TLDR;
Alright, so this video is all about the anatomy of the ear, broken down into three main parts: the external ear, the middle ear, and the internal ear. The video goes deep into the external ear, explaining the structures of the pinna (or oracle) and the external auditory meatus. It covers everything from the cartilage framework of the pinna to the skin lining of the ear canal, and even some important surgical considerations.
- The external ear is divided into the pinna (oracle) and the external auditory meatus.
- The pinna is mostly cartilage, except for the lobule, which is fatty.
- The external auditory meatus is not straight; it has a cartilaginous part and a bony part.
Introduction to Ear Anatomy [0:01]
The lecture will cover the anatomy of the ear, dividing it into three sections: the external ear, the middle ear, and the internal ear. The external ear includes the pinna (or oracle), the external auditory meatus, and the tympanic membrane. The middle ear section will discuss the middle ear cavity, its boundaries, and the ear ossicles. Finally, the lecture will touch upon the mechanism of hearing and the structures in the internal ear.
Anatomy of the Pinna (Oracle) [1:03]
The external ear consists of the pinna (or oracle) and the external auditory meatus. The pinna, except for the lobule, is made of yellow elastic cartilage covered by perichondrium. The skin on the lateral side of the pinna is tightly attached to the perichondrium, while on the medial side, it's loosely attached. Key features of the pinna include the lobule, tragus, anti-tragus, incisura terminalis (which lacks cartilage), helix, antihelix, concha, cymba conchae, and triangular fossa. The pinna's cartilage is useful for graft materials in middle ear reconstructive surgeries, depressed nasal bridge corrections, and nose jobs.
External Auditory Meatus: Structure and Details [7:30]
The external auditory meatus isn't a straight tube; the outer part goes upwards, backwards, and medially, while the inner part goes downwards, forwards, and medially. This is why you gotta pull the pinna upwards, backwards, and laterally to see the tympanic membrane properly. The auditory tube is 24 mm long, with the outer 8 mm being cartilaginous and the inner 16 mm being bony. The cartilaginous part is a continuation of the pinna's cartilage framework but has fissures of Santorini, which are gaps that can spread infections to the parotid gland or mastoid.
Cartilaginous vs. Bony Parts of the Auditory Canal [9:50]
The cartilaginous part of the auditory canal is 8 mm long and has fissures of Santorini, which can act as pathways for infections to spread between the outer ear, parotid gland, and mastoid. The skin covering this part is thick and contains ceruminous and sebaceous glands (which produce wax and oil) and hair follicles. This makes it prone to infections like furuncles. The bony part, making up the inner two-thirds (16 mm), has thinner skin without hair or glands. Six mm lateral to the tympanic membrane, the bony part narrows to form the isthmus.
Isthmus, Anterior Recess, and Foramen of Huschke [14:48]
The bony part of the external auditory meatus is 16 mm long, and 6 mm lateral to the tympanic membrane, it narrows to form the isthmus. Foreign bodies can get stuck here, leading to infections and perforations. Medial to the isthmus is the anterior recess, which can collect debris and discharge. The anteroinferior part of the bony canal may have the foramen of Huschke, a deficiency more common in children up to four years old, which can allow infections to spread to and from the parotid gland. The skin lining the bony part is thin, lacks hair, and has no glands.