The human mouth (or oral cavity) is covered by an upper and lower lip.
The mouth starts digestion by physically chewing the food and breaking it down with saliva.
The average male mouth holds a volume of about 100mL.
According to general etiquette, the mouth is kept closed, especially when chewing.
Piercings have been made popular by the younger generations. Lip, tongue, and the 'Monroe' (Monroe piercing is a stud piercing placed on one's face in the same area as Marilyn Monroe's well known and prominent birthmark was) are piercings seen in many varieties. Piercings of any sort besides two subtle earrings are seen as rebellious to the norm in many western cultures.
The philtrum is the vertical groove in the upper lip, formed where the nasomedial and maxillary processes meet during embryo development. When these processes fail to fuse fully, a hare lip and/or cleft palate can result.
The nasolabial folds are the deep creases of tissue that extend from the nose to the sides of the mouth. One of the first signs of age on the human face is the increase in prominence of the nasolabial folds.
Sagittal section of nose mouth, pharynx, and larynx.