![]() The lymphatic drainage of the external ear is to the superficial parotid, mastoid, upper deep cervical and superficial cervical nodes. The adult human ear canal extends from the pinna to the eardrum and is about 2.5 centimetres (1 in) in length and 0.7 centimetres (0.3 in) in diameter. Some individuals can complain of an involuntary cough when cleaning their ears - this is due to stimulation of the auricular branch of the vagus nerve (the vagus nerve is also responsible for the cough reflex). The ear canal ( external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. Branches of the facial and vagus nerves - innervates the deeper aspect of the auricle and external auditory meatus.Auriculotemporal nerve (branch of the mandibular nerve) - innervates the skin of the auricle and external auditory meatus.Lesser occipital nerve (branch of the cervical plexus) - innervates the skin of the auricle.Greater auricular nerve (branch of the cervical plexus) - innervates the skin of the auricle.The sensory innervation to the skin of the auricle comes from numerous nerves: Venous drainage is via veins following the arteries listed above. Maxillary artery (deep auricular branch) - supplies the deep aspect of the external acoustic meatus and tympanic membrane only.The external ear is supplied by branches of the external carotid artery: The parts of the tympanic membrane moving away from the lateral process are called the anterior and posterior malleolar folds. The handle of malleus continues superiorly, and at its highest point, a small projection called the lateral process of the malleus can be seen. ![]() On the inner surface of the membrane, the handle of malleus attaches to the tympanic membrane, at a point called the umbo of tympanic membrane. The translucency of the tympanic membrane allows the structures within the middle ear to be observed during otoscopy. The membrane is connected to the surrounding temporal bone by a fibrocartilaginous ring. It is a connective tissue structure, covered with skin on the outside and a mucous membrane on the inside. The tympanic membrane lies at the distal end of the external acoustic meatus. ![]() It ends by running in an inferoanterior direction.In then turns slightly to move superoposteriorly.Initially it travels in a superoanterior direction.The external acoustic meatus does not have a straight path, and instead travels in an S-shaped curve as follows: The walls of the external 1/3 are formed by cartilage, whereas the inner 2/3 are formed by the temporal bone. The narrowest part of the external auditory canal is called the isthmus and lies at the junction of the cartilaginous and bony portions of the canal 5.The external acoustic meatus is a sigmoid shaped tube that extends from the deep part of the concha to the tympanic membrane. A normal variant defect in the anteroinferior aspect of the osseous part of the canal that connects with the temporomandibular joint is known as the foramen tympanicum (foramen of Huschke). The skin of this inner part is directly applied to periosteum, with no subcutaneous tissue present. The roof and upper part of the posterior wall arise from the squamous part of the temporal bone 4. The anterior wall, floor, and lower part of the posterior wall arise from the tympanic part of the temporal bone 3,4. The medial two-thirds is surrounded by bone. Defects in the cartilaginous part of the canal, which allow transmission of infection and malignancy, are known as fissures of Santorini. The lateral one-third is bounded by a fibrocartilaginous tube continuous with the auricle 3. ![]() The external auditory canal is typically 2.5 cm in length and is S-shaped. As the term external auditory meatus is variably used to refer to the canal itself or the porus acusticus externus (the round lateral opening), it may be better to use the term external auditory canal rather than meatus to avoid potential confusion. ![]()
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