VAN 221: Veterinary Splanchnology and Applied Anatomy (1+1)

TRACHEA (OX)

• The trachea is a flexible cartilaginous tube extending from the larynx to the hilus of the lungs where it divides into right and left bronchi
• It is kept permanently open by a series of about 50 ‘C’ shaped cartilaginous rings embedded in its walls
• It occupies a median position except at is termination where it is pushed a little to the right of the median plane by the aortic arch
• Its average length is about 65 cm, the width about 4 cm and height 5 cm
• It is approximately cylindrical but its cervical part is for the most part compressed from above downwards whereas at its origin it is almost circular
• The trachea has cervical and thoracic parts
• The cervical part is related dorsally to the oesophagus for a short distance and for the rest of its extent to the longus colli muscles
• Laterally it is related to the lateral lobes of the thyroid gland, carotid artery, vagus, sympathetic and recurrent laryngeal nerves, tracheal lymph ducts and cervical lymph glands
• The oesophagus lies on its left from the third cervical vertebra backwards. Ventrally it is related to the ventral cervical muscles
• The sternocephalicus muscle crosses it obliquely, passing from the ventral surface forwards on its sides to reach the angles of the jaw
• The omohyoideus crosses it very obliquely, passing over the lateral surface of the cervical part of the trachea in its upper third
• The sternothyrohyoideus covers the ventral aspect of the trachea. The scalenus lie on either side near the entrance to the thorax
• This arrangement of the muscles leaves a small area of the ventral face of the trachea at its upper third covered only by the skin
• The thoracic part of the trachea passes backward between the two pleural sacs and divides into two bronchi opposite to the 5 th rib
• It is related dorsally to the oesophagus and longus colli muscle. Its left face is related to the aortic arch, left brachial artery and thoracic duct
• Its right face is crossed by the right vagus. Ventrally, the trachea is related to the cranial vena cava, brachio-cephalic trunk, cardiac and recurrent laryngeal nerves
• The trachea in the ox detaches a small apical bronchus to the apical lobe of right lung about the level of the third rib or intercostal space and beyond this it is adherent to the right lung

Structure

• The trachea is composed of cartilaginous rings
• The free ends of rings are separated by an interval and are C-shaped, in the cervical part
• The deficiency above is made up by the fibro-elastic membrane - membrana transversa, which encloses the tracheal rings and the trachealis muscle
• The adjacent cartilages are united by the tracheal annular ligaments
• In the thoracic part the two edges of the rings meet and form the ridge
• The mucous membrane is lined by ciliated epithelium.