[Biology Class Notes] on Abdominal Muscle Pdf

The abdomen is the region between the levis and the thorax in all vertebrates including human beings. Space that contains the abdomen is called the abdominal cavity. The abdomen is the front portion of the trunk’s abdominal segment. The abdominal cavity is the region that the liver occupies. The abdomen is the posterior tagma of the body of arthropods, and it follows the thorax or cephalothorax. The abdomen is also known as the stomach, tummy, or midriff. 

The abdominal cavity borders are composed of the posterior peritoneal surface, the anterior abdominal wall, the inferior pelvic inlet, and the superior thoracic diaphragm. The abdomen helps in containing the essential organs and also provides the muscles which are very essential for maintaining a perfect body posture, balance in the body, and also breathing. there are muscles in the abdomen that are actually responsible for all the functions in the abdomen. These muscles are complex and are very important. 

In this article, we are going to completely discuss the abdominal muscles, all the layers, and also a few frequently asked questions will also be answered.

About the Abdominal Muscles

The abdominal muscles mainly consist of three distinct layers which reside within the abdominal wall and extend to the pubis, iliac, lower ribs, and vertebral column. At the point known as the linea alba, the muscle fibres merged at this point after they merge at the midline and then surround the rectus abdominus. To add strength, the abdominal muscle fibres crisscross each other within the transverse abdominal muscle which extends horizontally forward and the internal and the external obliques running upward and downward respectively towards the front. 

The diagram given below has listed out all the abdominal muscles.

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The four main types of abdominal muscle groups that combine together to cover all the internal organs in the abdomen are given below. 

• Rectus Abdominis: The muscle which comprises the rectus abdominis is long and flat and also has three tendinous intersections crossing over the muscle. These are the well-known and the most prominent abdominal muscles. It is a long, flat muscle that extends vertically between the pubis and the fifth, sixth, and seventh ribs. There are three muscles that form a lateral abdominal wall that encloses the rectus abdominis in health. The rectus abdominis muscles begin at the pubis bone, line the sides of the linea alba, and then attach to the lower ribs. The xiphoid process which is a bony landmark at the bottom of the sternum connects the rectus abdominis. The rectus abdominis helps to flex the spinal column by narrowing the space between the pelvis and the ribs. These muscles also get activated during the side bending motions and help in stabilizing the trunk during movements that involve the extremities and the head. 

• Transverse Abdominis: The deepest layer of the abdominal muscles is called the transversus abdominis. The transverse abdominal muscles are known to be flat, triangulate in shape, and are composed of the horizontal fibres that are usually situated between the internal oblique and transverse fascia. The transverse abdominal muscle is known to be wrapped around the torso, from the front to the back and then from the ribs to the pelvis. The muscles in the transverse abdominis are known to run horizontally which is similar to a corset or the weight belt. The transverse abdominal muscles are attached to the inner lip of the ilium, the lumbar fascia, and the inner surface of the cartilage on the six lower ribs. The transverse abdominal muscle meets the linea alba behind the rectus abdominis. The transverse abdominal muscle, does not, in any way help in moving the spine or the pelvis but it does help in respiration and breathing. These muscles are known to facilitate a forceful expiration of the air from the lungs, stabilization of the spins, and also help to compress the internal organs. It also helps in compressing the abdomen and provides support to the abdominal wall. 

• External Oblique: The external oblique muscles are the pair of muscles that are located on each side of the rectus abdominis. The muscle fibres of the external obliques are known to run diagonally downward and inward from the lower ribs to the pelvis region which in turn forms the letter V. The external oblique muscles are found on each side of the rectus abdominis. The external oblique, muscles make it possible for the trunk to twist, but to the opposite side of whichever external oblique is contracting. For example, to turn the body to the left, the right external oblique contracts. The external obliques usually originate at the fifth to the twelfth ribs and then insert into the iliac crest. The main function of the external oblique muscle is that they allow flexion of the spine, rotation of the torso, sideways bending, and compression of the abdomen. 

• Internal Oblique Muscles: These are a pair of deep muscles that are just below the external oblique muscles. The external oblique and the internal oblique muscles are at the right angle to each other. Internal obliques attach the lower three ribs to the linea alba, the inguinal ligament to the iliac crest, and the lower back (thoracolumbar fascia). Internal obliques lower muscle fibres extend almost horizontally. The internal obliques work with the external obliques to stretch the spinal column, bend horizontally, rotate the trunk, and compress the abdomen. The internal and external obliques are known as opposite-side rotators because of their unusual orientation at right angles to each other. The external oblique on the left rotates the trunk/spine to the right, while the internal oblique on the left rotates the trunk/spine to the left.

Core Muscles 

• The core could be considered as the strong column that helps in linking the upper body and the lower body together. Having a strong core is very important as it helps in creating a foundation for all the activities. The abdominal and the back work together to support the spine when we sit, stand, bend over, or pick things up. The core muscles in the human body are the muscles that are rooted deep within the abdominal and the back, attaching to the spine or the pelvis. Transversus abdominis, the muscles of the pelvic floor, and the oblique muscles are some of these muscles that are included in the core muscles. 

• Another important core muscle that is involved in moving the trunk is the multifidus. This is considered to be a deep back muscle that runs along the spine of our body. It usually works together with the transversus abdominis to increase spinal stability and to protect against back injury or any kind of strain during movement or normal posture. 

Effective Abdominal Workouts

• After having a basic understanding of all the abdominal muscles, it is important to know the important stomach muscles exercises that are designed
  so that all the muscles in the abdomen are targeted. 

• Whenever a person decides to add some abdominal exercises to his or her exercise program, it is very important to be very careful about the type of exercises to be chosen as those exercises could either benefit that person or can cause muscle strains. A qualified fitness instructor can usually help a person to develop a safer, more effective program. 

• Add on exercises that will help in training the core ab muscles, rather than just the traditional crunches that usually target separate muscles. Pilates is one of the most effective abdominal muscle exercises. Pilates is usually used by the dancers for deep body conditions and improvement from an injury. A stability ball, swiss ball, football, or exercise ball is an extra-large, inflatable ball that is mainly used to improve balance while targeting specific muscle groups. The exercise balls could be used in various ways such as to improve the balance in the body, stability and to increase the torso strength. 

• Isometric exercises such as the planks and the bird dog can also be done as they focus on limiting the trunk movement and are great abdominal exercises. The abdominal crunch can also help in improving the abdominal core strength. 

The Muscle Action 

• The abdominal muscles have different muscle fibre orientations that usually act in three planes during the movements. These are linked together by having either a common site of connection or by lying fascia. When one muscle contracts the other muscle will also contract. 

• Our body is mainly designed to move and the muscles mainly help in achieving this goal of moving our body from one place to another. The muscles in our body usually work together to control the movement of the spine, pelvis, and rib cage and during the gait cycle, there is a counter-rotation between the upper and the lower part, and the arm and the leg are moving in the opposite direction to each other. 

• During regular gait, the rectus abdominis and external obliques on one side function eccentrically to decelerate the anterior pelvic tilting caused by that side’s hip extension, while the RA and external obliques on the other side operate eccentrically to regulate the thoracic extension and rotation caused by the shoulder extension.