Essentials of Anatomy and Physiology

SUMMARY

As you have learned, respiration is much more than
the simple mechanical actions of breathing. Inhalation
provides the body with the oxygen that is necessary for
the production of ATP in the process of cell respira-
tion. Exhalation removes the CO 2 that is a product of

cell respiration. Breathing also regulates the level of

CO 2 within the body, and this contributes to the

maintenance of the acid–base balance of body fluids.

Although the respiratory gases do not form structural

components of the body, their contributions to the

chemical level of organization are essential to the

functioning of the body at every level.

362 The Respiratory System

STUDY OUTLINE

The respiratory system moves air into and
out of the lungs, which are the site of
exchange for O 2 and CO 2 between the air
and the blood. The functioning of the respi-
ratory system depends directly on the
proper functioning of the circulatory system.

1. The upper respiratory tract consists of those parts
   outside the chest cavity.


2. The lower respiratory tract consists of those parts
   within the chest cavity.

Nose—made of bone and cartilage covered
with skin

1. Hairs inside the nostrils block the entry of dust.

Nasal Cavities—within the skull; separated
by the nasal septum (see Fig. 15–1)

1. Nasal mucosa is ciliated epithelium with goblet
   cells; surface area is increased by the conchae.


2. Nasal mucosa warms and moistens the incoming
   air; dust and microorganisms are trapped on mucus
   and swept by the cilia to the pharynx.


3. Olfactory receptors respond to vapors in inhaled
   air.


4. Paranasal sinuses in the maxillae, frontal, sphenoid,
   and ethmoid bones open into the nasal cavities:
   functions are to lighten the skull and provide reso-
   nance for the voice.

Pharynx—posterior to nasal and oral cavities
(see Fig. 15–1)

1. Nasopharynx—above the level of the soft palate,
   which blocks it during swallowing; a passageway
   for air only. The eustachian tubes from the middle
   ears open into it. The adenoid is a lymph nodule on
   the posterior wall.
   2. Oropharynx—behind the mouth; a passageway for
   both air and food. Palatine tonsils are on the lateral
   walls.
   3. Laryngopharynx—a passageway for both air and
   food; opens anteriorly into the larynx and posteri-
   orly into the esophagus.

Larynx—the voice box and the airway

between the pharynx and trachea (see Fig.

15–2)

1. Made of nine cartilages; the thyroid cartilage is the
   largest and most anterior.


2. The epiglottis is the uppermost cartilage; covers
   the larynx during swallowing.


3. The vocal cords are lateral to the glottis, the open-
   ing for air (see Fig. 15–3).


4. During speaking, the vocal cords are pulled across
   the glottis and vibrated by exhaled air, producing
   sounds that may be turned into speech.


5. The cranial nerves for speaking are the vagus and
   accessory.

Trachea—extends from the larynx to the pri-

mary bronchi (see Fig. 15–4)

1. Sixteen to 20 C-shaped cartilages in the tracheal
   wall keep the trachea open.


2. Mucosa is ciliated epithelium with goblet cells; cilia
   sweep mucus, trapped dust, and microorganisms
   upward to the pharynx.

Bronchial Tree—extends from the trachea to

the alveoli (see Fig. 15–4)

1. The right and left primary bronchi are branches of
   the trachea; one to each lung; same structure as the
   trachea.