In the human body, we often credit specific things for being very important features in our anatomy, parts such as bones, organs and skin are commonly spoken of and reffered to as being things we cannot live without, but there is another feature of the human anatomy which some people overlook and fail to give any real recognition to, this part of the make up of the human anatomy is muscle. Without muscles our bodies would not be capable of holding up its own weight, everything in our body, bones and skin and all, would be useless without muscles.

The human shoulder has a rounded contour which is formed by the deltoid muscle. This muscle consists of three sets of fibers which are distinct although there are suggestions via electromyography that the deltoid muscle may consist of a minimum of seven groups instead, each of which can be independently controlled by the human bodys central nervous system. In earlier times, the deltoid muscle was infact called the detoideus muscle and this name is at times still in use, mainly by some anatomists. The reason the muscle is given this name is because of the shape of the muscle. The muscle is shaped like a triangle, sharing its shape with the greek letter delta. The deltoid is well known as being the common shoulder muscle as well especially when speaking of comparative anatomy such as in lower animals. Many times, when a human being is given an injection of any kind for an intra-muscular injection, a frequent place for the injection to be administered is in the deltoid muscle. On average, the deltoid muscle of a human being weighs around 191.9 grams but ranges from 84 to 366 grams in weight. The three distinct sets of fibers in regards to the deltoid muscle are the anterior fibers, middle fibers and posterior fibers. The anterior fibers travel from the anterior border and across to the upper surface of the lateral clavicle. The middle fibers are known for spanning from the lateral margin and the upper surface of the acromion. The posterior fibers are placed from the lower lip of the posterior border of the spine of the scapula located as far back as the triangular surface at its full medial ending.

Nerves.
The deltoid muscle is innervated by the axillary nerve which originates from the ventral rami of both the c5 and the c6 nerves of the spine by way of the superior trunk, the cna training classes does teach this. This nerve can become damaged from surgical and other styles of operations performed on the axilla such as those performed to treat or remove breast cancer and may also become damaged and cause injury by a person who is on crutches but is not using them correctly.

The deltoid uses all of its fibers causing them to contract in a simultaneous manner, this will cause the deltoid to make the arm abduct along the frontal plane. In order for the deltoid have the maximum possible effect the arm needs to be internally rotated. The deltoid muscle allows our arm to elevate in the scapular plane.