The Muscles of the Thorax, Abdomen, Back, and Pelvis.

In my previous post, I decided to do the muscles of the body, and I said I was going to be doing it simply stupidly (not in that light, I meant it will be simple to comprehend), and I made sure it was. We aren't done with the series on muscles and as I said, I will still try to keep it very simple. Today, I will be discussing the thoracic musclses, the abdominal muscles, the back, and the muscles of the pelvis. So let's begin without any ado.

In the body, there are muscles that perform the same action and function even when they are not the same, these are known as synergists, and there are also muscles that work against one another, in a way that if one is working to constrict the muscle, the other is working to relax the muscles, they are known as antagonists and a lot of muscles oppose one another while other complement one another. I will be continuing with the pectoralis major which has functions that icnclude flexing of the arm and shoulder joint, adducting the arm inwards and medially rotating the shoulder. The Coracobrachialis also does the same thing with thee pectoralis major. Also, the latissimus dorsi also adductss the forearm which is what the pectoralis major does. Antagonists muscles to the function of the Pectoralis major, coracobrachialis, and the Latissimus dorsi are the deltoid muscle, and the supraspinatus muscle that abducts the shoulder. ,,,. Also in the thorax is the external intercostal muscle and the internal intercostal muscles, where the external intercostal muscles elevate and extend the sternum. They pull the rib upwards for inhalation while the internal intercostal muscles depress the ribs for a forced exhalation.,. In the thorax is the serratus anterior which is responsible in protracting the scapula. The pectoralis minor is a synergist muscle to the serratus anterior, protracting the scapula inserting the coracoid process of the scapula, while antagonist muscles that retract the scapula are the Rhomboids major and the Rhomboids minor, and the trapezius muscle. ,,. Under the clavicle is the subclavius muscle which depresses the clavicle and it is innervated by the Subclavian nerve.

In the abdominal wall, we have both the superficial and the deep muscles. The superficial muscles include the external oblique muscles which flex the vertebral column and compress the content of the abdomen increasing the intra-abdominal pressure during forced exhalation. The [internal oblique muscle(https://www.kenhub.com/en/library/anatomy/internal-abdominal-oblique-muscle) is another superficial muscle in the abdommenthat flexes the vertebral column and assists in forced exhalation, just like the external oblique muscle. In the abdominal region is the rectus abdominis which is the muscle we refer to as the six-pack muscle which does the function of flexing the vertebral column and compressiing the abdomen, thereby increasing the intra-abdominal pressure during exhalation. Also, the transverse abdominis is another muscle in the abdominal region which compresses the content of the abdomen to increase the intra-abdominal pressure during forced exhalation. In the abdomen is also the Linea Alba which is a connective tissue in the middle, running down and it is an aponeurosis allowing for the connection of other muscles. ,,,,.

Moving to the back, The Trapezius is a very important muscle that helps to elevate the scapula, retract the scapula and extend the neck. In the back, the infraspinatus muscle is a thick muscle that occupies the infraspinous fossa of the scapula, and it laterally rotates the shoulder joint. Another muscle that does the same thing as the infraspinatus muscle is the Teres minor which rotates the shoulder laterally and externally. While there is a Teres minor, there is also a Teres Major which performs the functions of extending the arm, adduction, and medially rotating the shoulder joint. Another back muscle is the Latissimus dorsi which is responsible for extending the arm at the shoulder joint, adducting at the shoulder joint, and medial rotation of the medial joint which is a synergy of Teres major.,,. The Rhomboid minor and Major retracts the scapula pulling it back.. In the back are also the Erector spinae which includes the spinal, the Longissimus, and iliocostalis.. These muscle helps to extend the neck and vertebral column and are antagonist to the abdominal muscles as they do the opposite of tthe abdominal muscles. Let's not forget another muscle known as the Serratus Posterior Inferior is an an accessory muscle for respiration, and it depresses the ribs. Another muscle known as the quadratus lumborum is responsible for extending the lower back, and fixates the rib from the lower back.

The muscles of the pelvis and I will begin with the bulbospongiosus muscle which in maless is responsible for expelling sperm out since it is wrapped around the bulb of the penis and the corpus spongiosum. Other muscle Ischiocavernosus, and superficial transverse perineal muscle, are responsible for maiintaining erection in the penis and the clitoris. In the urethra is the sphincter muscle which helps to evacuate the bowels when pressed. The Levator ani is another muscle set made up of the Iliococcygeus, the pubococcygeus, and the Coccygeus which are responnsiblefor supporting pelvic contents, elevating the anal canal during excretion, and to fight against gravity. ,,

We have come to the the end of this post on the muscles of the thorax, abdomen, back,, and pelvis. I am sure you enjoyed it. If you find it informative, please upvote and leavve a comment, it will encourage me more. I am not done with the muscles. While we are still in the easy aspects, we will gradually move into the more complex method of explanation but for now, this will help with a ground understanding of these muscles.

Image Reference

Image 1 || Wikimedia Commons || Posterior and Side Views of the Neck b and c

Image 2 || Wikimedia Commons || Muscles of the Abdomen Anterolateral

Image 3 || Wikimedia Commons || Muscles of the Neck Upper Back

Image 4 || Wikimedia Commons || Muscle of the Perineum