Question

Give a brief note of human respiratory system

Answer 1

human respiratory system consists of nostril, nasal passage, pharynx, laropharynx, trachea, bronchi, lungs and diaphragm.
nostril opens into nasal cavity.
the nasal cavity is lined by fine hair and mucus.
the dust particles and microbes in the air get trapped in mucus of nasal cavity.
nasal cavity ends in internal nostril through which air passes to pharynx.
pharynx leads to trachea, through a slit called glottis. Glottis is protected by a cartilaginous flap like epiglottis.
while swallowing food, glottis is covered by epiglottis so food cannot entre trachea.
trachea does not collapse even when there is no air because it is supported by 'C' shape cartilaginous ring.
at upper end of trachea there is voice box called larynx.
trachea runs down the neck and divides into two brochure which lead to lungs.
the smallest bronchioles terminate into alveoli.
the wall of alveoli is thin and covered by blood capillaries.
in alveoli the gaseous exchange take places.

Answer 2

Mammals

Anatomy

Main articles: Lung and Respiratory tract



Fig. 1. Respiratory system



Fig. 2. The lower respiratory tract, or "Respiratory Tree"

Trachea

Mainstem bronchus

Lobar bronchus

Segmental bronchus

Bronchiole

Alveolar duct

Alveolus

In humans and other mammals, the anatomy of a typical respiratory system is the respiratory tract. The tract is divided into an upper and a lower respiratory tract. The upper tract includes the nose, nasal cavities, sinuses, pharynx and the part of the larynx above the vocal folds. The lower tract (Fig. 2.) includes the lower part of the larynx, the trachea, bronchi, bronchioles and the alveoli.

The branching airways of the lower tract are often described as the respiratory tree or tracheobronchial tree (Fig. 2).[4]The intervals between successive branch points along the various branches of "tree" are often referred to as branching "generations", of which there are, in the adult human about 23. The earlier generations (approximately generations 0–16), consisting of the trachea and the bronchi, as well as the larger bronchioles which simply act as air conduits, bringing air to the respiratory bronchioles, alveolar ducts and alveoli (approximately generations 17–23), where gas exchange takes place.[5][6] Bronchioles are defined as the small airways lacking and cartilagenous support.[4]

The first bronchi to branch from the trachea are the right and left main bronchi. Second only in diameter to the trachea (1.8 cm), these bronchi (1 -1.4 cm in diameter)[5] enter the lungs at each hilum, where they branch into narrower secondary bronchi known as lobar bronchi, and these branch into narrower tertiary bronchi known as segmental bronchi. Further divisions of the segmental bronchi (1 to 6 mm in diameter)[7] are known as 4th order, 5th order, and 6th order segmental bronchi, or grouped together as subsegmental bronchi.[8][9]

Compared to the, on average, 23 number of branchings of the respiratory tree in the adult human, the mouse has only about 13 such branchings.

The alveoli are the dead end terminals of the "tree", meaning that any air that enters them has to exit via the same route. A system such as this creates dead space, a volume of air (about 150 ml in the adult human) that fills the airways after exhalation and is breathed back into the alveoli before environmental air reaches them.[10][11] At the end of inhalation the airways are filled with environmental air, which is exhaled without coming in contact with the gas exchanger.[10]