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In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint and the elbow joint. The distal part of the upper limb between the elbow and the radiocarpal joint is known as the forearm or "lower" arm, and the extremity beyond the wrist is the hand.
The biceps or biceps brachii is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join to form a single muscle belly which is attached to the upper forearm. While the biceps crosses both the shoulder and elbow joints, its main function is at the elbow where it flexes the forearm and supinates the forearm. Both these movements are used when opening a bottle with a corkscrew: first biceps screws in the cork (supination), then it pulls the cork out (flexion).
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.
The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus.
The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in anatomy, technically, means only the region of the upper arm, whereas the lower "arm" is called the forearm. It is homologous to the region of the leg that lies between the knee and the ankle joints, the crus.
In human anatomy, the radial artery is the main artery of the lateral aspect of the forearm.
The musculocutaneous nerve arises from the lateral cord of the brachial plexus, opposite the lower border of the pectoralis major, its fibers being derived from C5, C6 and C7.
The cubital fossa,chelidon, or elbow pit, is the triangular area on the anterior side of the upper limb between the arm and forearm of a human or other hominid animals. It lies anteriorly to the elbow when in standard anatomical position.
The flexor pollicis longus is a muscle in the forearm and hand that flexes the thumb. It lies in the same plane as the flexor digitorum profundus. This muscle is unique to humans, being either rudimentary or absent in other primates. A meta-analysis indicated accessory flexor pollicis longus is present in around 48% of the population.
The palmaris longus is a muscle visible as a small tendon located between the flexor carpi radialis and the flexor carpi ulnaris, although it is not always present. It is absent in about 14 percent of the population; this number can vary in African, Asian, and Native American populations, however. Absence of the palmaris longus does not have an effect on grip strength. The lack of palmaris longus muscle does result in decreased pinch strength in fourth and fifth fingers. The absence of palmaris longus muscle is more prevalent in females than males.
In human anatomy, the adductor pollicis muscle is a muscle in the hand that functions to adduct the thumb. It has two heads: transverse and oblique.
Palmaris brevis muscle is a thin, quadrilateral muscle, placed beneath the integument of the ulnar side of the hand. It acts to fold the skin of the hypothenar eminence transversally.
The bicipital aponeurosis is a broad aponeurosis of the biceps brachii, which is located in the cubital fossa of the elbow. It separates superficial from deep structures in much of the fossa.
In human anatomy, the median umbilical ligament is an unpaired midline ligamentous structure upon the lower inner surface of the anterior abdominal wall. It is covered by the median umbilical fold.
The fabella is a small sesamoid bone found in some mammals embedded in the tendon of the lateral head of the gastrocnemius muscle behind the lateral condyle of the femur. It is an accessory bone, an anatomical variation present in 39% of humans. Rarely, there are two or three of these bones. It can be mistaken for a loose body or osteophyte. The word fabella is a Latin diminutive of faba 'bean'.
A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala are often described as having "hands" instead of paws on their front limbs. The raccoon is usually described as having "hands" though opposable thumbs are lacking.
The elbow is the region between the arm and the forearm that surrounds the elbow joint. The elbow includes prominent landmarks such as the olecranon, the cubital fossa, and the lateral and the medial epicondyles of the humerus. The elbow joint is a hinge joint between the arm and the forearm; more specifically between the humerus in the upper arm and the radius and ulna in the forearm which allows the forearm and hand to be moved towards and away from the body. The term elbow is specifically used for humans and other primates, and in other vertebrates forelimb plus joint is used.
Pronator teres syndrome is a compression neuropathy of the median nerve at the elbow. It is rare compared to compression at the wrist or isolated injury of the anterior interosseous branch of the median nerve.
Struthers' ligament is a feature of human anatomy consisting of a band of connective tissue at the medial aspect of the distal humerus. It courses from the supracondylar process of the humerus to the medial humeral epicondyle. It is not a constant ligament, and can be acquired or congenital. The structure was highlighted by John Struthers, who discussed the feature's evolutionary significance with Charles Darwin. Struthers originally reported that the ligament usually arose at a position 3.2 to 6.4 cm from the medial condyle, being 1.2 to 1.9 cm in length, and nearer to the anterior than the medial border of the humerus.
Injuries to the arm, forearm or wrist area can lead to various nerve disorders. One such disorder is median nerve palsy. The median nerve controls the majority of the muscles in the forearm. It controls abduction of the thumb, flexion of hand at wrist, flexion of digital phalanx of the fingers, is the sensory nerve for the first three fingers, etc. Because of this major role of the median nerve, it is also called the eye of the hand. If the median nerve is damaged, the ability to abduct and oppose the thumb may be lost due to paralysis of the thenar muscles. Various other symptoms can occur which may be repaired through surgery and tendon transfers. Tendon transfers have been very successful in restoring motor function and improving functional outcomes in patients with median nerve palsy.
References
- ↑ Standring, Susan (2016). Gray's anatomy: the anatomical basis of clinical practice (41 ed.). Elsevier Limited. pp. 862–894. ISBN 978-0-7020-5230-9.
- ↑ Lucas, Teghan; Kumaratilake, Jaliya; Henneberg, Maciej (September 10, 2020). "Recently increased prevalence of the human median artery of the forearm: A microevolutionary change". Journal of Anatomy. 237 (4): 623–631. doi:10.1111/joa.13224. PMC 7495300 . PMID 32914433. S2CID 221622823.
- ↑ Lucas, T.; Kumaratilake, J.; Henneberg, M. (2020). "Recently increased prevalence of the human median artery of the forearm: A microevolutionary change". Journal of Anatomy. 237 (4): 623–631. doi:10.1111/joa.13224. PMC 7495300 . PMID 32914433.
- ↑ "Forearm artery reveals humans evolving from changes in natural selection".
