A mucocutaneous junction, or mucocutaneous boundary, is a region of the body in which
mucosa transitions to
skin
Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.
Other animal coverings, such as the arthropod exoskeleton, have different de ...
. Mucocutaneous zones occur in animals, at the
body orifice
A body orifice is any opening in the body of an animal.
External
In a typical mammalian body such as the human body, the external body orifices are:
* The nostrils, for breathing and the associated sense of smell
* The mouth, for eating, brea ...
s.
In humans, mucocutaneous junctions are found at the
lip
The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...
s,
nostril
A nostril (or naris , plural ''nares'' ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbi ...
s,
conjunctiva
The conjunctiva is a thin mucous membrane that lines the inside of the eyelids and covers the sclera (the white of the eye). It is composed of non-keratinized, stratified squamous epithelium with goblet cells, stratified columnar epithelium ...
e,
urethra
The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra c ...
,
vagina
In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen ...
(in females),
foreskin
In male human anatomy, the foreskin, also known as the prepuce, is the double-layered fold of skin, mucosal and muscular tissue at the distal end of the human penis that covers the glans and the urinary meatus. The foreskin is attached to the ...
(in males), and
anus.
In the nostrils the mucocutaneous junction has a dense microvascular network, and shows a marked similarity to that found in the mouth, between the oral mucosa and the lips.
At a mucocutaneous junction,
epithelium transitions to
epidermis,
lamina propria transitions to
dermis, and
smooth muscle transitions to
skeletal muscle. A mucocutaneous junction is often the site of an arterial
anastomosis, a watershed area of venous and lymphatic drainage, and sensory (but not motor) nerve overlap.
Winkelmann (1959) documented that the mucocutaneous boundary is a "specific erogenous zone with rete ridges where the nerve endings rise closer to the surface".
References
Histology
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