The<unk>  (commonly known as "abs") is a paired muscle running vertically on each side of the anterior wall of the human abdomen (and in some other animals). There are two parallel muscles, separated by a band of connective tissue called the linea alba (white line).  It extends from the pubic symphysis inferiorly to the xiphisternum and lower costal cartilages superiorly.
It is contained in the<unk>  sheath.
The<unk>  is crossed by fibrous bands, three in number, which are named the tendinous inscriptions. If well-defined, the<unk>  abdominis is colloquially called a "six pack".
Rectus abdominis muscle
Transversus abdominis muscle
Abdominal internal oblique muscle
Serratus posterior superior muscle
Splenius capitis muscle
Levatores costarum muscles
Pubococcygeus muscle
Obturator internus muscle