Are there muscles in the abdomen

The change in volume of the thoracic cavity during breathing is due to the alternate contraction and relaxation of the diaphragm Figure It separates the thoracic and abdominal cavities, and is dome-shaped at rest. The superior surface of the diaphragm is convex, creating the elevated floor of the thoracic cavity. The inferior surface is concave, creating the curved roof of the abdominal cavity. You hold your breath by a steady contraction of the diaphragm; this stabilizes the volume and pressure of the peritoneal cavity.

When the abdominal muscles contract, the pressure cannot push the diaphragm up, so it increases pressure on the intestinal tract defecation , urinary tract urination , or reproductive tract childbirth. The inferior surface of the pericardial sac and the inferior surfaces of the pleural membranes parietal pleura fuse onto the central tendon of the diaphragm. To the sides of the tendon are the skeletal muscle portions of the diaphragm, which insert into the tendon while having a number of origins including the xiphoid process of the sternum anteriorly, the inferior six ribs and their cartilages laterally, and the lumbar vertebrae and 12th ribs posteriorly.

The diaphragm also includes three openings for the passage of structures between the thorax and the abdomen. The inferior vena cava passes through the caval opening , and the esophagus and attached nerves pass through the esophageal hiatus. The aorta, thoracic duct, and azygous vein pass through the aortic hiatus of the posterior diaphragm. There are three sets of muscles, called intercostal muscles , which span each of the intercostal spaces.

The principal role of the intercostal muscles is to assist in breathing by changing the dimensions of the rib cage Figure The 11 pairs of superficial external intercostal muscles aid in inspiration of air during breathing because when they contract, they raise the rib cage, which expands it.

The 11 pairs of internal intercostal muscles, just under the externals, are used for expiration because they draw the ribs together to constrict the rib cage. The innermost intercostal muscles are the deepest, and they act as synergists for the action of the internal intercostals.

The pelvic floor is a muscular sheet that defines the inferior portion of the pelvic cavity. The pelvic diaphragm , spanning anteriorly to posteriorly from the pubis to the coccyx, comprises the levator ani and the ischiococcygeus. Its openings include the anal canal and urethra, and the vagina in women.

The large levator ani consists of two skeletal muscles, the pubococcygeus and the iliococcygeus Figure The levator ani is considered the most important muscle of the pelvic floor because it supports the pelvic viscera. It resists the pressure produced by contraction of the abdominal muscles so that the pressure is applied to the colon to aid in defecation and to the uterus to aid in childbirth assisted by the ischiococcygeus , which pulls the coccyx anteriorly.

The supraspinatus muscle is a rotator cuff muscle located in the shoulder, specifically in the supraspinatus fossa, a concave depression in the rear…. The quadratus plantae is a muscle in the foot that extends from the anterior front of the calcaneus heel bone to the tendons of the digitorum….

The depressor labii inferioris muscle is a four-sided facial muscle located in the jaw area that draws the lower lip down and to the side. The muscles of the face give it general form and contour, help you outwardly express your feelings, and enable you to chew your food. The quadriceps femoris is a group of muscles located in the front of the thigh.

The Latin translation of 'quadriceps' is 'four headed,' as the group…. The palmaris brevis muscle lies just underneath the skin. It is a short muscle on the flat of the hand. The muscle begins at the flexor retinaculum in….

The movement of the upper arm and shoulder is controlled by a group of four muscles that make up the rotator cuff. The largest and strongest muscle in…. The extensor pollicis longus muscle begins at the ulna and the interosseous membrane, a tough fibrous tissue that connects the ulna and the radius in…. The biceps brachii, sometimes known simply as the biceps, is a skeletal muscle that is involved in the movement of the elbow and shoulder.

It is a…. The skeletal system is the foundation of your body, giving it structure and allowing for movement. Health Conditions Discover Plan Connect.

Read this next. Supraspinatus Medically reviewed by the Healthline Medical Network. The palmaris brevis muscle lies just underneath the skin. It is a short muscle on the flat of the hand. The muscle begins at the flexor retinaculum in…. The movement of the upper arm and shoulder is controlled by a group of four muscles that make up the rotator cuff. The largest and strongest muscle in…. The extensor pollicis longus muscle begins at the ulna and the interosseous membrane, a tough fibrous tissue that connects the ulna and the radius in….

The biceps brachii, sometimes known simply as the biceps, is a skeletal muscle that is involved in the movement of the elbow and shoulder. It is a…. The skeletal system is the foundation of your body, giving it structure and allowing for movement. Health Conditions Discover Plan Connect. Read this next.

Supraspinatus Medically reviewed by the Healthline Medical Network. Quadratus plantae Medically reviewed by the Healthline Medical Network. Depressor labii inferioris Medically reviewed by the Healthline Medical Network. Quadriceps femoris Medically reviewed by the Healthline Medical Network. Palmaris brevis Medically reviewed by the Healthline Medical Network.