what are the main parts in respiratory system | human respiratory system notes with explanation

HUMAN RESPIRATORY SYSTEM

what are the main parts in respiratory system

The major respiratory organ in human are LUNGS. It is not applied to all the organisms, other animals have different organs for respiration.

Some major types of respiratory organs of some animals:-

• Earth worm - Moist cuticle
• Most aquatic Arthropods like prawn - Gills
• Limulus - Book gills
• Scorpion - Book lungs
• Insects - Trachea
• Aquatic molluscs -Ctenidia (gills)
• Terrestrial moluscs - Pulmonary sacs (gills)
• Echinoderms - Dermal branchiae,  Tube feet, Respiratory trees etc;
• Hemichordates - Gills
• Fishes - Gills
• Amphibian larvae - Skin, Bucco-pharyngeal lining, Lungs
• Adult frogs - Lungs

Now lets talk about human respiratory system;

what are the main parts in respiratory system

Human respiratory system consists of major respiratory organ as lungs, but it has a pathway. Our pathway starts from nostrils. Human respiratory system includes 2 tracts.

• UPPER RESPIRATORY TRACT- Nose, Pharynx, Larynx.
• LOWER RESPIRATORY TRACT- Trachea, Bronchi, Lungs.

The parts which are involved in respiration are;

• EXTERNAL NOSTRILS (NOSE)
• NASAL CHAMBER
• PHARYNX
• TRACHEA
• BRONCHI AND BRONCHIOLES
• LUNGS

1.EXTERNAL NOSTRILS:- A pair of external nostrils opens out above upper lip. This leads into nasal chambers through the nasal passage. External nostrils are nothing but nose.

2.NASAL CHAMBERS:- They lie above the palate and they are separated from each other by a nasal septum. Each nasal chamber can be differentiated into 3 parts.

i. VESTIBULAR PART:- Which has hair and sebaceous glands to prevent entry of dust particles.

ii. RESPIRATORY PART:- Which is involved in the conditions of temperature of inhaled air, it has three, thin , conchae/turbinals.

iii. OLFACTORY PART:- Which is lined by olfactory epithelium.

3.PHARYNX:- There are 3 regions of pharynx. They are; 

• NASOPHARYNX
• OROPHARYNX
• LARYNGOPHARYNX

* Among these, only nasopharynx is involved in the respiration.

NASOPHARYNX:- Nasal chambers lead into nasopharynx through a pair of internal nostrils, located above the soft palate. The nasopharynx is portion of pharynx, which is common chamber for passage of both food and air. Nasopharynx leads into oropharynx and opens through glottis of larynx into trachea.

4. LARYNX:- Larynx is a cartilagenous box which helps in the sound production called as voice box. The wall of larynx is supported by 9 cartilages.

• UNPAIRED CARTILAGE:- Thyroid, cricoid, and epiglottis.
• PAIRED CARTILAGE:- Corniculate cartilages (cartilage of santorini), arytenoids and cuneiform cartilages.

The epiglottis is a thin leaf like structure of elastic cartilagenous flap attached to thyroid cartilage to prevent entry of food into larynx through glottis. The yellow elastic fibers which connect the thyroid and arytenoid cartilages are called vocal cords. The space between true vocal cords and arytenoid cartilages is called "nima-glottidis". The mid-ventral part of thyroid cartilage forms the laryngeal prominence called as the "Adams-Apple".

5. TRACHEA:- Trachea is the wind pipe and it is the straight tube extending up to mid-thoracic cavity. The wall of trachea is supported by "C" shaped rings of hyalin cartilage. These rings are incomplete dorsally and keep the trachea always open, preventing collapse. Internally the trachea is lined by pseudo-stratified liliated epithelium.

6. BRONCHI AND BRONCHIOLES:- On entering mid thoracic cavity, trachea divides at level of the 5th thoracic vertebrate into right and left primary bronchi. Each primary bronchus enters the corresponding lung and divides into secondary bronchi that further divides into tertiary bronchi. Each tertiary bronchus divides and re-divides to form primary, secondary, tertiary, terminal and respiratory bronchioles terminates in a cluster of alveoli ducts which ends in alveolar sacs. Bronchi and initial bronchioles are supported by incomplete cartilageneous pings. The branching network of trachea, bronchi and bronchioles constitute the "pulmonary tree". (pulmonary tree- an upside down tree.)

7. LUNGS:- Lungs occupy the greater part of the thoracic cavity. Lungs are covered by the double layered pleura, with pleural fluid betwen them. It reduces friction on lung surfaces. Outer pleural membrane is close contact with thoracic lining where as inner pleural membrane is in contact with lung's surface. The part starting with external nostrils up to terminal bronchioles constitute the conducting part, where as the alveoli and their ducts form the respiratory or exchange part of the respiratory system. The conducting part transports the atmospheric air to alveoli, clears it from foreign particles, humidifies, and also brings the inhaled air to the body temperature. Exchange part is the site of actual diffusion of O₂ and CO₂ between blood and atmospheric air. The lungs are situated in thoracic chamber, which is anatomically an air-tight chamber. It is formed dorsally by vertebral column, ventrally by sternum, laterally by ribs and on the lower side by dome shaped diaphragm. The anatomical setup of lungs in thorax is such that any change in volume of thoracic cavity will be reflected in lung cavity. Such an arrangement is essential for breathing, as the pulmonary volume cannot be directly altered.