Our Lungs Anatomy and Physiology

Assalamualaikum wbt,

Hope that we’re all in His protection and may Allah favor everything that we do. It’s been a while since we posted an article in our blog. Alhamdulillah this semester, we decided to come out with some medical articles  and inshaAllah our main point is not to replace your  lecturer, but instead  we  would like to  try our very best to encourage  the  medical students  to be  more interested in what  they all are doing now and hopefully they will become a good doctor one day.

Topics: What you might not know about lungs? (Anatomy and Physiology)

#Facts1 :

Before you read this article, you should open one of the organ which is able detect light and convert it into electro-chemical impulses in neurons.That’s your eyes! :)

#Facts2 :

The word ‘lung’ probably comes from ‘lunge’, the Old English word for ‘light.’

#Facts3 :

There are about 600 million alveoli in your lungs. If you stretched all of them out, they would be about the size of a volleyball court in the Burevestnik hall!Subhanallah.

ANATOMY OF THE LUNGS

The anatomy of the respiratory system can be divided into 2 major parts, airway anatomy and lung anatomy.

Airway anatomy can be further subdivided into the following 2 segments:

• The extrathoracic (superior) airway, which includes the supraglottic, glottic, and infraglottic regions
• The intrathoracic (inferior) airway, which includes the trachea, the mainstem bronchi, and multiple bronchial generations (which have as their main function the conduction of air to the alveolar surface)

For a better understanding about our lungs and their system, first we need to have a detail information about anatomy and topography of the lungs.

Topography of lungs

This respiratory organs lie on either side of mediastinum normally the right one a little larger than the other one. This related to the fact that at the middle mediastinum containing the heart, bulges more to the left than to the right.

The topography of the lung:

1. The base sits on the diaphragm
2. The apex project above rib 1 and into the root of the neck
3. The 2 surface :

• The costal surface lies immediately adjacent to the ribs and intercostal spaces of the thoracic wall.
• The mediastinal surface lies against the mediastinum anteriorly and the vertebral column posteriorly and contain the comma-shaped hilum of the lung through which structures enter and leave.

4. The 3 border –

•  Inferior border is sharp and separated the base from the costal surface.
• Anterior and posterior borders separate the costal surface and the medial surface.
• The posterior surface is smooth and rough.

Lung anatomy: lobes and segments

#Facts 4 :

There are many tubes that connect your mouth to the insides of your lungs. Your trachea (or wind pipe) is the big tube which you can feel in your throat. This splits into main stem bronchi, which then split many more times into tiny tubes called bronchioles. There are around 30,000 bronchioles in your lungs! At the end of each of these tiny tubes are little sacks called alveoli. These get bigger and smaller with each breath, and contain lots of blood vessels which is where oxygen enters the blood and waste (like carbon dioxide) leaves the blood.

THE PHYSIOLOGY OF LUNGS

Pulmonary ventilation

• The process by which gases are exchanged between atmospheric air and the lungs is called 'pulmonary ventilation' (breathing).
• This process takes place due to alternating pressure differences as a result of  contraction and relaxation of the respiratory muscles.

• Inspiration (inhalation) occurs when the air pressure in the lungs is lower than the air pressure in the atmosphere. In accordance with Boyle's law the air pressure in the lungs is lowered by increasing the volume of the lungs, achieved during inspiration by contraction of muscles of respiration. This contraction causes expansion of the chest; the lungs are pulled outward and the alveolar pressure decreases.
  
  

Body changes in both respiration

• During expiration (exhalation) the respiratory muscles relax, the lungs recoil inward and the alveolar pressure increases, pushing air out of the lungs. Thus the expiration is a passive process because no muscle contraction is involved.

Control of breathing

• Your respiratory rate changes due to certain activities. For instance, when you’re active, your respiratory rate goes up; when less active, or sleeping, the rate goes down.

     Even though the respiratory muscles are voluntary, you can't consciously control them when you're sleeping.

So, how is respiratory rate altered? How is respiration controlled when you're not consciously thinking about respiration?

Our respiratory rate is controlled by respiratory centre (RC) located in medulla oblongata.

Medulla oblongata is the lowermost part of our brainstem.

Respiratory center in the brain

In healthy individuals the presence of elevated carbon dioxide levels in the blood is the stimulant that the RC responds to in order to signal the respiratory muscles to breathe.

•  Three centres in the brainstem which are involved in control breathing have been identified:

1) Medullary centre – This centre is found in the medulla oblongata and controls the basic rhythm of respiration. The medullary centre contains the inspiratory and expiratory neurones. Inspiration lasts about two seconds in the basic rhythm of respiration in resting state, while expiration lasts about three seconds.

2) Pneumotaxic centre – This centre is situated in the upper part of the pons. It coordinates the transition between inspiration and expiration. It inhibits the inspiratory area causing a limitation to the duration of inspiration and thus expiration starts. When this area is more active, respiration is more rapid.

     Still blur? Try to gasp. That’s how pneumotaxic centre works.

3) Apneustic centre – This centre is located in the lower part of the pons. It coordinates the transition between inspiration and expiration. This centre stimulates the inspiratory area and prolongs inspiration and inhibits expiration. Such stimulation takes place when the pneumotaxic area is inactive. Pneumotaxic stimulation overrides the apneustic stimulation.

-So, isn’t it MIRACLE how your lungs work even when you don’t have to control them?

-Aren’t we grateful to have all the complicated systems in our body which allow us to consume the very precious air?

Gaseous exchange

•  External respiration  → the process of exchanging O2 and CO2 between the body

                                and environment. Absorption of O2 and excretion of CO2  .

•  Internal respiration   →  intracellular use of O2  to make ATP and production of CO2.

5 main stages of respiration process :

1)     Gas exchange between atmosphere & alveolar space

2)     Gas exchange through alveolar capillary membrane

3)     Gas transport by blood

4)     Simple diffusion through capillary-tissue membrane

5)     Intracellular use of O2 producing ATP and CO2  .

Gaseous exchange in respiraton

 

#Facts 5 :

                 Let us sit and think for a while. Do we even ask for this blessings? Do we have to pay for every molecule of oxygen that entered our body? And let’s say that we have to pay for it, do we have money?. Indeed most blessings remain unnoticed by us, because they are too familiar to us.We only notices the importance of a blessing that we have taken for granted when it is withdrawn.So, let us be grateful with what Allah has given to us. Let us use the blessings that Allah gave to us to do something good to the ummah and may Allah grants us all Jannah in the ever-lasting hereafter. And as a final reminder,

And if you should count the favors of Allah , you could not enumerate them. Indeed, Allah is Forgiving and Merciful. 16:18