Respiratory system :
This broad process can be divided into 2 processes:
External respiration : It is the process of absorption of oxygen and removal of carbon dioxide. Here , no chemical changes occur.
Internal respiration : It is the process where oxygen is used to oxidise food to produce energy in the form of ATP and carbon dioxide. Here , chemical changes occur.
They moreover, can be direct ; no involvement of special organs just cells involved or indirect ; involvement of special organs like : skin, buccal cavity and lungs .
According to need of oxygen there are 2 types of respiration :
Aerobic respiration : oxygen is must.
Anaerobic respiration : oxygen is absent or very limited.
Respiratory tract :
Nostril →nasal chamber → internal nares → pharynx →larynx→ trachea → bronchi
Nasal cavity :
Vestibule: opening of two nostrils which possess or are lined with skin from which vibrissae grow .
This protects entry of large dust particles, so they act as a filtering chamber .
Respiratory part :
Here , there are 3 conchas richly supplied by blood vessels. They keep the air entering the chamber in equilibrium with the body's temperature. This is lined by ciliated columnar epithelium
Olfactory part :
This possesses olfactory epithelium for sense of smell.
3 sections :
Nasopharynx : lined by pseudo stratified epithelium which possess pharyngeal tonsils.
Oropharynx : back portion of the mouth that contains palatine tonsils for immune defense.
Laryngopharynx : bottom section of pharynx where the respiratory tract divides into the esophagus and larynx .
Both oro and laryngo pharynx are lined by stratified squamous epithelium.
Commonly called voice box . The voice box in birds lie below the larynx called syrinx.
Cartilage that makes up larynx :
Arytenoid : hyaline as well as elastic; a pair
Cricoid : hyaline; unpaired
Thyroid : hyaline ; unpaired ; largest
Corniculate : elastic ; paired
Cuneiform : elastic ; paired
Epiglottis : elastic ; unpaired
A pair of Vocal cords here, are made up of yellow dense connective tissue and in between these two there is a gap called rima -glottis.
This lies in the media sterna , inferior to the larynx in front of the oesophagus.
It is supported by twenty C shaped hyaline cartilage which prevents the collapse of the lumen.
It is internally lined by ciliated pseudo stratified epithelium.
Trachea bifurcates at the level of T4 cartilage .
After bifurcation this intercom begins . It starts with primary bronchus then divides to form secondary bronchus which again divides to form tertiary bronchioles. This further divides to form bronchioles, then to terminal bronchioles . Later it divides to respiratory bronchioles and lastly to alveolar duct and ends to pouch like alveoli.
Cells of alveoli :
There are 3 type of cells called pneumocyte here :
Type 1 pneumocyte : more in number , this helps in gaseous epithelium and are of simple squamous epithelial cells.
Type 2 pneumocyte : less in number , helps in secreting respiratory surfactant which is chemically phospholipid to prevent collapse of alveoli sac. COVID 19 virus affects this cell to cause asphyxia (oxygen starvation) as surfactants are deficient causing collapse of alveoli and filling with mucous . They can supplement type 1 cells on it’s deficiency.
Dust cells : they are phagocytic cells in lungs .
Respiratory organ :
The main respiratory organ in humans is LUNG.
This is triangular, pink colored inside a pleural cavity .
It is divided into right and left portions .
They can be studied under following difference table :
|Right lung||Left lung|
|1. It is 3 lobed with 2 fissures ; oblique and horizontal||1. It is 2 lobed and 1 fissure.|
|2. Wider and shorter .||2. Narrower and longer|
|3. Three secondary bronchi||3. Two secondary bronchi|
|4. More vertically placed bronchi so, more chance to infection||4. Less vertically placed bronchi so, less chance of protozoan infection.|
|5. No cardiac notch||5. Cardiac notch is present.|
Pleural cavity possess pleural fluid which is for ;
Reduce friction while breathing.
Acts as shock absorbers.
Functions of lungs :
It throws out harmful carbon dioxide out of the body.
It also supplies oxygen to the body .
This also maintains homeostasis by releasing water vapours and cools the body.
YOU CAN EVEN SEE THIS VIDEO :