The mammalian gaseous exchange system (basics)

The mammalian gaseous exchange system

Gaseous exchange: is the transfer of oxygen from the air into the blood and carbon dioxide in the blood to the air.

The gaseous exchange system has to keep a balance in providing gaseous exchange and making sure not too much water is lost from the body.

This is what the main gaseous exchange system looks like:

                       

Nasal  Cavity: warms air that enters the body and can trap dust and bacteria which protects the body from diseases, hairy nose hairs warm air breathed in to body temperature (37◦) this also reduced evaporation from the lungs by limiting the concentration gradient for diffusion to occur.

The main features of the nasal cavity is that it has good blood supply and lined with hairs and mucus secreting hairs called epithelial and goblet cells respectively).

Trachea: Prevents the collapse of the respiratory system and traps dust and bacteria and has cilia which sweeps mucus and dust away from the lungs.

-It is supported by flexible rings of incomplete rings of cartilage and lined with goblet cells and ciliated epithelium cells.

Bronchus: very similar to the trachea made from incomplete rings of cartilage and helps prevent collapse of the system.

Bronchioles:  Are able to constrict  and dilate (become smaller and wider) so to control the amount of the air reaching the lungs.

-Capable of doing some gaseous exchange and contains smooth muscles  with no cartilage and flattened epithelium cells.

Alveoli: A very important part of the system where most of the gaseous exchange happens, it is a small sac very much like a balloon.

provides a short diffusion pathway which increases the diffusion rate due to the single layer of flattened epithelium cells.

contains elastic fibers and collagen which enables the stretching and elastic recoil during ventilation this can help increase the amount of air that can breathed in and stops it from bursting.

Alveoli have large surface areas which can increase the rate of diffusion and has a good blood supply as many capillaries are very close by which provide a steep concentration of very high deoxygenated blood and very rich oxygenated blood coming together so the exchange can happen very quickly.

alveoli is  covered with a layer of surfactant which stop the alveoli from collapsing and keeps it remained open.

Here is what a Alveoli looks like:  note that there are many thousands of alveoli in the lungs possibly millions!

Ventilation: Air that moves in and out of the lungs.

Ventilation happens because of changes in pressure ventilation helps us have a steep concentration gradient in the lungs of low and high oxygen concentration which allows for very fast gaseous exchange.

There are two types of ventilation called inhalation and expiration more commonly known as breathing in and out.

the steps of how each process occurs is written below:

Inspiration (Inhalation- breathing in)

1-External intercostal muscles contract

2-Ribs move up and out

3-Diaphragm contracts and flattens

4-Throax volume increases

5-Air pressure in the lungs lower

6-Air moves into the lungs

Expiration (Exhalation-breathing out)

1-External intercostal muscles relax

2-Ribs move down and in

3-Diaphragm relaxes and goes to being domed shaped

4-Throax volume decreases

5-Air pressure rise

6-Air moves out of lungs

TIP: As you may have noticed that Inspiration is the opposite of Expiration so it may be easier to just learn one and just write the opposite if needed when it comes to the exams.

Inspiration is a active process which means it needs energy but Expiration at rest is passive and does not require energy. However forceful expiration does require energy such as when you are coughing.

**REMEMBER TO STAY POSITIVE LIKE A PROTON!**