The linea alba is a fibrous structure that runs down the midline of the abdomen

Abdomen

In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...

 in humans and other vertebrates. The name means white line and the linea alba is indeed white, being composed mostly of collagen connective tissue.

It is formed by the fusion of the aponeuroses of the abdominal muscles, and it separates the left and right rectus abdominis muscle

Rectus abdominis muscle

The rectus abdominis muscle, also known as the "six pack", is a paired muscle running vertically on each side of the anterior wall of the human abdomen . There are two parallel muscles, separated by a midline band of connective tissue called the linea alba...

s. In muscular individuals its presence can be seen on the skin, forming the depression between the left and right halves of a "six pack

Rectus abdominis muscle

The rectus abdominis muscle, also known as the "six pack", is a paired muscle running vertically on each side of the anterior wall of the human abdomen . There are two parallel muscles, separated by a midline band of connective tissue called the linea alba...

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Because it consists of only connective tissue

Connective tissue

"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...

, and doesn't contain important nerve

Nerve

A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

s or blood vessel

Blood vessel

The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...

s, a median incision through the linea alba is a common surgical

Surgery

Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...

approach.