Question

In the tympanic cavity, there is an aperture in which the stapes is fitted, it is
A. Foramen rotundum
B. Foramen triosseum
C. Fenestra ovalis
D. Fenestra rotundum

Answer 1

Hint:-Human ear, organ of hearing and equilibrium that detects and analyzes sound by transduction (or the conversion of sound waves into electrochemical impulses) and maintains the sense of balance.

Complete answer: human ear contains sense organs that serve two quite different functions: that of hearing which of postural equilibrium and coordination of head and eye movements. Anatomically, the ear has three distinguishable parts: the outer, middle, and internal ear. The external organ consists of the visible portion called the auricle, or pinna, which projects from the side of the top, and also the short external auditory meatus, the inner end of which is closed by the eardrum, commonly called the eardrum. The function of the external ear is to gather sound waves and guide them to the membrane. The center ear could be a narrow air-filled cavity within the os temporale. It's spanned by a sequence of three tiny bones—the malleus (hammer), incus (anvil), and stapes (stirrup), collectively called the auditory ossicles. This ossicular chain conducts sound from the tissue layer to the labyrinth. The internal ear consists of two functional units: the sensory system, consisting of the vestibule and semicircular canals, which contains the sensory organs of postural equilibrium; and therefore the snail-shell-like cochlea, which contains the sensory organ of hearing. These sensory organs are highly specialized endings of the eighth nerve, also called the acoustic nerve.

External or external ear, consisting of:
1. Pinna or auricle. This is often the surface of a part of the ear.
2. External auditory meatus or tube. This is often the tube that connects the external organ to the within or tympanum.
3. Tympanic membrane (eardrum). The tissue layer divides the external organ from the center ear.
 4. Middle ear (tympanic cavity), consisting of: ossicles. Three small bones that are connected and transmit the sound waves to the sensory receptor. The bones are called: Malleus, incus and stapes

Inner ear, consisting of:
- cochlea. This contains the nerves for hearing.
- vestibule. This contains receptors for balance.
- semicircular canals. This contains receptors for balance.
The middle ear lies within the os temporale, and extends from the tympanum to the lateral wall of the internal ear. The most function of the center ear is to transmit vibrations from the tympanum to the sensory receptor via the auditory ossicles.

The tympanum separates the external organ from the center ear and is created initially from the primary pharyngeal arch membrane. The center ear bones (ossicles) are derived from separate origins within the first and second arch mesenchyme. The space within which these bones sit (tympanic cavity) springs from the primary pharyngeal pouch and is connected on to the rima by a hollow tube (auditory tube). Additionally there are two muscles (tensor tympani and stapedius) formed from arch mesenchyme.

The middle ear may be divided into two parts:
- Tympanic cavity – located medially to the membrane. It contains three small bones referred to as the auditory ossicles: the malleus, incus and stapes. They transmit sound vibrations through the center ear.
- Epitympanic recess – an area superior to the tympanum, which lies next to the mastoid air cells. The malleus and incus partially extend upwards into the epitympanic recess.

The bones of the center ear are the auditory ossicles – the malleus, incus and stapes. They're connected in a very chain-like manner, linking the eardrum to the fenestra vestibuli of the interior ear. Sound vibrations cause a movement within the myringa which then creates movement, or oscillation, within the auditory ossicles. This movement helps to transmit the sound waves from the myringa of outer ear to the fenestra ovalis of the interior ear.
The malleus is the largest and most lateral of the ear bones, attaching to the membrane, via the handle of malleus. The top of the malleus lies within the epitympanic recess, where it articulates with the following bonelet, the incus.


Therefore, the correct option is (C), Fenestra ovalis

Note:- Muscles: there are two muscles which serve a protective function within the middle ear; the tensor and
Stapedius. They go for response to eruption, inhibiting the vibrations of the malleus, incus and stapes, and reducing the transmission of sound to the sense organ. This action is thought because the acoustic reflex.