Abdominal Wall

  The abdominal wall represents the boundaries of the abdominal cavity. The abdominal wall is split into the posterior (back), lateral (sides) and anterior (front) walls.

 

There is a common set of layers covering and forming all the walls: the deepest being the extraperitoneal fat, the parietal peritoneum, and a layer of fascia which has different names over where it covers (eg transversalis, psoas fascia).

Superficial to these, but not present in the posterior wall are the three layers of muscle, the transversus abdominis (transverse abdominal muscle), the internal (obliquus internus) and the external oblique (obliquus externus).

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Trapezius Muscle

In human anatomy, the trapezius is a large superficial muscle which extends longitudinally from the occipital bone to the lower thoracic vertebrae, and laterally to the spine of the scapula (shoulder blade).

 

The trapezius has three functional regions: The superior region (descending part) supports the weight of the upper limb. The intermediate region (transverse part) retracts the scapulae. The inferior region (ascending part) medially rotates and depresses the scapulae.

The two trapezius muscles together resemble a trapezium, or diamond-shaped quadrilateral; the four points of the diamond are:

  -the head (at the occipital protuberance),

  -the two shoulders, and

  -the middle of the back (at the spinous process of the twelfth thoracic vertebra, T12).

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Triceps Brachii Muscle

The triceps brachii muscle (Latin for "three-headed" [muscle] of the arm) is the large muscle on the back of the human upper limb. It is the muscle principally responsible for extension of the elbow joint (i.e. straightening of the arm).

Though a similarly-named muscle, the triceps surae, is found on the lower leg, the triceps brachii is commonly called simply the "triceps".

The three heads have the following names and origins:

* The "Long head": infraglenoid tubercle of the scapula

* The "Lateral head": posterior shaft of the humerus, lateral and superior to the radial (spiral) groove.

* The "Medial head": posterior shaft of the humerus, medial and inferior to the radial (spiral) groove.

The triceps is an extensor muscle of the elbow joint, and is an antagonist of the biceps and brachialis muscles. It can also fixate the elbow joint when the forearm and hand are used for fine movements, e.g., when writing.

The triceps accounts for approximately 60 percent of the upper arm's muscle mass.

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