Objectives
- Name the three divisions of the respiratory system and the components of each.
- Compare the right and left lungs.
- Describe the respiratory tract walls in terms of the arrangement, composition, and function of their layers and cells.
- Distinguish between respiratory tract components based on differences in wall structure.
- Describe the structure of the interalveolar septum.
- Describe the blood–air barrier’s structure and function. Identify its components in electron micrographs.
- Compare sympathetic and parasympathetic effects on bronchial smooth muscle.
- Describe the structure, function, and location of the pleura.
- Identify the organ, tissues, and cell types present and distinguish among the various components of the respiratory system in micrographs of respiratory tract or lung tissue.
MAX-Yield™ Study Questions
1. List the components of the ventilating mechanism involved in inhaling, exhaling, or both (I.A.1).
4. Name three ways in which inspired air is conditioned in the respiratory tract (en route to the alveoli) to optimize gaseous exchange (I.A.2.). Name the structure(s) associated with each type of conditioning (I.B.1.a; II.A and B).
5. Compare the right and left lungs in terms of the number of primary and secondary bronchi each receives (VII.A and B), the number of lobes in each (VII.B), and the angle at which the primary bronchi enter (VII.A).
6. Indicate whether the following components of the respiratory tract wall increase or decrease from the nose to the alveoli (I.B.1; Table 17–1):
Diameter of lumen
Thickness of walls
Height of epithelium
Number of cilia
Number of goblet cells
Number of glands
Amount of elastic tissue
Amount of smooth muscle
Amount of bone
Amount of cartilage
Size of individual cartilages
Number of alveoli
7. Indicate the level of the respiratory tree (Table 17–1) at which the following transitions occur:
Conducting portion to the respiratory portion
Ciliated pseudostratified columnar to nonkeratinized stratified squamous (and back to ciliated pseudostratified columnar) epithelium
Ciliated pseudostratified columnar to simple ciliated columnar epithelium
Simple columnar to simple cuboidal epithelium
Simple cuboidal to simple squamous epithelium
Vibrissae (II.A)
Swell bodies (II.B)
Elastic cartilage (V.A & B)
C-shaped cartilages (VI)
Platelike cartilage islands (VII.B)
Anastomoses (IX.A.2)
Clara cells (VII.E)
First appearance of alveoli (VII.F; Table 17–1)
Pulmonary surfactant (VIII.C)
Type I cells (VIII.B.1)
Type II cells (VIII.B.2)
Conchae (II.B)
Vibrissae (II.A)
Swell bodies (II.B)
Epiglottis (V.A)
Cilia (I.B.1.a)
Small granule cell (I.B.1.a)
Clara cells (VII.E)
Alveolar pores (VIII.A.2)
Pulmonary surfactant (VIII.C)
Type I cells (VIII.B.1)
Type II cells (VIII.B.2)
Alveolar macrophages (VIII.B.3)
11. Sketch a tissue section through three alveoli (Fig. 17–2; VIII.A–C) and include and label the following:
Alveolar sac
Type I cells
Type II cells
Alveolar macrophages
Alveolar septum
Interstitium
Alveolar pore
Capillaries
Endothelial cells
Fused basal laminae
Surfactant
Blood–air barrier
12. Compare the effects of sympathetic and parasympathetic stimulation on bronchial and vascular smooth muscle (X).
Synopsis
The respiratory system comprises the lungs, airways (i.e., pharynx, larynx, trachea, bronchi), and associated structures. Specialized for gaseous exchange between blood and air, including oxygen uptake and carbon dioxide release, it is functionally divisible into three major parts: its conducting and respiratory portions and the ventilating mechanism.
Ventilating mechanism. This mechanism creates the pressure differences that move air into (inspiration) and out of (expiration) the lungs. It includes the diaphragm, rib cage, intercostal muscles, abdominal muscles, and the lungs’ elastic connective tissue. Inspiration (inhalation) is active and involves muscle contraction. The intercostal muscles lift the ribs while the diaphragm and abdominal muscles lower the thoracic cavity floor. This enlarges the cavity, creating a vacuum that draws air in through the airways. The air expands the airways, inflates the lungs, and stretches the elastic connective tissue. Expiration (exhalation) is more passive: relaxing the muscles allows the elastic fibers to retract, contracting the lungs and forcing air out.
Conducting portion. The walls of this system of tubes are specialized to carry air to and from the site of gas exchange without collapsing under the pressures created by the ventilating mechanism. This portion also conditions the air; it warms, moistens, and cleans it to enhance gas exchange. The components of this portion include the nasal cavity (II), nasopharynx (IV), larynx (V), trachea (VI), bronchi (VII), bronchioles (VII.D), and terminal bronchioles (VII.E).
Respiratory portion. This portion is distinguished by the presence of alveoli (VIII), small saccular structures whose thin walls allow gas exchange between air and blood. Alveoli occur in clusters at the end of the bronchial tree. These clusters extend (like rooms from a hallway; Fig. 17-1) from the walls of respiratory bronchioles (VII.F), alveolar ducts (VII.G), and atria and alveolar sacs (VII.H).
Like the digestive tract, the respiratory tract has layered walls whose lining epithelium derives from endoderm. The wall layers include an epithelium, a lamina propria that contains mucous glands and cartilage that prevents the tract from collapsing under pressure, smooth muscle that regulates the luminal diameter, and an adventitia that contains collagen and elastic fibers. Each layer undergoes gradual changes as the wall’s overall thickness decreases from the nasal cavity to the alveoli (Table 17–1).
Respiratory epithelium. The epithelium that lines most of the tract is ciliated pseudostratified columnar with goblet cells (IV.B.4). As the respiratory tract branches and its luminal diameter decreases, the epithelium drops in height and loses first goblet cells and then cilia as it approaches the alveoli.
Epithelial cell types. Ciliated columnar cells predominate in the tract. Each has approximately 300 motile cilia (2.III.J; 4.IV.A.1) on its apical surface and associated basal bodies in the apical cytoplasm. Mucous goblet cells
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
