THE RESPIRATORY SYSTEM
Diane Hickson-Bick, PhD.
: Gartner and Hiatt, Chapter 12, p 235; Klein and McKenzie, pp199-210.
Understand the differences between the conducting and respiratory portion of the
respiratory system. Define the roles and composition of these two regions.
: Conducting, respiratory, alveoli, cartilage, trachea, bronchus, bronchioles, vocal cords.
The respiratory system
The means by which, through a system of tubes, the body exchanges carbon dioxide for oxygen, which is
then distributed throughout the body.
2 Parts: An upper
A. CONDUCTING PORTION
Consists of the extra-pulmonary nasal cavity, nasopharynx, larynx,
trachea, bronchi and the intrapulmonary bronchi, bronchioles and
It serves two main roles:
1. To provide a conduit through which air can travel to and from
2. To condition the inspired air.
Components of the Conducting System
(primarily hyaline) from C-shaped rings to irregular rings
and small plaques. Prevents collapse of the walls.
Tend to be oriented longitudinally in this area.
From trachea to alveolar ducts. Contraction
reduces diameter of tubes and restricts airflow
Lines the conducting portions
Ciliated, pseudostratified columnar epithelium
mediate gas exchange.
Functions to cleanse, moisten and warm air before it enters
Numerous serous and mucous glands and a rich superficial vascular network in lamina propria.
Goblet cells, producing a rich mucous secretion, abundant in the upper portions of the conducting
The number of goblet cells, along with the amount of ciliated epithelium and cartilage, decrease
as the conducting tubes gradually proceed into the respiratory portion.
At the same time the content of smooth muscle and elastic fibers progressively increases.
Ciliated pseudostratified columnar epithelium transitions to a simple columnar and finally a
simple squamous epithelium in the alveoli.
The rich goblet cell population tapers off in the smaller bronchi and these cells are absent from
the terminal bronchioles.
Ciliated cells continue beyond the goblet cells, preventing the accumulation of mucous.
Cilia move fluid and mucus toward the oral cavity where it is swallowed or expectorated.
Respiratory epithelium consists of 5 cell types:
Ciliated columnar cells;
Most abundant, each having about 300 cilia on their apical
surface. Many apical mitochondria provide energy for beating.