The coracoid process (from

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

κόραξ, raven) is a small hook-like structure on the lateral edge of the superior anterior portion of the

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...

(hence: coracoid, or "like a raven's beak"). Pointing laterally forward, it, together with the acromion, serves to stabilize the shoulder joint. It is palpable in the deltopectoral groove between the

deltoid Deltoid (delta-shaped) can refer to: * The deltoid muscle, a muscle in the shoulder * Kite (geometry), also known as a deltoid, a type of quadrilateral * A deltoid curve, a three-cusped hypocycloid * A leaf shape * The deltoid tuberosity, a part of ...

and

pectoralis major muscle The pectoralis major () is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor ...

Structure

The coracoid process is a thick curved process attached by a broad base to the upper part of the

neck of the scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eith ...

; it runs at first upward and medialward; then, becoming smaller, it changes its direction, and projects forward and lateralward. Anatomically it is divided into intervals of: base of coracoid process, angle of coracoid process, shaft and the apex of the coracoid process. The coracoglenoid notch is an indentation localized between the coracoid process and the glenoid. As the coracoid process projects laterally, it house underneath it the subcoracoid space. The ''ascending portion'', flattened from the frontal aspect backward, presents in front a smooth concave surface, across which the subscapularis passes. The ''horizontal portion'' appears flattened when viewed from above looking downward; its upper surface is convex and irregular, and gives attachment to the pectoralis minor; its under surface is smooth; its medial and lateral borders are rough; the former gives attachment to the pectoralis minor and the latter to the coracoacromial ligament; the apex is embraced by the Conjoint tendon of origin of the coracobrachialis and short head of the biceps brachii and gives attachment to the coracoclavicular fascia. On the medial part of the root of the coracoid process is a rough impression for the attachment of the conoid ligament; and running from it obliquely forward and lateralward, on to the upper surface of the horizontal portion, is an elevated ridge for the attachment of the trapezoid ligament. The coracoid process is a snare molded bone design projecting anterolaterally from the unrivaled part of the scapular neck. Surgeons refer to this part of the body as the “lighthouse of the shoulder” as it is close to the area where structures of veins and nerves (neurovascular) are bound together. The distances between the coracoid base and the neurovascular structures is like a 90 degree chair. The suprascapular ligament is right next to the coracoid process. The muscles that are attached are: Pectoralis Minor, Coracobrachialis, and Biceps Brachii. In addition, this structure attaches all the tendons and ligaments together. There are two purposes for this structure: it is the primary hold by which the clavicle is joined to the scapula and alongside the acromion and coraco-acromial tendon, it shapes the curve over the glenoid. By having the coracoid process, this allows the scapula to not be attached to the skeletons by the bone so that it can only support the limbs. Although there are minor instances where the coracoid process can be damaged by itself, there can still be damage to the structure with an acute subscapularis tear. Usually a disruption in the coracoid process can indicate a shoulder injury such as dislocation and instability.

Function

It is the site of attachment for several structures: * The

pectoralis minor muscle Pectoralis minor muscle () is a thin, triangular muscle, situated at the upper part of the chest, beneath the pectoralis major in the human body. Structure Attachments Pectoralis minor muscle arises from the upper margins and outer surface ...

– to 3rd, 4th, 5th and on some rare occasions, 6th rib. * The short head of biceps brachii muscle – to radial tuberosity. * The coracobrachialis muscle – to medial

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

. * The coracoclavicular ligament – to the

clavicle The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the rig ...

. (The ligament is formed by the conoid ligament and trapezoid ligament.) * The coracoacromial ligament – to the acromion * The coracohumeral ligament – to the

* The

superior transverse scapular ligament The superior transverse ligament (transverse or suprascapular ligament) converts the suprascapular notch into a foramen or opening. It is a thin and flat fascicle, narrower at the middle than at the extremities, attached by one end to the base o ...

– from the base of the

coracoid A coracoid (from Greek κόραξ, ''koraks'', raven) is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is pre ...

to the medial portion of the suprascapular notch

Clinical significance

The coracoid process is palpable just below the lateral end of the clavicle (collar bone). It is otherwise known as the "Surgeon's Lighthouse" because it serves as a landmark to avoid neurovascular damage. Major neurovascular structures enter the upper limb medial to the coracoid process, so that surgical approaches to the shoulder region should always take place laterally to the coracoid process.

Other animals

monotreme Monotremes () are prototherian mammals of the order Monotremata. They are one of the three groups of living mammals, along with placentals ( Eutheria), and marsupials (Metatheria). Monotremes are typified by structural differences in their bra ...

s, the

is a separate bone. Reptiles,

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s, and

frog A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" '' Triadobatrachus'' is ...

s (but not

salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten ...

s) also possess a bone by this name, but is not

homologous Homology may refer to: Sciences Biology *Homology (biology), any characteristic of biological organisms that is derived from a common ancestor *Sequence homology, biological homology between DNA, RNA, or protein sequences * Homologous chrom ...

with the coracoid process of mammals. Analyses of the size and shape of the coracoid process in ''

Australopithecus africanus ''Australopithecus africanus'' is an extinct species of australopithecine which lived between about 3.3 and 2.1 million years ago in the Late Pliocene to Early Pleistocene of South Africa. The species has been recovered from Taung, Sterkfont ...

'' (STS 7) have shown that in this species it displayed a prominent dorsolateral tubercle placed more laterally than in

modern humans Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...

. This reflect, according to one interpretation, a scapula positioned high on a funnel-shaped thorax and a clavicle positioned obliquely as in extant

great apes The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic family of primates that includes eight extant species in four genera: '' Pongo'' (the Bornean, Sumatran and Tapanuli orangutan); '' Gorilla'' (the ...

. Anthropologists use the coracoid process to study shoulder morphology in order to find out if the upper limbs provided support for bipedalism in the early hominin ages. The shoulder is an area of primate life structures that previous examinations have demonstrated to emphatically mirror the varying useful requests forced by contrasts in locomotor modes. Since the morphology of early hominin upper appendage components comprises a blend of derived traits, it is noted that these primitive features are of continuous usage throughout the evolution of hominins. When ''Australopithecus africanus'' (known as Sts 7 within the realms of Anthropology) was being examined, it was observed that the scapular orientation was higher as compared to modern day humans (Homo sapiens). However, Homo Sapiens do not have distinct features in terms of shape or size when it comes to the coracoid process. Within the research of Elizabeth Vrbua, a paleoanthropologist who made a study called “A New Study of the Scapula of Australopithecus africanus from Sterkfontein”, it was seen that ''A. africanus'' had a higher scapular position which could infer that this position is likely to be seen in earlier hominins as well. According to the authors of “The human acromion viewed from an evolutionary perspective”, there were different shapes of surface of the coracoid process within the various hominins. The

gorilla Gorillas are herbivorous, predominantly ground-dwelling great apes that inhabit the tropical forests of equatorial Africa. The genus ''Gorilla'' is divided into two species: the eastern gorilla and the western gorilla, and either four ...

s had a wide shape, chimpanzees,

orangutan Orangutans are great apes native to the rainforests of Indonesia and Malaysia. They are now found only in parts of Borneo and Sumatra, but during the Pleistocene they ranged throughout Southeast Asia and South China. Classified in the gen ...

s and

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...

s had an intermediate shape, and the

gibbon Gibbons () are apes in the family Hylobatidae (). The family historically contained one genus, but now is split into four extant genera and 20 species. Gibbons live in subtropical and tropical rainforest from eastern Bangladesh to Northeast Indi ...

had a small shape. This can further be analyzed as the different hominids have variability in their shape of the coracoid process. The latest contributions to the evolutionary coracoid process were from Doctor M. Hussan in 2016 where he added further insight on the significance of the subacromial impingement and coracoacromial arch’s importance with the aid of pathology.

Additional images

File:Coracoid process of left scapula - animation01.gif, Left

. Coracoid process shown in red. File:Coracoid process of scapula - animation01.gif, Animation. Coracoid process shown in red. File:Coracoid process of left scapula01.png, Left scapula. Lateral view. Coracoid process shown in red.

References

External links

*
Coracoid Process
- BlueLink Anatomy, University of Michigan Medical School {{Authority control Scapula