Milk bar

The milk ridge is a strip-like thickening of the epidermis that occurs in mammals of both sexes during embryonic development and extends on both sides of the trunk from the attachment of the front legs to that of the rear legs. The mammary gland arises from it .

The milk bar in humans

In humans, the milk bar develops in the seventh week of embryonic development and recedes shortly afterwards, with the exception of a small part in the breast region. The remaining part of the epithelium sprouts into the underlying mesenchyme and forms 16 to 24 branches, which are transformed into the milk ducts at the end of intrauterine life .

Schematic representation of the human milk ridges loco typico

Only after the birth is the milk pit , into which the milk ducts open, lifted up, as the underlying tissue increases and thus the nipple forms.

The milk bar in animals

Similar processes lead to the development of udders and teats in animals . The sequence of teats in small mammals is known as the teat bar .

Malformations

Polythelia - extra nipple under the left female breast

Only partial regression of the milk bar can lead to additional nipples (accessory nipples ). In medical terminology, this is known as polythelia . The excess nipples (running in the teat line in mammals) are congenital malformations that occur in women and men and usually occur on one side. Normally they have no disease value, but can be removed for cosmetic reasons.

It is even more seldom that the remaining tissue of the milk ridge develops into a complete additional mammary gland - a mammary accessory . This appearance is known as polymastia .

If there is no increase in the mesenchymal tissue under the milk pit, a inverted nipple develops .

Trivia

In the James Bond film The Man with the Golden Gun , Bond's opponent Scaramanga has a third nipple, which is at the same time his distinguishing mark. Pop singer Lily Allen presented her third nipple on a TV show in 2009.

Individual evidence

1. ^ Klaus Holldack, Klaus Gahl: Auscultation and percussion. Inspection and palpation. Thieme, Stuttgart 1955; 10th, revised edition, ibid 1986, ISBN 3-13-352410-0 , p. 59.
2. ↑ Lily shows her third nipple! Blick.ch, January 17, 2009, accessed on February 24, 2014 .