What is the embryological origin of the ear structures?

The cartilage origin of the three middle ear ossicles arises from neural crest-derived mesenchyme of the first and second pharyngeal arches. The malleus and incus develop from Meckel’s cartilage of the first pharyngeal arch, while the stapes arises from Reichert’s cartilage of the second pharyngeal arch.

How does the inner ear develop?

During week 4 of embryonic development, the human inner ear develops from the auditory placode, a thickening of the ectoderm that gives rise to the bipolar neurons of the cochlear and vestibular ganglions. As the auditory placode invaginates towards the embryonic mesoderm, it forms the auditory vesicle or otocysts.

Which part of the ear has origin from all the three layers of germ layers?

The eardrum is made up of three layers (ectoderm, endoderm and connective tissue). The pinna originates as a fusion of six hillocks.

What is the origin of tympanic membrane?

The tympanic membrane is derived from the invagination and meeting of the first pharyngeal groove (cleft) with the first pharyngeal pouch, and as such, it is comprised of two germ layers (ectoderm and endoderm).

What is a Modiolus?

The modiolus (plural: modioli) is part of the cochlea and is a conical-shaped structure that consists of spongy (porous) bone located in the center of the cochlea and contains the spiral ganglion. The spiral lamina projects from the modiolus. Abnormality of the modiolus results in sensorineural hearing loss.

Which part of the ear does the tympanic membrane separate?

outer ear
The tympanic membrane is also called the eardrum. It separates the outer ear from the middle ear.

What equalizes pressure on both sides of the tympanic membrane?

The eustachian tube helps to equalize the pressure in the middle ear.

What do Jake and Sam learn about at the Science Museum?

At the museum, Jake and Sam decided to find out if Sam’s mom was right. They headed over to the human body exhibit and stood in front of a gigantic model of an ear. A museum guide was explaining how ears help you hear.

What is the mastoid antrum?

The mastoid antrum ( tympanic antrum, antrum mastoideum, Valsalva’s antrum) is an air space in the petrous portion of the temporal bone, communicating posteriorly with the mastoid cells and anteriorly with the epitympanic recess of the middle ear via the aditus to mastoid antrum (entrance to the mastoid antrum).

Are mastoid air cells always present in the middle ear?

Occasionally, they are entirely absent. Mastoid air cells communicate with the middle ear via the mastoid antrum and the aditus ad antrum .

What happens to the mastoid process after birth?

The mastoid process continues to grow until puberty and even beyond. At birth, the mastoid process contains only the antrum. After birth, mastoid air cells develop as an outgrowth of the antrum; epithelial air tracts bud from the antrum and extend to the adjacent areas of the temporal bone to form the mastoid air cells (Fig. 5.2 ).

What bone forms the anterosuperior portion of the mastoid process?

The squamous bone forms the anterosuperior portion of the mastoid process. The petrous bone forms its postero-inferior part. The junction of the two parts forms the petrosquamous suture. The petrosquamous suture runs vertically from the superior border of the mastoid process to join its antero-inferior border just above the mastoid tip (Fig. 5.3).