ANA 206SYSTEMIC EMBRYOLOGY

DEVELOPMENTOF THE TRACHEA

Brief insight into the Anatomical & Physiological

Characteristics of the Trachea

The trachea is a flexible pipe which travels from

the throat down into the thorax. It is supported

by rings of a flexible but strong material called

cartilage. It prevents the trachea from collapsing

as inspired and expired air move through it. The

cartilage rings also allow for continue breathing

when the neck is bent. The inside of the trachea

is covered by millions of microscopic hairs called

cilia.

The cilia are covered with a layer of liquid called

mucus. Very fine dust particles and microbes

get trapped in the mucus and cilia. Although the

cilia are attached at one end, each one is able to

move (beat). As the cilia beat they tend to push

the dust-containing mucus toward the nose and

the mouth. In this way the lungs are kept free of

most of the dust and microbes inhaled.

Development of the Trachea

The trachea develops caudal to the larynx.

The endodermal lining of the laryngotracheal

tube differentiates into the epithelium and

glands of the trachea and the pulmonary

epihelium.

The epithelium develops from the endoderm

and the tracheal cartilage and muscles develop

from splanchnic mesoderm.

Early in development, the trachea bifurcates

into the left and right bronchi.

Tracheoesophageal fistula is an abnormal communication

between the trachea and esophagus that results from improper

division of foregut by the tracheoesophageal septum. It is

generally associated with esophageal atresia and

polyhydramnios.

CLINICAL CORRELATES

Clinical features include excessive accumulation of saliva or

mucus in the nose and mouth; episodes of gagging and

cyanosis after swallowing milk; abdominal distention after

crying; and reflux of gastric contents into lungs, causing

pneumonitis.

Diagnostic features include inability to pass a catheter into the

stomach and radiographs demonstrating air in the infant's

stomach. There are five different anatomical types of

esophagus and trachea malformations as follows:

Esophageal atresia with a tracheoesophageal fistula at the

distal one-third end of the trachea. This is the most common

type, occurring in 82% of cases. The anteroposterior (AP)

radiograph (the image on the next slide) of this malformation

shows an enteric tube (arrow) coiled in the upper esophageal

pouch. The air in the bowel indicates a distal

tracheoesophageal fistula.

Esophageal atresia with a tracheoesophageal fistula at the distal one-third end of the trachea

Esophageal atresia only. This malformation occurs in 9% of cases.

H-type tracheoesophageal fistula only. This malformation occurs in 6% of cases. The barium swallow radiograph (in the image below) shows a normal esophagus (E), but dye has spilled into the trachea (T) through the fistula and outlines the upper trachea and larynx.

Esophageal atresia with a tracheoesophageal fistula at both proximal and distal ends. This malformation occurs in 2% of cases.

Esophageal atresia with a tracheoesophageal fistula at the proximal end. This malformation occurs in 1% of cases

COMPLIMENT OF THE SEASON

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