HUMAN RESPIRATORY SYSTEM
Following are the main structures in the human respiratory system:
Nostrils:
- There two nostrils which converge to form a nasal passage.
- The inner line of the nostrils is lined by hairs and remains wet due to mucus secretion.
- The mucus and the hairs help in filtering the dust particles out from inhaled air.
- Further, air is warmed up when it enters the nasal passage.
Pharynx:
- It is a tube-like structure which continues after the nasal passage.
Larynx:
- This part comes after the pharynx. This is also called the voice box.
Trachea:
- This is composed of rings of cartilage.
- Cartilaginous rings prevent the collapse of trachea in the absence of air.
Bronchi:
- A pair of bronchi comes out from the trachea; with one bronchus going to each lung.
Bronchioles: A bronchus divides into branches and sub-branches; inside the lung.
Alveoli: These are air-sacs at the end of bronchioles
Alveolus
- It is composed of a very thin membrane and is the place where blood capillaries open.
- This is alveolus; where oxygen mixes with the blood and carbon dioxide exits from the blood.
MECHANISM OF BREATHING
- The cycle of breathing consists of two phases, i.e. inspiration and expiration.
- Both these processes, i.e. inspiration and expiration are together referred to as respiratory movements
- Inhalation – involves contraction of diaphragm and external intercostal muscles resulting in relaxation of rectus abdomen
- Expiration involves contraction of abdomen and inner intercostal muscles resulting in relaxation of external intercostal muscles and diaphragm (become dome-shaped).
