Immunoglobulin a (IgA), immunoglobulin m (IgM), and immunoglobulin g (IgG).

Resistance factors of the second defensive zone include: (1) nonspecific

protective factors and structures such as the ground substance and fibrils,

micro- and macrophages, mast cells, vessels, the autonomic nervous system,

hormones, interferon, protease inhibitors, complement, etc.; and (2) specific

defensive factors such as sensitized B- and T-lymphocytes, eosinophil

granulocytes, immunoglobulin IgG, IgM, and IgE.

The Nose as a Reflex Organ

Specific nasal reflex mechanisms may arise: - Within the nose and affect the

nose itself - From other parts of the body or organs and affect the nose - In

the nose and affect other parts of the body. A reflex system which is obviously

confined to the nose is the nasal cycle. One cycle lasts between 2 and 6 h.

Provided that both halves of the nasal cavity are of normal patency, the lumen

widens and narrows alternately, lowering or increasing the respiratory

resistance in each half of the nose. However, the resistance of the entire nose

remains constant in the ideal case. This reflex phenomenon is controlled by the

action of the autonomic nervous system on the cavernous spaces of the vascular

system of the nasal mucosa.

Nasopetal reflexes arise, e.g., from cooling of the extremities, which changes

the respiratory resistance. They may also arise from the lungs and bronchi and

from other autonomic control points.

Important nasofugal communications exist between the nose and the lung, the

heart and circulation, the metabolic organs, and the genitals.

In addition, there are sneezing, lacrimal, and cough reflexes, and under certain

emergency situations, reflex respiratory arrest.

Influence of the Nose on Speech

The nose influences the sound of speech. During the formation of the resonants

"m", "n", and "ng", e.g., the air streams passes through the open nose, whereas

during the formation of the vowels the nose and the nasopharynx are more or less

closed off by the soft palate from the resonating cavity of the mouth.

Function of the Paranasal Sinuses

The biologic purpose of the nasal sinuses is largely speculative. The main

function of the paranasal sinuses is the protection of the cranial cavity. It

is obvious that the pneumatized cavities of the bone of the skull reduce the

weight, at the same time increasing the superficial extent of the bones of the

skull.

The existence of the ostia causes particular pathophysiologic problems affecting

ventilation and drainage.

Ostial obstruction interrupts the self-cleaning mechanism of the affected sinus:

therefore, the secretions stagnate and change in composition. The retained

secretions form an ideal medium for saprophytic bacteria which are often present

in normal sinuses.

The causes of closure of the ostium include:

1. Environmental factors such as relative dryness of the nose, toxic gases, or

agents in the air.

2. Local congenital or acquired anomalies, including: deviation of the septum,

scars, lesions of the turbinates, infections of the nose or nasal cavities,

dental diseases, allergic diseases of the nose or nasal sinuses (particularly in

children), vasomotor dysfunctions with a neurogenic or hormonal basis, metabolic

diseases such as avitaminoses, diabetes, disordered electrolytes, mechanical

obstruction due to crusts, polypi, foreign bodies, prolonged use of a

nasogastric tube or prolonged nasal tracheal intubation, and benign and

malignant tumors.

The vicious circle of ostial occlusion can only be broken in the long term by

dealing with the causal factors by appropriate medical or surgical measures.

The nasal sinuses are only minimally involved in the respiratory phases of the

nasal cavity.

The change in pressure which can be recorded in the sinuses during respiration

is relatively slight.

ANATOMY OF THE PHARYNX

The pharynx extends from the base of the skull to the level of sixth cervical

vertebrae. This is a 12 to 13 cm long muscular tube in the adult; it narrows

from above downward, is covered with mucosa, and is divided into three

compartments each of which has an anterior opening (Fig. 26).

The nasopharynx is limited superiorly by the base of the skull, inferiorly by an

imaginary plane through the soft palate, and it opens into the nasal cavity. The

most important anatomic structures are as follows: anteriorly the choanae,

posterosuperiorly the adenoid, laterally the pharyngeal ostium of the eustachian

tube and the cartilaginous torus tubarius immediately posterior to which is

Rosenmueller's fossa and the tubal tonsil, and anteriorly and inferiorly the

soft palate (Fig. 28). The embryonic pharyngeal bursa may persist in the

posterior wall of the nasopharynx causing chronic inflammation and retention of

secretions. The posterior wall of the nasopharynx is separated from the spinal

column by the tough prevertebral fascia which lies on the longus capitis

muscles, the deep muscles of the neck, and the arch of the first cervical