Venous returns drain into the pterygoid venous plexus, and lymphatics drain into the retropharyngeal lymph nodes. Blood Supply and Lymphaticsīlood is supplied to the Eustachian tube by several arteries of the external carotid, including the ascending pharyngeal branch and two branches of the maxillary artery, the middle meningeal artery, and the artery of the pterygoid canal. The skeletal elements have two parts, the boney lateral portion that arises from the anterior wall of the auditory bulla and the cartilage portion that covers the dorsal region along the length of the tube. The stalk of the recess forms the Eustachian tube. After contact with the outer ear canal, mesoderm between 2 canals forms the tympanic membrane this expands to form the tympanic recess.

The Eustachian tube partially originates from the first pharyngeal pouch and extends as tubotympanic recess. The discontinuous opening of the pharyngeal ostium in the nasopharynx causes peristaltic-like movements that may be due to the visco-elastic features of the tubular structure of the cartilage. It then proceeds forward, downward, and medially, to form a 45-degree angle to the sagittal plane, and about a 30-degree angle to the horizontal plane. The Eustachian tube is located in the para-pharyngeal space and is closely linked to the infratemporal fossa. The Eustachian tube continues from the front wall of the middle ear to the sidewall of the nasopharynx, progressing along the posterior edge of the medial pterygoid plate. The active opening of the Eustachian tube to relieve positive or negative pressure in the middle ear commonly is called “clearing the ear.” These can be actively pulled apart to open the tube with the help of accessory muscles or passively pushed apart by air exiting or entering the middle ear under pressure. Partly a hollow tube in bone and partly a potential space in fibroelastic cartilage, the Eustachian tube is normally closed, as its proximal walls are collapsed. Patency of the tube allows for air exchange in the tympanic cavity to replenish oxygen to the middle ear, in addition to providing an outlet for mucus and other fluid from the middle ear. It is believed that the Eustachian tube also may be involved in sound transformation through reverberation phenomena.

It thus influences the tension in this structure and the attached ossicles, and in this way indirectly affects the effectiveness of sound wave transmission. In doing so, the Eustachian tube allows for regulation of the pressure across the tympanic membrane. More specifically, the Eustachian tube permits equalization of pressure in the middle ear with respect to ambient pressure. The Eustachian tube plays a role in equalization, oxygenation, and drainage of the tympanic cavity in the middle ear. The Eustachian tube is also known as the pharyngotympanic tube or the auditory tube. The Eustachian tube is named after the Italian anatomist, Bartolomeo Eustachi, who observed that it was a canal that connected the nasopharynx to the middle ear.

Adenoid auditory tube