In human anatomy

Human anatomy

Human anatomy is primarily the scientific study of the morphology of the human body. Anatomy is subdivided into gross anatomy and microscopic anatomy. Gross anatomy is the study of anatomical structures that can be seen by the naked eye...

, the deltoid tuberosity is a rough, triangular area on the anterolateral (exterior-front) surface of the middle of the humerus

Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....

 to which the deltoid muscle

Deltoid muscle

In human anatomy, the deltoid muscle is the muscle forming the rounded contour of the shoulder. Anatomically, it appears to be made up of three distinct sets of fibers though electromyography suggests that it consists of at least seven groups that can be independently coordinated by the central...

 attaches.

Development

The deltoid tuberosity develops through endochondral ossification

Endochondral ossification

Endochondral ossification is one of the two essential processes during fetal development of the mammalian skeletal system by which bone tissue is created. Unlike intramembranous ossification, which is the other process by which bone tissue is created, cartilage is present during endochondral...

 in a two-phase process. The initiating signal is tendon-dependent, whilst the growth phase is muscle-dependent.

Evolutionary variation

In mammals, the humerus displays a wide morphological

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

 variation. The size and orientation of its functionally important features, including the deltoid tubercle, greater tubercle

Greater tubercle

The greater tubercle of the humerus is situated lateral to the head of the humerus and posteriolateral to the lesser tubercle.Its upper surface is rounded and marked by three flat impressions....

, and medial epicondyle

Medial epicondyle of the humerus

The medial epicondyle of the humerus, larger and more prominent than the lateral epicondyle, is directed a little backward. In birds, where the arm is somewhat rotated compared to other tetrapods, it is called ventral epicondyle of the humerus....

, are pivotal to an animal's style of locomotion and habitat. In cursorial

Cursorial

Cursorial is a biological term that describes an organism as being adapted specifically to run. It is typically used in conjunction with an animal's feeding habits or another important adaptation. For example, a horse can be considered a "cursorial grazer", while a wolf may be considered a...

 (running) animals such as the Pronghorn Antelope

Pronghorn

The pronghorn is a species of artiodactyl mammal endemic to interior western and central North America. Though not an antelope, it is often known colloquially in North America as the prong buck, pronghorn antelope, or simply antelope, as it closely resembles the true antelopes of the Old World and...

, the deltoid tubercle is located about a quarter of the way down the shaft, which allows for rapid but relatively weak limb flexion and extension. In natatorial (swimming) animals such as the North American River Otter, the tubercle is located nearly half way down the shaft, which allows for powerful limb flexion and extension. The tuberosity can be very pronounced in fossorial

Fossorial

A fossorial organism is one that is adapted to digging and life underground such as the badger, the naked mole rat, and the mole salamanders Ambystomatidae...

 (digging) animals, such as the Mountain Beaver

Mountain Beaver

The Mountain Beaver is the most primitive extant rodent. Not to be confused with the North American beaver Castor canadensis, or its relative the Eurasian beaver, Castor fiber, it has several common names including Aplodontia, Boomer, Ground Bear, and Giant Mole...

.