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[Origin of the human stapedius muscle]
Insights
The stapedius muscle originates from the posterior belly of the digastric muscle, not independently. This anatomical finding explains why both muscles share innervation from the facial nerve.
Area of Science:
- Anatomy
- Embryology
- Otolaryngology
Background:
- The stapedius muscle, located in the tympanic cavity, plays a role in auditory function.
- Its precise developmental origin and relationship with adjacent muscles have been a subject of anatomical inquiry.
Purpose of the Study:
- To investigate the developmental origin of the stapedius muscle (m. stapedius) in human embryos and fetuses.
- To clarify the anatomical relationship between the m. stapedius and the posterior belly of the digastric muscle (musculi digastrii posterior belly).
Main Methods:
- Histological serial sections of over 100 human embryos and fetuses (6 mm to newborn stage).
- Macro- and micropreparation of the tympanic cavity.
Main Results:
- The m. stapedius is not an independent muscle.
- It originates from muscle fascicles of the musculi digastrii posterior belly.
- These fascicles enter the tympanic cavity, pass through the stylomastoid foramen, and insert onto the neck of the malleus, forming the m. stapedius.
Conclusions:
- The stapedius muscle develops as an anterior derivative of the posterior belly of the digastric muscle.
- This shared origin explains the common innervation of both muscles by the facial nerve.
Abstract:
More than 100 human embryos and fetuses, beginning from 6 mm (25-26 days) up to newborns have been investigated by means of histological serial sections, as well as by means of macro- micropreparation of the tympanic cavity. The m. stapedius is not independent, but takes origin from muscle fasciculi of the musculi digastrii posterior belly. The latter approaches the eminence of the future mastoid process, gives a part of muscle fasciculi into the tympanic cavity; they get through the stilomastoid cleft and run to the hammer neck, forming the m. stapedius. That is why both muscles are innervated from the facial nerve.