Upper limb
Upper limb | |
---|---|
Details | |
System | Musculoskeletal |
Identifiers | |
Latin | membrum superius |
MeSH | D034941 |
TA98 | A01.1.00.019 |
TA2 | 138 |
FMA | 7183 |
Anatomical terminology |
The upper
Definition
In formal usage, the term "arm" only refers to the structures from the shoulder to the elbow, explicitly excluding the forearm, and thus "upper limb" and "arm" are not synonymous.[2] However, in casual usage, the terms are often used interchangeably. The term "upper arm" is redundant in anatomy, but in informal usage is used to distinguish between the two terms.
Structure
In the human body, the muscles of the upper limb can be classified by origin, topography, function, or innervation. While a grouping by innervation reveals embryological and phylogenetic origins, the functional-topographical classification below reflects the similarity in action between muscles (with the exception of the shoulder girdle, where muscles with similar action can vary considerably in their location and orientation.[3]
Musculoskeletal system
Shoulder girdle
The shoulder girdle
The mobility of the shoulder girdle is supported by a large number of muscles. The most important of these are muscular sheets rather than fusiform or strap-shaped muscles and they thus never act in isolation but with some fibres acting in coordination with fibres in other muscles.[5]
- Muscles
- of shoulder girdle excluding the glenohumeral joint[3]
- Migrated from head
- omohyoideus
- Posterior
- levator scapulae
- Anterior
- serratus anterior
Shoulder joint
The
The large muscles acting at this joint perform multiple actions and seemingly simple movements are often the result of composite antagonist and protagonist actions from several muscles. For example,
- Muscles
- of shoulder joint proper[3]
- Posterior
- teres major
- Anterior
- coracobrachialis
Bones of upper limb
The bones forming the human upper limb are
- Clavicle
- Scapula
- Humerus
- Radius
- Ulna
- Carpal bones
- Scaphoid
- Lunate
- Triquetral
- Pisiform
- Trapezium
- Trapezoid
- Capitate
- Hamate
- 5 Metacarpal bones
- 14 Phalanges
Arm
The arm proper (brachium), sometimes called the upper arm,[4] the region between the shoulder and the elbow, is composed of the humerus with the elbow joint at its distal end.
The elbow joint is a complex of three joints — the
- Muscles
- of the arm[3]
- Posterior
- anconeus
- Anterior
- biceps brachii
Forearm
The forearm (
; the latter is the main distal part of the elbow joint, while the former composes the main proximal part of the wrist joint.Most of the large number of muscles in the forearm are divided into the wrist, hand, and finger extensors on the dorsal side (back of hand) and the ditto flexors in the superficial layers on the ventral side (side of palm). These muscles are attached to either the
Biceps is the major supinator (drive a screw in with the right arm) and
- Muscles
- of the forearm[3]
- Posterior
- (Superficial) extensor indicis
- Anterior
- (Superficial) pronator quadratus
- Radial
- extensor carpi radialis brevis
Wrist
The
How muscles act on the wrist is complex to describe. The five muscles acting on the wrist directly —
Hand
The hand (
Of the joints between the carpus and metacarpus, the carpometacarpal joints, only the saddle-shaped joint of the thumb offers a high degree of mobility while the opposite is true for the metacarpophalangeal joints. The joints of the fingers are simple hinge joints. [9]
The primary role of the hand itself is grasping and manipulation; tasks for which the hand has been adapted to two main grips — power grip and precision grip. In a power grip an object is held against the palm and in a precision grip an object is held with the fingers, both grips are performed by intrinsic and extrinsic hand muscles together. Most importantly, the relatively strong thenar muscles of the thumb and the thumb's flexible first joint allow the special opposition movement that brings the distal thumb pad in direct contact with the distal pads of the other four digits. Opposition is a complex combination of thumb flexion and abduction that also requires the thumb to be rotated 90° about its own axis. Without this complex movement, humans would not be able to perform a precision grip. [10]
In addition, the central group of intrinsic hand muscles give important contributions to human dexterity. The palmar and dorsal interossei adduct and abduct at the MCP joints and are important in pinching. The lumbricals, attached to the tendons of the
- Muscles
- of the hand[3]
- Metacarpal
- Lumbricals, palmar introssei, dorsal interossei
- Thenar
- opponens pollicis
- Hypothenar
- palmaris brevis
Neurovascular system
Nerve supply
The motor and sensory supply of the upper limb is provided by the brachial plexus which is formed by the ventral rami of spinal nerves C5-T1. In the posterior triangle of the neck these rami form three trunks from which fibers enter the axilla region (armpit) to innervate the muscles of the anterior and posterior compartments of the limb. In the axilla, cords are formed to split into branches, including the five terminal branches listed below. [11] The muscles of the upper limb are innervated segmentally proximal to distal so that the proximal muscles are innervated by higher segments (C5–C6) and the distal muscles are innervated by lower segments (C8–T1). [12]
Motor innervation of upper limb by the five terminal nerves of the brachial plexus:[12]
- The anterior compartment of the arm.
- The thenar muscles and the first and second lumbricals.
- The ulnar nerve innervates the muscles of the forearm and hand not innervated by the median nerve.
- The teres minor.
- The radial nerve innervates the posterior muscles of the arm and forearm
Collateral branches of the brachial plexus:[12]
- The levator scapulae.
- The serratus anterior.
- The infraspinatus
- The lateral pectoral nerve innervates pectoralis major
- The medial pectoral nerve innervates pectoralis major and minor
- The subscapularis
- The latissimus dorsi
- The teres major
- The medial brachial cutaneous nerveinnervates the skin of medial arm
- The medial antebrachial cutaneous nerveinnervates the skin of medial forearm
Blood supply and drainage
Arteries of the upper limb:
- The .
- The inferior ulnar collateral, radial,
- The radialis indicis branches of the radial artery.
- The posterior interosseous and superficial branches of the ulnar artery.
Veins of the upper limb:
- Basilic vein
- Cephalic vein
- Median cubital vein
- Median antebrachial vein
- Dorsal venous arch
As for the upper limb blood supply, there are many anatomical variations.[13]
Other animals
Evolutionary variation
This section relies largely or entirely on a single source. (July 2011) |
The skeletons of all
In
In
In species in the order
The
, have limbs so highly adapted to hanging in branches that it is unable to walk on the ground where it has to drag its own body using the large curved claws on its foredigits. [14]See also
Notes
- ^ "Upper Extremity". MeSH. Retrieved 26 June 2011.
- ^ "Arm". MeSH. Retrieved 26 June 2011.
- ^ a b c d e f Ross & Lamperti 2006, p. 256
- ^ a b c d e Ross & Lamperti 2006, p. 208
- ^ a b c Sellers 2002, pp. 1–3
- ^ a b Sellers 2002, pp. 3–5
- ^ Sellers 2002, p. 5
- ^ a b Sellers 2002, pp. 6–7
- ^ a b c Sellers 2002, pp. 8–9
- ^ a b Sellers 2002, pp. 10–11
- ^ Seiden 2002, p. 243
- ^ a b c Seiden 2002, pp. 233–36
- ^ Konarik M, Musil V, Baca V, Kachlik D. Upper limb principal arteries variations: A cadaveric study with terminological implication. Bosn J of Basic Med Sci. 2020;20(4):502-13. DOI: https://doi.org/10.17305/bjbms.2020.4643 PMID 32343941 PMCID: PMC7664784
- ^ a b c d e Gough-Palmer, Maclachlan & Routh 2008, pp. 502–510
References
- Gough-Palmer, Antony L; Maclachlan, Jody; Routh, Andrew (March 2008). "Paws for Thought: Comparative Radiologic Anatomy of the Mammalian Forelimb" (PDF). RadioGraphics. 28 (2): 501–510. PMID 18349453.
- Ross, Lawrence M; Lamperti, Edward D, eds. (2006). Thieme Atlas of Anatomy: General Anatomy and Musculoskeletal System. Thieme. ISBN 1-58890-419-9.
- Sellers, Bill (2002). "Functional Anatomy of the Upper Limb". Retrieved 19 June 2011.
- Seiden, David (2002). USMLE Step 1 Anatomy Notes. Kaplan Medical.