Is therefore of interest to the otolaryngologist. Furthermore, endoscopic

diagnosis and treatment (bronchoscopy) was developed by ear, nose, and throat

surgeons and is still practiced by them although other specialists in bronchial

diseases such as chest physicians and thoracic surgeons practice diagnostic

bronchoscopy.

Basic anatomy

The trachea begins at the level of CVI-CVII and ends at the level of TIV-TV.

The trachea is attached to the cricoid cartilage which is the most narrow rigid

element of the airway and moves in response to movements of the floor of the

mouth and the cervical muscles It is 10 to 13 cm long in the adult and its lumen

Is held open by 16 to 20 horseshoe-shaped cartilaginous rings. The posterior

part of the tube is formed by the membranous part which lies in contact with the

anterior esophageal wall.

The carina. i.e., the origin of the two main bronchi, lies at the level of the

fourth-fifth thoracic vertebra. It has an angle of 55o open inferiorly. The

right main bronchus lies at an angle of about 17o to the midline and is

therefore almost a direct continuation of the trachea. Since it is in this

alignment and since the lumen is larger than that of the left main bronchus,

foreign bodies are most liable to enter it. The left main bronchus is longer

than the right main bronchus and lies at an angle of about 35o to the midline.

The bronchial tree has an extra- and an intrapulmonary course. The

horseshoe-shaped cartilaginous rings of the bronchial wall gradually become

complete rings, encircling the bronchus fully in the more peripheral parts. The

bronchioles do not possess cartilaginous elements in the wall but only a spiral

muscle. Changes in the lumen are produced by the bronchial musculature and

additionally in the middle and small bronchi by the bronchial veins.

The trachea and bronchi are lined by respiratory mucosa which becomes flatter

toward the periphery and passes into a single layer of cubical epithelium in the

bronchioles.

Vascular supply. The trachea is mainly supplied by the inferior thyroid artery

(thyrocervical trunk of the subclavian artery), but there are also connections

with the superior thyroid artery (E.C.A.). The bronchi and the carina derive

their blood supply directly from the aorta through bronchial arteries. There are

numerous anastomoses with the pulmonary arteries for the lung tissue.

Lymphatic drainage. The trachea mainly drains to the lymphatic network of the

neck but also connects with the thoracic lymph system which is important in the

spread of metastases.

Nerve supply. This is provided by the vagus nerve and the sympathetic trunk.

Basic physiology

The main function of the trachea and bronchi is respiration.

Warming, humidification, and cleaning of the inspired air begin in the nose and

are completed in the lower airway so that under normal anatomic conditions the

intratracheal air temperature is maintained about 35oC. This temperature is

considerably lower during mouth breathing. The relative humidity of the

intratracheal air is 95% in normal breathing but considerably lower during mouth

breathing.

ESOPHAGUS

Anatomy

The esophagus begins at the level of the lower border of the cricoid cartilage,

at the level of the sixth cervical vertebra, and ends at the cardia which lies

at the level of the eleventh thoracic vertebra. The opening of the esophagus in

the adult lies about 15 cm from the upper incisor teeth and the cardia at about

(35 to) 41 cm. The entire length of the esophagus is thus approximately 26 cm.

The wall of the esophagus is capable of expanding and contracting and is

resistant to considerable mechanical stress. The wall has four layers: layer of

connective tissue(superficial), muscular layer, submucosa and mucosa. The

internal lining is of stratified nonkeratinized squamous epithelium. The

external longitudinal musculature and internal circular muscle layer form

separate layers of the wall. There are also muscle fibers running spirally.

The esophageal musculature is striated in the upper third, consists of mixed

smooth muscle fibers and striated fibers in the middle third, and is almost

exclusively smooth muscle in the lower third.

The esophagus has 3 anatomical and 2 physiological constrictions.

The anatomical constrictions are:

1. Cricopharyngeal constriction at its mouth.

2. At the bifurcation of trachea.

3. As it passes through the diaphragm.

The physiological constrictions are:

1. At the crossing with the aorta.

2. At the level of the esophageal hiatus, the cardia.

There are cervical, thoracic and abdominal portion of the esophagus.

The blood supply is segmental as is the lymphatic drainage. Innervation is mixed

somatic from the IX-th and X-th cranial nerves and autonomic from the

sympathetic nervous system.

Physiology

The esophagus possesses its own active mobility and also a passive mobility due

to respiration and to movement of the neighbouring great vessels and the heart.

The act of swallowing may be divided into an oral phase which is under voluntary

control and a pharyngeal and esophageal phase. The latter are under reflex

control depending on stimulation of the posterior pharyngeal wall and can be

recognized by the elevation of the larynx.

This entrance of the esophagus and the cardia are usually closed. The entrance

of the esophagus opens during swallowing, and the cardia opens in response to

the oncoming peristaltic wave.

The sphincteric and transport functions can be investigated by the following:

radiography with contrast medium and manometry (intraluminal measurement of

pressure in the esophagus).

Disorders of peristalsis and tone are possible in the following: (1) mechanical

obstruction and narrowing and (2) paralysis of the muscles or nerves.

In presbyesophagus there is a disorder of coordination of the various phases of

mobility with increased tertiary contractions and atonic phases. This causes

prolonged transit time of the food.

Part 4

DISEASES OF THE EAR

DISEASES OF THE EXTERNAL EAR

Otitis externa

The origin of disorders of the skin involving the external ear may not be

immediately recognized, particularly those involving the meatus, and even

manifest disease of the auricle and adjacent skin areas may arise in the meatus

or middle ear. Otitis externa has been classified as localized or generalized.

When it is confined within the external meatus two clinical forms are

recognized: (1) circumscribed otitis extenra or furuncle and (2) diffuse otitis

externa.

The generalized form affecting the meatus, auricle and adjoining areas of skin

may be primarily otological or primary dermatological. In addition, the

condition may be classified as infective, due to bacterial, fungal or viral

agents, and reactive, from contact with numerous external sensitizing agents or

resulting from constitutional allergies. In many cases the disease is of mixed

origin, a primary infective lesion developing an eczematous reaction and vice

versa.

INCIDENCE. The incidence of otitis externa is highest in tropical country with a

high humidity where the symptoms are often severe and recurrences are frequent.

AETIOLOGY. Many factors can be implicated in the onset of otitis externa.

Scratcing the ears with dirty fingers or with contaminated objects such as a

matchstick or a hair-grip, or the use of dirty instruments may introduce

pathogenic organisms to the meatus. If the skin is traumatized infection may

penetrate the barrier of the stratum corneum. Syringing the ear for the removal

of hard wax or badly fitting and infrequently cleaned hearing-aid earpieces may

also cause minor injury and subsequent infection. In other causes allergy is the

primary factor. The development of skin allergy may be due to a large variety of

antigens, many of which are contained in topical applications such as cosmetics

and antibiotic preparations. Intense itching is an early symptom of

sensitization and scratching often leads to secondary infection. A sensitivity

reaction may result from psychological factors such as prolonged mental stress.

BACTERIOLOGY. The normal external meatus contains Staphylococcus albus alone or