The Respiratory System Chapter 15

Function Brings oxygen into the body so it can be transported to body cells by the blood stream Also removes carbon dioxide from blood The term respiration encompasses all activities that transport oxygen from the environment to the body’s cells and carbon dioxide from the body’s cells to the environment

Forms of Respiration The first is referred to as pulmonary ventilation; accomplished by breathing in and out—moves air between external environment and air sacs of lungs External respiration — gas molecules diffuse between air sacs and blood in capillaries that surround them Internal respiration — exchange of gases between blood and body cells

Organs of the Respiratory System: Structural Divisions Structurally divided into upper and lower respiratory system The upper portion includes those parts found in the head and neck: the nose, the pharynx, and the larynx The lower portion includes those parts found mainly in the thoracic cavity: the trachea, the bronchi, bronchioles, and the alveoli (air sacs)

Functional Divisions These organs can also be divided into the conduction zone, which conduct air toward and away from the alveoli, and the respiratory zone, which includes only the alveoli and capillaries associated with them

The Nose Provides an initial receiving chamber for outside air; formed by the two nasal bones and numerous cartilages Includes the external nares (nostrils) which are separated by the nasal septum The small chamber that the external nares open into is referred to as the vestibule The vestibules’ walls contain coarse hairs to help remove particles from the air

Nose cont’d The vestibule opens into the nasal cavity which contains nasal conchae, scroll-like bony shelves which divide the nasal cavity into narrow passageways called meati Nasal conchae maximize contact between air and nasal cavity walls, where it can be warmed by the nearby bloodstream The entire cavity is lined with mucous, which filters and adds moisture to air entering body

Sinuses Sinuses are hollow cavities that are lined with mucous and connected to the nose for drainage during infection (sinusitis) Play the role of reducing weight of the skull and resonate sound from the voice

Pharynx The pharynx is also known as the throat It connects the nasal cavity to the larynx Its walls are formed of skeletal muscle and lined with mucous membranes Receives air from nasal cavity by way of two small openings called the internal nares Can be divided into three regions: nasopharynx, oropharynx, and laryngopharynx

Nasopharynx receives the internal nares and two auditory tubes which extend to the middle ear Oropharynx is the region that you can see if you look in the mirror with your mouth wide open Laryngopharynx begins at base of tongue and extends to the larynx, or voice box The oro- and laryngopharynx provide a common passageway for both food and air

Larynx Connects the pharynx to the trachea Prevents solid materials from passing into the trachea; also contains the vocal cords for the production of sound Made from 9 pieces of hyaline cartilage that form a box-like structure, including the thyroid cartilage (enlarged in males to form “Adam’s apple”) and epiglottic cartilage which forms the epiglottis that channels food and drink into the esophagus, away from the glottis, or opening to the trachea

Vocal Cords The vocal cords are contained within the larynx and are made of in-foldings of the mucous membrane that are rich in elastic fibers These flaps vibrate when air is passed between them causing sound waves These sound waves are converted into speech by movement of muscles of the pharynx, jaws, lips, and tongue which change the shape of the openings of exhaled air, altering its sound