The respiratory system is responsible for obtaining oxygen and getting rid of carbon dioxide, and aiding in speech production and in sensing odors. From a functional perspective, the respiratory system can be divided into two major areas: the conducting zone and the respiratory zone. The conducting zone consists of all of the structures that provide passageways for air to travel into and out of the lungs: the nasal cavity, pharynx, trachea, bronchi, and most bronchioles. The nasal passages contain the conchae and meatuses that expand the surface area of the cavity, which helps to warm and humidify incoming air, while removing debris and pathogens. The pharynx is composed of three major sections: the nasopharynx, which is continuous with the nasal cavity; the oropharynx, which borders the nasopharynx and the oral cavity; and the laryngopharynx, which borders the oropharynx, trachea, and esophagus. The respiratory zone includes the structures of the lung that are directly involved in gas exchange: the terminal bronchioles and alveoli.
The lining of the conducting zone is composed mostly of pseudostratified ciliated columnar epithelium with goblet cells. The mucus traps pathogens and debris, whereas beating cilia move the mucus superiorly toward the throat, where it is swallowed. As the bronchioles become smaller and smaller, and nearer the alveoli, the epithelium thins and is simple squamous epithelium in the alveoli. The endothelium of the surrounding capillaries, together with the alveolar epithelium, forms the respiratory membrane. This is a blood-air barrier through which gas exchange occurs by simple diffusion.
ala
(plural = alae) small, flaring structure of a nostril that forms the lateral side of the nares
alar cartilage
cartilage that supports the apex of the nose and helps shape the nares; it is connected to the septal cartilage and connective tissue of the alae
alveolar duct
small tube that leads from the terminal bronchiole to the respiratory bronchiole and is the point of attachment for alveoli
alveolar macrophage
immune system cell of the alveolus that removes debris and pathogens
alveolar pore
opening that allows airflow between neighboring alveoli
alveolar sac
cluster of alveoli
alveolus
small, grape-like sac that performs gas exchange in the lungs
apex
tip of the external nose
bronchial tree
collective name for the multiple branches of the bronchi and bronchioles of the respiratory system
bridge
portion of the external nose that lies in the area of the nasal bones
bronchiole
branch of bronchi that are 1 mm or less in diameter and terminate at alveolar sacs
bronchus
tube connected to the trachea that branches into many subsidiaries and provides a passageway for air to enter and leave the lungs
conducting zone
region of the respiratory system that includes the organs and structures that provide passageways for air and are not directly involved in gas exchange
cricoid cartilage
portion of the larynx composed of a ring of cartilage with a wide posterior region and a thinner anterior region; attached to the esophagus
dorsum nasi
intermediate portion of the external nose that connects the bridge to the apex and is supported by the nasal bone
epiglottis
leaf-shaped piece of elastic cartilage that is a portion of the larynx that swings to close the trachea during swallowing
external nose
region of the nose that is easily visible to others
fauces
portion of the posterior oral cavity that connects the oral cavity to the oropharynx
fibroelastic membrane
specialized membrane that connects the ends of the C-shape cartilage in the trachea; contains smooth muscle fibers
glottis
opening between the vocal folds through which air passes when producing speech
laryngeal prominence
region where the two lamina of the thyroid cartilage join, forming a protrusion known as “Adam’s apple”
laryngopharynx
portion of the pharynx bordered by the oropharynx superiorly and esophagus and trachea inferiorly; serves as a route for both air and food
larynx
cartilaginous structure that produces the voice, prevents food and beverages from entering the trachea, and regulates the volume of air that enters and leaves the lungs
lingual tonsil
lymphoid tissue located at the base of the tongue
meatus
one of three recesses (superior, middle, and inferior) in the nasal cavity attached to the conchae that increase the surface area of the nasal cavity
naris
(plural = nares) opening of the nostrils
nasal bone
bone of the skull that lies under the root and bridge of the nose and is connected to the frontal and maxillary bones
nasal septum
wall composed of bone and cartilage that separates the left and right nasal cavities
nasopharynx
portion of the pharynx flanked by the conchae and oropharynx that serves as an airway
oropharynx
portion of the pharynx flanked by the nasopharynx, oral cavity, and laryngopharynx that is a passageway for both air and food
palatine tonsil
one of the paired structures composed of lymphoid tissue located anterior to the uvula at the roof of isthmus of the fauces
paranasal sinus
one of the cavities within the skull that is connected to the conchae that serve to warm and humidify incoming air, produce mucus, and lighten the weight of the skull; consists of frontal, maxillary, sphenoidal, and ethmoidal sinuses
pharyngeal tonsil
structure composed of lymphoid tissue located in the nasopharynx
pharynx
region of the conducting zone that forms a tube of skeletal muscle lined with respiratory epithelium; located between the nasal conchae and the esophagus and trachea
philtrum
concave surface of the face that connects the apex of the nose to the top lip
pulmonary surfactant
substance composed of phospholipids and proteins that reduces the surface tension of the alveoli; made by type II alveolar cells
respiratory bronchiole
specific type of bronchiole that leads to alveolar sacs
respiratory epithelium
ciliated lining of much of the conducting zone that is specialized to remove debris and pathogens, and produce mucus
respiratory membrane
alveolar and capillary wall together, which form an air-blood barrier that facilitates the simple diffusion of gases
respiratory zone
includes structures of the respiratory system that are directly involved in gas exchange
root
region of the external nose between the eyebrows
thyroid cartilage
largest piece of cartilage that makes up the larynx and consists of two lamina
trachea
tube composed of cartilaginous rings and supporting tissue that connects the lung bronchi and the larynx; provides a route for air to enter and exit the lung
trachealis muscle
smooth muscle located in the fibroelastic membrane of the trachea
true vocal cord
one of the pair of folded, white membranes that have a free inner edge that oscillates as air passes through to produce sound
type I alveolar cell
squamous epithelial cells that are the major cell type in the alveolar wall; highly permeable to gases
type II alveolar cell
cuboidal epithelial cells that are the minor cell type in the alveolar wall; secrete pulmonary surfactant
vestibular fold
part of the folded region of the glottis composed of mucous membrane; supports the epiglottis during swallowing
Visit this site to learn more about what happens during an asthma attack. What are the three changes that occur inside the airways during an asthma attack?
Inflammation and the production of a thick mucus; constriction of the airway muscles, or bronchospasm; and an increased sensitivity to allergens.
1. Which of the following anatomical structures is not part of the conducting zone?
A) pharynx
B) nasal cavity
C) alveoli
D) bronchi
C
2. What is the function of the conchae in the nasal cavity?
A) increase surface area
B) exchange gases
C) maintain surface tension
D) maintain air pressure
A
3. The fauces connects which of the following structures to the oropharynx?
A) nasopharynx
B) laryngopharynx
C) nasal cavity
D) oral cavity
D
4. Which of the following are structural features of the trachea?
A) C-shaped cartilage
B) smooth muscle fibers
C) cilia
D) all of the above
A
5. Which of the following structures is not part of the bronchial tree?
A) alveolar ducts
B) bronchi
C) terminal bronchioles
D) respiratory bronchioles
A
6. What is the role of alveolar macrophages?
A) to secrete pulmonary surfactant
B) to secrete antimicrobial proteins
C) to remove pathogens and debris
D) to facilitate gas exchange
C
1. Describe the three regions of the pharynx and their functions.
The pharynx has three major regions. The first region is the nasopharynx, which is connected to the posterior nasal cavity and functions as an airway. The second region is the oropharynx, which is continuous with the nasopharynx and is connected to the oral cavity at the fauces. The laryngopharynx is connected to the oropharynx and the esophagus and trachea. Both the oropharynx and laryngopharynx are passageways for air and food and drink.
2. If a person sustains an injury to the epiglottis, what would be the physiological result?
The epiglottis is a region of the larynx that is important during the swallowing of food or drink. As a person swallows, the pharynx moves upward and the epiglottis closes over the trachea, preventing food or drink from entering the trachea. If a person’s epiglottis were injured, this mechanism would be impaired. As a result, the person may have problems with food or drink entering the trachea, and possibly, the lungs. Over time, this may cause infections such as pneumonia to set in.
3. Compare and contrast the conducting and respiratory zones.
The conducting zone of the respiratory system includes the organs and structures that are not directly involved in gas exchange, but perform other duties such as providing a passageway for air, trapping and removing debris and pathogens, and warming and humidifying incoming air. Such structures include the nasal cavity, pharynx, larynx, trachea, and most of the bronchial tree. The respiratory zone includes all the organs and structures that are directly involved in gas exchange, including the respiratory bronchioles, alveolar ducts, and alveoli.