Development of the human external ear


Human embryo stages


External ear development is a lengthy snd complex precess that extends from early embryogenic life until well into the postnatal period. Initial development of the auricle and external auditory canal during the fourth and fifth weeks of gestation is closely associated with anotomycal changes involving the pharingeal arch apparatus of the human embryo. The auricle and external canal are well formed by the time of birth but do not attaintheir full size and adult configuration until about 9 years of age. Sebaceous and modified apocrine glands, which are responsible for cerumen production, begin their development at about 5 months gestation in association with hair follicles in the outer portion of the external canal. Although they appear anatomically mature before birth, these glands do not reach full fuctional capacity until puberty.

As emphasized throughout this special issue, the external ear plays an essential role in auditory function and occupies an important place in the clinical practice in audiology and otology. Its major component, the auricle and external auditory canal, receive sound energy from the environtment and provide some degree of directional and frequency selectivity for the incoming sound and stimulus. They also serve to protect the tympanic membrane from mechanical injury and from abrupt changes in temperature and humidity. Various abnormalities affecting the external ear, particularly those involving congenital defects, are best understood from a developmental perspective.

External ear development is a process that begins in embryonic life, progresses through the fetal period to the time of birth, and continoues postnatally until the age of puberty, when the glands of the external canal become fully functional. (As ussually defined, the embryonic phase of human development extends from 2 weeks gestational age up to the seventh or eight week, while the fetal period is the interval from about 8 weeks gestation to term).

The embryonioc pharingeal arch apparatus provide the structural foundation for formation of the external ear.  The pharingeal arches are conspicious external feature of the human embryo and are significantly involved in various aspects of head and neck development.

By the end of the forth week of gestation, four well-defined pairs of pharingeal arches are externally visible in the neck region of the human embryo. The first two of these, the mandibular and hyoid arches, are important contributors to external ear development. During the fifth gestational week, nodular swellings of tissue known as the hillocks of his appear on the first and second pharingeal arches. Six such hillocks , three on either side of the first pharingeal cleft, can be distinguished. Most investigators believe that the auricle is formed by growth, differentiation and fusion of these six tissue condensation. During the initial stages of its development, the auricleis located in the general area of the neck, behind the lower jaw, but by the 20th week of gestation it has moved upward to attain its adult location and overal configuration. In a 4-5 years old child, the auricle is about 80 percent adult size. It reaches full adult size by approximately 9 years of age.




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24 Responses to Development of the human external ear

  1. Pingback: Development of the human external ear | MEDICINE FOR ALL

  2. lorieb says:

    In my job in the pathology department of a hospital, I performed mini autopsies on aborted/miscarried fetuses. It always amazed me how anatomically complicated they were. The only thing that seemed out of place was the ears, as they were always lower on the neck than expected. This article explains it well!

    Liked by 4 people

    • azaleaazelia says:

      I am glad to hear that.

      Liked by 1 person

    • da-AL says:

      interesting to know, loreib – interesting post, azaleaazelia 🙂

      Liked by 2 people

    • When I was a pathology resident and saw how human a tiny fetus looks, I immediately changed my mind on whether they were people or “non-people” with no innate human rights. It had nothing to do with politics for me. Still doesn’t. 🙂

      Liked by 3 people

      • lorieb says:

        agreed! isn’t it amazing how perfectly they are formed so early? Anti-abortion groups should use this fact (pictures)

        Liked by 2 people

      • The more I learn about genetics, the more convinced I am that life is a “miracle” beyond our wildest imagination. The DNA code really seems to have been written by an intelligent mind. I’ve tried, and to a great extent succeeded in giving up believing that modern US politics provides a useful tool, because our political divide seems to promote black-and-white thinking which I believe is humanity’s most self-destructive tendency. But I do reject the “scientific” notion that right and wrong are always relative issues (that nothing is ever absolute). And it’s true, a fetus is perfectly formed and beautiful in a way words can’t describe. A person has to see one and hold it in her/his hands to know the feeling that a human fetus conveys. It’s a way of knowing that flies under the radar of science.

        Liked by 4 people

      • lorieb says:

        seeing is believing! In my work as a pathologist assistant I learned so much more from seeing cases (specimens) than reading about them

        Liked by 2 people

      • Same here as a pathologist (no retired).

        Liked by 1 person

  3. Dreamtemples says:

    Thank you so much for visiting my blog!

    Liked by 1 person

  4. Maria Holm says:

    What you describe in your post reminds me so much of these verses from King David’s Psalms in the Old Testament

    Psalm 139:13 For You formed my innermost parts; You knit me together in my mother’s womb.
    verse 15: My frame was not hidden from You when I was being formed in secret, and intricately and skillfully formed as if embroidered in the depth of the earth.
    Thank you so much for this post
    P.S. One of my boys asked me many years ago: ” How did God knit me”? He was three years old

    Liked by 4 people

  5. divesh9022 says:

    An informative one …keep going on

    Liked by 3 people

  6. tref says:

    I knew a kid in school who had abnormally large ears. He didn’t have super-hearing, & he couldn’t fly, so far as we knew. He couldn’t even comically wiggle them without assistance. I guess my disillusionment over his lack of abilities is why, deep down, I knew otolaryngology was not for me.

    Liked by 3 people

  7. floatinggold says:

    The amount of in-depth interesting knowledge is astounding!

    Liked by 1 person

  8. I just take them for granted – didn’t know there was so much to it.

    Liked by 2 people

  9. Shimky says:

    A fascinating read.

    I have tinnitus – quite bad – so I’m hoping for a breakthrough in that area one day.

    Liked by 1 person

  10. Interesting post and informative too for a layman…..

    Liked by 1 person

  11. Fascinating for me as a musician and singer. The ear is so important. Lovely visit.

    Liked by 2 people

  12. I love that picture of the unborn baby (fetus). Thank you.

    Liked by 2 people

  13. granonine says:

    After seeing you read post after post of mine, I finally got around to checking out your blog. Wow! You are so knowledgeable! I am fascinated by what I’ve seen in just a few minutes of scanning titles. Sorry I didn’t get here sooner, but I followed you, so you’ll be in my Reader from now on 🙂

    Liked by 1 person

  14. 76sanfermo says:

    Astounding post. Thank you!

    Liked by 1 person

  15. zatahashura says:

    thank you for your is very important to improve our knowledge.

    Liked by 1 person

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