The serratus anterior pron. Each of these elongated muscle strips attaches on a separate rib, beginning with the first rib, and wraps around the side of the rib cage to insert into the medial inner border of the scapula. The serratus anterior is mostly hidden by the pectoralis major and the latissimus dorsi muscles, but the lower three or four digitations can be visible on the surface, appearing as small, riblike forms between the outer edge of the pectoralis major and the outer edge of the latissimus dorsi.
The main actions of the serratus anterior are the protraction and upward rotation of the scapula. Protraction of the scapula is the action of moving the scapula in a forward direction and occurs when the arm is reaching forward in front of the torso, as shown in the following drawing.
Upward rotation is the tilting the scapula in a upward direction and occurs when the arm is raised overhead. Between the rich outer edge of the latissimus dorsi and pectoralis major appear some small riblike forms that are the partly exposed shapes of the serratus anterior. Occupying the anterior and lateral regions of the abdominal area of the torso are three layers of muscles: The superficial muscle layer contains the external oblique and rectus abdominis—the two abdominal muscles seen on the surface form.
The intermediate layer contains the internal oblique, and the deep layer contains the transversus abdominis. The abdominal muscle group helps move the vertebral column and rib cage in the actions of forward bending flexion , side bending lateral flexion and rotation, as well as causing the compression of the abdominal wall. Muscles belonging to each of the layers are shown in the following drawing. Three abdominal muscles—the transversus abdominis, internal oblique, and external oblique—are layered atop each other on the lateral region of the lower torso; their muscle fibers run in different directions, producing a twisting or swiveling action of the torso when these muscles contract.
Each of these muscles has its own large tendinous sheathing that continues across the abdomen to attach into the linea alba—a fibrous vertical form that attaches from the base of the sternum to the pubic bone of the pelvis. The layered sheathings act as a fibrous sleeve in which the rectus abdominis muscle located in the anterior region of the lower torso is encased.
When the anterior front layer of this sheath is removed, the rectus abdominis muscle is exposed to reveal its eight muscle segments. The various layers of sheathing of the abdomen have different names, which can cause confusion when studying this region. Adding to the potential difficulty, the anterior layer positioned over the rectus abdominis muscle is referred to by several names: the external oblique aponeurosis, or the rectus sheath anterior layer , or sometimes the abdominal sheathing.
The sheathing of the internal oblique is usually called the internal oblique aponeurosis, and the sheathing of the tranversus abdominis is called the rectus sheath posterior layer , because it is positioned beneath the rectus abdominis muscle. The rectus abdominis pron. Below the navel, the muscle is divided into an additional two segments more on some individuals , but a layer of fatty tissue usually softens the lower two segments into one shape.
Differences between the rectus abdominis as it appears on males and females are examined in the sidebar on this page. The rectus abdominis begins on the pubic bone and pulls straight up to attach into the xiphoid process of the sternum and the costal cartilages of the fifth, sixth, and seventh ribs. The muscle helps bend the torso forward in the movement known as the flexion of the vertebral column.
It also helps raise the body from a supine position to an upright sitting position. The pyramidalis pron. It is hard to detect on the surface form because its muscle fibers blend with those of the rectus abdominis.
The muscle begins on the pubic symphysis of the pelvis and inserts into the lower portion of the linea alba. The pyramidalis does not help move any bones. Its main function is to help tense the linea alba. Both the rectus abdominis and the pyramidalis are shown in the following drawing. The external oblique pron. The muscle consists of eight elongated muscle digitations and is divided into two portions: the thoracic portion and the abdominal portion, also called the flank pad.
The thoracic portion hugs the rib cage like a girdle and is hard to detect on the surface except in muscularly defined torsos. The individual muscle strips of the thoracic portion begin on the ribs and appear to interweave with the muscle digitations of the serratus anterior. The flank pad portion is more noticeable as a bulbous shape beginning below the waistline. At the bottom portion, its muscle fibers anchor along the upper rim of the pelvis iliac crest , slightly cascading over it near the ASIS of the pelvis.
While this is a muscle form, it is usually enhanced with a layer of fatty tissue, giving it a rounded, more prominent shape. Artists use this form as an important landmark in torso studies.
The external oblique begins on the lower eight ribs ribs 5 through 12 and inserts into the iliac crest of the pelvis, the inguinal ligament, and the aponeurosis of the external oblique and linea alba. When the external oblique contracts, it helps bend the torso in a forward direction flexion as well as sideways lateral flexion. It also helps move the torso in a twisting action rotation. The flank pad portion can stretch or compress, especially when the torso bends at the side in a dynamic way.
In the life study Male Figure with Left Hand on Hip, we see the abdominal region rectus abdominis and the external oblique , along with the pectoralis major of the thoracic group. The diagram accompanying the drawing reveals the actions of the muscles in this pose. Graphite pencil, brown ink, watercolor wash, and white chalk on toned paper. The drawings here present idealized versions of male and female torsos.
Problems with this muscle can cause everything from pain and sensations of tightness in the neck and head to a chronic runny nose and watery eyes. The pectoralis muscles, both major and minor, lie across the shoulders and chest. This large muscle group allows people to move their arms up and down and rotate their arms.
When humans breathe in deep, the pectoralis muscles help to raise up the ribs allowing even more air into the lungs. This is the muscle group that fitness enthusiasts target when they want to build a more muscular chest. The serratus anterior muscles, underneath both arms, fan from the back to the shoulders. This muscle group is responsible for allowing humans to make a punching motion, among other things. For this reason, the two serrated muscles have earned the nickname the boxer's muscle.
Two sets of intercostal muscles, internal and external, lie between the ribs that make up the ribcage. Along with the diaphragm, these muscles control breathing. The external intercostals contract the ribcage and the internal intercostals release it. These movements allow humans to breathe in and out. By contracting or releasing more, these muscles control the pace, depth, and intensity of breathing.
The muscle group commonly called abdominals, or abs, is made up of four sets of muscles, including rectus abdominis, transverse abdominis, and the internal and external obliques. The rectus abdominis allows humans to flex and extend the lower part of the torso. This set of abdominal muscles works hard when a person does crunches.
The deeper transverse abdominis muscles lie horizontally and help to stabilize and cushion the organs of the abdomen. The trunk of a statue of the nude human figure, esp. Any unfinished or fragmentary piece of work. The trunk of the human body. A truncated or unfinished thing. The human body excluding the head and limbs; trunk. A statue of the human body with the head and limbs omitted or removed. Nothing presented here is intended as a substitute for prescription medication or any other medical treatment prescribed by your doctor.
Friday, November 12th, Food Science. Health Sciences. Plant Sciences. Alchemy Center. Trunk Muscles Muscles of the Trunk. Trunk Torso. Regional Anatomy. Head Face and Neck Regions. Pelvis and Leg Regions.
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