Navel Structure and Biological Role in Humans

It is very well-known what a navel is. A navel is a small depression in the abdomen of placental mammals. The navel body part is also known as the belly button in common parlance. Clinically, the navel is known as umbilicus (in singular and umbilici/umbilicuses in plural). 

The navel part of the body is a protruding and flat or hollowed area present on the abdomen at the site of the umbilical cord which provides nourishment in the developing fetus. Because of this, all placental animals have a navel body part.

Umbilicus Anatomy or Navel Anatomy

The umbilicus shows the separation of the abdomen into different quadrants. It is a prominent scar that appears on the abdomen and is a remnant of the connection of the umbilical cord with the developing child. The navel body position is relatively consistent amongst humans. The skin around the navel body part at the waist is usually supplied by the tenth thoracic spinal nerve or the T10 afferent nerve. It is clearly seen in the umbilicus anatomy that it is typically located vertically, corresponding to the junction present between the L3 and L4 vertebrae with some normal variation amongst the people between the L3 and L5 vertebrae.

In an adult umbilicus anatomy parts of the navel include “umbilical tip” (or the “umbilical cord remnant”), a scar left from the detachment of the umbilical cord. This scar is usually protruding and lies at the centre of the navel and hence is described as the belly button. There is an “umbilical collar” present around the cord remnant that is formed by the dense fibrous umbilical ring. Around the umbilical collar, there is periumbilical skin. Behind the navel, there is the thick fibrous cord that is formed from the umbilical cord which is known as urachus that originates from the bladder.

Navel Types

The umbilicus anatomy is unique to each individual because it is a scar. Many different naval types have been classified by different medical practitioners. The different naval types that have been classified are as follows:

1. Outie: When the umbilical tip is protruding out of the periumbilical skin, it is known as an outie. The shape of such a navel is not concave. Such naval types are further sub-classified as given below:

• Swirly/Spiral: In this case, the navel is in the shape of a swirl and is a rare navel body form.

• Split Navel: This kind of navel is like a coffee bean, as the protruding umbilical scar is extending outward but is split into two by a fissure either in part or fully.

• Protrusion: In this type, the navel is completely and fully exposed and divulged.

• Circlet: It is of a doughnut shape because the fissure is located in the centre of the umbilical scar. The centre of the knot is inset by the deep fissure.

2. Innie: Any navel that is concave and the tip does not protrude past the periumbilical skin is known as an innie.

• Round Shape: Navels that are round and are completely circular with no hooding.

• Vertical Shape: These navels are in the form of an elongate hollow parallel with linea alba.

• Oval: There are three variants of this form that are superior hooding, inferior hooding and no hooding.

• T-Shaped: This scar is in T-shape and may have superior hooding to various extents.

• Horizontal: This type of scar is less visible because the natural lines of the fibrous band of tendinous intersection fold over the scar. 

3. Distorted: Any of the navel types that cannot be classified into either of the classes is classified under distorted. 

Images of two navel types are shown below:

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Clinical and Cultural Significance of Navel

Clinical Significance of Navel

Clinically there are umbilical diseases like umbilical hernia that occurs when umbilical scar protrudes around 5 cm in length and ½ inch diameter. Another rare disorder involving the navel is the umbilical sinus which can lead to menstrual or faecal discharge. Other conditions involve inflammatory conditions of the umbilicus in newborn babies that may be caused because of bacterial infection. Many times to minimize scarring, the navel is the recommended choice for incision site in various surgeries such as transgastric appendectomy, gallbladder surgery, and umbilicoplasty.

Cultural Significance of Navel

There are varying levels of importance of navel in different cultures sometimes ranging on extreme ends. On one hand, the Western World had always emphasized keeping the navel and midriff hidden and considered a taboo, while on the other hand, in countries in the Eastern World, like India the exposure of the navel had been a common practice, especially for women when they wore sarees or lehengas. But in modern times, the culture of navel exposure has gained a significant level of prominence among both males and females all over the world. Along with the exposure of the navel and the midriff, the piercing of the navel has also gained wide popularity across the world. Exposure and piercing of the navel function as a fashion statement amongst the youth and older ages as well. It has been a centre in the art world as well an example of which is the belly-dancing form popular in Arabic-Levantine culture.

Apart from such cultural popularity, navel has found spiritual importance and a place of importance in some religions as well. In Japanese culture, the navel has always had a special place as they have believed for long that the navel symbolized the centre of the starting of life. In Buddhism, the navel refers to the third chakra or the Manipura. In Qigong culture, the navel is seen as the main energy centre. In Hinduism, the Kundalini energy is said to be located at the navel.