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A bronchus (/ ˈ b r ɒ ŋ k ə s / BRONG-kəs; pl.: bronchi, / ˈ b r ɒ ŋ k aɪ / BRONG-ky) is a passage or airway in the lower respiratory tract that conducts air into the lungs.The first or primary bronchi to branch from the trachea at the carina are the right main bronchus and the left main bronchus.
Three sectors according to Fourastié Clark's sector model This figure illustrates the percentages of a country's economy made up by different sector. The figure illustrates that countries with higher levels of socio-economic development tend to have less of their economy made up of primary and secondary sectors and more emphasis in tertiary sectors.
The main or primary bronchi enter the lungs at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of the lung. The lobar bronchi branch into tertiary bronchi also known as segmental bronchi and these supply air to the further divisions of the lobes known as bronchopulmonary segments.
The lower respiratory tract or lower airway is derived from the developing foregut and consists of the trachea, bronchi (primary, secondary and tertiary), bronchioles (including terminal and respiratory), and lungs (including alveoli). [7] It also sometimes includes the larynx.
Lungs showing bronchi and bronchioles. The trachea divides into the left main bronchus which supplies the left lung, and the right main bronchus which supplies the right lung. As they enter the lungs these primary bronchi branch into secondary bronchi known as lobar bronchi which supply each lobe of the lung.
The primary bronchi enter the lungs to become the intrapulmonary bronchi, which give off a set of parallel branches called ventrobronchi and, a little further on, an equivalent set of dorsobronchi (Fig. 16). [46] The ends of the intrapulmonary bronchi discharge air into the posterior air sacs at the caudal end of the bird.
Percentages of a country's economy made up by different sectors. Countries with higher levels of socio-economic development tend to have proportionally less of their economies operating in the primary and secondary sectors and more emphasis on the tertiary sector. The less developed countries exhibit the inverse pattern.
The primary sector tends to make up a larger portion of the economy in developing countries than it does in developed countries. For example, in 2018, agriculture, forestry, and fishing comprised more than 15% of GDP in sub-Saharan Africa [4] but less than 1% of GDP in North America. [5]