Chapter 10 - Section 10.1 - The Respiratory System - Check Your Progress - Page 196: 1

During (inspiration) air enters the nostrils (external nares). The path the air travels from there includes: Nasal cavity Pharynx Larynx Trachea Bronchi Bronchioles Alveolar ducts Alveolar ducts Alveoli Note: The right lung has three lobes but the left lung has only two (regular) lobes. Therefore, the right primary bronchus has three branches and the left has two. Secondary bronchi are at the level of lung tissue

In (inspiration) air enters the nostrils (external nares) and passes on through the upper respiratory tract, thence through the lower respiratory tract, eventually reaching the alveoli of the lungs where gaseous exchange takes place. Path of inspired air A. Through upper respiratory tract a. Through nostrils to nasal cavities Into nasal cavity; here the air passes over and between the nasal conchae, and also enters the nasal sinuses. The air is filtered by the vibrissae, and nasal mucosa ; it is also warmed and moistened. b. Through pharynx Distal/inferior to the nasal cavity in the respiratory tract is the pharynx --the upper nasopharynx, the oropharynx in the middle, and the laryngo-pharynx that connects the pharynx with the larynx. The larynx is sometimes included with the lower respiratory tract, but it is more reasonable to consider it part of the upper tract Glottis and epiglottis: The larynx is a cartilaginous voice box that contains the vocal cords. A slitlike opening at the top of the larynx which allows air to pass in and through the voice box. However, in swallowing , food or drink may fall into the larynx and get to the lungs; this could set up an infection. Therefore, a flap of cartilage, the epiglottis, covers the glottis when we swallow. The lower respiratory tract: Trachea. The trachea is a tube that connects the upper respiratory tract with the lungs. The trachea is held open by C-shaped rings of cartilage Bronchi The trachea It gives off two branches-- these are the primary bronchi (left and right) close to the lungs. These primary bronchi branch repeatedly to give off lobar and segmental branches to the divisions of the left and right lungs. Bronchioles Conducting brochioles branch off from tertiary bronchi and give rise to terminal and respiratory bronchioles Alveolar ducts derive from respiratory bronchioles. From alveolar ducts the air travels to alveolar sacs and thence to alveoli, where the major fraction of gaseous exchange takes place.