Accessory muscle

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An accessory muscle is a relatively rare anatomical variation where duplication of a muscle may appear anywhere in the muscular system. Treatment is not indicated unless the accessory muscle interferes with normal function. [1]

Contents

Examples

Examples are the accessory soleus muscle in the calf or ankle, the extensor digitorum brevis manus in the hand and epitrochleoanconeus muscle of the upper arm.

Additional examples in the hand include Flexor carpi radialis brevis which can compress the anterior interosseous nerve. [2] Also see palmaris profundus muscle.

On the extensor side: extensor digitorum brevis manus, extensor carpi radialis intermedius, extensor medii proprius muscle

Accessory muscles of the anterior thoracic wall include the sternalis muscle, the axillary arch (Langer's), variations of pectoralis major such as the pectoralis minimus, pectoralis quartus, and pectoralis intermedius, the chondrocoracoideus and chondrofascialis. [3] The whole pectoral region is subject to a high degree of variability. The pectoralis major or pectoralis minor may be absent, or in some cases the pectoralis major may be doubled. Other variants noted in this region are the chondroepitrochleas originating in one or more ribs, or directly from the pectoralis major; the costocoracoideus from the 6th to 8th ribs, and a chondrocoracoideus and another variant of this waiting to be named. Most of these accessory muscles are implicated in neurovascular compression. Of clinical use the newly described chondrocoracoideus has potential for use in reconstructive surgery. [4]

Axillary accessory muscles may be encountered in axillary lymph node removal, the awareness of which could avoid complications. [5]

An accessory muscle can also refer to a muscle that is not primarily responsible for movement but does provide assistance. [1] Examples of such muscles are the accessory muscles of respiration where the sternocleidomastoid and the scalene muscles (anterior, middle and posterior scalene) are typically considered accessory muscles of respiration. [6]

See also

Related Research Articles

<span class="mw-page-title-main">Carpal bones</span> Eight small bones that make up the wrist (or carpus) that connects the hand to the forearm

The carpal bones are the eight small bones that make up the wrist (carpus) that connects the hand to the forearm. The term "carpus" and "carpal" is derived from the Latin carpus and the Greek καρπός (karpós), meaning "wrist". In human anatomy, the main role of the carpal bones is to articulate with the radial and ulnar heads to form a highly mobile condyloid joint, to provide attachments for thenar and hypothenar muscles, and to form part of the rigid carpal tunnel which allows the median nerve and tendons of the anterior forearm muscles to be transmitted to the hand and fingers.

<span class="mw-page-title-main">Radial nerve</span> Nerve in the human body that supplies the posterior portion of the upper limb

The radial nerve is a nerve in the human body that supplies the posterior portion of the upper limb. It innervates the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm and the associated joints and overlying skin.

<span class="mw-page-title-main">Wrist</span> Part of the arm between the lower arm and the hand

In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; (2) the wrist joint or radiocarpal joint, the joint between the radius and the carpus and; (3) the anatomical region surrounding the carpus including the distal parts of the bones of the forearm and the proximal parts of the metacarpus or five metacarpal bones and the series of joints between these bones, thus referred to as wrist joints. This region also includes the carpal tunnel, the anatomical snuff box, bracelet lines, the flexor retinaculum, and the extensor retinaculum.

<span class="mw-page-title-main">Radius (bone)</span> One of the two long bones of the forearm

The radius or radial bone is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna. The ulna is longer than the radius, but the radius is thicker. The radius is a long bone, prism-shaped and slightly curved longitudinally.

<span class="mw-page-title-main">Upper limb</span> Consists of the arm, forearm, and hand

The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist and knuckle joints. In humans, each upper limb is divided into the shoulder, arm, elbow, forearm, wrist and hand, and is primarily used for climbing, lifting and manipulating objects. In anatomy, just as arm refers to the upper arm, leg refers to the lower leg.

<span class="mw-page-title-main">Pectoralis major</span> Main human chest muscle

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

In human anatomy, the extensor pollicis longus muscle (EPL) is a skeletal muscle located dorsally on the forearm. It is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together with this muscle.

<span class="mw-page-title-main">Sternalis muscle</span> Muscle seen in some humans

The rectus sternalis muscle is an anatomical variation that lies in front of the sternal end of the pectoralis major parallel to the margin of the sternum. The sternalis muscle may be a variation of the pectoralis major or of the rectus abdominis.

The posterior compartment of the forearm contains twelve muscles which primarily extend the wrist and digits. It is separated from the anterior compartment by the interosseous membrane between the radius and ulna.

<span class="mw-page-title-main">Mobile wad</span>

The mobile wad is a group of the following three muscles found in the lateral compartment of the forearm:

<span class="mw-page-title-main">Muscles of respiration</span> Muscles involved in breathing

The muscles of respiration are the muscles that contribute to inhalation and exhalation, by aiding in the expansion and contraction of the thoracic cavity. The diaphragm and, to a lesser extent, the intercostal muscles drive respiration during quiet breathing. The elasticity of these muscles is crucial to the health of the respiratory system and to maximize its functional capabilities.

<span class="mw-page-title-main">Outline of human anatomy</span> Overview of and topical guide to human anatomy

The following outline is provided as an overview of and topical guide to human anatomy:

<span class="mw-page-title-main">Cervical spinal nerve 8</span> Spinal nerve of the cervical segment

The cervical spinal nerve 8 (C8) is a spinal nerve of the cervical segment.

Extensor digitorum brevis manus is an extra or accessory muscle on the backside (dorsum) of the hand. It was first described by Albinus in 1758. The muscles lies in the fourth extensor compartment of the wrist, and is relatively rare. It has a prevalence of 4% in the general population according to a meta-analysis. This muscle is commonly misdiagnosed as a ganglion cyst, synovial nodule or cyst.

In human anatomy, a brevis muscle derives its name from the Latin brevis meaning "short", and can refer to:

<span class="mw-page-title-main">Extrinsic extensor muscles of the hand</span>

The extrinsic extensor muscles of the hand are located in the back of the forearm and have long tendons connecting them to bones in the hand, where they exert their action. Extrinsic denotes their location outside the hand. Extensor denotes their action which is to extend, or open flat, joints in the hand. They include the extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), extensor digitorum (ED), extensor digiti minimi (EDM), extensor carpi ulnaris (ECU), abductor pollicis longus (APL), extensor pollicis brevis (EPB), extensor pollicis longus (EPL), and extensor indicis (EI).

References

  1. 1 2 "accessory muscle". Farlex. Retrieved June 6, 2013.
  2. ↑ Xiao, Cong; Gao, Zhixiang; Zhang, Shaoyun; Long, Nangji; Yu, Wei; Jiang, Yishan (2021). "Flexor carpi radialis brevis muscle, a rare anomalous muscle of the forearm; a case report and literature review". American Journal of Translational Research. 13 (9): 10850–10855. PMC   8507061 . PMID   34650765.
  3. ↑ Douvetzemis, S; Natsis, K; Piagkou, M; Kostares, M; Demesticha, T; Troupis, T (2019). "Accessory muscles of the anterior thoracic wall and axilla. Cadaveric, surgical and radiological incidence and clinical significance during breast and axillary surgery". Folia Morphologica. 78 (3): 606–616. doi: 10.5603/FM.a2019.0005 . PMID   30664230.
  4. ↑ Zielinska, N; Ruzik, K; Georgiev, GP; Dimitrova, IN; Tubbs, RS; Olewnik, Ł (February 2022). "A new variety of chondrocoracoideus muscle, or an additional head of pectoralis major muscle". Surgical and Radiologic Anatomy. 44 (2): 233–237. doi:10.1007/s00276-022-02887-x. PMC   8831266 . PMID   35064323.
  5. ↑ Natsis, K; Vlasis, K; Totlis, T; Paraskevas, G; Noussios, G; Skandalakis, P; Koebke, J (February 2010). "Abnormal muscles that may affect axillary lymphadenectomy: surgical anatomy" (PDF). Breast Cancer Research and Treatment. 120 (1): 77–82. doi:10.1007/s10549-009-0374-5. PMID   19306056.
  6. ↑ Netter FH. Atlas of Human Anatomy 3rd ed. Icon Learning Systems. Teterboro, New Jersey 2003 - plate 191
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