fficient gas exchange

- sac/lobular structure increases surface area for gas exchange

- surfactant excreted by alveolar cells (can't remember cell type, google it) because gas exchange is more effective in liquid medium

- ultra thin layer of alveolar epithelium allows for rapid movement of gases across alveolar membranes into circulation

- countercurrent exchange allows for optimal release of CO2 and uptake of O2

Answer 4

when you breath the air, containing oxygen, etc. passes over the air sacs and oxygen is absorbed which is then transported to the brain...

Edit:

Yoni had a better answer!