Human respiratory system #17 | Human physiology

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.

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