CHAPTER TWENTY-TWO The Respiratory System
Introduction to the Respiratory System A. What is Respiration? Respiration is defined as the exchange of gases (most notably oxygen and carbon dioxide) between the atmosphere, lungs, blood, and tissues. B. What are the functions of the Respiratory System? 1. Provide an extensive surface area for gas exchange between air and the circulating blood. 2. Moving air to and from the exchange surfaces of the lungs along the respiratory passageways. 3. Protecting respiratory surfaces from dehydration, temperature changes, or other environmental variations, and defending the respiratory system and other tissues from invasion by pathogens. 4. Producing sounds involved in speaking, singing, and other forms of communication. 5. Facilitating the detection of olfactory stimuli by olfactory receptors in the superior portions of the nasal cavity.
22.1 Organs and Structures of the Respiratory System A. The two anatomical divisions of the respiratory system are: 1. Upper Respiratory Tract -- (URT) filters, warms, and humidifies incoming air which protects the more delicate surfaces of the lower respiratory system and reabsorbs heat and water from the outgoing air. Includes the following: nose, nasal cavity, paranasal sinuses, and pharynx. 2. Lower Respiratory Tract -- (LRT) conducts air to and from the gas exchange surfaces and includes: larynx, trachea, bronchi, bronchioles and alveoli. 3. All of the upper and most of the lower respiratory tract make up the conducting zone. That is, they are for the purposes of transporting the air only. The last part of the lower respiratory tract, however, is designed for gas exchange and is therefore called the respiratory zone. The respiratory zone includes the smallest, most delicate branches of the respiratory tree called the respiratory bronchioles and their associated air-filled pockets called the alveoli. B. Upper Respiratory Tract 1. NosE -- the primary passageway for air entering the respiratory when you are resting and breathing quietly. a. Bridge of the nose is formed from the nasal bones (2) and is supported by the anterior portions of the nasal septum and nasal cartilages. b. Nasal septum - composed of the vomer and perpendicular plate of the ethmoid bone and divides the nasal cavity into a right and left portion. C. Nasal cartilages - small, hyaline cartilages that extend laterally from the bridge of the
collapse during a strong inhalation.
d. External nares - or nostrils, open into the nasal cavity.
2. NASAL CAVITY -- space between the external nares and the internal nares at the back of the nasal cavitv. Lined with pseudostratified columnar epithelium. a. Nasal vestibule -- the space contained within the flexible tissues of the nose. Filled with coarse hairs called vibrissae that trap large airborne particles preventing them from entering the nasal cavity. b. Cribriform plate of the ethmoid bone -- forms the roof of the nasal cavity. The tiny holes in the cribriform plate allow the olfactory bulbs to extend their neural fibers down into the nasal cavity for sensation of smell. Hard palate -- forms the anterior portion of the flo