Final answer:
The rectus abdominis attaches at the pubic crest and symphysis and to the xiphoid process and keeps the cartilage of ribs 5-7, enclosed within the rectus sheath which is part of the abdominal aponeurosis meeting at the linea alba.
Step-by-step explanation:
The attachment site for the rectus abdominis muscle is along the pubic crest and symphysis at the lower end and attaches to the xiphoid process of the sternum and the cartilage of the 5th, 6th, and 7th ribs at the upper end. The rectus abdominis is enclosed within the rectus sheath, a fibrous sleeve of the abdominal aponeurosis, consisting of the external oblique, internal oblique, and transversus abdominis muscles' tendons.
You can think of the aponeurosis as a strong, flat sheet that acts like a tendon to connect these muscles of the abdomen with the linea alba. The linea alba is that white line you see in the middle of a toned, 'six-pack ab' stomach and is where the connective tissues from either side of the rectus abdominis meet.