HUMAN RESPIRATORY SYSTEM
It is formed of two parts :
I. Respiratory tract
II. Respiratory organs
I. Respiratory tract
(1) Nostrils
(2) Nasal chambers
(3) Nasal choanae
(4) Laryngopharynx
(5) Larynx
(6) Trachea (wind pipe)
(1) Nostrils - Nostrils are 1 pair, small, oval apertures present at the lower end of nose and just above the mouth.
(2) Nasal chambers - These are a pair of large chambers enclosed in the natural capsule and present above the palate. These are separated by nasal septum. Each nasal chamber is divided into three parts :
(a) Vestibular part - The broad portion which carries hair. It helps in trapping the dust particles.
(b) Respiratory part -
• Mucus cells secret mucus in this zone.
• Cilia and mucus help in trapping dust particles and pathogens.
• Mucus also adds moisture to air and make it humid.
(c) Olfactory part - Lined by olfactory epithelium. Olfactory epithelium has receptor cell,bowmans cell and supporting cell.
(3) Nasal choanae -
• There are three nasal turbinels upon dorsal side of nasal cavity.
• They help in turbining the air and raise its temperature equal to body temperature.
(4) Laryngopharynx - It is lower part of pharynx and has a slit like aperture called glottis which can be closed by a leaf like bilobed cartilage,epiglottis, during the swallowing of food.
(5) Larynx (voice box) -
• It is also called Adam's Apple.
• Larynx(voice box) is small thin walled tubular part present in the neck.
• To prevent its collapsing, it is supported by four cartilages.
VOCAL CORD :
• There are two pairs of vocal cord which form lateral wall of larynx.
• Males vocal cord = Low pitch voice and thick and long.
• Female vocal cord = High pitch voice thin and short.
(6) Trachea (windpipe) -
• Length = 10-12 cm
• Diameter = 2.5 cm
• Anterior opening into pharynx = glottis
• Supported by C-shaped hyaline cartilage ring(prevent collapsing of trachea) complete ventrally and incomplete dorsally.
• The tall cells where cilia and short cell secrete mucus(trap dust particles).
• Dysplasia / Smokers cough :-
Less movement of cilia due to smoking.
• Aplasia :-
No movement of cilia due to excessive smoking results in suffocation.
• Trachea divides at level of fifth thoracic vertebra to form primary bronchi.
• Bronchial tree :
Trachea divides to form 1° bronchi 2° bronchi 3° bronchi initial bronchioles terminal bronchioles Alveolar duct Alveolar sac
• Alveolar duct + Alveolar sac = Alveoli
• Alveolar sac is the main site of exchange of respiratory gases.
II. Respiratory organ
Lungs :
• Lungs are present in the thoracic cavity which is enclosed by sternum upon ventral side, vertebral column upon dorsal side.
• Ribs forming lateral wall and diaphragm posterior covering.
• Lungs are externally covered by two plural membrane - (1) Outer parietal pleura (2) Inner visceral pleura
• Space between pleural membrane is called plural cavity filled with pleural fluid.
• Pleural fluid prevent friction between pleura during expansion of lung.
Right lung :-
• Broad, short and heavy lung.
• Divided into three lobes - superior, middle and inferior by 2 fissure (transverse and oblique).
Left lung :-
• Long and narrow, lighter lung.
• Divided into two lobes - superior and inferior by 1 oblique fissure.
• It has cardiac notch towards inner side into which heart apex is fitted.