![]() ![]() Interestingly, outer portions of the stapes footplate are derived from the mesoderm. The stapes is formed from the second arch from a structure called Reichert's cartilage. The malleus and incus are predominantly derived from the first arch from a structure called Meckel's cartilage. The three ossicles are derived from the neural crest of the first and second pharyngeal arches during the sixth week of development. There are two muscles of the ossicular chain, namely the tensor muscle of the tympanum or malleus and the stapedius or stapes muscle. The ossicular chain is held in its position by the connections of the malleus handle with the tympanic membrane, the annular ligament of the stapes, and the ligaments of the malleus and incus. The incudomallear joint is a saddle joint, which starts to move with sounds starting at 2 kHz. On average, the malleus has a height of about 8.0 millimeters and about 2.7 millimeters in width the incus has about a height of 6.8 millimeters and a width of about 5.3 millimeters the stapes has a height of about 3.5 millimeters and a width of about 2.4 millimeters. The stapes has an angle of approximately 10.7 degrees to the surface of the tympanic membrane. Incudostapedial joint (ISJ) is organized as a synovial joint, with the presence of a meniscus and intra-articular fluids, a capsule the joint has the typical characteristics of a viscoelastic joint. The tympanic membrane vibrates, leading to the movement of the chain of ossicles. The attachment of the footplate of the stapes to the oval window allows the displacement of fluid within the inner ear. The sound waves initially make contact with the external ear and tympanic membrane. The main function of the middle ear is to transmit the sound waves from the external environment to the inner ear. The stapes articulates with the oval window of the inner ear. ![]() It is known as the smallest bone within the human body. The stapes is the third ossicle and consists of the head, legs, and footplate. The incus connects with the stapes and forms the incudo-stapedial joint. The incus is the second ossicle and is divided into the body, short process, and long process. The head of the malleus attaches to the incus and forms the incudo-malleolar joint. The handle of the malleus attaches loosely to the tympanic membrane. It is divided into four parts: the head, neck, short process, and handle. The malleus is the first ossicle and attaches to and moves with the tympanic membrane. These three ossicles connect the tympanic membrane to the inner ear allowing for the transmission of sound waves. The middle ear consists of the tympanic membrane and the bony ossicles called the malleus, incus, and stapes. The ear structures are classically divided into three parts: the external ear, middle ear, and inner ear. The ossicles play a role in multiple clinical scenarios, including otosclerosis, choleastoma, and facial nerve palsy. ![]() Middle ear anatomy consists of intricate relationships between nerves, blood supply, and muscles. The stapes connects to the oval window allowing for mechanical energy to be transferred to the fluid-filled inner ear. The malleus connects to the tympanic membrane transferring auditory oscillations to the incus and then the stapes. The auditory ossicles (malleus, incus, and stapes) play a key role in this function. The middle ear functions to connect the sound waves from the external environment and transfer them to the inner ear for auditory transduction. ![]()
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